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Sample records for nitride dielectric thin

  1. Dielectric screening in atomically thin boron nitride nanosheets.

    PubMed

    Li, Lu Hua; Santos, Elton J G; Xing, Tan; Cappelluti, Emmanuele; Roldán, Rafael; Chen, Ying; Watanabe, Kenji; Taniguchi, Takashi

    2015-01-14

    Two-dimensional (2D) hexagonal boron nitride (BN) nanosheets are excellent dielectric substrate for graphene, molybdenum disulfide, and many other 2D nanomaterial-based electronic and photonic devices. To optimize the performance of these 2D devices, it is essential to understand the dielectric screening properties of BN nanosheets as a function of the thickness. Here, electric force microscopy along with theoretical calculations based on both state-of-the-art first-principles calculations with van der Waals interactions under consideration, and nonlinear Thomas-Fermi theory models are used to investigate the dielectric screening in high-quality BN nanosheets of different thicknesses. It is found that atomically thin BN nanosheets are less effective in electric field screening, but the screening capability of BN shows a relatively weak dependence on the layer thickness.

  2. Dielectric Screening in Atomically Thin Boron Nitride Nanosheets

    NASA Astrophysics Data System (ADS)

    Li, Lu Hua; Santos, Elton J. G.; Xing, Tan; Cappelluti, Emmanuele; Roldán, Rafael; Chen, Ying; Watanabe, Kenji; Taniguchi, Takashi

    2015-01-01

    Two-dimensional (2D) hexagonal boron nitride (BN) nanosheets are excellent dielectric substrate for graphene, molybdenum disulfide and many other 2D nanomaterials based electronic and photonic devices. To optimize the performance of these 2D devices, it is essential to understand the dielectric screening properties of BN nanosheets as a function of the thickness. Here, electric force microscopy along with theoretical calculations based on both state-of-the-art first-principles calculations with van der Waals interactions under consideration and non-linear Thomas-Fermi theory models are used to investigate the dielectric screening in high-quality BN nanosheets of different thicknesses. It is found that atomically thin BN nanosheets are less effective in electric field screening, but the screening capability of BN shows a relatively weak dependence on the layer thickness.

  3. Investigation on the dielectric behavior of aluminum nitride thin films at different temperatures applying a time-zero approach

    NASA Astrophysics Data System (ADS)

    Schneider, Michael; Bittner, Achim; Schmid, Ulrich

    2013-05-01

    In MEMS (micro electromechanical system) devices, piezoelectric aluminum nitride (AlN) thin films are commonly used as functional material for sensing and actuating purposes. Additionally, AlN features excellent dielectric properties as well as a high chemical and thermal stability, making it also a good choice for passivation purposes for microelectronic devices. With those aspects and current trends towards minimization in mind, the dielectric reliability of thin AlN films is of utmost importance for the realization of advanced device concepts. In this study, we present results on the transversal dielectric strength of 100 nm AlN thin films deposited by dc magnetron sputtering. The dielectric strength was measured using a time-zero approach, where the film is stressed using a fast voltage ramp up to the point of breakdown. The measurements were performed using different contact pad sizes, different voltage ramping speeds and device temperatures, respectively. In order to achieve statistical significance, at least 12 measurements were performed for each environment parameter set and the results analyzed using the Weibull approach. The results show, that the breakdown field in positive direction rises with the pad size, as expected. Furthermore, lower breakdown fields with increasing temperatures up to 300°C are observed with the mean field to failure following an exponential law typical for temperature activated processes. The activation energy was determined to 27 meV, allowing an estimation of the breakdown field towards even higher temperatures. In negative field direction no breakdown occurred, which is attributed to the metal-insulator-semiconductor configuration of the sample and hence, the larger depletion layer forming in the silicon dominates the observed current behavior.

  4. Carbon attachment on the aluminum nitride gate dielectric in the pentacene-based organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Zan, Hsiao-Wen; Chou, Cheng-Wei; Wang, Chung-Hwa; Song, Ho-Tsung; Hwang, Jenn-Chang; Lee, Po-Tsung

    2009-03-01

    This study presents carbon attachment on an aluminum nitride (AlN) gate dielectric to improve the device performance of pentacene-based organic thin-film transistors (OTFTs). This approach produces high OTFT performance on an aged AlN surface. A high mobility of 0.67 cm2/V s was achieved on an AlN surface aged for 14 days, compared to a mobility of 0.05 cm2/V s on an as-deposited AlN surface. This improvement in device performance is correlated with carbon attachment on the AlN surface, which lowers surface energy. The lowered surface energy made the surface less polar, as measured by a contact angle instrument. The chemical composition of the aged AlN surface was analyzed using x-ray photoelectron spectroscopy before pentacene deposition. Enhanced C=C bonding at 284.5 eV was observed on the aged AlN surface. These enhanced C=C bonds favored the growth of large pentacene islands in the initial growth stage, which may improve OTFT device performance.

  5. Infrared Dielectric Properties of Low-stress Silicon Nitride

    NASA Technical Reports Server (NTRS)

    Cataldo, Giuseppe; Beall, James A.; Cho, Hsiao-Mei; McAndrew, Brendan; Niemack, Michael D.; Wollack, Edward J.

    2012-01-01

    Silicon nitride thin films play an important role in the realization of sensors, filters, and high-performance circuits. Estimates of the dielectric function in the far- and mid-IR regime are derived from the observed transmittance spectra for a commonly employed low-stress silicon nitride formulation. The experimental, modeling, and numerical methods used to extract the dielectric parameters with an accuracy of approximately 4% are presented.

  6. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    SciTech Connect

    Ji, Yanfeng; Pan, Chengbin; Hui, Fei; Shi, Yuanyuan; Lanza, Mario; Zhang, Meiyun; Long, Shibing; Lian, Xiaojuan; Miao, Feng; Larcher, Luca; Wu, Ernest

    2016-01-04

    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO{sub 2}, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications.

  7. Scattering from Thin Dielectric Disks

    NASA Technical Reports Server (NTRS)

    Levine, D. M.; Schneider, A.; Lang, R. H.; Carter, H. G.

    1984-01-01

    A solution was obtained for scattering from thin dielectric disks by approximating the currents induced inside the disk with the currents which would exist inside a dielectric slab of the same thickness, orientation and dielectric properties. This approximation reduces to an electrostatic approximation when the disk thickness, T, is small compared to the wavelength of the incident radiation and the approximation yields a conventional physical optics solution when the dimension, A, characteristic of the geometrical cross section of the disk (e.g., the diameter of a circular disk) is large compared to wavelength. When the ratio A/T is sufficiently large the disk will always be in one or the other of these regimes (T lambda or kA1. Consequently, when A/T is large this solution provides a conventional approximation for the scattered fields which can be applied at all frequencies. As a check on this conclusion, a comparison was made between the theoretical and measured radar cross section of thin dielectric disks. Agreement was found for thin disks with both large and small values of kA.

  8. Scattering from thin dielectric disks

    NASA Technical Reports Server (NTRS)

    Le Vine, D. M.; Schneider, A.; Lang, R. H.; Carter, H. G.

    1985-01-01

    A solution was obtained for scattering from thin dielectric disks by approximating the currents induced inside the disk with the currents which would exist inside a dielectric slab of the same thickness, orientation and dielectic properties. This approximation reduces to an electrostatic approximation when the disk thickness, T, is small compared to the wavelength of the incident radiation and the approximation yields a conventional physical optics solution when the dimension, A, characteristic of the geometrical cross section of the disk (e.g., the diameter of a circular disk) is large compared to wavelength. When the ratio A/T sufficiently large the disk will always be in one or the other of these regimes, T lambda or kA1. Consequently, when A/T is large this solution provides a conventional approximation for the scattered fields which can be applied at all frequencies. As a check on this conclusion, a comparison was made between the theoretical and measured radar cross section of thin dielectric disks. Agreement was found for thin disks with both large and small values of kA.

  9. Solution-Processed Dielectrics Based on Thickness-Sorted Two-Dimensional Hexagonal Boron Nitride Nanosheets

    SciTech Connect

    Zhu, Jian; Kang, Joohoon; Kang, Junmo; Jariwala, Deep; Wood, Joshua D.; Seo, Jung-Woo T.; Chen, Kan-Sheng; Marks, Tobin J.; Hersam, Mark C.

    2015-10-14

    Gate dielectrics directly affect the mobility, hysteresis, power consumption, and other critical device metrics in high-performance nanoelectronics. With atomically flat and dangling bond-free surfaces, hexagonal boron nitride (h-BN) has emerged as an ideal dielectric for graphene and related two-dimensional semiconductors. While high-quality, atomically thin h-BN has been realized via micromechanical cleavage and chemical vapor deposition, existing liquid exfoliation methods lack sufficient control over h-BN thickness and large-area film quality, thus limiting its use in solution-processed electronics. Here, we employ isopycnic density gradient ultracentrifugation for the preparation of monodisperse, thickness-sorted h-BN inks, which are subsequently layer-by-layer assembled into ultrathin dielectrics with low leakage currents of 3 × 10–9 A/cm2 at 2 MV/cm and high capacitances of 245 nF/cm2. The resulting solution-processed h-BN dielectric films enable the fabrication of graphene field-effect transistors with negligible hysteresis and high mobilities up to 7100 cm2 V–1 s–1 at room temperature. These h-BN inks can also be used as coatings on conventional dielectrics to minimize the effects of underlying traps, resulting in improvements in overall device performance. Overall, this approach for producing and assembling h-BN dielectric inks holds significant promise for translating the superlative performance of two-dimensional heterostructure devices to large-area, solution-processed nanoelectronics.

  10. Solution-Processed Dielectrics Based on Thickness-Sorted Two-Dimensional Hexagonal Boron Nitride Nanosheets.

    PubMed

    Zhu, Jian; Kang, Joohoon; Kang, Junmo; Jariwala, Deep; Wood, Joshua D; Seo, Jung-Woo T; Chen, Kan-Sheng; Marks, Tobin J; Hersam, Mark C

    2015-10-14

    Gate dielectrics directly affect the mobility, hysteresis, power consumption, and other critical device metrics in high-performance nanoelectronics. With atomically flat and dangling bond-free surfaces, hexagonal boron nitride (h-BN) has emerged as an ideal dielectric for graphene and related two-dimensional semiconductors. While high-quality, atomically thin h-BN has been realized via micromechanical cleavage and chemical vapor deposition, existing liquid exfoliation methods lack sufficient control over h-BN thickness and large-area film quality, thus limiting its use in solution-processed electronics. Here, we employ isopycnic density gradient ultracentrifugation for the preparation of monodisperse, thickness-sorted h-BN inks, which are subsequently layer-by-layer assembled into ultrathin dielectrics with low leakage currents of 3 × 10(-9) A/cm(2) at 2 MV/cm and high capacitances of 245 nF/cm(2). The resulting solution-processed h-BN dielectric films enable the fabrication of graphene field-effect transistors with negligible hysteresis and high mobilities up to 7100 cm(2) V(-1) s(-1) at room temperature. These h-BN inks can also be used as coatings on conventional dielectrics to minimize the effects of underlying traps, resulting in improvements in overall device performance. Overall, this approach for producing and assembling h-BN dielectric inks holds significant promise for translating the superlative performance of two-dimensional heterostructure devices to large-area, solution-processed nanoelectronics.

  11. Titanium nitride thin films for minimizing multipactoring

    DOEpatents

    Welch, Kimo M.

    1979-01-01

    Applying a thin film coating to the surface of a workpiece, in particular, applying a coating of titanium nitride to a klystron window by means of a crossed-field diode sputtering array. The array is comprised of a cohesive group of numerous small hollow electrically conducting cylinders and is mounted so that the open ends of the cylinders on one side of the group are adjacent a titanium cathode plate. The workpiece is mounted so as to face the open ends of the other side of the group. A magnetic field is applied to the array so as to be coaxial with the cylinders and a potential is applied across the cylinders and the cathode plate, the cylinders as an anode being positive with respect to the cathode plate. The cylinders, the cathode plate and the workpiece are situated in an atmosphere of nitrogen which becomes ionized such as by field emission because of the electric field between the cylinders and cathode plate, thereby establishing an anode-cathode discharge that results in sputtering of the titanium plate. The sputtered titanium coats the workpiece and chemically combines with the nitrogen to form a titanium nitride coating on the workpiece. Gas pressure, gas mixtures, cathode material composition, voltages applied to the cathode and anode, the magnetic field, cathode, anode and workpiece spacing, and the aspect ratio (ratio of length to inner diameter) of the anode cylinders, all may be controlled to provide consistent optimum thin film coatings of various compositions and thicknesses. Another facet of the disclosure is the coating of microwave components per se with titanium nitride to reduce multipactoring under operating conditions of the components.

  12. Thin film dielectric composite materials

    DOEpatents

    Jia, Quanxi; Gibbons, Brady J.; Findikoglu, Alp T.; Park, Bae Ho

    2002-01-01

    A dielectric composite material comprising at least two crystal phases of different components with TiO.sub.2 as a first component and a material selected from the group consisting of Ba.sub.1-x Sr.sub.x TiO.sub.3 where x is from 0.3 to 0.7, Pb.sub.1-x Ca.sub.x TiO.sub.3 where x is from 0.4 to 0.7, Sr.sub.1-x Pb.sub.x TiO.sub.3 where x is from 0.2 to 0.4, Ba.sub.1-x Cd.sub.x TiO.sub.3 where x is from 0.02 to 0.1, BaTi.sub.1-x Zr.sub.x O.sub.3 where x is from 0.2 to 0.3, BaTi.sub.1-x Sn.sub.x O.sub.3 where x is from 0.15 to 0.3, BaTi.sub.1-x Hf.sub.x O.sub.3 where x is from 0.24 to 0.3, Pb.sub.1-1.3x La.sub.x TiO.sub.3+0.2x where x is from 0.23 to 0.3, (BaTiO.sub.3).sub.x (PbFeo.sub.0.5 Nb.sub.0.5 O.sub.3).sub.1-x where x is from 0.75 to 0.9, (PbTiO.sub.3).sub.- (PbCo.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.1 to 0.45, (PbTiO.sub.3).sub.x (PbMg.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.2 to 0.4, and (PbTiO.sub.3).sub.x (PbFe.sub.0.5 Ta.sub.0.5 O.sub.3).sub.1-x where x is from 0 to 0.2, as the second component is described. The dielectric composite material can be formed as a thin film upon suitable substrates.

  13. Boron Nitride Surface Activity as Route to Composite Dielectric Films.

    PubMed

    Cui, Zhenhua; Cao, Zhen; Ma, Rui; Dobrynin, Andrey V; Adamson, Douglas H

    2015-08-12

    The propensity of boron nitride sheets to stack creates obstacles for their application as multifunctional materials despite their unique thermal, mechanical, and electrical properties. To address this challenge, we use a combination of molecular dynamics simulations and experimental techniques to demonstrate surfactant-like properties of BN sheets at the interface between immiscible solvents. The spreading of two-dimensional BN sheets at a high-energy oil/water interface lowers the free energy of the system, creating films of overlapping BN sheets that are more thermodynamically favorable than stacked sheets. Coating such films onto polymers results in composite materials with exceptional barrier and dielectric properties.

  14. Boron nitride hollow nanospheres: Synthesis, formation mechanism and dielectric property

    SciTech Connect

    Zhong, B.; Tang, X.H.; Huang, X.X.; Xia, L.; Zhang, X.D.; Wang, C.J.; Wen, G.W.

    2015-04-15

    Highlights: • BN hollow nanospheres are fabricated in large scale via a new CVD method. • Morphology and structure are elucidated by complementary analytical techniques. • Formation mechanism is proposed based on experimental observations. • Dielectric properties are investigated in the X-band microwave frequencies. • BN hollow nanospheres show lower dielectric loss than regular BN powders. - Abstract: Boron nitride (BN) hollow nanospheres have been successfully fabricated by pyrolyzing vapors decomposed from ammonia borane (NH{sub 3}BH{sub 3}) at 1300 °C. The final products have been extensively characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The BN hollow nanospheres were ranging from 100 to 300 nm in diameter and around 30–100 nm in thickness. The internal structure of the products was found dependent on the reaction temperatures. A possible formation mechanism of the BN hollow nanospheres was proposed on the basis of the experimental observations. Dielectric measurements in the X-band microwave frequencies (8–12 GHz) showed that the dielectric loss of the paraffin filled by the BN hollow nanospheres was lower than that filled by regular BN powders, which indicated that the BN hollow nanospheres could be potentially used as low-density fillers for microwave radomes.

  15. Device performance of in situ steam generated gate dielectric nitrided by remote plasma nitridation

    NASA Astrophysics Data System (ADS)

    Al-Shareef, H. N.; Karamcheti, A.; Luo, T. Y.; Bersuker, G.; Brown, G. A.; Murto, R. W.; Jackson, M. D.; Huff, H. R.; Kraus, P.; Lopes, D.; Olsen, C.; Miner, G.

    2001-06-01

    In situ steam generated (ISSG) oxides have recently attracted interest for use as gate dielectrics because of their demonstrated reliability improvement over oxides formed by dry oxidation. [G. Minor, G. Xing, H. S. Joo, E. Sanchez, Y. Yokota, C. Chen, D. Lopes, and A. Balakrishna, Electrochem. Soc. Symp. Proc. 99-10, 3 (1999); T. Y. Luo, H. N. Al-Shareef, G. A. Brown, M. Laughery, V. Watt, A. Karamcheti, M. D. Jackson, and H. R. Huff, Proc. SPIE 4181, 220 (2000).] We show in this letter that nitridation of ISSG oxide using a remote plasma decreases the gate leakage current of ISSG oxide by an order of magnitude without significantly degrading transistor performance. In particular, it is shown that the peak normalized transconductance of n-channel devices with an ISSG oxide gate dielectric decreases by only 4% and the normalized drive current by only 3% after remote plasma nitridation (RPN). In addition, it is shown that the reliability of the ISSG oxide exhibits only a small degradation after RPN. These observations suggest that the ISSG/RPN process holds promise for gate dielectric applications.

  16. Magnetoresistance measurements of superconducting molybdenum nitride thin films

    SciTech Connect

    Baskaran, R. Arasu, A. V. Thanikai; Amaladass, E. P.

    2016-05-23

    Molybdenum nitride thin films have been deposited on aluminum nitride buffered glass substrates by reactive DC sputtering. GIXRD measurements indicate formation of nano-crystalline molybdenum nitride thin films. The transition temperature of MoN thin film is 7.52 K. The transition width is less than 0.1 K. The upper critical field Bc{sub 2}(0), calculated using GLAG theory is 12.52 T. The transition width for 400 µA current increased initially upto 3 T and then decreased, while that for 100 µA current transition width did not decrease.

  17. Low temperature aluminum nitride thin films for sensory applications

    SciTech Connect

    Yarar, E.; Zamponi, C.; Piorra, A.; Quandt, E.; Hrkac, V.; Kienle, L.

    2016-07-15

    A low-temperature sputter deposition process for the synthesis of aluminum nitride (AlN) thin films that is attractive for applications with a limited temperature budget is presented. Influence of the reactive gas concentration, plasma treatment of the nucleation surface and film thickness on the microstructural, piezoelectric and dielectric properties of AlN is investigated. An improved crystal quality with respect to the increased film thickness was observed; where full width at half maximum (FWHM) of the AlN films decreased from 2.88 ± 0.16° down to 1.25 ± 0.07° and the effective longitudinal piezoelectric coefficient (d{sub 33,f}) increased from 2.30 ± 0.32 pm/V up to 5.57 ± 0.34 pm/V for film thicknesses in the range of 30 nm to 2 μm. Dielectric loss angle (tan δ) decreased from 0.626% ± 0.005% to 0.025% ± 0.011% for the same thickness range. The average relative permittivity (ε{sub r}) was calculated as 10.4 ± 0.05. An almost constant transversal piezoelectric coefficient (|e{sub 31,f}|) of 1.39 ± 0.01 C/m{sup 2} was measured for samples in the range of 0.5 μm to 2 μm. Transmission electron microscopy (TEM) investigations performed on thin (100 nm) and thick (1.6 μm) films revealed an (002) oriented AlN nucleation and growth starting directly from the AlN-Pt interface independent of the film thickness and exhibit comparable quality with the state-of-the-art AlN thin films sputtered at much higher substrate temperatures.

  18. Vertical III-nitride thin-film power diode

    DOEpatents

    Wierer, Jr., Jonathan; Fischer, Arthur J.; Allerman, Andrew A.

    2017-03-14

    A vertical III-nitride thin-film power diode can hold off high voltages (kV's) when operated under reverse bias. The III-nitride device layers can be grown on a wider bandgap template layer and growth substrate, which can be removed by laser lift-off of the epitaxial device layers grown thereon.

  19. Layer-by-layer dielectric breakdown of hexagonal boron nitride.

    PubMed

    Hattori, Yoshiaki; Taniguchi, Takashi; Watanabe, Kenji; Nagashio, Kosuke

    2015-01-27

    Hexagonal boron nitride (BN) is widely used as a substrate and gate insulator for two-dimensional (2D) electronic devices. The studies on insulating properties and electrical reliability of BN itself, however, are quite limited. Here, we report a systematic investigation of the dielectric breakdown characteristics of BN using conductive atomic force microscopy. The electric field strength was found to be ∼ 12 MV/cm, which is comparable to that of conventional SiO2 oxides because of the covalent bonding nature of BN. After the hard dielectric breakdown, the BN fractured like a flower into equilateral triangle fragments. However, when the applied voltage was terminated precisely in the middle of the dielectric breakdown, the formation of a hole that did not penetrate to the bottom metal electrode was clearly observed. Subsequent I-V measurements of the hole indicated that the BN layer remaining in the hole was still electrically inactive. On the basis of these observations, layer-by-layer breakdown was confirmed for BN with regard to both physical fracture and electrical breakdown. Moreover, statistical analysis of the breakdown voltages using a Weibull plot suggested the anisotropic formation of defects. These results are unique to layered materials and unlike the behavior observed for conventional 3D amorphous oxides.

  20. Hexagonal boron nitride: Ubiquitous layered dielectric for two-dimensional electronics

    NASA Astrophysics Data System (ADS)

    Jain, Nikhil

    Hexagonal boron nitride (h-BN), a layer-structured dielectric with very similar crystalline lattice to that of graphene, has been studied as a ubiquitous dielectric for two-dimensional electronics. While 2D materials may lead to future platform for electronics, traditional thin-film dielectrics (e.g., various oxides) make highly invasive interface with graphene. Multiple key roles of h-BN in graphene electronics are explored in this thesis. 2D graphene/h-BN heterostructures are designed and implemented in diverse configurations in which h-BN is evaluated as a supporting substrate, a gate dielectric, a passivation layer, or an interposing barrier in "3D graphene" superlattice. First, CVD-grown graphene on h-BN substrate shows improved conductivity and resilience to thermally induced breakdown, as compared with graphene on SiO2, potentially useful for high-speed graphene devices and on-chip interconnects. h-BN is also explored as a gate dielectric for graphene field-effect transistor with 2D heterostructure design. The dielectric strength and tunneling behavior of h-BN are investigated, confirming its robust nature. Next, h-BN is studied as a passivation layer for graphene electronics. In addition to significant improvement in current density and breakdown threshold, fully encapsulated graphene exhibits minimal environmental sensitivity, a key benefit to 2D materials which have only surfaces. Lastly, reduction in interlayer carrier scattering is observed in a double-layered graphene setup with ultrathin h-BN multilayer as an interposing layer. The DFT simulation and Raman spectral analysis indicate reduction in interlayer scattering. The decoupling of the two graphene monolayers is further confirmed by electrical characterization, as compared with other referencing mono- and multilayer configurations. The heterostructure serves as the building element in "3D graphene", a versatile platform for future electronics.

  1. Dielectric strength, optical absorption, and deep ultraviolet detectors of hexagonal boron nitride epilayers

    NASA Astrophysics Data System (ADS)

    Li, J.; Majety, S.; Dahal, R.; Zhao, W. P.; Lin, J. Y.; Jiang, H. X.

    2012-10-01

    Hexagonal boron nitride (hBN) epilayers have been synthesized by metal organic chemical vapor deposition and their dielectric strength, optical absorption, and potential as a deep ultraviolet (DUV) detector material have been studied. Based on the graphene optical absorption concept, the estimated band-edge absorption coefficient of hBN is about 7 × 105/cm, which is more than 3 times higher than the value for wurtzite AlN (˜2 × 105 /cm). The dielectric strength of hBN epilayers exceeds that of AlN and is greater than 4.4 MV/cm based on the measured result for an hBN epilayer released from the host sapphire substrate. The hBN epilayer based DUV detectors exhibit a sharp cut-off wavelength around 230 nm, which coincides with the band-edge photoluminescence emission peak and virtually no responses in the long wavelengths. Based on the present study, we have identified several advantageous features of hBN DUV photodetectors: (1) low long wavelength response or high DUV to visible rejection ratio; (2) requiring very thin active layers due to high optical absorption; (3) high dielectric strength and chemical inertness and resistance to oxidation and therefore suitable for applications in extreme conditions; (4) high prospects of achieving flexible devices; and (5) possible integration with graphene optoelectronics due to their similar structures and lattice constants.

  2. Charge trapping in nitrided HfSiO gate dielectric layers

    SciTech Connect

    Vellianitis, G.; Rittersma, Z. M.; Petry, J.

    2006-08-28

    The effects of HfSiO nitridation on charge trapping and long-term dielectric reliability are investigated. A comparison between decoupled plasma nitridation, annealing in NH{sub 3}, and no nitridation is made. It was found that thinner HfSiO layers show less trapped charge. Decoupled plasma nitridation resulted always in a larger hysteresis in the characteristics. A common behavior in all samples was seen at elevated temperatures, which corresponds to lower trapped charge and higher leakage current. Dependence between the trapped charge and the leakage current changes with temperature was established.

  3. Approaching Defect-free Amorphous Silicon Nitride by Plasma-assisted Atomic Beam Deposition for High Performance Gate Dielectric

    PubMed Central

    Tsai, Shu-Ju; Wang, Chiang-Lun; Lee, Hung-Chun; Lin, Chun-Yeh; Chen, Jhih-Wei; Shiu, Hong-Wei; Chang, Lo-Yueh; Hsueh, Han-Ting; Chen, Hung-Ying; Tsai, Jyun-Yu; Lu, Ying-Hsin; Chang, Ting-Chang; Tu, Li-Wei; Teng, Hsisheng; Chen, Yi-Chun; Chen, Chia-Hao; Wu, Chung-Lin

    2016-01-01

    In the past few decades, gate insulators with a high dielectric constant (high-k dielectric) enabling a physically thick but dielectrically thin insulating layer, have been used to replace traditional SiOx insulator and to ensure continuous downscaling of Si-based transistor technology. However, due to the non-silicon derivative natures of the high-k metal oxides, transport properties in these dielectrics are still limited by various structural defects on the hetero-interfaces and inside the dielectrics. Here, we show that another insulating silicon compound, amorphous silicon nitride (a-Si3N4), is a promising candidate of effective electrical insulator for use as a high-k dielectric. We have examined a-Si3N4 deposited using the plasma-assisted atomic beam deposition (PA-ABD) technique in an ultra-high vacuum (UHV) environment and demonstrated the absence of defect-related luminescence; it was also found that the electronic structure across the a-Si3N4/Si heterojunction approaches the intrinsic limit, which exhibits large band gap energy and valence band offset. We demonstrate that charge transport properties in the metal/a-Si3N4/Si (MNS) structures approach defect-free limits with a large breakdown field and a low leakage current. Using PA-ABD, our results suggest a general strategy to markedly improve the performance of gate dielectric using a nearly defect-free insulator. PMID:27325155

  4. Approaching Defect-free Amorphous Silicon Nitride by Plasma-assisted Atomic Beam Deposition for High Performance Gate Dielectric.

    PubMed

    Tsai, Shu-Ju; Wang, Chiang-Lun; Lee, Hung-Chun; Lin, Chun-Yeh; Chen, Jhih-Wei; Shiu, Hong-Wei; Chang, Lo-Yueh; Hsueh, Han-Ting; Chen, Hung-Ying; Tsai, Jyun-Yu; Lu, Ying-Hsin; Chang, Ting-Chang; Tu, Li-Wei; Teng, Hsisheng; Chen, Yi-Chun; Chen, Chia-Hao; Wu, Chung-Lin

    2016-06-21

    In the past few decades, gate insulators with a high dielectric constant (high-k dielectric) enabling a physically thick but dielectrically thin insulating layer, have been used to replace traditional SiOx insulator and to ensure continuous downscaling of Si-based transistor technology. However, due to the non-silicon derivative natures of the high-k metal oxides, transport properties in these dielectrics are still limited by various structural defects on the hetero-interfaces and inside the dielectrics. Here, we show that another insulating silicon compound, amorphous silicon nitride (a-Si3N4), is a promising candidate of effective electrical insulator for use as a high-k dielectric. We have examined a-Si3N4 deposited using the plasma-assisted atomic beam deposition (PA-ABD) technique in an ultra-high vacuum (UHV) environment and demonstrated the absence of defect-related luminescence; it was also found that the electronic structure across the a-Si3N4/Si heterojunction approaches the intrinsic limit, which exhibits large band gap energy and valence band offset. We demonstrate that charge transport properties in the metal/a-Si3N4/Si (MNS) structures approach defect-free limits with a large breakdown field and a low leakage current. Using PA-ABD, our results suggest a general strategy to markedly improve the performance of gate dielectric using a nearly defect-free insulator.

  5. Catastrophic Thinning of Dielectric Elastomers

    NASA Astrophysics Data System (ADS)

    Zurlo, G.; Destrade, M.; DeTommasi, D.; Puglisi, G.

    2017-02-01

    We provide an energetic insight into the catastrophic nature of thinning instability in soft electroactive elastomers. This phenomenon is a major obstacle to the development of giant actuators, yet it is neither completely understood nor modeled accurately. In excellent agreement with experiments, we give a simple formula to predict the critical voltages for instability patterns; we model their shape and show that reversible (elastic) equilibrium is impossible beyond their onset. Our derivation is fully analytical, does not require finite element simulations, and can be extended to include prestretch and various material models.

  6. Cellulose triacetate, thin film dielectric capacitor

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S. (Inventor); Jow, T. Richard (Inventor)

    1993-01-01

    Very thin films of cellulose triacetate are cast from a solution containing a small amount of high boiling temperature, non-solvent which evaporates last and lifts the film from the casting surface. Stretched, oriented, crystallized films have high electrical breakdown properties. Metallized films less than about 2 microns in thickness form self-healing electrodes for high energy density, pulsed power capacitors. Thicker films can be utilized as a dielectric for a capacitor.

  7. Cellulose triacetate, thin film dielectric capacitor

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S. (Inventor); Jow, T. Richard (Inventor)

    1995-01-01

    Very thin films of cellulose triacetate are cast from a solution containing a small amount of high boiling temperature, non-solvent which evaporates last and lifts the film from the casting surface. Stretched, oriented, crystallized films have high electrical breakdown properties. Metallized films less than about 2 microns in thickness form self-healing electrodes for high energy density, pulsed power capacitors. Thicker films can be utilized as a dielectric for a capacitor.

  8. Dielectric response of wurtzite gallium nitride in the terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Hibberd, M. T.; Frey, V.; Spencer, B. F.; Mitchell, P. W.; Dawson, P.; Kappers, M. J.; Oliver, R. A.; Humphreys, C. J.; Graham, D. M.

    2016-12-01

    We report on the characterization of the intrinsic, anisotropic, dielectric properties of wurtzite gallium nitride in the spectral range of 0.5-11 THz, using terahertz time-domain spectroscopy. The ordinary (ε˜⊥) and extraordinary (ε˜∥) components of the complex dielectric function were determined experimentally for a semi-insulating, m-plane gallium nitride single crystal, providing measurements of the refractive indices (n⊥,∥) and absorption coefficients (α⊥,∥) . These material parameters were successfully modeled by considering the contribution of the optical phonon modes, measured using Raman spectroscopy, to the dielectric function, giving values for the relative static dielectric constants of ε0⊥ = 9.22 ± 0.02 and ε0∥ = 10.32 ± 0.03 for wurtzite gallium nitride.

  9. Characterization and properties of highly adhesive titanium nitride and tungsten nitride thin films

    NASA Astrophysics Data System (ADS)

    Martev, I. N.; Dechev, D. A.; Ivanov, N. P.; Uzunov, T. D.; Kashchieva, E. P.

    2008-05-01

    The paper presents results on the physical characteristics and mechanical properties of titanium nitride (TiN) and tungsten nitride (W2N) thin films grown by reactive DC magnetron sputtering. The films were deposited in a system with several magnetron modules of different sputtering materials suitable for deposition of single-layer metal nitride films and multilayer nitride coatings. The deposition conditions were optimized to obtain films with the highest adhesion to substrates of machine steel and sintered hard alloy. The adhesion of the films was measured in dependence on two principal process parameters: the nitrogen partial pressure in the magnetron discharge gas mixture of nitrogen and argon and the substrate temperature. The composition of the TiN films was determined by Auger electron spectroscopy. The microstructure and the crystallization trend of the films were studied by transmission electron microscopy and selected area electron diffraction. The hardness of the films was examined using standard measuring methods.

  10. Direct growth of nanocrystalline hexagonal boron nitride films on dielectric substrates

    SciTech Connect

    Tay, Roland Yingjie; Tsang, Siu Hon; Loeblein, Manuela; Chow, Wai Leong; Loh, Guan Chee; Toh, Joo Wah; Ang, Soon Loong; Teo, Edwin Hang Tong

    2015-03-09

    Atomically thin hexagonal-boron nitride (h-BN) films are primarily synthesized through chemical vapor deposition (CVD) on various catalytic transition metal substrates. In this work, a single-step metal-catalyst-free approach to obtain few- to multi-layer nanocrystalline h-BN (NCBN) directly on amorphous SiO{sub 2}/Si and quartz substrates is demonstrated. The as-grown thin films are continuous and smooth with no observable pinholes or wrinkles across the entire deposited substrate as inspected using optical and atomic force microscopy. The starting layers of NCBN orient itself parallel to the substrate, initiating the growth of the textured thin film. Formation of NCBN is due to the random and uncontrolled nucleation of h-BN on the dielectric substrate surface with no epitaxial relation, unlike on metal surfaces. The crystallite size is ∼25 nm as determined by Raman spectroscopy. Transmission electron microscopy shows that the NCBN formed sheets of multi-stacked layers with controllable thickness from ∼2 to 25 nm. The absence of transfer process in this technique avoids any additional degradation, such as wrinkles, tears or folding and residues on the film which are detrimental to device performance. This work provides a wider perspective of CVD-grown h-BN and presents a viable route towards large-scale manufacturing of h-BN substrates and for coating applications.

  11. Electroless plating of thin gold films directly onto silicon nitride thin films and into micropores.

    PubMed

    Whelan, Julie C; Karawdeniya, Buddini Iroshika; Bandara, Y M Nuwan D Y; Velleco, Brian D; Masterson, Caitlin M; Dwyer, Jason R

    2014-07-23

    A method to directly electrolessly plate silicon-rich silicon nitride with thin gold films was developed and characterized. Films with thicknesses <100 nm were grown at 3 and 10 °C between 0.5 and 3 h, with mean grain sizes between ∼20 and 30 nm. The method is compatible with plating free-standing ultrathin silicon nitride membranes, and we successfully plated the interior walls of micropore arrays in 200 nm thick silicon nitride membranes. The method is thus amenable to coating planar, curved, and line-of-sight-obscured silicon nitride surfaces.

  12. Optical dielectric response of gallium nitride studied by variable angle spectroscopy ellipsometry

    SciTech Connect

    Yao, H.; Yan, C.H.; Jenkinson, H.A.; Zavada, J.M.; Speck, J.S.; Denbaars, S.P.

    1997-12-31

    Variable angle spectroscopic ellipsometry (VASE) and transmission measurements have been employed to study the dielectric response of gallium nitride (GaN) thin films -- an important material for light emitting diodes (LEDs) and laser diodes applications. The GaN films were grown by atmosphere pressure metal organic chemical vapor deposition (MOCVD) on c-plane sapphire substrates ({alpha}-Al{sub 2}O{sub 3}). Room temperature VASE measurements were made, in the range of 0.75 to 5.5eV, at the angle of incidence of 73, 75, and 77 degree, respectively. Evidence of anisotropy is observed especially in the spectral range under the band gap ({approximately}3.4 eV), reflecting the nature of wurtzite crystal structure of GaN. The ordinary dielectric function {var_epsilon}{sub {perpendicular}}({omega}) of GaN were obtained through the analysis of transmission and VASE data in the range below and above the band gap. The thickness of these GaN films is also determined via the analysis.

  13. Electrical conduction mechanism in silicon nitride and oxy-nitride-sputtered thin films

    NASA Astrophysics Data System (ADS)

    Vila, M.; Román, E.; Prieto, C.

    2005-06-01

    We have studied the effect of reactive and nonreactive sputtering preparations on the composition and properties of silicon nitride thin films. Films were prepared from both silicon nitride ceramic and pure silicon targets under different Ar /N2 gas mixtures. For the different resulting samples, we have performed optical, x-ray photoemission spectroscopy (XPS), and transport measurements. The preparation conditions change the sample atomic composition and the effect of oxygen in the films, which in turn determines the dominant conduction mechanism. It becomes important to determine both the nonstoichiometry of the film and the phase where the oxygen is incorporated. Oxygen may appear as silicon oxide, forming a secondary phase inside silicon nitride; or it may consist of silicon oxy-nitride phases. The presence of these different phases, as revealed by XPS, determines the electrical properties and conduction mechanisms. Samples presenting space-charge-limited current as the dominant conduction mechanism correspond to those where a silicon oxy-nitride phase is formed (that becomes Ohmic for overstoichiometric Si content samples), while a Poole-Frenkel conduction behavior is characteristic of the silicon nitride phase.

  14. Nitrogen incorporation in sputter deposited molybdenum nitride thin films

    SciTech Connect

    Stöber, Laura Patocka, Florian Schneider, Michael Schmid, Ulrich; Konrath, Jens Peter Haberl, Verena

    2016-03-15

    In this paper, the authors report on the high temperature performance of sputter deposited molybdenum (Mo) and molybdenum nitride (Mo{sub 2}N) thin films. Various argon and nitrogen gas compositions are applied for thin film synthetization, and the amount of nitrogen incorporation is determined by Auger measurements. Furthermore, effusion measurements identifying the binding conditions of the nitrogen in the thin film are performed up to 1000 °C. These results are in excellent agreement with film stress and scanning electron microscope analyses, both indicating stable film properties up to annealing temperatures of 500 °C.

  15. Mid-infrared optical properties of thin films of aluminum oxide, titanium dioxide, silicon dioxide, aluminum nitride, and silicon nitride.

    PubMed

    Kischkat, Jan; Peters, Sven; Gruska, Bernd; Semtsiv, Mykhaylo; Chashnikova, Mikaela; Klinkmüller, Matthias; Fedosenko, Oliana; Machulik, Stephan; Aleksandrova, Anna; Monastyrskyi, Gregorii; Flores, Yuri; Masselink, W Ted

    2012-10-01

    The complex refractive index components, n and k, have been studied for thin films of several common dielectric materials with a low to medium refractive index as functions of wavelength and stoichiometry for mid-infrared (MIR) wavelengths within the range 1.54-14.29 μm (700-6500 cm(-1)). The materials silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, and titanium oxide are prepared using room temperature reactive sputter deposition and are characterized using MIR variable angle spectroscopic ellipsometry. The investigation shows how sensitive the refractive index functions are to the O2 and N2 flow rates, and for which growth conditions the materials deposit homogeneously. It also allows conclusions to be drawn on the degree of amorphousness and roughness. To facilitate comparison of the materials deposited in this work with others, the index of refraction was also determined and provided for the near-IR and visible ranges of the spectrum. The results presented here should serve as a useful information base for designing optical coatings for the MIR part of the electromagnetic spectrum. The results are parameterized to allow them to be easily used for coating design.

  16. Reactive ion beam deposition of aluminum nitride thin films

    NASA Astrophysics Data System (ADS)

    Bhat, S.; Ashok, S.; Fonash, S. J.; Tongson}, L.

    1985-07-01

    Aluminum nitride thin films have been prepared at room temperature by reactive ion beam sputtering for potential use as a passivant and diffusion/anneal cap in compound semiconductor technology. The electrical and optical pro-perties of these films have been studied along with the in-fluence of thermal annealing on the material characteristics. The quality of the films has also been found to improve in the presence of atomic hydrogen during the deposition.

  17. Grafting titanium nitride surfaces with sodium styrene sulfonate thin films.

    PubMed

    Zorn, Gilad; Migonney, Véronique; Castner, David G

    2014-09-01

    The importance of titanium nitride lies in its high hardness and its remarkable resistance to wear and corrosion, which has led to its use as a coating for the heads of hip prostheses, dental implants and dental surgery tools. However, the usefulness of titanium nitride coatings for biomedical applications could be significantly enhanced by modifying their surface with a bioactive polymer film. The main focus of the present work was to graft a bioactive poly(sodium styrene sulfonate) (pNaSS) thin film from titanium nitride surfaces via a two-step procedure: first modifying the surface with 3-methacryloxypropyltrimethoxysilane (MPS) and then grafting the pNaSS film from the MPS modified titanium through free radical polymerization. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used after each step to characterize success and completeness of each reaction. The surface region of the titanium nitride prior to MPS functionalization and NaSS grafting contained a mixture of titanium nitride, oxy-nitride, oxide species as well as adventitious surface contaminants. After MPS functionalization, Si was detected by XPS, and characteristic MPS fragments were detected by ToF-SIMS. After NaSS grafting, Na and S were detected by XPS and characteristic NaSS fragments were detected by ToF-SIMS. The XPS determined thicknesses of the MPS and NaSS overlayers were ∼1.5 and ∼1.7 nm, respectively. The pNaSS film density was estimated by the toluidine blue colorimetric assay to be 260 ± 70 ng/cm(2).

  18. Trapping of hydrogen in hafnium-based high kappa dielectric thin films for advanced CMOS applications

    NASA Astrophysics Data System (ADS)

    Ukirde, Vaishali

    In recent years, advanced high kappa gate dielectrics are under serious consideration to replace SiO2 and SiON in semiconductor industry. Hafnium-based dielectrics such as hafnium oxides, oxynitrides and Hf-based silicates/nitrided silicates are emerging as some of the most promising alternatives to SiO2/SiON gate dielectrics in complementary metal oxide semiconductor (CMOS) devices. Extensive efforts have been taken to understand the effects of hydrogen impurities in semiconductors and its behavior such as incorporation, diffusion, trapping and release with the aim of controlling and using it to optimize the performance of electronic device structures. In this dissertation, a systematic study of hydrogen trapping and the role of carbon impurities in various alternate gate dielectric candidates, HfO2/Si, HfxSi1-xO2/Si, HfON/Si and HfON(C)/Si is presented. It has been shown that processing of high kappa dielectrics may lead to some crystallization issues. Rutherford backscattering spectroscopy (RBS) for measuring oxygen deficiencies, elastic recoil detection analysis (ERDA) for quantifying hydrogen and nuclear reaction analysis (NRA) for quantifying carbon, X-ray diffraction (XRD) for measuring degree of crystallinity and X-ray photoelectron spectroscopy (XPS) were used to characterize these thin dielectric materials. ERDA data are used to characterize the evolution of hydrogen during annealing in hydrogen ambient in combination with preprocessing in oxygen and nitrogen.

  19. First-principles investigation of band offsets and dielectric properties of Silicon-Silicon Nitride interfaces

    NASA Astrophysics Data System (ADS)

    Pham, Tuan Anh; Li, Tianshu; Gygi, Francois; Galli, Giulia

    2011-03-01

    Silicon Nitride (Si3N4) is a possible candidate material to replace or be alloyed with SiO2 to form high-K dielectric films on Si substrates, so as to help prevent leakage currents in modern CMOS transistors. Building on our previous work on dielectric properties of crystalline and amorphous Si3N4 slabs, we present an analysis of the band offsets and dielectric properties of crystalline-Si/amorphous Si3N4 interfaces based on first principles calculations. We discuss shortcomings of the conventional bulk-plus line up approach in band offset calculations for systems with an amorphous component, and we present the results of band offsets obtained from calculations of local density of states. Finally, we describe the role of bonding configurations in determining band edges and dielectric constants at the interface. We acknowledge financial support from Intel Corporation.

  20. Dynamic Properties of Dielectric Susceptibility in Ferroelectric Thin Films

    NASA Astrophysics Data System (ADS)

    Cui, Lian; Cui, Haiying; Wu, Chunmei; Yang, Guihua; He, Zelong; Wang, Yuling; Che, Jixin

    2016-02-01

    In this paper, frequency, temperature, film thickness, surface effects, and various parameters dependence of dielectric susceptibility is investigated theoretically for ferroelectric thin films by the modified Landau theory under an AC applied field. The dielectric susceptibility versus AC applied field shows butterfly-shaped behavior, and depends strongly on the frequency and amplitude of the field and temperature. Our study shows that the existence of the surface transition layer can depress the dielectric susceptibility of a ferroelectric thin film. These results are well consistent with the phenomena reported in experiments.

  1. Carbon Nitride Thin Films Deposited by Cathodic Electrodeposition

    NASA Astrophysics Data System (ADS)

    Cao, Chuanbao; Fu, Jiyu; Zhu, Hesun

    Carbon nitride thin films were prepared by cathodic electrodeposition. The dicyandiamide compound dissovled in acetone was selected as the organic precursor. Single crystal silicon wafers and conductive glass (ITO) wafers were used as substrates. XPS measurements indicated that the films composed of carbon and nitrogen elements. The nitrogen content reached 41%. The polycrystalline β-C3N4 should exit in the prepared film from TED measurements. The nano hardness of the films on ITO substrates were as high as 13 GPa. The structure and properties were studies.

  2. Upper critical field of niobium nitride thin films

    NASA Astrophysics Data System (ADS)

    Vasyutin, M. A.; Kuz'michev, N. D.; Shilkin, D. A.

    2016-02-01

    The temperature dependences of the superconducting transition of niobium nitride (NbN) thin films have been investigated via the first harmonic of the voltage in dc magnetic fields of up to 8 T. The temperature dependence of the second critical field of NbN has been determined. The parameter responsible for the effect of spin paramagnetism in this material and the temperature dependence of the upper critical field that describes well the experimental data have been found in terms of the Werthamer-Helfand-Hohenberg (WHH) theory. The key parameters of the superconductor have been estimated from the transport and optical measurements.

  3. Zinc nitride thin films: basic properties and applications

    NASA Astrophysics Data System (ADS)

    Redondo-Cubero, A.; Gómez-Castaño, M.; García Núñez, C.; Domínguez, M.; Vázquez, L.; Pau, J. L.

    2017-02-01

    Zinc nitride films can be deposited by radio frequency magnetron sputtering using a Zn target at substrate temperatures lower than 250°C. This low deposition temperature makes the material compatible with flexible substrates. The asgrown layers present a black color, polycrystalline structures, large conductivities, and large visible light absorption. Different studies have reported about the severe oxidation of the layers in ambient conditions. Different compositional, structural and optical characterization techniques have shown that the films turn into ZnO polycrystalline layers, showing visible transparency and semi-insulating properties after total transformation. The oxidation rate is fairly constant as a function of time and depends on environmental parameters such as relative humidity or temperature. Taking advantage of those properties, potential applications of zinc nitride films in environmental sensing have been studied in the recent years. This work reviews the state-of-the-art of the zinc nitride technology and the development of several devices such as humidity indicators, thin film (photo)transistors and sweat monitoring sensors.

  4. Growth and characterization of thin and thick gallium nitride

    NASA Astrophysics Data System (ADS)

    Mastro, Michael Anthony

    2001-07-01

    The III-nitrides have received considerable attention in recent years for applications that require a wide band gap semiconductor. Specifically, short wavelength light emitters are required for full color displays, laser printers, high-density information storage, and underwater communication. High-temperature and high-power devices are needed for a number of applications including avionics, automobile engines and future advanced power distribution systems. Unfortunately, III-nitride substrates are not available. This dissertation explores three alternative substrates (LiGaO2, LiAlO2, and Si) for the growth of thick and potentially freestanding GaN substrates. The requirement to grow a protective layer of GAN by metal organic chemical vapor deposition (MOCVD) and the need for high rate deposition by hydride vapor phase epitaxy (HVPE) motivated the development of a single deposition system capable of growing in both modes. The successful growth of high quality GaN on LiGaO2 by MOCVD was first demonstrated. Nitridation of the LiGaO2 substrate using NH3 prior to growth leads to the reconstruction of the substrate surface and to the formation of a thin layer of nitrided material having the same orientation as the substrate. It was found that the thick GaN layer grown by HVPE spontaneously separated from the underlying LiGaO2 substrate upon cooling if proper nitridation was performed. This then eliminates the need for substrate removal by HCl etching and gives a reusable template substrate. The related substrate LiAlO2 is also closely lattice matched to GaN. LiAlO2, however, is more stable, particularly in an HCl ambient making it suitable for thick HVPE growth of GaN. Finally, it was shown that epitaxial GaN could be fabricated by a low-temperature deposition sequence on silicon substrates. Measurements revealed that a thin compliant SiOx layer was an effective intermediate layer for the GaN film grown epitaxially on Si. The deposition temperature of 560°C is one of

  5. Temperature effect on titanium nitride nanometer thin film in air

    NASA Astrophysics Data System (ADS)

    Cen, Z. H.; Xu, B. X.; Hu, J. F.; Ji, R.; Toh, Y. T.; Ye, K. D.; Hu, Y. F.

    2017-02-01

    Titanium nitride (TiN) is a promising alternative plasmonic material to conventional novel metals. For practical plasmonic applications under the influence of air, the temperature-dependent optical properties of TiN thin films in air and its volume variation are essential. Ellipsometric characterizations on a TiN thin film at different increasing temperatures in ambient air were conducted, and optical constants along with film thickness were retrieved. Below 200 °C, the optical properties varied linearly with temperature, in good agreement with other temperature dependent studies of TiN films in vacuum. The thermal expansion coefficient of the TiN thin film was determined to be 10.27  ×  10‑6 °C‑1. At higher temperatures, the TiN thin film gradually loses its metallic characteristics and has weaker optical absorption, impairing its plasmonic performance. In addition, a sharp increase in film thickness was observed at the same time. Changes in the optical properties and film thickness with temperatures above 200 °C were revealed to result from TiN oxidation in air. For the stability of TiN-based plasmonic devices, operation temperatures of lower than 200 °C, or measures to prevent oxidation, are required. The present study is important to fundamental physics and technological applications of TiN thin films.

  6. Anisotropic Dielectric Breakdown Strength of Single Crystal Hexagonal Boron Nitride.

    PubMed

    Hattori, Yoshiaki; Taniguchi, Takashi; Watanabe, Kenji; Nagashio, Kosuke

    2016-10-11

    Dielectric breakdown has historically been of great interest from the perspectives of fundamental physics and electrical reliability. However, to date, the anisotropy in the dielectric breakdown has not been discussed. Here, we report an anisotropic dielectric breakdown strength (EBD) for h-BN, which is used as an ideal substrate for two-dimensional (2D) material devices. Under a well-controlled relative humidity, EBD values in the directions both normal and parallel to the c axis (EBD⊥c and EBD∥c) were measured to be 3 and 12 MV/cm, respectively. When the crystal structure is changed from sp(3) of cubic-BN (c-BN) to sp(2) of h-BN, EBD⊥c for h-BN becomes smaller than that for c-BN, while EBD∥c for h-BN drastically increases. Therefore, h-BN can possess a relatively high EBD concentrated only in the direction parallel to the c axis by conceding a weak bonding direction in the highly anisotropic crystal structure. This explains why the EBD∥c for h-BN is higher than that for diamond. Moreover, the presented EBD value obtained from the high quality bulk h-BN crystal can be regarded as the standard for qualifying the crystallinity of h-BN layers grown via chemical vapor deposition for future electronic applications.

  7. Investigation of temperature dependent dielectric constant of a sputtered TiN thin film by spectroscopic ellipsometry

    SciTech Connect

    Tripura Sundari, S. Ramaseshan, R.; Jose, Feby; Dash, S.; Tyagi, A. K.

    2014-01-21

    The temperature dependence of optical constants of titanium nitride thin film is investigated using Spectroscopic Ellipsometry (SE) between 1.4 and 5 eV in the temperature range of 300 K to 650 K in steps of 50 K. The real and imaginary parts of the dielectric functions ε{sub 1}(E) and ε{sub 2}(E) marginally increase with increase in temperature. A Drude Lorentz dielectric analysis based on free electron and oscillator model are carried out to describe the temperature behavior. With increase in temperature, the unscreened plasma frequency and broadening marginally decreased and increased, respectively. The parameters of the Lorentz oscillator model also showed that the relaxation time decreased with temperature while the oscillator energies increased. This study shows that owing to the marginal change in the refractive index with temperature, titanium nitride can be employed for surface plasmon sensor applications even in environments where rise in temperature is imminent.

  8. Investigation of temperature dependent dielectric constant of a sputtered TiN thin film by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Tripura Sundari, S.; Ramaseshan, R.; Jose, Feby; Dash, S.; Tyagi, A. K.

    2014-01-01

    The temperature dependence of optical constants of titanium nitride thin film is investigated using Spectroscopic Ellipsometry (SE) between 1.4 and 5 eV in the temperature range of 300 K to 650 K in steps of 50 K. The real and imaginary parts of the dielectric functions ɛ1(E) and ɛ2(E) marginally increase with increase in temperature. A Drude Lorentz dielectric analysis based on free electron and oscillator model are carried out to describe the temperature behavior. With increase in temperature, the unscreened plasma frequency and broadening marginally decreased and increased, respectively. The parameters of the Lorentz oscillator model also showed that the relaxation time decreased with temperature while the oscillator energies increased. This study shows that owing to the marginal change in the refractive index with temperature, titanium nitride can be employed for surface plasmon sensor applications even in environments where rise in temperature is imminent.

  9. Dielectric and acoustical high frequency characterisation of PZT thin films

    NASA Astrophysics Data System (ADS)

    Conde, Janine; Muralt, Paul

    2010-02-01

    Pb(Zr, Ti)O3 (PZT) is an interesting material for bulk acoustic wave resonator applications due to its high electromechanical coupling constant, which would enable fabrication of large bandwidth frequency filters. The major challenge of the PZT solid solution system is to overcome mechanical losses generally observed in PZT ceramics. To increase the understanding of these losses in textured thin films, thin film bulk acoustic resonators (TFBAR's) based on PZT thin films with compositions either in the tetragonal region or at the morphotropic phase boundary and (111) or {100} textures were fabricated and studied up to 2 GHz. The dielectric and elastic materials coefficients were extracted from impedance measurements at the resonance frequency. The dispersion of the dielectric constant was obtained from impedance measurements up to 2 GHz. The films with varying compositions, textures and deposition methods (sol-gel or sputtering) were compared in terms of dielectric and acoustical properties.

  10. Reactive pulsed laser deposition of gold nitride thin films

    NASA Astrophysics Data System (ADS)

    Caricato, A. P.; Fernàndez, M.; Leggieri, G.; Luches, A.; Martino, M.; Romano, F.; Tunno, T.; Valerini, D.; Verdyan, A.; Soifer, Y. M.; Azoulay, J.; Meda, L.

    2007-07-01

    We report on the growth and characterization of gold nitride thin films on Si <1 0 0> substrates at room temperature by reactive pulsed laser ablation. A pure (99.95%) Au target was ablated with KrF excimer laser pulses in nitrogen containing atmosphere (N 2 or NH 3). The gas ambient pressure was varied in the range 0.1-100 Pa. The morphology of the films was studied by using optical, scanning electron and atomic force microscopy, evidencing compact films with RMS roughness in the range 3.6-35.1 nm, depending on the deposition pressure. Rutherford backscattering spectrometry and energy dispersion spectroscopy (EDS) were used to detect the nitrogen concentration into the films. The EDS nitrogen peak does not decrease in intensity after 2 h annealing at 250 °C. Film resistivity was measured using a four-point probe and resulted in the (4-20) × 10 -8 Ω m range, depending on the ambient pressure, to be compared with the value 2.6 × 10 -8 Ω m of a pure gold film. Indentation and scratch measurements gave microhardness values of 2-3 GPa and the Young's modulus close to 100 GPa. X-ray photoemission spectra clearly showed the N 1s peak around 400 eV and displaced with respect to N 2 phase. All these measurements point to the formation of the gold nitride phase.

  11. The electrical breakdown of thin dielectric elastomers: thermal effects

    NASA Astrophysics Data System (ADS)

    Zakaria, Shamsul; Morshuis, Peter H. F.; Benslimane, Mohamed Y.; Gernaey, Krist V.; Skov, Anne L.

    2014-03-01

    Dielectric elastomers are being developed for use in actuators, sensors and generators to be used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. In order to obtain maximum efficiency, the devices are operated at high electrical fields. This increases the likelihood for electrical breakdown significantly. Hence, for many applications the performance of the dielectric elastomers is limited by this risk of failure, which is triggered by several factors. Amongst others thermal effects may strongly influence the electrical breakdown strength. In this study, we model the electrothermal breakdown in thin PDMS based dielectric elastomers in order to evaluate the thermal mechanisms behind the electrical failures. The objective is to predict the operation range of PDMS based dielectric elastomers with respect to the temperature at given electric field. We performed numerical analysis with a quasi-steady state approximation to predict thermal runaway of dielectric elastomer films. We also studied experimentally the effect of temperature on dielectric properties of different PDMS dielectric elastomers. Different films with different percentages of silica and permittivity enhancing filler were selected for the measurements. From the modeling based on the fitting of experimental data, it is found that the electrothermal breakdown of the materials is strongly influenced by the increase in both dielectric permittivity and conductivity.

  12. Tunable surface plasmon resonances in sputtered titanium nitride thin films

    NASA Astrophysics Data System (ADS)

    Shankernath, V.; Naidu, K. Lakshun; Krishna, M. Ghanashyam; Padmanabhan, K. A.

    2016-05-01

    Thin films of titanium nitride were deposited on alpha-brass and gold electroplated brass (GCB) substrates by DC reactive magnetron sputtering at different N2 partial pressures (10%, 50% and 100 %). The measured specular reflectance spectra of the films indicate the existence of surface plasmon resonance peaks whose positions are dependent on the substrate and nitrogen pressure during deposition. In the case of films on brass, the SPR (surface plasmon resonance) is centered around 600, 550 and 510 nm at 10,50 and 100% Nitrogen. In contrast, the SPR occurs at 510 nm for the films deposited at 10% and 50% nitrogen which red shifts to 570 nm for the film deposited in 100% nitrogen. The observed behavior is correlated with morphology, microstructure and structure of the films.

  13. Anisotropies in magnetron sputtered carbon nitride thin films

    NASA Astrophysics Data System (ADS)

    Hellgren, Niklas; Johansson, Mats P.; Broitman, Esteban; Hultman, Lars; Sundgren, Jan-Eric

    2001-04-01

    Carbon nitride CNx (0⩽x⩽0.35) thin films, deposited by reactive dc magnetron sputtering in Ar/N2 discharges have been studied with respect to microstructure using electron microscopy, and elastic modulus using nanoindentation and surface acoustic wave analyses. For growth temperature of 100 °C, the films were amorphous, and with an isotropic Young's modulus of ˜170-200 GPa essentially unaffected by the nitrogen fraction. The films grown at elevated temperatures (350-550 °C) show anisotropic mechanical properties due to a textured microstructure with standing basal planes, as observed from measuring the Young's modulus in different directions. The modulus measured in the plane of the film was ˜60-80 GPa, while in the vertical direction the modulus increased considerably from ˜25 to ˜200 GPa as the nitrogen content was increased above ˜15 at. %.

  14. Raman signature and phonon dispersion of atomically thin boron nitride.

    PubMed

    Cai, Qiran; Scullion, Declan; Falin, Aleksey; Watanabe, Kenji; Taniguchi, Takashi; Chen, Ying; Santos, Elton J G; Li, Lu Hua

    2017-03-02

    Raman spectroscopy has become an essential technique to characterize and investigate graphene and many other two-dimensional materials. However, there is still a lack of consensus on the Raman signature and phonon dispersion of atomically thin boron nitride (BN), which has many unique properties distinct from graphene. Such a knowledge gap greatly affects the understanding of the basic physical and chemical properties of atomically thin BN as well as the use of Raman spectroscopy to study these nanomaterials. Here, we use both experiment and simulation to reveal the intrinsic Raman signature of monolayer and few-layer BN. We find experimentally that atomically thin BN without interaction with a substrate has a G band frequency similar to that of bulk hexagonal BN (hBN), but strain induced by the substrate can cause a pronounced Raman shift. This is in excellent agreement with our first-principles density functional theory (DFT) calculations at two levels of theory, including van der Waals dispersion forces (opt-vdW) and a fraction of the exact exchange from Hartree-Fock (HF) theory through the hybrid HSE06 functional. Both calculations demonstrate that the intrinsic E2g mode of BN does not depend sensibly on the number of layers. Our simulations also suggest the importance of the exact exchange mixing parameter in calculating the vibrational modes in BN, as it determines the fraction of HF exchange included in the DFT calculations.

  15. Technique for measuring the dielectric constant of thin materials

    NASA Technical Reports Server (NTRS)

    Sarabandi, K.; Ulaby, F. T.

    1988-01-01

    A practical technique for measuring the dielectric constant of vegetation leaves and similarly thin materials is presented. A rectangular section of the leaf is placed in the tranverse plane in a rectangular waveguide and the magnitude and phase of the reflection coefficient are measured over the desired frequency band using a vector network analyzer. By treating the leaf as an infinitesimally thin resistive sheet, an explicit expression for its dielectric constant is obtained in terms of the reflection coefficient. Because of the thin-sheet approximation, however, this approach is valid only at frequencies below 1.5 GHz. To extend the technique to higher frequencies, higher order approximations are derived and their accuracies are compared to the exact dielectric-slab solution. For a material whose thickness is 0.5 mm or less, the proposed technique was found to provide accurate values of its dielectric constant up to frequencies of 12 GHz or higher. The technique was used to measure the 8 to 12 GHz dielectric spectrum for vegetation leaves, teflon and rock samples.

  16. Method of manufacture of atomically thin boron nitride

    DOEpatents

    Zettl, Alexander K

    2013-08-06

    The present invention provides a method of fabricating at least one single layer hexagonal boron nitride (h-BN). In an exemplary embodiment, the method includes (1) suspending at least one multilayer boron nitride across a gap of a support structure and (2) performing a reactive ion etch upon the multilayer boron nitride to produce the single layer hexagonal boron nitride suspended across the gap of the support structure. The present invention also provides a method of fabricating single layer hexagonal boron nitride. In an exemplary embodiment, the method includes (1) providing multilayer boron nitride suspended across a gap of a support structure and (2) performing a reactive ion etch upon the multilayer boron nitride to produce the single layer hexagonal boron nitride suspended across the gap of the support structure.

  17. Dielectric properties of inorganic fillers filled epoxy thin film

    SciTech Connect

    Norshamira, A. Mariatti, M.

    2015-07-22

    The demand on the small size and high performance electronics has driven changes in the electronic packaging requirements from discrete capacitor to embedded capacitor. Embedded capacitor can improve electrical performance compared with discrete capacitor. This study aimed to achieve high dielectric of epoxy thin film composite that were targeted for application as embedded capacitor. In this study, inorganic fillers such as Calcium Copper Titanate (CCTO), Iron(III) Oxide (Fe{sub 2}O{sub 3}) and Titanium Dioxide (TiO{sub 2}) were loaded in epoxy system at 5 and 20vol%. Morphology and dielectric properties were investigated to identify the effect of fillers loading and types of fillers on the properties of epoxy thin film composite. Based on the study, CCTO with 20vol% loading was found to have good dielectric properties compared to other type of fillers.

  18. Dielectric properties of inorganic fillers filled epoxy thin film

    NASA Astrophysics Data System (ADS)

    Norshamira, A.; Mariatti, M.

    2015-07-01

    The demand on the small size and high performance electronics has driven changes in the electronic packaging requirements from discrete capacitor to embedded capacitor. Embedded capacitor can improve electrical performance compared with discrete capacitor. This study aimed to achieve high dielectric of epoxy thin film composite that were targeted for application as embedded capacitor. In this study, inorganic fillers such as Calcium Copper Titanate (CCTO), Iron(III) Oxide (Fe2O3) and Titanium Dioxide (TiO2) were loaded in epoxy system at 5 and 20vol%. Morphology and dielectric properties were investigated to identify the effect of fillers loading and types of fillers on the properties of epoxy thin film composite. Based on the study, CCTO with 20vol% loading was found to have good dielectric properties compared to other type of fillers.

  19. Plasmonic versus dielectric enhancement in thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Dühring, Maria B.; Asger Mortensen, N.; Sigmund, Ole

    2012-05-01

    Several studies have indicated that broadband absorption of thin-film solar cells can be enhanced by use of surface-plasmon induced resonances of metallic parts like strips or particles. The metallic parts may create localized modes or scatter incoming light to increase absorption in thin-film semiconducting material. For a particular case, we show that coupling to the same type of localized slab-waveguide modes can be obtained by a surface modulation consisting of purely dielectric strips. The purely dielectric device turns out to have a significantly higher broadband enhancement factor compared to its metallic counterpart. We show that the enhanced normalized short-circuit current for a cell with silicon strips can be increased 4 times compared to the best performance for strips of silver, gold, or aluminium. For this particular case, the simple dielectric grating may outperform its plasmonic counterpart due to the larger Ohmic losses associated with the latter.

  20. Dielectric Spectroscopy of Localized Electrical Charges in Ferrite Thin Film

    NASA Astrophysics Data System (ADS)

    Abdellatif, M. H.; Azab, A. A.; Moustafa, A. M.

    2017-09-01

    A thin film of Gd-doped Mn-Cr ferrite has been prepared by pulsed laser deposition from a bulk sample of the same ferrite prepared by the conventional double sintering ceramic technique. The charge localization and surface conduction in the ferromagnetic thin film were studied. The relaxation of the dielectric dipoles after exposure to an external alternating-current (AC) electric field was investigated. The effect of charge localization on the real and imaginary parts of the dielectric modulus was studied. The charge localization in the thin film was enhanced and thereby the Maxwell-Wagner-type interfacial polarization. The increase in interfacial polarization is a direct result of the enhanced charge localization. The sample was characterized in terms of its AC and direct-current (DC) electrical conductivity, and thermally stimulated discharge current.

  1. Electron transport and dielectric breakdown in silicon nitride using a charge transport model

    NASA Astrophysics Data System (ADS)

    Ogden, Sean P.; Lu, Toh-Ming; Plawsky, Joel L.

    2016-10-01

    Silicon nitride is an important material used in the electronics industry. As such, the electronic transport and reliability of these materials are important to study and understand. We report on a charge transport model to predict leakage current and failure trends based on previously published data for a stoichiometric silicon nitride dielectric. Failure occurs when the defect density increases to a critical value of approximately 6 × 1025 traps/m3. The model's parameters are determined using voltage ramp data only, and yet, the model is also able to predict constant voltage stress failure over a time scale ranging from minutes to months. The successful fit of the model to the experimental data validates our assumption that the dominant defect in the dielectric is the Si dangling bond, located approximately 2.2 eV below the conduction band. A comparison with previous SiCOH simulations shows SiN and SiCOH have similar defect-related material properties. It is also speculated that, based on the estimated parameter values of 2.75 eV for the defect formation activation energy, the materials' TDDB wear-out are caused by broken Si-H bonds, resulting in Si dangling bond defects.

  2. Residual ferroelectricity in barium strontium titanate thin film tunable dielectrics

    SciTech Connect

    Garten, L. M. Trolier-McKinstry, S.; Lam, P.; Harris, D.; Maria, J.-P.

    2014-07-28

    Loss reduction is critical to develop Ba{sub 1−x}Sr{sub x}TiO{sub 3} thin film tunable microwave dielectric components and dielectric energy storage devices. The presence of ferroelectricity, and hence the domain wall contributions to dielectric loss, will degrade the tunable performance in the microwave region. In this work, residual ferroelectricity—a persistent ferroelectric response above the global phase transition temperature—was characterized in tunable dielectrics using Rayleigh analysis. Chemical solution deposited Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} films, with relative tunabilities of 86% over 250 kV/cm at 100 kHz, demonstrated residual ferroelectricity 65 °C above the ostensible paraelectric transition temperature. Frequency dispersion observed in the dielectric temperature response was consistent with the presence of nanopolar regions as one source of residual ferroelectricity. The application of AC electric field for the Rayleigh analysis of these samples led to a doubling of the dielectric loss for fields over 10 kV/cm at room temperature.

  3. The thickness dependence of dielectric permittivity in thin films

    NASA Astrophysics Data System (ADS)

    Starkov, Ivan A.; Starkov, Alexander S.

    2016-08-01

    It is well known that the physical properties of thin films depend on their thickness. For a description of such dependences, it is proposed to use a classical model taking into account the presence of film interfaces. A dielectric ball near the half-space was chosen to adopt the approach. The dependence of the effective permittivity of the ball on geometrical and physical parameters of the system is analyzed. It is demonstrated that the dielectric constant of a film can be presented as a sum of the constant of a bulk material and the interface term.

  4. Ellipsometric study of silicon nitride on gallium arsenide

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Bu-Abbud, G. H.; Woollam, J. A.; Liu, D.; Chung, Y.; Langer, D.

    1982-01-01

    A method for optimizing the sensitivity of ellipsometric measurements for thin dielectric films on semiconductors is described in simple physical terms. The technique is demonstrated for the case of sputtered silicon nitride films on gallium arsenide.

  5. Mechanical and electrochemical characterization of vanadium nitride (VN) thin films

    NASA Astrophysics Data System (ADS)

    Caicedo, J. C.; Zambrano, G.; Aperador, W.; Escobar-Alarcon, L.; Camps, E.

    2011-10-01

    Vanadium nitride (V-N) thin films were grown using a reactive d.c. magnetron sputtering process, from a vanadium target (99.999%) in an Ar/N 2 gas mixture at different deposition bias voltage. Films were deposited onto silicon (1 0 0) and RUS-3 steel substrates at 400 °C. Structural, compositional, mechanical and electrochemical characterizations were performed by X-ray diffraction (XRD), elastic forward analysis (EFA), nanoindentation, electrochemical impedance spectroscopy (EIS), and Tafel polarization curves, respectively. X-ray diffraction patterns show the presence of (1 1 1) and (2 0 0) crystallographic orientations associated to the V-N cubic phase. Nanoindentation measurements revealed that when the bias voltage increases from 0 V to -150 V the hardness and elastic modulus are increased from 11 GPa to 20 GPa and from 187 GPa to 221 GPa, respectively. EIS and Tafel curves showed that the corrosion rate of steel, coated with V-N single layer films deposited without bias voltage, diminishes 90% compared to the steel without this coating. On the other hand, when the V-N coating was deposited at the highest d.c. bias voltage (-150 V), the corrosion rate was greater than in the steel coated with zero-voltage (0 V) V-N films. This last result could be attributed to the formation of porosities produced by the ion bombardment during the deposition process.

  6. Reactive sputter deposition of tungsten nitride thin films

    NASA Astrophysics Data System (ADS)

    Baker, Colin C.; Shah, S. Ismat

    2002-09-01

    Tungsten nitride (WNx) thin films were deposited by reactively sputtering a pure W target in an argon/nitrogen atmosphere. The nitrogen concentration in the growth chamber was varied from 2% to 60%. Film growth and properties were studied as a function of nitrogen concentration in the films. The cathode current and voltage variations during the film growth indicated cathode poisoning when the nitrogen concentration in the chamber was in the range of 2%-5%. This poisoning was accompanied by a reduced film growth rate. However, both the cathode current and deposition rate decrease were small due to the low resistivity and similar sputter yield of the WNx phase formed at the surface of the target and pure W. X-ray photoelectron spectroscopy analyses showed that the films were composed of approx33 at. % nitrogen when the nitrogen concentration in the chamber was greater than 10%. X-ray diffraction (XRD) analysis confirmed that the films were predominantly W2N with the characteristic (111) peak at 2theta]=37.7[deg. Slight shifts in the (111) peak position were due to excess nitrogen incorporation in interstitial positions, which caused lattice distortions. Postdeposition annealing removed the excess interstitial nitrogen and the XRD peaks shifted closer to the characteristic value. copyright 2002 American Vacuum Society.

  7. Micromachined ultrasonic transducers with piezoelectric aluminum nitride thin films

    NASA Astrophysics Data System (ADS)

    Wang, Qianghua

    In this research, a laboratory prototype of micromachined ultrasonic transducer (MUT) has been designed and fabricated with the application of piezoelectric aluminum nitride (AlN) thin films. The fabrication process of MUT device, especially the deposition of AlN thin film, is compatible with a standard integrated circuits (IC) technology. Preliminary results have demonstrated the feasibility of AlN thin film applied in MUT for medical ultrasonic detection. AlN thin film was grown on aluminum metal layer by plasma source molecular beam epitaxy (PSMBE) system. X-ray diffraction (XRD) shows the films exhibit a high c-axis texture for a thickness of 1.2 mum grown at a temperature of 450°C. For the AlN film of 1.20 mum, residual stress was a compressive stress of 883 Mpa, which reduced with increasing thickness of the film. Based on the fundamentals of vibration and piezoelectricity, MUT device including silicon resonator and AlN sandwich structure has been designed. A prototype of 8 x 8 devices on a 3″ silicon (100) wafer has been fabricated. A series of experiments were conducted to find the process flow and the optimum process parameters. MUT devices were characterized by optical, electrical, and acoustic measurements. The measured resonant frequencies AlN MUT and PVDF MUT devices were larger than the calculated value in order of 5% to 12%. The ratios of the flexural frequencies to the fundamental frequency were much close to the MUT design model within a 3% error for AlN MUT devices. Resonant frequencies of AlN MUT devices were also verified by the reflection coefficient with a network analyzer and the electrical impedance with an impendence analyzer. Effective coupling factors of AlN MUT devices were determined to be 0.18 from the resonant frequency and the antiresonant frequency. Fractional bandwidth of an AlN MUT was 8.30% at the center frequency of 2.65 MHz. Pressure sensitivity was stable between 14 mV/MPa and 18 mV/MPa independent on the pressure intensity

  8. High frequency scattering by a thin dielectric slab

    NASA Technical Reports Server (NTRS)

    Burnside, W. D.; Pathak, P. H.

    1981-01-01

    The geometrical theory of diffraction (GTD) is applied to the problem of a source in the presence of a three-dimensional thin dielectric slab. It is assumed that the reflection and transmission properties of the slab are known, and the slab is not lossy and/or multilayered. Two-dimensional thin dielectric layer scattering is analyzed when diffraction emanates from a single point, the source is not near the slab, and random energy approaching tangentially due to transmission is negligible. Coefficients are obtained for the scattering and the GTD solution is extended to the three dimensional case after development of a ray fixed coordinate system. The results are applied to a half wavelength dipole mounted above a square polystyrene covered ground plane.

  9. Thin film transistors for flexible electronics: contacts, dielectrics and semiconductors.

    PubMed

    Quevedo-Lopez, M A; Wondmagegn, W T; Alshareef, H N; Ramirez-Bon, R; Gnade, B E

    2011-06-01

    The development of low temperature, thin film transistor processes that have enabled flexible displays also present opportunities for flexible electronics and flexible integrated systems. Of particular interest are possible applications in flexible sensor systems for unattended ground sensors, smart medical bandages, electronic ID tags for geo-location, conformal antennas, radiation detectors, etc. In this paper, we review the impact of gate dielectrics, contacts and semiconductor materials on thin film transistors for flexible electronics applications. We present our recent results to fully integrate hybrid complementary metal oxide semiconductors comprising inorganic and organic-based materials. In particular, we demonstrate novel gate dielectric stacks and semiconducting materials. The impact of source and drain contacts on device performance is also discussed.

  10. High frequency scattering by a thin lossless dielectric slab

    NASA Technical Reports Server (NTRS)

    Burnside, W. D.; Burgener, K. W.

    1983-01-01

    A high frequency solution for scattering from a thin dielectric slab is developed, based on a modification of the uniform geometrical theory of diffraction solution for a half-plane, with the intention of developing a model for a windshield of a small private aircraft. Results of the theory are compared with experimental measurements and moment method calculations showing good agreement. Application of the solution is also addressed.

  11. Low Temperature Reactive Sputtering of Thin Aluminum Nitride Films on Metallic Nanocomposites

    PubMed Central

    Ramadan, Khaled Sayed Elbadawi; Evoy, Stephane

    2015-01-01

    Piezoelectric aluminum nitride thin films were deposited on aluminum-molybdenum (AlMo) metallic nanocomposites using reactive DC sputtering at room temperature. The effect of sputtering parameters on film properties was assessed. A comparative study between AlN grown on AlMo and pure aluminum showed an equivalent (002) crystallographic texture. The piezoelectric coefficients were measured to be 0.5±0.1 C m-2 and 0.9±0.1 C m-2, for AlN deposited on Al/0.32Mo and pure Al, respectively. Films grown onto Al/0.32Mo however featured improved surface roughness. Roughness values were measured to be 1.3nm and 5.4 nm for AlN films grown on AlMo and on Al, respectively. In turn, the dielectric constant was measured to be 8.9±0.7 for AlN deposited on Al/0.32Mo seed layer, and 8.7±0.7 for AlN deposited on aluminum; thus, equivalent within experimental error. Compatibility of this room temperature process with the lift-off patterning of the deposited AlN is also reported. PMID:26193701

  12. Vertically self-ordered orientation of nanocrystalline hexagonal boron nitride thin films for enhanced thermal characteristics.

    PubMed

    Cometto, Olivier; Sun, Bo; Tsang, Siu Hon; Huang, Xi; Koh, Yee Kan; Teo, Edwin Hang Tong

    2015-12-07

    Vertically self-ordered hexagonal boron nitride (ordered h-BN) is a highly ordered turbostratic BN (t-BN) material similar to hexagonal BN, with its planar structure perpendicularly oriented to the substrate. The ordered h-BN thin films were grown using a High Power Impulse Magnetron Sputtering (HiPIMS) system with a lanthanum hexaboride (LaB6) target reactively sputtered in nitrogen gas. The best vertical alignment was obtained at room temperature, with a grounded bias and a HiPIMS peak power density of 60 W cm(-2). Even though the film contains up to 7.5 at% lanthanum, it retains its highly insulative properties and it was observed that an increase in compressive stress is correlated to an increase in film ordering quality. Importantly, the thermal conductivity of vertically ordered h-BN is considerably high at 5.1 W m(-1) K(-1). The favourable thermal conductivity coupled with the dielectric properties of this novel material and the low temperature growth could outperform SiO2 in high power density electronic applications.

  13. Low Temperature Reactive Sputtering of Thin Aluminum Nitride Films on Metallic Nanocomposites.

    PubMed

    Ramadan, Khaled Sayed Elbadawi; Evoy, Stephane

    2015-01-01

    Piezoelectric aluminum nitride thin films were deposited on aluminum-molybdenum (AlMo) metallic nanocomposites using reactive DC sputtering at room temperature. The effect of sputtering parameters on film properties was assessed. A comparative study between AlN grown on AlMo and pure aluminum showed an equivalent (002) crystallographic texture. The piezoelectric coefficients were measured to be 0.5±0.1 C m(-2) and 0.9±0.1 C m(-2), for AlN deposited on Al/0.32Mo and pure Al, respectively. Films grown onto Al/0.32Mo however featured improved surface roughness. Roughness values were measured to be 1.3nm and 5.4 nm for AlN films grown on AlMo and on Al, respectively. In turn, the dielectric constant was measured to be 8.9±0.7 for AlN deposited on Al/0.32Mo seed layer, and 8.7±0.7 for AlN deposited on aluminum; thus, equivalent within experimental error. Compatibility of this room temperature process with the lift-off patterning of the deposited AlN is also reported.

  14. Secret of formulating a selective etching or cleaning solution for boron nitride (BN) thin film

    NASA Astrophysics Data System (ADS)

    Hui, Wing C.

    2004-04-01

    Boron nitride thin film has a very unique characteristic of extremely high chemical inertness. Thus, it is a better hard mask than silicon nitride for aggressive etching solutions, such as the isotropic HF/HNO3/CH3COOH (or HNA) etchant for silicon. However, because of its high chemical inertness, it is also difficult to remove it. Plasma etching with Freon gases can etch the boron nitride film, but it is unselective to silicon, silicon dioxide or silicon nitride. Cleaning up the boron nitride film with plasma etching will usually leave a damaged or foggy surface. A special wet chemical solution has been developed for etching or cleaning boron nitride film selectively. It can etch boron nitride, but not the coatings or substrates of silicon, silicon nitride and silicon dioxide. It is a very strong oxidizing agent consisting of concentrated sulfuric acid (H2SO4) and hydrogen peroxide (H2O2), but different from the common Piranha Etch. It may be even more interesting to understand the logic or secret behind of how to formulate a new selective etching solution. Various chemical and chemical engineering aspects were considered carefully in our development process. These included creating the right electrochemical potential for the etchant, ensuring large differences in chemical kinetics to make the reactions selective, providing proper mass transfer for removing the by products, etc.

  15. Tetrahedron-model analysis of silicon nitride thin films and the effect of hydrogen and temperature on their optical properties

    NASA Astrophysics Data System (ADS)

    Petalas, J.; Logothetidis, S.

    1994-10-01

    A series of silicon nitride thin films prepared by different techniques are investigated with respect to their optical properties with spectroscopic ellipsometry in the energy region 1.5-9.5 eV, using conventional and synchrotron-radiation light sources. The dielectric-function spectra of the films are analyzed with the microscopic Si-centered tetrahedron model and thus the applied growth techniques are compared, with respect to the resulting tetrahedron types and volume fractions, and the superiority of the chemical-vapor deposition techique is distinctly denoted. Moreover, a model is developed for the deduction of the films' stoichiometry from the above analysis and the results are compared with corresponding ones from Rutherford backscattering spectroscopy and elastic recoil detection. The effect of stoichiometry on the film quality and optical parameters is discussed. In addition, the effect of hydrogen on the fundamental and mean optical gaps of silicon nitride is investigated and it is concluded that in both cases hydrogen causes a shift to the red, which is interpreted as due to the existence of a significant number of Si-H bonds. Temperature-dependent optical studies on SiN bulk materials and thin films are performed in order to examine the temperature shifts of the fundamental and mean optical gaps, which are found to be redshifted and blueshifted, respectively. The effect of stoichiometry on the observed temperature coefficients is discussed.

  16. Improvement in interfacial characteristics of low-voltage carbon nanotube thin-film transistors with solution-processed boron nitride thin films

    NASA Astrophysics Data System (ADS)

    Jeon, Jun-Young; Ha, Tae-Jun

    2017-08-01

    In this article, we demonstrate the potential of solution-processed boron nitride (BN) thin films for high performance single-walled carbon nanotube thin-film transistors (SWCNT-TFTs) with low-voltage operation. The use of BN thin films between solution-processed high-k dielectric layers improved the interfacial characteristics of metal-insulator-metal devices, thereby reducing the current density by three orders of magnitude. We also investigated the origin of improved device performance in SWCNT-TFTs by employing solution-processed BN thin films as an encapsulation layer. The BN encapsulation layer improves the electrical characteristics of SWCNT-TFTs, which includes the device key metrics of linear field-effect mobility, sub-threshold swing, and threshold voltage as well as the long-term stability against the aging effect in air. Such improvements can be achieved by reduced interaction of interfacial localized states with charge carriers. We believe that this work can open up a promising route to demonstrate the potential of solution-processed BN thin films on nanoelectronics.

  17. Logic circuits composed of flexible carbon nanotube thin-film transistor and ultra-thin polymer gate dielectric.

    PubMed

    Lee, Dongil; Yoon, Jinsu; Lee, Juhee; Lee, Byung-Hyun; Seol, Myeong-Lok; Bae, Hagyoul; Jeon, Seung-Bae; Seong, Hyejeong; Im, Sung Gap; Choi, Sung-Jin; Choi, Yang-Kyu

    2016-05-17

    Printing electronics has become increasingly prominent in the field of electronic engineering because this method is highly efficient at producing flexible, low-cost and large-scale thin-film transistors. However, TFTs are typically constructed with rigid insulating layers consisting of oxides and nitrides that are brittle and require high processing temperatures, which can cause a number of problems when used in printed flexible TFTs. In this study, we address these issues and demonstrate a method of producing inkjet-printed TFTs that include an ultra-thin polymeric dielectric layer produced by initiated chemical vapor deposition (iCVD) at room temperature and highly purified 99.9% semiconducting carbon nanotubes. Our integrated approach enables the production of flexible logic circuits consisting of CNT-TFTs on a polyethersulfone (PES) substrate that have a high mobility (up to 9.76 cm(2) V(-1) sec(-)1), a low operating voltage (less than 4 V), a high current on/off ratio (3 × 10(4)), and a total device yield of 90%. Thus, it should be emphasized that this study delineates a guideline for the feasibility of producing flexible CNT-TFT logic circuits with high performance based on a low-cost and simple fabrication process.

  18. Logic circuits composed of flexible carbon nanotube thin-film transistor and ultra-thin polymer gate dielectric

    NASA Astrophysics Data System (ADS)

    Lee, Dongil; Yoon, Jinsu; Lee, Juhee; Lee, Byung-Hyun; Seol, Myeong-Lok; Bae, Hagyoul; Jeon, Seung-Bae; Seong, Hyejeong; Im, Sung Gap; Choi, Sung-Jin; Choi, Yang-Kyu

    2016-05-01

    Printing electronics has become increasingly prominent in the field of electronic engineering because this method is highly efficient at producing flexible, low-cost and large-scale thin-film transistors. However, TFTs are typically constructed with rigid insulating layers consisting of oxides and nitrides that are brittle and require high processing temperatures, which can cause a number of problems when used in printed flexible TFTs. In this study, we address these issues and demonstrate a method of producing inkjet-printed TFTs that include an ultra-thin polymeric dielectric layer produced by initiated chemical vapor deposition (iCVD) at room temperature and highly purified 99.9% semiconducting carbon nanotubes. Our integrated approach enables the production of flexible logic circuits consisting of CNT-TFTs on a polyethersulfone (PES) substrate that have a high mobility (up to 9.76 cm2 V‑1 sec‑1), a low operating voltage (less than 4 V), a high current on/off ratio (3 × 104), and a total device yield of 90%. Thus, it should be emphasized that this study delineates a guideline for the feasibility of producing flexible CNT-TFT logic circuits with high performance based on a low-cost and simple fabrication process.

  19. Logic circuits composed of flexible carbon nanotube thin-film transistor and ultra-thin polymer gate dielectric

    PubMed Central

    Lee, Dongil; Yoon, Jinsu; Lee, Juhee; Lee, Byung-Hyun; Seol, Myeong-Lok; Bae, Hagyoul; Jeon, Seung-Bae; Seong, Hyejeong; Im, Sung Gap; Choi, Sung-Jin; Choi, Yang-Kyu

    2016-01-01

    Printing electronics has become increasingly prominent in the field of electronic engineering because this method is highly efficient at producing flexible, low-cost and large-scale thin-film transistors. However, TFTs are typically constructed with rigid insulating layers consisting of oxides and nitrides that are brittle and require high processing temperatures, which can cause a number of problems when used in printed flexible TFTs. In this study, we address these issues and demonstrate a method of producing inkjet-printed TFTs that include an ultra-thin polymeric dielectric layer produced by initiated chemical vapor deposition (iCVD) at room temperature and highly purified 99.9% semiconducting carbon nanotubes. Our integrated approach enables the production of flexible logic circuits consisting of CNT-TFTs on a polyethersulfone (PES) substrate that have a high mobility (up to 9.76 cm2 V−1 sec−1), a low operating voltage (less than 4 V), a high current on/off ratio (3 × 104), and a total device yield of 90%. Thus, it should be emphasized that this study delineates a guideline for the feasibility of producing flexible CNT-TFT logic circuits with high performance based on a low-cost and simple fabrication process. PMID:27184121

  20. Thermal conductivity of ultra-thin chemical vapor deposited hexagonal boron nitride films

    NASA Astrophysics Data System (ADS)

    Alam, M. T.; Bresnehan, M. S.; Robinson, J. A.; Haque, M. A.

    2014-01-01

    Thermal conductivity of freestanding 10 nm and 20 nm thick chemical vapor deposited hexagonal boron nitride films was measured using both steady state and transient techniques. The measured value for both thicknesses, about 100 ± 10 W m-1 K-1, is lower than the bulk basal plane value (390 W m-1 K-1) due to the imperfections in the specimen microstructure. Impressively, this value is still 100 times higher than conventional dielectrics. Considering scalability and ease of integration, hexagonal boron nitride grown over large area is an excellent candidate for thermal management in two dimensional materials-based nanoelectronics.

  1. Temperature effect on low-k dielectric thin films studied by ERDA

    SciTech Connect

    Jensen, Jens; Possnert, Göran; Zhang, Yanwen

    2008-09-23

    Low-k dielectric materials are becoming increasingly interesting as alternative to SiO2 with device geometries shrinking beyond the 65 nm technology node. At elevated temperatures hydrogen migration becomes an important degradation mechanism for conductivity breakdown in semiconductor devices. The possibility of hydrogen release during the fabrication process is, therefore, of great interest in the understanding of device reliability. In this study, various low-k dielectric films were subjected to thermal annealing at temperatures that are generally used for device fabrication. Elastic recoil detection analysis (ERDA) was used to investigate compositional changes and hydrogen redistribution in thin films of plasma-enhanced tetraethylortho-silicate (PETEOS), phosphorus doped silicon glass (PSG), silicon nitride (SiN) and silicon oxynitride (SiON). Except for an initial hydrogen release from the surface region in films of PETEOS and PSG, the results indicate that the elemental composition of the films was stable for at least 2 hours at 450°C.

  2. Crystallographic investigation of aluminium nitride thin films on stainless steel foil for highly efficient piezoelectric vibration energy harvesters

    NASA Astrophysics Data System (ADS)

    Moriwaki, N.; Minh, L. V.; Ohigashi, R.; Shimada, O.; Kitayoshi, H.; Kuwano, H.

    2016-11-01

    This study reports piezoelectric properties and crystallographic microstructures of aluminium nitride (AlN, wurtzite structure) thin films on 50 μm thick stainless steel foil. The transverse piezoelectric coefficient d31f and e31f of 10 pm thick AlN films were estimated as -1.42 ± 0.08 μm/V and -0.48 ± 0.03 C/m2 from a tip displacement of the piezoelectric cantilevers. Dielectric constant s33 was measured as 10.5 ± 1.0. An electron beam diffraction pattern by a high-resolution transmission electron microscope and x-ray diffraction pattern showed that abundance ratio of the orientation such as <101>, <102> and <103> of AlN crystal on stainless steel foils increased with increasing thickness.

  3. Thin film phase diagram of iron nitrides grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Gölden, D.; Hildebrandt, E.; Alff, L.

    2017-01-01

    A low-temperature thin film phase diagram of the iron nitride system is established for the case of thin films grown by molecular beam epitaxy and nitrided by a nitrogen radical source. A fine-tuning of the nitridation conditions allows for growth of α ‧ -Fe8Nx with increasing c / a -ratio and magnetic anisotropy with increasing x until almost phase pure α ‧ -Fe8N1 thin films are obtained. A further increase of nitrogen content below the phase decomposition temperature of α ‧ -Fe8N (180 °C) leads to a mixture of several phases that is also affected by the choice of substrate material and symmetry. At higher temperatures (350 °C), phase pure γ ‧ -Fe4N is the most stable phase.

  4. Chemical vapor deposition and atomic layer deposition of metal oxide and nitride thin films

    NASA Astrophysics Data System (ADS)

    Barton, Jeffrey Thomas

    Processes for depositing thin films with various electronic, optical, mechanical, and chemical properties are indispensable in many industries today. Of the many deposition methods available, chemical vapor deposition (CVD) has proved over time to be one of the most flexible, efficient, and cost-effective. Atomic layer deposition (ALD) is a newer process that is gaining favor as a method for depositing films with excellent properties and unparalleled precision. This work describes the development of novel CVD and ALD processes to deposit a variety of materials. Hafnium oxide and zirconium oxide show promise as replacements for SiO 2 as gate dielectrics in future-generation transistors. These high-k materials would provide sufficient capacitance with layers thick enough to avoid leakage from tunneling. An ALD method is presented here for depositing conformal hafnium oxide from tetrakis-(diethylamido)hafnium and oxygen gas. A CVD method for depositing zirconium oxide from tetrakis-(dialkylamido)zirconium and either oxygen gas or water vapor is also described. The use of copper for interconnects in integrated circuits requires improved diffusion barrier materials, given its high diffusivity compared to the previously-used aluminum and tungsten. Tungsten nitride has a low resistivity among barrier materials, and can be deposited in amorphous films that are effective diffusion barriers in layers as thin as a few nanometers. Here we demonstrate CVD and plasma-enhanced CVD methods to deposit tungsten nitride films from bis-(dialkylamido)bis-( tert-butylimido)tungsten precursors and ammonia gas. Recent findings had shown uniform copper growth on tantalum silicate films, without the dewetting that usually occurs on oxide surfaces. Tantalum and tungsten silicates were deposited by a CVD reaction from the reaction of either tris-(diethylamido)ethylimido tantalum or bis-(ethylmethylamido)-bis-( tert-butylimido)tungsten with tris-(tert-butoxy)silanol. The ability of evaporated

  5. Boosting the Transparency of Thin Layers by Coatings of Opposing Susceptibility: How Metals Help See Through Dielectrics

    PubMed Central

    Shakhs, Mohammed Al; Augusto, Lucian; Markley, Loïc; Chau, Kenneth J.

    2016-01-01

    We propose a hypothesis that a very thin layer can be made more transparent by adding a thin coating with susceptibility of opposing sign. Two experimental tests backed by a theoretical model support this hypothesis. First, we show that the visible and near-infrared transmission through a semi-transparent silver film can be enhanced by up to ~70% and spectrally tailored depending on the type and thickness of the dielectric coating. Material types explored as dielectric coating layers include conventional metal oxides (titanium dioxide) and lesser-explored elemental semiconductors (undoped silicon, p-type silicon, and germanium). Second, and more surprisingly, we show that coating a 50-nm-thick silicon nitride membrane with a 10-nm-thick silver layer can modestly enhance the transmission by up to 6 ± 1% in the blue part of the spectrum. Transmission enhancements are observed for three silver-coated membranes in different configurations. Thinner silver coatings are theoretically capable of enhancement factors greater than 10%, but implementation is restricted by challenges in making smooth and continuous silver films below 10 nm in thickness. This study is important because it is the first demonstration of reciprocity with respect to the transmission enhancements achieved by combining thin metallic and dielectric layers. PMID:26860979

  6. Dielectric Properties of Boron Nitride-Ethylene Glycol (BN-EG) Nanofluids

    NASA Astrophysics Data System (ADS)

    Fal, Jacek; Cholewa, Marian; Gizowska, Magdalena; Witek, Adam; ŻyŁa, GaweŁ

    2017-02-01

    This paper presents the results of experimental investigation of the dielectric properties of ethylene glycol (EG) with various load of boron nitride (BN) nanoparticles. The nanofuids were prepared by using a two-step method on the basis of commercially available BN nanoparticles. The measurements were carried out using the Concept 80 System (NOVOCONTROL Technologies GmbH & Co. KG, Montabaur, Germany) in a frequency range from 10 Hz to 10 MHz and temperatures from 278.15 K to 328.15 K. The frequency-dependent real (ɛ ^' }) and imaginary (ɛ ^' ' }) parts of the complex permittivity (ɛ ^*) and the alternating current (AC) conductivity are presented. Also, the effect of temperature and mass concentrations on the dielectric properties of BN-EG nanofluids are demonstrated. The results show that the most significant increase can be achieved for 20 wt.% of BN nanoparticles at 283.15 K and 288.15 K, that is eleven times larger than in the case of pure EG.

  7. Nanocharacterization of Titanium Nitride Thin Films Obtained by Reactive Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Merie, Violeta Valentina; Pustan, Marius Sorin; Bîrleanu, Corina; Negrea, Gavril

    2015-05-01

    Titanium nitride thin films are used in applications such as tribological layers for cutting tools, coating of some medical devices (scalpel blades, prosthesis, implants, etc.), sensors, electrodes for bioelectronics, microelectronics, diffusion barrier, bio-micro-electromechanical systems, and so on. This work is a comparative study concerning the influence of substrate temperature on some mechanical and tribological characteristics of titanium nitride thin films. The researched thin films were obtained by the reactive magnetron sputtering method. The experiments employed two kinds of substrates: a steel substrate and a silicon one. The elaboration of titanium nitride thin films was done at two temperatures. First, when the substrates were at room temperature, and second, when the substrates were previously heated at 250°C. The temperature of 250°C was kept constant during the deposition of the films. The samples were then investigated by atomic force microscopy in order to establish their mechanical and tribological properties. The nanohardness, Young's modulus, roughness, and friction force were some of the determined characteristics. The results demonstrated that the substrate which was previously heated at 250°C led to the obtaining of more adherent titanium nitride thin films than the substrate used at room temperature. The preheating of both substrates determined the decrease of thin films roughness. The friction force, nanohardness and Young's modulus of the tested samples increased when the substrates were preheated at 250°C.

  8. Dielectric breakdown in nano-porous thin films

    NASA Astrophysics Data System (ADS)

    Borja, Juan Pablo

    Unknown to most computer users and mobile device enthusiasts, we have finally entered into a critical age of chip manufacturing. January of 2014 marks the official start of the quest by the semiconductor industry to successfully integrate sub 14nm process technology nodes in accordance to the International Technology Roadmap for Semiconductors (ITRS). The manufacturing of nano-scale features represents a major bottleneck of its own. However, a bigger challenge lies in reliably isolating the massive chip interconnect network. The present work is aimed at generating a theoretical and experimental framework to predict dielectric breakdown for thin films used in computer chip components. Here, a set of experimental techniques are presented to assess and study dielectric failure in novel thin films. A theory of dielectric breakdown in thin nano-porous films is proposed to describe combined intrinsic and metal ion catalyzed failure. This theory draws on experimental evidence as well as fundamental concepts from mass and electronic charge transport. The drift of metal species was found to accelerate intrinsic dielectric failure. The solubility of metals species such as Cu was found to range from 7.0x1025 ions/m3 to 1.86x1026 ions/m3 in 7% porous SiCOH films. The diffusion coefficient for Cu species was found to span from 4.2x10-19 m2/s to 1.86x10-21 m2/s. Ramped voltage stress experiments were used to identify intrinsic failure from metal catalyzed failure. Intrinsic breakdown is defined when time to failure against applied field ramp rate results in ∂(ln(TTF))/∂(ln(R)) ≈ -1. Intrinsic failure was studied using Au. Here, ∂(ln(TTF))/∂(ln(R)) ≈ -0.95, which is an experimental best case scenario for intrinsic failure. Au is commonly reluctant to ionize which means that failure occurs in the absence of ionic species. Metal catalyzed failure was investigated using reactive electrodes such as Cu, and Ag. Here, trends for ∂(ln(TTF))/∂(ln(R)) significantly

  9. Nanocharacterization of titanium nitride thin films obtained by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Merie, V. V.; Pustan, M. S.; Bîrleanu, C.; Negrea, G.

    2014-08-01

    Titanium nitride thin films are used in applications such as tribological layers for cutting tools, coating of some medical devices (scalpel blades, prosthesis, implants etc.), sensors, electrodes for bioelectronics, microelectronics, diffusion barrier, bio-microelectromechanical systems (Bio-MEMS) and so on. This work is a comparative study concerning the influence of substrate temperature on some mechanical and tribological characteristics of titanium nitride thin films. The researched thin films were obtained by reactive magnetron sputtering method. The experiments employed two kinds of substrates: a steel substrate and a silicon one. The elaboration of titanium nitride thin films was done at two temperatures. First, the obtaining was realized when the substrates were at room temperature, and second, the obtaining was realized when the substrates were previously heated at 250 °C. The elaborated samples were then investigated by atomic force microscopy in order to establish their mechanical and tribological properties. The nanohardness, roughness, friction force are some of the determined characteristics. The results marked out that the substrate which was previously heated at 250 °C led to the obtaining of more adherent titanium nitride thin films than the substrate used at room temperature.

  10. Improving dielectric properties of epitaxial Gd{sub 2}O{sub 3} thin films on silicon by nitrogen doping

    SciTech Connect

    Roy Chaudhuri, Ayan; Osten, H. J.; Fissel, A.; Archakam, V. R.

    2013-01-14

    We report about the effect of nitrogen doping on the electrical properties of epitaxial Gd{sub 2}O{sub 3} thin films. Epitaxial Gd{sub 2}O{sub 3}:N thin films were grown on Si (111) substrates by solid source molecular beam epitaxy using nitrous oxide as the nitridation agent. Substitutional nitrogen incorporation into the dielectric layer was confirmed by secondary ion mass spectroscopy and X-ray photoelectron spectroscopy analysis. Substantial reduction of the leakage current density and disappearance of hysteresis in capacitance-voltage characteristics observed in the Gd{sub 2}O{sub 3}:N layers indicate that nitrogen incorporation in Gd{sub 2}O{sub 3} effectively eliminates the adverse effects of the oxygen vacancy induced defects in the oxide layer.

  11. Electrical dependence on the chemical composition of the gate dielectric in indium gallium zinc oxide thin-film transistors

    SciTech Connect

    Tari, Alireza Lee, Czang-Ho; Wong, William S.

    2015-07-13

    Bottom-gate thin-film transistors were fabricated by depositing a 50 nm InGaZnO (IGZO) channel layer at 150 °C on three separate gate dielectric films: (1) thermal SiO{sub 2}, (2) plasma-enhanced chemical-vapor deposition (PECVD) SiN{sub x}, and (3) a PECVD SiO{sub x}/SiN{sub x} dual-dielectric. X-ray photoelectron and photoluminescence spectroscopy showed the V{sub o} concentration was dependent on the hydrogen concentration of the underlying dielectric film. IGZO films on SiN{sub x} (high V{sub o}) and SiO{sub 2} (low V{sub o}) had the highest and lowest conductivity, respectively. A PECVD SiO{sub x}/SiN{sub x} dual-dielectric layer was effective in suppressing hydrogen diffusion from the nitride layer into the IGZO and resulted in higher resistivity films.

  12. Epitaxial ternary nitride thin films prepared by a chemical solution method

    SciTech Connect

    Luo, Hongmei; Feldmann, David M; Wang, Haiyan; Bi, Zhenxing

    2008-01-01

    It is indispensable to use thin films for many technological applications. This is the first report of epitaxial growth of ternary nitride AMN2 films. Epitaxial tetragonal SrTiN2 films have been successfully prepared by a chemical solution approach, polymer-assisted deposition. The structural, electrical, and optical properties of the films are also investigated.

  13. Bandwidth Enhancement of Cylindrical Dielectric Resonator Antenna Using Thin Dielectric Layer Fed by Resonating Slot

    NASA Astrophysics Data System (ADS)

    Mishra, Nipun K.; Das, Soma; Vishwakarma, Dinesh K.

    2016-09-01

    In this paper Cylindrical Dielectric Resonator Antenna (CDRA) has been designed for X-band frequency range applications with slot feeding. Bandwidth of designed cylindrical dielectric resonator antenna has been enhanced by making the slot to be resonating and inserting very thin low permittivity dielectric layer between the slot and CDRA. Resonating slot excites the closely spaced HEM11δ and HEM21δ mode inside the antenna as well as provides the resonance at the upper side of desired X-band. Low profile low permittivity layer provides the excellent matching of these modes and shift the HEM21δ mode to higher frequency side at 11.25 GHz with better impedance matching. By combining all of three resonances, nearly 85 % increment in impedance Bandwidth has been obtained with reference to non resonating slot excited CDRA. Fractional impedance bandwidth for proposed design is 48 % and average Gain of 6 dB with more than 92 % radiation efficiency has been shown by the antenna throughout the desired band with broadside pattern.

  14. Agglomeration of Pt thin films on dielectric substrates

    NASA Astrophysics Data System (ADS)

    Galinski, H.; Ryll, T.; Elser, P.; Rupp, J. L. M.; Bieberle-Hütter, A.; Gauckler, L. J.

    2010-12-01

    The agglomeration of metal thin films on dielectric materials is a topic of high technological importance. In this contribution, a coupled morphology-agglomeration approach has been chosen to reveal the basic mechanism of rupture, mass transport, and the substrate dependence of agglomeration. The morphological evolution of Pt thin films has been investigated by means of scanning electron microscopy, atomic force microscopy, and focused ion-beam (FIB) etching techniques. Pt thin films were deposited on amorphous Si3N4 and polycrystalline yttria stabilized ZrO2 substrates and subjected to heat treatments up to 1193 K for 2 h. Three main observations have been made: (i) the early stage of rupture can be described via basic thermodynamics as an order-disorder transition. The dominating mechanism of initial film rupture is a defect associated barrierless nucleation of holes in the spinodal regime of the Pt thin film as shown by means of Minkowski measures. (ii) Up to 1073 K the hole growth is found to be a surface-diffusion limited process, and in first approximation it is in agreement with Brandon and Bradshaw’s theory for the morphological evolution of thin metal films at elevated temperatures. Values for mass transport have been derived. (iii) It is shown that two in general independent physical processes control the morphological evolution and kinetics of thin-film agglomeration: one attributes to the film-ambient interface and the other to the film-substrate interface. Void formation at the film-substrate interface is enhanced by a factor of 9 in the case of the amorphous-crystalline interface due to a lower adhesion energy of the film. The corresponding adhesion energies have been determined experimentally using FIB techniques and the Wulff-Kaishew theorem for equilibrium crystal shapes.

  15. Effect of gate-dielectrics on the electrical characteristics of solution-processed single-wall-carbon-nanotube thin-film transistors

    NASA Astrophysics Data System (ADS)

    Ha, Tae-Jun

    2017-02-01

    High performance of solution-processed, single-wall-carbon-nanotube (SWCNT) thin-film transistors (TFTs) is investigated through the use in the different gate-dielectrics of silicon dioxide (SiO2), silicon nitride (SiNx), the bilayers of SiO2 and SiNx, and hexagonal boron-nitride (h-BN) thin films. The different interfacial characteristics affect the electrical characteristics of the SWCNT-TFTs including key device metrics. Significantly, the hysteresis window that is normally observed in drop-casted SWCNT-TFTs was majorly suppressed by the employment of a thin lower dielectric-constant material on a higher dielectricconstant material. Sub-2V operating SWCNT-TFTs with solution-processed h-BN gate dielectrics with good above- and sub-threshold characteristics are also investigated on the basis of interfacial characteristics underlying the device physics. Such performance can be realized by the suppressed interfacial impurity scattering through the chemically clean interface combined with optimized solution-process below 100 °C. [Figure not available: see fulltext.

  16. Launching Phonon Polaritons by Natural Boron Nitride Wrinkles with Modifiable Dispersion by Dielectric Environments.

    PubMed

    Duan, Jiahua; Chen, Runkun; Li, Jingcheng; Jin, Kuijuan; Sun, Zhigang; Chen, Jianing

    2017-10-01

    Interference-free hyperbolic phonon polaritons (HPPs) excited by natural wrinkles in a hexagonal boron nitride (hBN) microcrystal are reported both experimentally and theoretically. Although their geometries are off-resonant with the excitation wavelength, the wrinkles compensate for the large momentum mismatch between photon and phonon polariton, and launch the HPPs without interference. The spatial feature of wrinkles is about 200 nm, which is an order of magnitude smaller than resonant metal antennas at the same excitation wavelength. Compared with phonon polaritons launched by an atomic force microscopy tip, the phonon polaritons launched by wrinkles are interference-free, independent of the launcher geometry, and exhibit a smaller damping rate (γ ≈ 0.028). On the same hBN microcrystal, in situ nanoinfrared imaging of HPPs launched by different mechanisms is performed. In addition, the dispersion of HPPs is modified by changing the dielectric environments of hBN crystals. The wavelength of HPPs is compressed twofold when the substrate is changed from SiO2 to gold. The findings provide insights into the intrinsic properties of hBN-HPPs and demonstrate a new way to launch and control polaritons in van der Waals materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Comparison of device structures for the dielectric breakdown measurement of hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Hattori, Yoshiaki; Taniguchi, Takashi; Watanabe, Kenji; Nagashio, Kosuke

    2016-12-01

    Improving the film quality in the synthesis of large-area hexagonal boron nitride films (h-BN) for two-dimensional material devices remains a great challenge. The measurement of electrical breakdown dielectric strength (EBD) is one of the most important methods to elucidate the insulating quality of h-BN. In this work, the EBD of high quality exfoliated single-crystal h-BN was investigated using three different electrode structures under different environmental conditions to determine the ideal electrode structure and environment for EBD measurement. A systematic investigation revealed that EBD is not sensitive to contact force or electrode area but strongly depends on the relative humidity during measurement. Once the measurement environment is properly managed, it was found that the EBD values are consistent within experimental error regardless of the electrode structure, which enables the evaluation of the crystallinity of synthesized h-BN at the microscopic and macroscopic level by utilizing the three different electrode structures properly for different purposes.

  18. Heat resistive dielectric multi-layer micro-mirror array in epitaxial lateral overgrowth gallium nitride.

    PubMed

    Huang, Chen-Yang; Ku, Hao-Min; Liao, Wei-Tsai; Chao, Chu-Li; Tsay, Jenq-Dar; Chao, Shiuh

    2009-03-30

    Ta2O5 / SiO2 dielectric multi-layer micro-mirror array (MMA) with 3mm mirror size and 6mm array period was fabricated on c-plane sapphire substrate. The MMA was subjected to 1200 degrees C high temperature annealing and remained intact with high reflectance in contrast to the continuous multi-layer for which the layers have undergone severe damage by 1200 degrees C annealing. Epitaxial lateral overgrowth (ELO) of gallium nitride (GaN) was applied to the MMA that was deposited on both sapphire and sapphire with 2:56 mm GaN template. The MMA was fully embedded in the ELO GaN and remained intact. The result implies that our MMA is compatible to the high temperature growth environment of GaN and the MMA could be incorporated into the structure of the micro-LED array as a one to one micro backlight reflector, or as the patterned structure on the large area LED for controlling the output light.

  19. Aligned Growth of Millimeter-Size Hexagonal Boron Nitride Single-Crystal Domains on Epitaxial Nickel Thin Film.

    PubMed

    Meng, Junhua; Zhang, Xingwang; Wang, Ye; Yin, Zhigang; Liu, Heng; Xia, Jing; Wang, Haolin; You, Jingbi; Jin, Peng; Wang, Denggui; Meng, Xiang-Min

    2017-03-07

    Atomically thin hexagonal boron nitride (h-BN) is gaining significant attention for many applications such as a dielectric layer or substrate for graphene-based devices. For these applications, synthesis of high-quality and large-area h-BN layers with few defects is strongly desirable. In this work, the aligned growth of millimeter-size single-crystal h-BN domains on epitaxial Ni (111)/sapphire substrates by ion beam sputtering deposition is demonstrated. Under the optimized growth conditions, single-crystal h-BN domains up to 0.6 mm in edge length are obtained, the largest reported to date. The formation of large-size h-BN domains results mainly from the reduced Ni-grain boundaries and the improved crystallinity of Ni film. Furthermore, the h-BN domains show well-aligned orientation and excellent dielectric properties. In addition, the sapphire substrates can be repeatedly used with almost no limit. This work provides an effective approach for synthesizing large-scale high-quality h-BN layers for electronic applications.

  20. Tunable electrical and optical properties of hafnium nitride thin films

    NASA Astrophysics Data System (ADS)

    Farrell, I. L.; Reeves, R. J.; Preston, A. R. H.; Ludbrook, B. M.; Downes, J. E.; Ruck, B. J.; Durbin, S. M.

    2010-02-01

    We report structural and electronic properties of epitaxial hafnium nitride films grown on MgO by plasma-assisted pulsed laser deposition. The electronic structure measured using soft x-ray absorption and emission spectroscopy is in excellent agreement with the results of a band structure calculation. We show that by varying the growth conditions we can extend the films' reflectance further toward the UV, and we relate this observation to the electronic structure.

  1. Dielectric relaxation of thin films of polyamide random copolymers

    NASA Astrophysics Data System (ADS)

    Taniguchi, Natsumi; Fukao, Koji; Sotta, Paul; Long, Didier R.

    2015-05-01

    We investigate the relaxation behavior of thin films of a polyamide random copolymer, PA66/6I, with various film thicknesses using dielectric relaxation spectroscopy. Two dielectric signals are observed at high temperatures, the α process and the relaxation process due to electrode polarization (the EP process). The relaxation time of the EP process has a Vogel-Fulcher-Tammann type of temperature dependence, and the glass transition temperature, Tg, evaluated from the EP process agrees very well with the Tg determined from the thermal measurements. The fragility index derived from the EP process increases with decreasing film thickness. The relaxation time and the dielectric relaxation strength of the EP process are described by a linear function of the film thickness d for large values of d , which can be regarded as experimental evidence for the validity of attributing the observed signal to the EP process. Furthermore, there is distinct deviation from this linear law for thicknesses smaller than a critical value. This deviation observed in thinner films is associated with an increase in the mobility and/or diffusion constant of the charge carriers responsible for the EP process. The α process is located in a higher-frequency region than the EP process at high temperatures but merges with the EP process at lower temperatures near the glass transition region. The thickness dependence of the relaxation time of the α process is different from that of the EP process. This suggests that there is decoupling between the segmental motion of the polymers and the translational motion of the charge carriers in confinement.

  2. Nanoscale electrochemistry using dielectric thin films as solid electrolytes

    NASA Astrophysics Data System (ADS)

    Valov, Ilia; Lu, Wei D.

    2016-07-01

    It is now well known that at the nanoscale matters behave differently compared to bulk phases. Increased reactivity, deviations in structural, thermodynamic and kinetic properties make nanoscale materials and processes attractive for both fundamental research and applications. Here we show that nanometer thin films of materials with dielectric properties at the macroscopic level such as SiO2, Ta2O5 and HfO2 behave as solid electrolytes and exhibit evident ionic transport and electrochemical redox reactions. Experimental studies demonstrate that classical electrochemical potentiodynamic and steady state methods can be used to study the mass and charge transport at the nanoscale. We believe these reported properties of nanomatter open new opportunities for fundamental research and applications.

  3. Structural and Magnetic Properties of Thin Film of Iron Nitride

    NASA Astrophysics Data System (ADS)

    Kayani, Zohra Nazir; Riaz, Saira; Naseem, Shahzad

    2014-12-01

    The nano-crystalline iron nitride films with a mixture of γ-Fe4N, ɛFe3N and αFe2N phases were synthesized on copper substrate by sol-gel technology. The structure, morphology and magnetic properties of the samples were characterized using X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. The films are ferromagnetic at room temperature. Magnetic properties such as coercive forces and saturation magnetization were found to be 398 Oestered and 32.92 emu/cm3, respectively.

  4. Thin films of pure vanadium nitride: Evidence for anomalous non-faradaic capacitance

    NASA Astrophysics Data System (ADS)

    Bondarchuk, Oleksandr; Morel, Alban; Bélanger, Daniel; Goikolea, Eider; Brousse, Thierry; Mysyk, Roman

    2016-08-01

    An impressive gravimetric capacitance of 1300 F g-1 (surface capacitance ∼3.3 mF cm-2) reported by Choi et al., 2006 for nanosized vanadium nitride has stimulated considerable interest in vanadium nitride as a potential electrode material for energy storing systems - supercapacitors. The postulated mechanism of charge storage in vanadium nitride materials involves redox reactions in the thin surface layer of vanadium oxide while the core vanadium nitride serves exclusively as a conducting platform. In this study we have synthesized pure oxygen-free vanadium nitride films and have found that they are capable of delivering a surface capacitance of up to ∼3 mF cm-2 at a potential scan rate of 3 mV s-1 and ∼2 mF cm-2 at a potential scan rate of 1 V s-1 in aqueous electrolytes. Combining electrochemical testing with X-ray photoelectron spectroscopy characterization has revealed that redox reactions play no or little role in the electrochemical response of pure VN, in contrast to the common wisdom stemming from the electrochemical response of oxygen-containing films. An alternative charge storage mechanism - space charge accumulation in a subsurface layer of ∼100 nm - was put forward to explain the experimentally observed capacitance of VN films in aqueous electrolytes.

  5. Marine corrosion protective coatings of hexagonal boron nitride thin films on stainless steel.

    PubMed

    Husain, Esam; Narayanan, Tharangattu N; Taha-Tijerina, Jose Jaime; Vinod, Soumya; Vajtai, Robert; Ajayan, Pulickel M

    2013-05-22

    Recently, two-dimensional, layered materials such as graphene and hexagonal boron nitride (h-BN) have been identified as interesting materials for a range of applications. Here, we demonstrate the corrosion prevention applications of h-BN in marine coatings. The performance of h-BN/polymer hybrid coatings, applied on stainless steel, were evaluated using electrochemical techniques in simulated seawater media [marine media]. h-BN/polymer coating shows an efficient corrosion protection with a low corrosion current density of 5.14 × 10(-8) A/cm(2) and corrosion rate of 1.19 × 10(-3) mm/year and it is attributed to the hydrofobic, inert and dielectric nature of boron nitride. The results indicated that the stainless steel with coatings exhibited improved corrosion resistance. Electrochemical impedance spectroscopy and potentiodynamic analysis were used to propose a mechanism for the increased corrosion resistance of h-BN coatings.

  6. Thermal conductivity of ultra-thin chemical vapor deposited hexagonal boron nitride films

    SciTech Connect

    Alam, M. T.; Haque, M. A.; Bresnehan, M. S.; Robinson, J. A.

    2014-01-06

    Thermal conductivity of freestanding 10 nm and 20 nm thick chemical vapor deposited hexagonal boron nitride films was measured using both steady state and transient techniques. The measured value for both thicknesses, about 100 ± 10 W m{sup −1} K{sup −1}, is lower than the bulk basal plane value (390 W m{sup −1} K{sup −1}) due to the imperfections in the specimen microstructure. Impressively, this value is still 100 times higher than conventional dielectrics. Considering scalability and ease of integration, hexagonal boron nitride grown over large area is an excellent candidate for thermal management in two dimensional materials-based nanoelectronics.

  7. Temporally and Spatially Resolved Plasma Spectroscopy in Pulsed Laser Deposition of Ultra-Thin Boron Nitride Films (Postprint)

    DTIC Science & Technology

    2015-04-24

    in the plasma plume. Boron, being the lighter of the two species ( atomic weights: B¼ 10.81, N¼ 14.01), will escape the Knudsen layer of plasma plume...AFRL-RX-WP-JA-2016-0196 TEMPORALLY AND SPATIALLY RESOLVED PLASMA SPECTROSCOPY IN PULSED LASER DEPOSITION OF ULTRA-THIN BORON NITRIDE...AND SPATIALLY RESOLVED PLASMA SPECTROSCOPY IN PULSED LASER DEPOSITION OF ULTRA-THIN BORON NITRIDE FILMS (POSTPRINT) 5a. CONTRACT NUMBER FA8650

  8. Largely enhanced dielectric properties of carbon nanotubes/polyvinylidene fluoride binary nanocomposites by loading a few boron nitride nanosheets

    NASA Astrophysics Data System (ADS)

    Yang, Minhao; Zhao, Hang; He, Delong; Bai, Jinbo

    2016-08-01

    The ternary nanocomposites of boron nitride nanosheets (BNNSs)/carbon nanotubes (CNTs)/polyvinylidene fluoride (PVDF) are fabricated via a combination of solution casting and extrusion-injection processes. The effects of BNNSs on the electrical conductivity, dielectric behavior, and microstructure changes of CNTs/PVDF binary nanocomposites are systematically investigated. A low percolation value (fc) for the CNTs/PVDF binary system is obtained due to the integration of solution and melting blending procedures. Two kinds of CNTs/PVDF binary systems with various CNTs contents (fCNTs) as the matrix are discussed. The results reveal that compared with CNTs/PVDF binary systems at the same fCNTs, the ternary BNNSs/CNTs/PVDF nanocomposites exhibit largely enhanced dielectric properties due to the improvement of the CNTs dispersion state and the conductive network. The dielectric constant of CNTs/PVDF binary nanocomposite with 6 vol. % CNTs (fCNTs < fc) shows a 79.59% enhancement from 49 to 88 after the incorporation of 3 vol. % BNNSs. For the other CNTs/PVDF system with 8 vol. % CNTs (fCNTs > fc), it displays a 43.32% improvement from 1325 to 1899 after the addition of 3 vol. % BNNSs. The presence of BNNSs facilitates the formation of the denser conductive network. Meanwhile, the ternary BNNSs/CNTs/PVDF systems exhibit a low dielectric loss. The adjustable dielectric properties could be obtained by employing the ternary systems due to the microstructure changes of nanocomposites.

  9. Boron Nitride Nanotube Mat as a Low- k Dielectric Material with Relative Dielectric Constant Ranging from 1.0 to 1.1

    NASA Astrophysics Data System (ADS)

    Hong, Xinghua; Wang, Daojun; Chung, D. D. L.

    2016-01-01

    This paper reports that a boron nitride nanotube (BNNT) mat containing air and 1.4 vol.% BNNTs is a low- k dielectric material for microelectronic packaging, exhibiting relative dielectric constant of 1.0 to 1.1 (50 Hz to 2 MHz) and elastic modulus of 10 MPa. The mat is prepared by compacting BNNTs at 5.8 kPa. This paper also presents measurements of the dielectric properties of BNNTs (mostly multiwalled). The relative dielectric constant of the BNNT solid in the mat decreases with increasing frequency, with attractively low values ranging from 3.0 to 6.2; the alternating-current (AC) electrical conductivity increases with increasing frequency, with attractively low values ranging from 10-10 S/m to 10-6 S/m and an approximately linear relationship between log conductivity and log frequency. The specific contact capacitance of the interface between BNNTs and the electrical contact decreases with increasing frequency, with attractively high values ranging from 1.6 μF/m2 to 2.3 μF/m2. The AC electrical resistivity of the BNNT-contact interface decreases with increasing frequency, with high values ranging from 0.14 MΩ cm2 to 440 MΩ cm2.

  10. Application of thin dielectric films in low coherence fiber-optic Fabry-Pérot sensing interferometers: comparative study

    NASA Astrophysics Data System (ADS)

    Hirsch, Marzena; Wierzba, Paweł; Jedrzejewska-Szczerska, Małgorzata

    2016-11-01

    We examine the application of selected thin dielectric films, deposited by atomic layer deposition (ALD), in a low coherence fiber-optic Fabry-Pérot interferometer designed for sensing applications. Such films can be deposited on the end-face of a single mode optical fiber (SMF-28) in order to modify the reflectivity of the Fabry-Pérot cavity, to provide protection of the fibers from aggressive environments or to create a multi-cavity interferometric sensor. Spectral reflectance of films made from zinc oxide (ZnO), titanium dioxide (TiO2), aluminum oxide (Al2O3) and boron nitride (BN) was calculated for various thickness of the films and compared. The results show that the most promising materials for use in fiber-optic Fabry-Pérot interferometer are TiO2 and ZnO, although Al2O3 is also suitable for this application.

  11. Structural and mechanical properties of CVD deposited titanium aluminium nitride (TiAlN) thin films

    NASA Astrophysics Data System (ADS)

    Das, Soham; Guha, Spandan; Ghadai, Ranjan; Kumar, Dhruva; Swain, Bibhu P.

    2017-06-01

    Titanium aluminium nitride (TiAlN) thin films were deposited by chemical vapour deposition using TiO2 powder, Al powder and N2 gas. The morphology and mechanical properties of the films were characterized by scanning electron microscopy and nanoindentation technique, respectively. The structural properties were characterized by Raman spectroscopy and X-ray diffraction. The XRD result shows TiAlN films are of NaCl-type metal nitride structure. Micro-Raman peaks of the TiAlN thin film were observed within 450 and 642 cm-1 for acoustic and optic range, respectively. A maximum hardness and Young modulus up to 22 and 272.15 GPa, respectively, were observed in the TiAlN film deposited at 1200 °C.

  12. Selective sputtering and atomic resolution imaging of atomically thin boron nitride membranes.

    PubMed

    Meyer, Jannik C; Chuvilin, Andrey; Algara-Siller, Gerardo; Biskupek, Johannes; Kaiser, Ute

    2009-07-01

    We report on the preparation, atomic resolution imaging, and element selective damage mechanism in atomically thin boron nitride membranes. Flakes of less than 10 layers are prepared by mechanical cleavage and are thinned down to single layers in a high-energy electron beam. At our beam energies, we observe a highly selective sputtering of only one of the elements and predominantly at the exit surface of the specimen, and then subsequent removal of atoms next to a defect. Triangle-shaped holes appear in accordance with the crystallographic orientation of each layer. Defects are compared to those observed in graphene membranes. The observation of clean single-layer membranes shows that hexagonal boron nitride is a further material (in addition to graphene) that can exist in a quasi-two-dimensional allotrope without the need for a substrate.

  13. Nitride passivation of the interface between high-k dielectrics and SiGe

    NASA Astrophysics Data System (ADS)

    Sardashti, Kasra; Hu, Kai-Ting; Tang, Kechao; Madisetti, Shailesh; McIntyre, Paul; Oktyabrsky, Serge; Siddiqui, Shariq; Sahu, Bhagawan; Yoshida, Naomi; Kachian, Jessica; Dong, Lin; Fruhberger, Bernd; Kummel, Andrew C.

    2016-01-01

    In-situ direct ammonia (NH3) plasma nitridation has been used to passivate the Al2O3/SiGe interfaces with Si nitride and oxynitride. X-ray photoelectron spectroscopy of the buried Al2O3/SiGe interface shows that NH3 plasma pre-treatment should be performed at high temperatures (300 °C) to fully prevent Ge nitride and oxynitride formation at the interface and Ge out-diffusion into the oxide. C-V and I-V spectroscopy results show a lower density of interface traps and smaller gate leakage for samples with plasma nitridation at 300 °C.

  14. Ultrathin, wafer-scale hexagonal boron nitride on dielectric surfaces by diffusion and segregation mechanism

    NASA Astrophysics Data System (ADS)

    Sonde, Sushant; Dolocan, Andrei; Lu, Ning; Corbet, Chris; Kim, Moon J.; Tutuc, Emanuel; Banerjee, Sanjay K.; Colombo, Luigi

    2017-06-01

    Chemical vapor deposition (CVD) of two-dimensional (2D) hexagonal boron nitride (h-BN) is at the center of numerous studies for its applications in novel electronic devices. However, a clear understanding of the growth mechanism is lacking for its wider industrial adoption on technologically relevant substrates such as SiO2. Here, we demonstrate a controllable growth method of thin, wafer scale h-BN films on arbitrary substrates. We also clarify the growth mechanism to be diffusion and surface segregation (D-SS) of boron (B) and nitrogen (N) in Ni and Co thin films on SiO2/Si substrates after exposure to diborane and ammonia precursors at high temperature. The segregation was found to be independent of the cooling rates employed in this report, and to our knowledge has not been found nor reported for 2D h-BN growth so far, and thus provides an important direction for controlled growth of h-BN. This unique segregation behavior is a result of a combined effect of high diffusivity, small film thickness and the inability to achieve extremely high cooling rates in CVD systems. The resulting D-SS h-BN films exhibit excellent electrical insulating behavior with an optical bandgap of about 5.8 eV. Moreover, graphene-on-h-BN field effect transistors using the as-grown D-SS h-BN films show a mobility of about 6000 cm2 V-1 s-1 at room temperature.

  15. Elemental composition and microstructure of reactively sputtered carbon nitride thin films

    NASA Astrophysics Data System (ADS)

    Kumar, Sunil; Tansley, T. L.

    1994-10-01

    Thin films of carbon nitride have been grown on various substrates using low power radio frequency reactive sputtering of graphite in pure nitrogen plasma. A quantitative composition analysis using Rutherford backscattering spectrometry shows that the film contains about 51 at. % C, 44 at. % N, and 5 at.% O. The study of the microstructure of the films using cross-sectional scanning electron microscopy reveals highly oriented columnar structures.

  16. Parallel writing on zirconium nitride thin films by local oxidation nanolithography

    NASA Astrophysics Data System (ADS)

    Farkas, N.; Comer, J. R.; Zhang, G.; Evans, E. A.; Ramsier, R. D.; Wight, S.; Dagata, J. A.

    2004-12-01

    Parallel pattern transfer of submicrometer-scale oxide features onto zirconium nitride thin films is reported. The oxidation reaction was verified by Auger microprobe analysis and secondary ion mass spectrometry. Oxide features of ˜70nm in height can be formed and selectively etched in a dilute aqueous hydrogen fluoride solution. This provides an interesting route to potential new applications for high-melting point, biocompatible surfaces that possess small feature sizes with controlled geometries.

  17. Effect of gate-dielectrics on the electrical characteristics of solution-processed single-wall-carbon-nanotube thin-film transistors

    NASA Astrophysics Data System (ADS)

    Ha, Tae-Jun

    2017-07-01

    High performance of solution-processed, single-wall-carbon-nanotube (SWCNT) thin-film transistors (TFTs) is investigated through the use in the different gatedielectrics of silicon dioxide (SiO2), silicon nitride (SiNx), the bilayers of SiO2 and SiNx, and hexagonal boron-nitride (h-BN) thin films. The different interfacial characteristics affect the electrical characteristics of the SWCNT-TFTs including key device metrics. Significantly, the hysteresis window that is normally observed in drop-casted SWCNT-TFTs was majorly suppressed by the employment of a thin lower dielectric-constant material on a higher dielectricconstant material. Sub-2V operating SWCNT-TFTs with solution-processed h-BN gate dielectrics with good above- and sub-threshold characteristics are also investigated on the basis of interfacial characteristics underlying the device physics. Such performance can be realized by the suppressed interfacial impurity scattering through the chemically clean interface combined with optimized solution-process below 100 °C.[Figure not available: see fulltext.

  18. Pulsed DC magnetron sputtered piezoelectric thin film aluminum nitride – Technology and piezoelectric properties

    SciTech Connect

    Stoeckel, C. Kaufmann, C.; Hahn, R.; Schulze, R.; Billep, D.; Gessner, T.

    2014-07-21

    Pulsed DC magnetron sputtered aluminum nitride (AlN) thin films are prepared on several seed layers and at different sputtering conditions. The piezoelectric c-axis (002) orientation of the AlN is analyzed with X-ray diffraction method. The transverse piezoelectric coefficient d{sub 31} is determined with a Laser-Doppler-Vibrometer at cantilevers and membranes by analytical calculations and finite element method. Additionally, thin film AlN on bulk silicon is used to characterize the longitudinal piezoelectric charge coefficient d{sub 33}.

  19. Giant Dielectric Permittivity in Ferroelectric Thin Films: Domain Wall Ping Pong

    PubMed Central

    Quan Jiang, An; Jian Meng, Xiang; Wei Zhang, David; Hyuk Park, Min; Yoo, Sijung; Jin Kim, Yu; Scott, James F.; Seong Hwang, Cheol

    2015-01-01

    The dielectric permittivity in ferroelectric thin films is generally orders of magnitude smaller than in their bulk. Here, we discover a way of increasing dielectric constants in ferroelectric thin films by ca. 500% by synchronizing the pulsed switching fields with the intrinsic switching time (nucleation of domain plus forward growth from cathode to anode). In a 170-nm lead zirconate titanate thin film with an average grain size of 850 nm this produces a dielectric constant of 8200 with the maximum nucleus density of 3.8 μm−2, which is one to three orders of magnitude higher than in other dielectric thin films. This permits smaller capacitors in memory devices and is a step forward in making ferroelectric domain-engineered nano-electronics. PMID:26440528

  20. Surface scattering mechanisms of tantalum nitride thin film resistor

    NASA Astrophysics Data System (ADS)

    Chen, Huey-Ru; Chen, Ying-Chung; Chang, Ting-Chang; Chang, Kuan-Chang; Tsai, Tsung-Ming; Chu, Tian-Jian; Shih, Chih-Cheng; Chuang, Nai-Chuan; Wang, Kao-Yuan

    2014-04-01

    In this letter, we utilize an electrical analysis method to develop a TaN thin film resistor with a stricter spec and near-zero temperature coefficient of resistance (TCR) for car-used electronic applications. Simultaneously, we also propose a physical mechanism mode to explain the origin of near-zero TCR for the TaN thin film resistor (TFR). Through current fitting, the carrier conduction mechanism of the TaN TFR changes from hopping to surface scattering and finally to ohmic conduction for different TaN TFRs with different TaN microstructures. Experimental data of current-voltage measurement under successive increasing temperature confirm the conduction mechanism transition. A model of TaN grain boundary isolation ability is eventually proposed to influence the carrier transport in the TaN thin film resistor, which causes different current conduction mechanisms.

  1. Thin boron nitride nanotubes with exceptionally high strength and toughness

    NASA Astrophysics Data System (ADS)

    Huang, Yang; Lin, Jing; Zou, Jin; Wang, Ming-Sheng; Faerstein, Konstantin; Tang, Chengchun; Bando, Yoshio; Golberg, Dmitri

    2013-05-01

    Bending manipulation and direct force measurements of ultrathin boron nitride nanotubes (BNNTs) were performed inside a transmission electron microscope. Our results demonstrate an obvious transition in mechanics of BNNTs when the external diameters of nanotubes are in the range of 10 nm or less. During in situ transmission electron microscopy bending tests, characteristic ``hollow'' ripple-like structures formed in the bent ultrathin BNNTs with diameters of sub-10 nm. This peculiar buckling/bending mode makes the ultrathin BNNTs hold very high post-buckling loads which significantly exceed their initial buckling forces. Exceptional compressive/bending strength as high as ~1210 MPa was observed. Moreover, the analysis of reversible bending force curves of such ultrathin nanotubes indicates that they may store/adsorb strain energy at a density of ~400 × 106 J m-3. Such nanotubes are thus very promising for strengthening and toughening of structural ceramics and may find potential applications as effective energy-absorbing materials like armor.Bending manipulation and direct force measurements of ultrathin boron nitride nanotubes (BNNTs) were performed inside a transmission electron microscope. Our results demonstrate an obvious transition in mechanics of BNNTs when the external diameters of nanotubes are in the range of 10 nm or less. During in situ transmission electron microscopy bending tests, characteristic ``hollow'' ripple-like structures formed in the bent ultrathin BNNTs with diameters of sub-10 nm. This peculiar buckling/bending mode makes the ultrathin BNNTs hold very high post-buckling loads which significantly exceed their initial buckling forces. Exceptional compressive/bending strength as high as ~1210 MPa was observed. Moreover, the analysis of reversible bending force curves of such ultrathin nanotubes indicates that they may store/adsorb strain energy at a density of ~400 × 106 J m-3. Such nanotubes are thus very promising for strengthening and

  2. Strong oxidation resistance of atomically thin boron nitride nanosheets.

    PubMed

    Li, Lu Hua; Cervenka, Jiri; Watanabe, Kenji; Taniguchi, Takashi; Chen, Ying

    2014-02-25

    Investigation of oxidation resistance of two-dimensional (2D) materials is critical for many of their applications because 2D materials could have higher oxidation kinetics than their bulk counterparts due to predominant surface atoms and structural distortions. In this study, the oxidation behavior of high-quality boron nitride (BN) nanosheets of 1-4 layers thick has been examined by heating in air. Atomic force microscopy and Raman spectroscopy analyses reveal that monolayer BN nanosheets can sustain up to 850 °C, and the starting temperature of oxygen doping/oxidation of BN nanosheets only slightly increases with the increase of nanosheet layer and depends on heating conditions. Elongated etch lines are found on the oxidized monolayer BN nanosheets, suggesting that the BN nanosheets are first cut along the chemisorbed oxygen chains and then the oxidative etching grows perpendicularly to these cut lines. The stronger oxidation resistance of BN nanosheets makes them more preferable for high-temperature applications than graphene.

  3. Pulsed laser deposition of niobium nitride thin films

    NASA Astrophysics Data System (ADS)

    Farha, Ashraf Hassan; Ufuktepe, Yüksel; Myneni, Ganapati; Elsayed-Ali, Hani E.

    2015-12-01

    Niobium nitride (NbNx) films were grown on Nb and Si(100) substrates using pulsed laser deposition. NbNx films were deposited on Nb substrates using PLD with a Q-switched Nd:YAG laser (λ = 1064 nm, ˜40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, nitrogen background pressures and deposition substrate temperatures. When all the fabrication parameters are fixed, except for the laser fluence, the surface roughness, nitrogen content, and grain size increase with increasing laser fluence. Increasing nitrogen background pressure leads to a change in the phase structure of the NbNx films from mixed β-Nb2N and cubic δ-NbN phases to single hexagonal β-Nb2N. The substrate temperature affects the preferred orientation of the crystal structure. The structural and electronic, properties of NbNx deposited on Si(100) were also investigated. The NbNx films exhibited a cubic δ-NbN with a strong (111) orientation. A correlation between surface morphology, electronic, and superconducting properties was found. The observations establish guidelines for adjusting the deposition parameters to achieve the desired NbNx film morphology and phase.

  4. Pulsed laser deposition of niobium nitride thin films

    SciTech Connect

    Farha, Ashraf Hassan Elsayed-Ali, Hani E.; Ufuktepe, Yüksel; Myneni, Ganapati

    2015-12-04

    Niobium nitride (NbN{sub x}) films were grown on Nb and Si(100) substrates using pulsed laser deposition. NbN{sub x} films were deposited on Nb substrates using PLD with a Q-switched Nd:YAG laser (λ = 1064 nm, ∼40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, nitrogen background pressures and deposition substrate temperatures. When all the fabrication parameters are fixed, except for the laser fluence, the surface roughness, nitrogen content, and grain size increase with increasing laser fluence. Increasing nitrogen background pressure leads to a change in the phase structure of the NbN{sub x} films from mixed β-Nb{sub 2}N and cubic δ-NbN phases to single hexagonal β-Nb{sub 2}N. The substrate temperature affects the preferred orientation of the crystal structure. The structural and electronic, properties of NbN{sub x} deposited on Si(100) were also investigated. The NbN{sub x} films exhibited a cubic δ-NbN with a strong (111) orientation. A correlation between surface morphology, electronic, and superconducting properties was found. The observations establish guidelines for adjusting the deposition parameters to achieve the desired NbN{sub x} film morphology and phase.

  5. Post-deposition annealing study of tantalum nitride thin-film resistors

    SciTech Connect

    Au, Chi Lok.

    1989-01-01

    With the present integrated circuit design, the use of hybrid metallic thin film resistor networks leads to more design flexibility, economical chip area consumption, reduced processing steps, higher precision and stability for the integrated circuits. To meet the hybrid circuit requirements, the thin film resistors must have high sheet resistivity for compact design, chemical and mechanical stability, and precise resistance which is temperature independent. The nickel-chrome (NiCr) alloy, with its very low temperature coefficient of resistance (TCR), is currently used in the industry. The non-linear TCR behavior and the ease of hydrolytic dissociation of NiCr give place to a more stable material, such as tantalum nitride. Due to technical difficulties in heating the substrate to a high temperature during deposition, which is the controlling parameter for achieving the stable Ta{sub 2}N structure, post deposition annealing becomes the central theme for this project. Preliminary TCR studies of the reactive sputtered tantalum nitride thin films shows that films with sheet resistivity less than 60 ohm/sq. can be air annealed to improve the TCR to less than 30 ppm/{degree}C in magnitude. The deposition parameters may influence the annealing conditions. For films with higher sheet resistivity, high vacuum annealing must be used for the TCR improvement. The TCR can be adjusted to an almost zero value by the combination of annealing temperature and time. With the electrical stability and chemically inertness in water and acids, tantalum nitride is likely to become a major thin-film resistor material in the industry. A systematic study of this thin film material is conducted, covering both electrical and structural properties.

  6. Thin-ribbon tapered coupler for dielectric waveguides

    NASA Technical Reports Server (NTRS)

    Yeh, C.; Otoshi, T. Y.; Shimabukuro, F. I.

    1994-01-01

    A recent discovery shows that a high-dielectric constant, low-loss, solid material can be made into a ribbon-like waveguide structure to yield an attenuation constant of less than 0.02 dB/m for single-mode guidance of millimeter/submillimeter waves. One of the crucial components that must be invented in order to guarantee the low-loss utilization of this dielectric-waveguide guiding system is the excitation coupler. The traditional tapered-to-a-point coupler for a dielectric rod waveguide fails when the dielectric constant of the dielectric waveguide is large. This article presents a new way to design a low-loss coupler for a high- or low-dielectric constant dielectric waveguide for millimeter or submillimeter waves.

  7. Bismuth pyrochlore thin films for dielectric energy storage

    SciTech Connect

    Michael, Elizabeth K. Trolier-McKinstry, Susan

    2015-08-07

    Thin films of cubic pyrochlore bismuth zinc niobate, bismuth zinc tantalate, and bismuth zinc niobate tantalate were fabricated using chemical solution deposition. This family of materials exhibited moderate relative permittivities between 55 ± 2 and 145 ± 5 for bismuth zinc tantalate and bismuth zinc niobate, respectively, and low loss tangents on the order of 0.0008 ± 0.0001. Increases in the concentration of the tantalum end member increased the dielectric breakdown strength. For example, at 10 kHz, the room temperature breakdown strength of bismuth zinc niobate was 5.1 MV/cm, while that of bismuth zinc tantalate was 6.1 MV/cm. This combination of a high breakdown strength and a moderate permittivity led to a high discharged energy storage density for all film compositions. For example, at a measurement frequency of 10 kHz, bismuth zinc niobate exhibited a maximum recoverable energy storage density of 60.8 ± 2.0 J/cm{sup 3}, while bismuth zinc tantalate exhibited a recoverable energy storage density of 60.7 ± 2.0 J/cm{sup 3}. Intermediate compositions of bismuth zinc niobate tantalate offered higher energy storage densities; at 10 mol. % tantalum, the maximum recoverable energy storage density was ∼66.9 ± 2.4 J/cm{sup 3}.

  8. Ultraviolet-assisted oxidation and nitridation of hafnium and hafnium aluminum alloys as potential gate dielectrics for metal oxide semiconductor applications

    NASA Astrophysics Data System (ADS)

    Essary, Chad Robert

    The continued miniaturization of silicon-based complimentary metal oxide semiconductor (CMOS) devices is pushing the limits of the silicon dioxide (SiO2) gate dielectric. As the channel widths are decreased to increase packing densities and functionality of new chips, proportional vertical scaling of the dielectric must be maintained to keep constant capacitances. Silicon dioxide is approaching its fundamental limit in which it can be used as the gate dielectric due to high leakage currents resulting from direct tunneling through the layer. In order for the continued use of current CMOS gate design, an alternative material with a higher dielectric constant must be found. Several materials have been proposed but are still not providing the electrical characteristics favorable for use in the devices due to problems with excessive leakage and hysteresis resulting from the quality of the film and oxygen defects. The goal of this study is to create higher quality films at lower processing temperatures with low leakage and less hysteresis than has been achieved with hafnium oxide films. This study first examines the formation of the interfacial layer in pulsed laser deposited hafnium oxide films to understand the kinetics behind its formation. The second section focuses on the oxidation of pulsed laser deposited (PLD) hafnium metal thin films using ultraviolet (UV) assisted post-deposition annealing. Another set of samples was deposited in an ammonia atmosphere in order to incorporate nitrogen into the films. Comparisons of microstructure and stoichiometry of oxidized hafnium and oxy-nitride films were made using x-ray photospectroscopy, variable angle spectroscopic ellipsometry, glancing angle x-ray spectroscopy, x-ray reflectivity, and atomic force microscopy. Analysis of the interface between the films and the silicon substrate was carried out using x-ray reflectivity. The electrical characteristics of the films were characterized using capacitance-voltage and current

  9. Foreign Object Damage of Two Gas-Turbine Grade Silicon Nitrides in a Thin Disk Configuration

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Pereira, J. Michael; Janosik, Lesley A.; Bhatt, Ramakrishna T.

    2003-01-01

    Foreign object damage (FOD) behavior of two commercial gas-turbine grade silicon nitrides, AS800 and SN282, was determined at ambient temperature through post-impact strength testing for thin disks impacted by steel-ball projectiles with a diameter of 1.59 mm in a velocity range from 115 to 440 m/s. AS800 silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness (K(sub IC)). The critical impact velocity in which the corresponding post-impact strength yielded the lowest value was V(sub c) approx. 440 and 300 m/s for AS800 and SN282, respectively. A unique lower-strength regime was typified for both silicon nitrides depending on impact velocity, attributed to significant radial cracking. The damages generated by projectile impact were typically in the forms of ring, radial, and cone cracks with their severity and combination being dependent on impact velocity. Unlike thick (3 mm) flexure bar specimens used in the previous studies, thin (2 mm) disk target specimens exhibited a unique backside radial cracking occurring on the reverse side just beneath the impact sites at and above impact velocity of 160 and 220 m/s for SN282 and AS800, respectively.

  10. Mechanisms of Low-Temperature Nitridation Technology on a TaN Thin Film Resistor for Temperature Sensor Applications

    NASA Astrophysics Data System (ADS)

    Chen, Huey-Ru; Chen, Ying-Chung; Chang, Ting-Chang; Chang, Kuan-Chang; Tsai, Tsung-Ming; Chu, Tian-Jian; Shih, Chih-Cheng; Chuang, Nai-Chuan; Wang, Kao-Yuan

    2016-06-01

    In this letter, we propose a novel low-temperature nitridation technology on a tantalum nitride (TaN) thin film resistor (TFR) through supercritical carbon dioxide (SCCO2) treatment for temperature sensor applications. We also found that the sensitivity of temperature of the TaN TFR was improved about 10.2 %, which can be demonstrated from measurement of temperature coefficient of resistance (TCR). In order to understand the mechanism of SCCO2 nitridation on the TaN TFR, the carrier conduction mechanism of the device was analyzed through current fitting. The current conduction mechanism of the TaN TFR changes from hopping to a Schottky emission after the low-temperature SCCO2 nitridation treatment. A model of vacancy passivation in TaN grains with nitrogen and by SCCO2 nitridation treatment is eventually proposed to increase the isolation ability in TaN TFR, which causes the transfer of current conduction mechanisms.

  11. Mechanisms of Low-Temperature Nitridation Technology on a TaN Thin Film Resistor for Temperature Sensor Applications.

    PubMed

    Chen, Huey-Ru; Chen, Ying-Chung; Chang, Ting-Chang; Chang, Kuan-Chang; Tsai, Tsung-Ming; Chu, Tian-Jian; Shih, Chih-Cheng; Chuang, Nai-Chuan; Wang, Kao-Yuan

    2016-12-01

    In this letter, we propose a novel low-temperature nitridation technology on a tantalum nitride (TaN) thin film resistor (TFR) through supercritical carbon dioxide (SCCO2) treatment for temperature sensor applications. We also found that the sensitivity of temperature of the TaN TFR was improved about 10.2 %, which can be demonstrated from measurement of temperature coefficient of resistance (TCR). In order to understand the mechanism of SCCO2 nitridation on the TaN TFR, the carrier conduction mechanism of the device was analyzed through current fitting. The current conduction mechanism of the TaN TFR changes from hopping to a Schottky emission after the low-temperature SCCO2 nitridation treatment. A model of vacancy passivation in TaN grains with nitrogen and by SCCO2 nitridation treatment is eventually proposed to increase the isolation ability in TaN TFR, which causes the transfer of current conduction mechanisms.

  12. Electrical stress in CdS thin film transistors using HfO2 gate dielectric

    NASA Astrophysics Data System (ADS)

    García, R.; Mejia, I.; Molinar-Solis, J. E.; Salas-Villasenor, A. L.; Morales, A.; García, B.; Quevedo-Lopez, M. A.; Alemán, M.

    2013-05-01

    During thin film transistor (TFT) operation, gate dielectric is under a bias stress condition. In this work, bias stress effect for CdS TFT using HfO2 as gate dielectric is analyzed. Threshold voltage, Ion/Ioff ratio, and subthreshold slope were studied in order to understand changes produced at the dielectric semiconductor interface. We observed that threshold voltage shift is related with negative charge trapping in the dielectric/semiconductor interface and for this phenomenon we propose a trapping charge model. Finally, the TFT output characteristic was modeled considering a shift in the threshold voltage for each gate voltage curve.

  13. Adhesion analysis for chromium nitride thin films deposited by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Rusu, F. M.; Merie, V. V.; Pintea, I. M.; Molea, A.

    2016-08-01

    The thin film industry is continuously growing due to the wide range of applications that require the fabrication of advanced components such as sensors, biological implants, micro-electromechanical devices, optical coatings and so on. The selection regarding the deposition materials, as well as the deposition technology influences the properties of the material and determines the suitability of devices for certain real-world applications. This paper is focused on the adhesion force for several chromium nitride thin films obtained by reactive magnetron sputtering. All chromium nitride thin films were deposited on a silicon substrate, the discharge current and the argon flow being kept constant. The main purpose of the paper is to determine the influence of deposition parameters on the adhesion force. Therefore some of the deposition parameters were varied in order to study their effect on the adhesion force. Experimentally, the values of the adhesion force were determined in multiple points for each sample using the spectroscopy in point mode of the atomic force microscope. The obtained values were used to estimate the surface energy of the CrN thin films based on two existing mathematical models for the adhesion force when considering the contact between two bodies.

  14. Impact of annealing temperature on the mechanical and electrical properties of sputtered aluminum nitride thin films

    NASA Astrophysics Data System (ADS)

    Gillinger, M.; Schneider, M.; Bittner, A.; Nicolay, P.; Schmid, U.

    2015-02-01

    Aluminium nitride (AlN) is a promising material for challenging sensor applications such as process monitoring in harsh environments (e.g., turbine exhaust), due to its piezoelectric properties, its high temperature stability and good thermal match to silicon. Basically, the operational temperature of piezoelectric materials is limited by the increase of the leakage current as well as by enhanced diffusion effects in the material at elevated temperatures. This work focuses on the characterization of aluminum nitride thin films after post deposition annealings up to temperatures of 1000 °C in harsh environments. For this purpose, thin film samples were temperature loaded for 2 h in pure nitrogen and oxygen gas atmospheres and characterized with respect to the film stress and the leakage current behaviour. The X-ray diffraction results show that AlN thin films are chemically stable in oxygen atmospheres for 2 h at annealing temperatures of up to 900 °C. At 1000 °C, a 100 nm thick AlN layer oxidizes completely. For nitrogen, the layer is stable up to 1000 °C. The activation energy of the samples was determined from leakage current measurements at different sample temperatures, in the range between 25 and 300 °C. Up to an annealing temperature of 700 °C, the leakage current in the thin film is dominated by Poole-Frenkel behavior, while at higher annealing temperatures, a mixture of different leakage current mechanisms is observed.

  15. Nitride passivation of the interface between high-k dielectrics and SiGe

    SciTech Connect

    Sardashti, Kasra; Hu, Kai-Ting; Tang, Kechao; McIntyre, Paul; Madisetti, Shailesh; Oktyabrsky, Serge; Siddiqui, Shariq; Sahu, Bhagawan; Yoshida, Naomi; Kachian, Jessica; Dong, Lin; Fruhberger, Bernd; Kummel, Andrew C.

    2016-01-04

    In-situ direct ammonia (NH{sub 3}) plasma nitridation has been used to passivate the Al{sub 2}O{sub 3}/SiGe interfaces with Si nitride and oxynitride. X-ray photoelectron spectroscopy of the buried Al{sub 2}O{sub 3}/SiGe interface shows that NH{sub 3} plasma pre-treatment should be performed at high temperatures (300 °C) to fully prevent Ge nitride and oxynitride formation at the interface and Ge out-diffusion into the oxide. C-V and I-V spectroscopy results show a lower density of interface traps and smaller gate leakage for samples with plasma nitridation at 300 °C.

  16. Largely enhanced dielectric properties of carbon nanotubes/polyvinylidene fluoride binary nanocomposites by loading a few boron nitride nanosheets

    SciTech Connect

    Yang, Minhao; Zhao, Hang; He, Delong; Bai, Jinbo

    2016-08-15

    The ternary nanocomposites of boron nitride nanosheets (BNNSs)/carbon nanotubes (CNTs)/polyvinylidene fluoride (PVDF) are fabricated via a combination of solution casting and extrusion-injection processes. The effects of BNNSs on the electrical conductivity, dielectric behavior, and microstructure changes of CNTs/PVDF binary nanocomposites are systematically investigated. A low percolation value (f{sub c}) for the CNTs/PVDF binary system is obtained due to the integration of solution and melting blending procedures. Two kinds of CNTs/PVDF binary systems with various CNTs contents (f{sub CNTs}) as the matrix are discussed. The results reveal that compared with CNTs/PVDF binary systems at the same f{sub CNTs}, the ternary BNNSs/CNTs/PVDF nanocomposites exhibit largely enhanced dielectric properties due to the improvement of the CNTs dispersion state and the conductive network. The dielectric constant of CNTs/PVDF binary nanocomposite with 6 vol. % CNTs (f{sub CNTs} < f{sub c}) shows a 79.59% enhancement from 49 to 88 after the incorporation of 3 vol. % BNNSs. For the other CNTs/PVDF system with 8 vol. % CNTs (f{sub CNTs} > f{sub c}), it displays a 43.32% improvement from 1325 to 1899 after the addition of 3 vol. % BNNSs. The presence of BNNSs facilitates the formation of the denser conductive network. Meanwhile, the ternary BNNSs/CNTs/PVDF systems exhibit a low dielectric loss. The adjustable dielectric properties could be obtained by employing the ternary systems due to the microstructure changes of nanocomposites.

  17. Submillimeter and Far-Infrared Dielectric Properties of Thin Films

    NASA Technical Reports Server (NTRS)

    Cataldo, Giuseppe; Wollack, Edward J.

    2016-01-01

    The complex dielectric function enables the study of a material's refractive and absorptive properties and provides information on a material's potential for practical application. Commonly employed line shape profile functions from the literature are briefly surveyed and their suitability for representation of dielectric material properties are discussed. An analysis approach to derive a material's complex dielectric function from observed transmittance spectra in the far-infrared and submillimeter regimes is presented. The underlying model employed satisfies the requirements set by the Kramers-Kronig relations. The dielectric function parameters derived from this approach typically reproduce the observed transmittance spectra with an accuracy of less than 4%.

  18. Submillimeter and Far-Infrared Dielectric Properties of Thin Films

    NASA Technical Reports Server (NTRS)

    Cataldo, Giuseppe; Wollack, Edward J.

    2016-01-01

    The complex dielectric function enables the study of a material's refractive and absorptive properties and provides information on a material's potential for practical application. Commonly employed line shape profile functions from the literature are briefly surveyed and their suitability for representation of dielectric material properties are discussed. An analysis approach to derive a material's complex dielectric function from observed transmittance spectra in the far-infrared and submillimeter regimes is presented. The underlying model employed satisfies the requirements set by the Kramers-Kronig relations. The dielectric function parameters derived from this approach typically reproduce the observed transmittance spectra with an accuracy of less than 4%.

  19. Seed-layer mediated orientation evolution in dielectric Bi-Zn-Ti-Nb-O thin films

    NASA Astrophysics Data System (ADS)

    Kim, Jin Young; Noh, Jun Hong; Lee, Sangwook; Yoon, Sung-Hun; Cho, Chin Moo; Hong, Kug Sun; Jung, Hyun Suk; Lee, Jung-Kun

    2007-12-01

    Highly (hhh)-oriented pyrochlore Bi-Zn-Ti-Nb-O (BZTN) thin films were fabricated via metal-organic decomposition using orientation template layers. The preferred orientation was ascribed to the interfacial layer, the lattice parameter of which is similar to BZTN. High-resolution transmission electron microscopy supported that the interfacial layer consists of Bi and Pt. The (hhh)-oriented thin films exhibited a highly insulating nature enabling feasible applications in electronic devices, particularly voltage tunable application. The BZTN thin films did not show any apparent dielectric anisotropy and the slightly enhanced dielectric properties were discussed in connection to the internal stress and the grain boundary effect.

  20. Atomic Layer Deposition of Silicon Nitride Thin Films: A Review of Recent Progress, Challenges, and Outlooks

    PubMed Central

    Meng, Xin; Byun, Young-Chul; Kim, Harrison S.; Lee, Joy S.; Lucero, Antonio T.; Cheng, Lanxia; Kim, Jiyoung

    2016-01-01

    With the continued miniaturization of devices in the semiconductor industry, atomic layer deposition (ALD) of silicon nitride thin films (SiNx) has attracted great interest due to the inherent benefits of this process compared to other silicon nitride thin film deposition techniques. These benefits include not only high conformality and atomic-scale thickness control, but also low deposition temperatures. Over the past 20 years, recognition of the remarkable features of SiNx ALD, reinforced by experimental and theoretical investigations of the underlying surface reaction mechanism, has contributed to the development and widespread use of ALD SiNx thin films in both laboratory studies and industrial applications. Such recognition has spurred ever-increasing opportunities for the applications of the SiNx ALD technique in various arenas. Nevertheless, this technique still faces a number of challenges, which should be addressed through a collaborative effort between academia and industry. It is expected that the SiNx ALD will be further perceived as an indispensable technique for scaling next-generation ultra-large-scale integration (ULSI) technology. In this review, the authors examine the current research progress, challenges and future prospects of the SiNx ALD technique. PMID:28774125

  1. Phase formation, thermal stability and magnetic moment of cobalt nitride thin films

    SciTech Connect

    Gupta, Rachana; Pandey, Nidhi; Tayal, Akhil; Gupta, Mukul E-mail: dr.mukul.gupta@gmail.com

    2015-09-15

    Cobalt nitride (Co-N) thin films prepared using a reactive magnetron sputtering process are studied in this work. During the thin film deposition process, the relative nitrogen gas flow (R{sub N{sub 2}}) was varied. As R{sub N{sub 2}} increases, Co(N), Co{sub 4}N, Co{sub 3}N and CoN phases are formed. An incremental increase in R{sub N{sub 2}}, after emergence of Co{sub 4}N phase at R{sub N{sub 2}} = 10%, results in a linear increase of the lattice constant (a) of Co{sub 4}N. For R{sub N{sub 2}} = 30%, a maximizes and becomes comparable to its theoretical value. An expansion in a of Co{sub 4}N, results in an enhancement of the magnetic moment, to the extent that it becomes even larger than pure Co. Such larger than pure metal magnetic moment for tetra-metal nitrides (M{sub 4}N) have been theoretically predicted. Incorporation of N atoms in M{sub 4}N configuration results in an expansion of a (relative to pure metal) and enhances the itinerary of conduction band electrons leading to larger than pure metal magnetic moment for M{sub 4}N compounds. Though a higher (than pure Fe) magnetic moment for Fe{sub 4}N thin films has been evidenced experimentally, higher (than pure Co) magnetic moment is evidenced in this work.

  2. Sigma-pi molecular dielectric multilayers for low-voltage organic thin-film transistors.

    PubMed

    Yoon, Myung-Han; Facchetti, Antonio; Marks, Tobin J

    2005-03-29

    Very thin (2.3-5.5 nm) self-assembled organic dielectric multilayers have been integrated into organic thin-film transistor structures to achieve sub-1-V operating characteristics. These new dielectrics are fabricated by means of layer-by-layer solution phase deposition of molecular silicon precursors, resulting in smooth, nanostructurally well defined, strongly adherent, thermally stable, virtually pinhole-free, organosiloxane thin films having exceptionally large electrical capacitances (up to approximately 2,500 nF.cm(-2)), excellent insulating properties (leakage current densities as low as 10(-9) A.cm(-2)), and single-layer dielectric constant (k)of approximately 16. These 3D self-assembled multilayers enable organic thin-film transistor function at very low source-drain, gate, and threshold voltages (<1 V) and are compatible with a broad variety of vapor- or solution-deposited p- and n-channel organic semiconductors.

  3. Lorentz factor determination for local electric fields in semiconductor devices utilizing hyper-thin dielectrics

    SciTech Connect

    McPherson, J. W.

    2015-11-28

    The local electric field (the field that distorts, polarizes, and weakens polar molecular bonds in dielectrics) has been investigated for hyper-thin dielectrics. Hyper-thin dielectrics are currently required for advanced semiconductor devices. In the work presented, it is shown that the common practice of using a Lorentz factor of L = 1/3, to describe the local electric field in a dielectric layer, remains valid for hyper-thin dielectrics. However, at the very edge of device structures, a rise in the macroscopic/Maxwell electric field E{sub diel} occurs and this causes a sharp rise in the effective Lorentz factor L{sub eff}. At capacitor and transistor edges, L{sub eff} is found to increase to a value 2/3 < L{sub eff} < 1. The increase in L{sub eff} results in a local electric field, at device edge, that is 50%–100% greater than in the bulk of the dielectric. This increase in local electric field serves to weaken polar bonds thus making them more susceptible to breakage by standard Boltzmann and/or current-driven processes. This has important time-dependent dielectric breakdown (TDDB) implications for all electronic devices utilizing polar materials, including GaN devices that suffer from device-edge TDDB.

  4. Fullerenelike arrangements in carbon nitride thin films grown by direct ion beam sputtering

    SciTech Connect

    Gago, R.; Abrasonis, G.; Muecklich, A.; Moeller, W.; Czigany, Zs.; Radnoczi, G.

    2005-08-15

    Carbon nitride (CN{sub x}) thin films were grown by direct N{sub 2}/Ar ion beam sputtering of a graphite target at moderate substrate temperatures (300-750 K). The resulting microstructure of the films was studied by high-resolution transmission electron microscopy. The images showed the presence of curved basal planes in fullerenelike arrangements. The achievement and evolution of these microstructural features are discussed in terms of nitrogen incorporation, film-forming flux, and ion bombardment effects, thus adding to the understanding of the formation mechanisms of curved graphitic structures in CN{sub x} materials.

  5. Variation of the intrinsic stress gradient in thin aluminum nitride films

    NASA Astrophysics Data System (ADS)

    Mehner, H.; Leopold, S.; Hoffmann, M.

    2013-09-01

    The intrinsic stress gradient variation of thin aluminum nitride (AlN) films is the central objective in this paper. For the first time, significant influence parameters on the stress gradient are identified and varied during the deposition process. The process power induced in the plasma and the gas flow ratio of the sputter gases argon and nitrogen are the two major parameters for controlling the stress gradient of deposited AlN films. The controlled avoidance as well as the controlled generation of positive and negative gradients is shown. The stress gradient was investigated by analysis of released one-side clamped cantilever test structures.

  6. Pulsed photothermal reflectance measurement of the thermal conductivity of sputtered aluminum nitride thin films

    SciTech Connect

    Zhao Yimin; Zhu Chunlin; Wang Sigen; Tian, J.Z.; Yang, D.J.; Chen, C.K.; Cheng Hao; Hing, Peter

    2004-10-15

    We report on measurements of the thermal conductivity of reactively sputtered aluminum nitride (AlN) thin films with different thickness, ranging from 100 nm to 1 {mu}m, on silicon substrates. The measurements were made at room temperature using the pulsed photothermal reflectance technique. The thermal conductivities of the sample are found to be significantly lower than the single-crystal bulk AlN and increase with an increasing thickness. The thermal resistance at the interface between the AlN film and the silicon substrate is found to be about 7-8x10{sup -8} m{sup 2} K/W.

  7. High-K Lanthanum Zirconium Oxide Thin Film Dielectrics from Aqueous Solution Precursors.

    PubMed

    Woods, Keenan Navarre; Chiang, Tsung-Han; Plassmeyer, Paul N; Kast, Matthew G; Lygo, Alexander C; Grealish, Aidan K; Boettcher, Shannon W; Page, Catherine J

    2017-03-06

    Metal oxide thin films are critical in modern electronic applications. In particular, high-κ dielectrics are of interest for reducing power consumption in metal-insulator-semiconductor (MIS) field-effect transistors. Although thin-film materials are typically produced via vacuum-based methods, solution deposition offers a scalable and cost-efficient alternative. We report an all-inorganic aqueous solution route to amorphous lanthanum zirconium oxide (La2Zr2O7, "LZO") dielectric thin films. LZO films were spin-cast from aqueous solutions of metal nitrates and annealed at temperatures between 300 and 600 °C to produce dense, defect-free, and smooth films with sub-nm roughness. Dielectric constants of 12.2 to 16.4 and loss tangents < 0.6% were obtained for MIS devices utilizing LZO as the dielectric layer (1 kHz). Leakage currents < 10-7 A cm-2 at 4 MV cm-1 were measured for samples annealed at 600 °C. The excellent surface morphology, high dielectric constants, and low leakage current densities makes these LZO dielectrics promising candidates for thin-film transistor devices.

  8. Dielectric response of fully and partially depleted ferroelectric thin films and inversion of the thickness effect

    NASA Astrophysics Data System (ADS)

    Misirlioglu, I. B.; Yildiz, M.

    2013-03-01

    We study the effect of full and partial depletion on the dielectric response characteristics of ferroelectric thin films with impurities via a computational approach. Using a thermodynamic approach along with the fundamental equations for semiconductors, we show that films with partial depletion display unique features and an enhanced dielectric response compared with those fully depleted. We find that the capacitance peak at switching can be significantly suppressed in the case of high impurity densities (>1025 m-3) with relatively low ionization energy, of the order of 0.5 eV. For conserved number of species in films, electromigration of ionized impurities at room temperature is negligible and has nearly no effect on the dielectric response. In films with high impurity density, the dielectric response at zero bias is enhanced with respect to charge-free films or those with relatively low impurity density (<1024 m-3). We demonstrate that partially depleted films should be expected to exhibit peculiar capacitance-voltage characteristics at low and high bias and that the thickness effect probed in experiments in ferroelectric thin films could be entirely inverted in thin films with depletion charges where a higher dielectric response can be measured in thicker films. Therefore, depletion charge densities in ferroelectric thin films should be estimated before size-effect-related studies. Finally, we noted that these findings are in good qualitative agreement with dielectric measurements carried out on PbZrxTi1-xO3.

  9. Dielectric and Ferroelectric Properties of Lead Lanthanum Zirconate Titanate Thin Films for Capacitive Energy Storage

    NASA Astrophysics Data System (ADS)

    Tong, Sheng

    As the increasing requirement of alternative energy with less pollution influence and higher energy efficient, new energy source and related storage methods are hot topic nowadays. Capacitors that supply high instant power are one of the keys in this application for both economic and functional design aspects. To lower the cost and increases the volumetric efficiency and reliability, relaxor thin films are considered as one of the candidates of the next generation capacitors. The research mainly focuses on dielectric and ferroelectric properties of lead lanthanum zirconate titanate or Pb1-xLax(ZryTi1-y)O3 (PLZT, x/y/1-y) relaxor thin films deposited on silicon (Si) and nickel (Ni) substrates in a range of thickness with different bottom electrodes, e.g. Platinum (Pt) and LaNiO3 (LNO). The final fabricated PLZT film capacitors will show strong potential for the energy storage application. The method adopted is the acetic acid assisted sol-gel deposition for the PLZT thin films. The wet chemical process is cost-effective and easily to scale up for plant/industrial products. We investigated the different bottom electrode/substrate influence in structure, microstructure, phases/defects, and heat-treatment conditions to achieve the optimized PLZT thin films. Issues of basic physical size effects in the PLZT thin films were also investigated, including thickness effects in the dielectric and ferroelectric properties of the films in a wide range of temperatures, the phase transition of the thin-film relaxors, lanthanum content effect, electrode-dielectric junction, misfit strain effect, etc. Based on the results and analysis, optimum PLZT film capacitors can be determined of proper substrate/electrode/dielectric that achieves the desired dielectric properties required for different applications, especially a more cost-effective method to develop volumetrically efficient capacitors with high charge density, energy density, dielectric breakdown strength, energy storage

  10. Scattering from thin dielectric straps surrounding a perfectly conducting structure

    NASA Technical Reports Server (NTRS)

    Al-Hekail, Zeyad O.; Gupta, Inder J.; Burnside, Walter D.

    1993-01-01

    Dielectric straps can support very heavy targets and have low backscattering levels, especially at low frequencies (below 8 GHz); thus, they can be used effectively to support targets during backscattered field measurements. In this paper, the scattered fields of nonmagnetic dielectric straps surrounding a perfectly conducting structure are presented, and the computed results are compared with experimental data. Empirical formulas for the strap scattered fields are also given. These formulas are good for general convex structures whose radii of curvature are large compared with the wavelength and are expected to give a reasonable estimate of the true backscattered fields from the dielectric straps when used as a target support structure.

  11. Scattering from thin dielectric straps surrounding a perfectly conducting structure

    NASA Technical Reports Server (NTRS)

    Al-Hekail, Zeyad O.; Gupta, Inder J.; Burnside, Walter D.

    1993-01-01

    Dielectric straps can support very heavy targets and have low backscattering levels, especially at low frequencies (below 8 GHz); thus, they can be used effectively to support targets during backscattered field measurements. In this paper, the scattered fields of nonmagnetic dielectric straps surrounding a perfectly conducting structure are presented, and the computed results are compared with experimental data. Empirical formulas for the strap scattered fields are also given. These formulas are good for general convex structures whose radii of curvature are large compared with the wavelength and are expected to give a reasonable estimate of the true backscattered fields from the dielectric straps when used as a target support structure.

  12. Synthesis of atomically thin hexagonal boron nitride films on nickel foils by molecular beam epitaxy

    SciTech Connect

    Nakhaie, S.; Wofford, J. M.; Schumann, T.; Jahn, U.; Ramsteiner, M.; Hanke, M.; Lopes, J. M. J. Riechert, H.

    2015-05-25

    Hexagonal boron nitride (h-BN) is a layered two-dimensional material with properties that make it promising as a dielectric in various applications. We report the growth of h-BN films on Ni foils from elemental B and N using molecular beam epitaxy. The presence of crystalline h-BN over the entire substrate is confirmed by Raman spectroscopy. Atomic force microscopy is used to examine the morphology and continuity of the synthesized films. A scanning electron microscopy study of films obtained using shorter depositions offers insight into the nucleation and growth behavior of h-BN on the Ni substrate. The morphology of h-BN was found to evolve from dendritic, star-shaped islands to larger, smooth triangular ones with increasing growth temperature.

  13. Microstructure and dielectric properties of pyrochlore Bi2Ti2O7 thin films

    NASA Astrophysics Data System (ADS)

    Cagnon, Joël; Boesch, Damien S.; Finstrom, Nicholas H.; Nergiz, Saide Z.; Keane, Sean P.; Stemmer, Susanne

    2007-08-01

    Bi2Ti2O7 thin films were grown by radio-frequency magnetron sputtering on bare and Pt-coated sapphire substrates at low substrate temperatures (˜200 °C). Postdeposition anneals were carried out at different temperatures to crystallize the films. Nearly phase-pure Bi2Ti2O7 thin films with the cubic pyrochlore structure were obtained at annealing temperatures up to 800 °C. Impurity phases, in particular Bi4Ti3O12, formed at higher temperatures. At 1 MHz, the dielectric constants were about 140-150 with a very small tunability and the dielectric loss was about 4×10-3. The dielectric loss increased with frequency. The dielectric properties of Bi2Ti2O7 films are compared to those of pyrochlore bismuth zinc niobate films.

  14. The Behavior of Thin Dielectrics Under Electron Irradiation

    DTIC Science & Technology

    1980-03-01

    occurred if a dielectric sheet was pre- sent in the chamber under vacuum . (The original experiments will be discussed in detail shortly.) This...breakdown through the dielectric, surface flashover , and ion production. However, the responsi- ble mechanism was not identified. The behavior of...one of the principal surface materials used in satellites. As such, their behavior is of concern in SGEMP (system- generated electromagnetic pulse

  15. Electric breakdown of dielectric thin films for high-voltage display applications

    NASA Astrophysics Data System (ADS)

    Mozolevskis, Gatis; Nitiss, Edgars; Medvids, Arturs

    2016-10-01

    Smectic A liquid crystal is one of the most promising material for smart glass application due to infinite bistability and low haze at clear state. Voltage is needed to switch from scattering to transparent and it is likely for dielectric breakdown to occur. In order to reduce the probability of dielectric breakdown to occur, a dielectric insulating coating is usually employed. In this work we have compared electrical and optical properties of SiO2 thin films with thickness up to 500 nm coated by flexographic printing and reactive magnetron sputtering. IV characteristics and dielectric breakdown values show sputtered coatings to have higher dielectric strength. For sputtered coatings with thickness >240 nm also self-healing effect can be observed.

  16. Reactive DC magnetron sputtered zirconium nitride (ZrN) thin film and its characterization

    NASA Astrophysics Data System (ADS)

    Subramanian, B.; Ashok, K.; Sanjeeviraja, C.; Kuppusami, P.; Jayachandran, M.

    2008-05-01

    Zirconium nitride (ZrN) thin films were prepared by using reactive direct current (DC) magnetron sputtering onto different substrates. A good polycrystalline nature with face centered cubic structure was observed from X-ray Diffraction for ZrN thin films. The observed 'd' values from the X-ray Diffraction pattern were found to be in good agreement with the standard 'd' values (JCPDS-89-5269). An emission peak is observed at 587nm from Photoluminescence studies for the excitation at 430nm. The resistivity value (ρ) of 2.1798 (μΩ cm) was observed. ZrN has high wear resistance and low coefficient of friction. A less negative value of Ecorr and lower value of Icorr observed for ZrN / Mild Steel (MS) clearly confirm the better corrosion resistance than the bare substrate. Also the higher Rct value and lower Cdl value was observed for ZrN / MS from Nyquist - plot.

  17. Effects of deposition temperature on the mechanical and physical properties of silicon nitride thin films

    NASA Astrophysics Data System (ADS)

    Walmsley, B. A.; Liu, Y.; Hu, X. Z.; Bush, M. B.; Winchester, K. J.; Martyniuk, M.; Dell, J. M.; Faraone, L.

    2005-08-01

    This study investigates the mechanical and physical properties of low-temperature plasma-enhanced chemical-vapor-deposited silicon nitride thin films, with particular respect to the effect of deposition temperature. The mechanical properties of the films were evaluated by both nanoindentation and microcantilever beam-bending techniques. The cantilever beam specimens were fabricated from silicon nitride thin films deposited on (100) silicon wafer by bulk micromachining. The density of the films was determined from quartz crystal microbalance measurements, as well as from the resonant modes of the cantilever beams, which were mechanically excited using an atomic force microscope. It was found that both the Young's modulus and density of the films were significantly reduced with decreasing deposition temperature. The decrease in Young's modulus is attributed to the decreasing material density. The decrease in density with decreasing deposition temperature is believed to be due to the slower diffusion rates of the deposited species, which retarded the densification of the film during the deposition process.

  18. Hexagonal boron nitride thin film thermal neutron detectors with high energy resolution of the reaction products

    NASA Astrophysics Data System (ADS)

    Doan, T. C.; Majety, S.; Grenadier, S.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2015-05-01

    Hexagonal boron nitride (h-BN) is highly promising for solid-state thermal neutron detector applications due to its many outstanding physical properties, especially its very large thermal neutron capture cross-section (~3840 barns for 10B), which is several orders of magnitude larger than those of most other isotopes. The focus of the present work is to carry out studies on h-BN thin film and detector properties to lay the foundation for the development of a direct-conversion solid-state thermal neutron detector with high sensitivity. The measured carrier mobility-lifetime (μτ) product of h-BN thin films grown on sapphire substrates is 2.83×10-7 cm2/V for electrons and holes, which is comparable to the value of about 10-7 cm2/V for GaN thin films grown on sapphire. Detectors based on h-BN thin films were fabricated and the nuclear reaction product pulse height spectra were measured. Under a bias of 20 V, very narrow individual peaks corresponding to the reaction product energies of α and Li particles as well as the sum peaks have been clearly resolved in the pulse height spectrum for the first time by a B-based direct-conversion semiconductor neutron detector. Our results indicate that h-BN thin film detectors possess unique advantages including small size, low weight, portability, low voltage operation and high energy resolution of specific reaction products.

  19. Exciton-dominated dielectric function of atomically thin MoS2 films

    SciTech Connect

    Yu, Yiling; Yu, Yifei; Cai, Yongqing; Li, Wei; Gurarslan, Alper; Peelaers, Hartwin; Aspnes, David E.; Van de Walle, Chris G.; Nguyen, Nhan V.; Zhang, Yong -Wei; Cao, Linyou

    2015-11-24

    We systematically measure the dielectric function of atomically thin MoS2 films with different layer numbers and demonstrate that excitonic effects play a dominant role in the dielectric function when the films are less than 5–7 layers thick. The dielectric function shows an anomalous dependence on the layer number. It decreases with the layer number increasing when the films are less than 5–7 layers thick but turns to increase with the layer number for thicker films. We show that this is because the excitonic effect is very strong in the thin MoS2 films and its contribution to the dielectric function may dominate over the contribution of the band structure. We also extract the value of layer-dependent exciton binding energy and Bohr radius in the films by fitting the experimental results with an intuitive model. The dominance of excitonic effects is in stark contrast with what reported at conventional materials whose dielectric functions are usually dictated by band structures. Lastly, the knowledge of the dielectric function may enable capabilities to engineer the light-matter interactions of atomically thin MoS2 films for the development of novel photonic devices, such as metamaterials, waveguides, light absorbers, and light emitters.

  20. Exciton-dominated dielectric function of atomically thin MoS2 films

    DOE PAGES

    Yu, Yiling; Yu, Yifei; Cai, Yongqing; ...

    2015-11-24

    We systematically measure the dielectric function of atomically thin MoS2 films with different layer numbers and demonstrate that excitonic effects play a dominant role in the dielectric function when the films are less than 5–7 layers thick. The dielectric function shows an anomalous dependence on the layer number. It decreases with the layer number increasing when the films are less than 5–7 layers thick but turns to increase with the layer number for thicker films. We show that this is because the excitonic effect is very strong in the thin MoS2 films and its contribution to the dielectric function maymore » dominate over the contribution of the band structure. We also extract the value of layer-dependent exciton binding energy and Bohr radius in the films by fitting the experimental results with an intuitive model. The dominance of excitonic effects is in stark contrast with what reported at conventional materials whose dielectric functions are usually dictated by band structures. Lastly, the knowledge of the dielectric function may enable capabilities to engineer the light-matter interactions of atomically thin MoS2 films for the development of novel photonic devices, such as metamaterials, waveguides, light absorbers, and light emitters.« less

  1. Exciton-dominated Dielectric Function of Atomically Thin MoS2 Films

    NASA Astrophysics Data System (ADS)

    Yu, Yiling; Yu, Yifei; Cai, Yongqing; Li, Wei; Gurarslan, Alper; Peelaers, Hartwin; Aspnes, David E.; van de Walle, Chris G.; Nguyen, Nhan V.; Zhang, Yong-Wei; Cao, Linyou

    2015-11-01

    We systematically measure the dielectric function of atomically thin MoS2 films with different layer numbers and demonstrate that excitonic effects play a dominant role in the dielectric function when the films are less than 5-7 layers thick. The dielectric function shows an anomalous dependence on the layer number. It decreases with the layer number increasing when the films are less than 5-7 layers thick but turns to increase with the layer number for thicker films. We show that this is because the excitonic effect is very strong in the thin MoS2 films and its contribution to the dielectric function may dominate over the contribution of the band structure. We also extract the value of layer-dependent exciton binding energy and Bohr radius in the films by fitting the experimental results with an intuitive model. The dominance of excitonic effects is in stark contrast with what reported at conventional materials whose dielectric functions are usually dictated by band structures. The knowledge of the dielectric function may enable capabilities to engineer the light-matter interactions of atomically thin MoS2 films for the development of novel photonic devices, such as metamaterials, waveguides, light absorbers, and light emitters.

  2. Impact of annealing temperature on the mechanical and electrical properties of sputtered aluminum nitride thin films

    SciTech Connect

    Gillinger, M.; Schneider, M.; Bittner, A.; Schmid, U.; Nicolay, P.

    2015-02-14

    Aluminium nitride (AlN) is a promising material for challenging sensor applications such as process monitoring in harsh environments (e.g., turbine exhaust), due to its piezoelectric properties, its high temperature stability and good thermal match to silicon. Basically, the operational temperature of piezoelectric materials is limited by the increase of the leakage current as well as by enhanced diffusion effects in the material at elevated temperatures. This work focuses on the characterization of aluminum nitride thin films after post deposition annealings up to temperatures of 1000 °C in harsh environments. For this purpose, thin film samples were temperature loaded for 2 h in pure nitrogen and oxygen gas atmospheres and characterized with respect to the film stress and the leakage current behaviour. The X-ray diffraction results show that AlN thin films are chemically stable in oxygen atmospheres for 2 h at annealing temperatures of up to 900 °C. At 1000 °C, a 100 nm thick AlN layer oxidizes completely. For nitrogen, the layer is stable up to 1000 °C. The activation energy of the samples was determined from leakage current measurements at different sample temperatures, in the range between 25 and 300 °C. Up to an annealing temperature of 700 °C, the leakage current in the thin film is dominated by Poole-Frenkel behavior, while at higher annealing temperatures, a mixture of different leakage current mechanisms is observed.

  3. Total absorption in ultra-thin lossy layer on transparent substrate using dielectric resonance structure

    NASA Astrophysics Data System (ADS)

    Matsui, T.; Iizuka, H.

    2017-03-01

    A resonant sub-wavelength structure made of a high-refractive-index dielectric material exhibits a resonator-like response and provides unity reflection. We show that near-unity absorption is obtained by using a sub-wavelength resonant structure, which consists of periodic high-refractive-index nano-blocks, when an ultra-thin absorption layer is attached to a transparent dielectric substrate. The resonant structure does not necessarily touch the absorption layer and, therefore, a coating film can be inserted between the absorption layer and the periodic structure. Our results significantly extend application scenarios of detectors and optoelectronic devices that can be implemented on transparent dielectric substrates.

  4. Electrical conduction and dielectric relaxation properties of AlN thin films grown by hollow-cathode plasma-assisted atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Altuntas, Halit; Bayrak, Turkan; Kizir, Seda; Haider, Ali; Biyikli, Necmi

    2016-07-01

    In this study, aluminum nitride (AlN) thin films were deposited at 200 °C, on p-type silicon substrates utilizing a capacitively coupled hollow-cathode plasma source integrated atomic layer deposition (ALD) reactor. The structural properties of AlN were characterized by grazing incidence x-ray diffraction, by which we confirmed the hexagonal wurtzite single-phase crystalline structure. The films exhibited an optical band edge around ˜5.7 eV. The refractive index and extinction coefficient of the AlN films were measured via a spectroscopic ellipsometer. In addition, to investigate the electrical conduction mechanisms and dielectric properties, Al/AlN/p-Si metal-insulator-semiconductor capacitor structures were fabricated, and current density-voltage and frequency dependent (7 kHz-5 MHz) dielectric constant measurements (within the strong accumulation region) were performed. A peak of dielectric loss was observed at a frequency of 3 MHz and the Cole-Davidson empirical formula was used to determine the relaxation time. It was concluded that the native point defects such as nitrogen vacancies and DX centers formed with the involvement of Si atoms into the AlN layers might have influenced the electrical conduction and dielectric relaxation properties of the plasma-assisted ALD grown AlN films.

  5. The growth, dielectric and lattice dynamical properties of strontium titanate and barium strontium titanate thin films

    NASA Astrophysics Data System (ADS)

    Clark, Anna Maria

    Ferroelectric materials have become increasingly important in microelectronic applications, such as dynamic random access memory, ferroelectric random access memory, and tunable microwave devices. This requires the growth of high quality ferroelectric thin films, as well as fundamental understanding of their structural and dielectric properties, which often differ from those in respective bulk materials. The present thesis focuses on the investigation of the perovskite type ferroelectrics strontium titanate, SrTiO3 (STO) and barium strontium titanate, BaxSr1- xTiO3 (BST). Pulsed laser deposition is considered as one of the most advantageous methods for the growth of thin ferroelectric films, and was used to produce STO films of high quality for this thesis. Influence of several deposition conditions, such as type of substrate, deposition temperature and chemical treatments of the substrate were investigated to determine their effects on the structural and electrical properties of STO films and to optimize deposition process and improve film quality. The surface morphology of films was studied by atomic force microscopy. X-ray diffraction was used to study their crystalline structure. It is shown in this thesis that the substrate has a pronounced effect on the crystalline quality and surface morphology of the film. Temperature and electric field dependencies of dielectric constant and loss tangent in STO films were studied by low frequency electric measurements. Improvements of the measured dielectric properties are correlated to the film deposition parameters. Raman spectroscopy was used to characterize the film structure and study the lattice dynamics of the thin films. Raman spectra show the STO films grown on STO single crystal substrates have a structural phase transition near the phase transition temperature in bulk STO. The soft TO1 phonon, related to the ferroelectric state, was observed in the STO thin films. Raman results of the soft-mode study show a

  6. Functional Design of Dielectric-Metal-Dielectric-Based Thin-Film Encapsulation with Heat Transfer and Flexibility for Flexible Displays.

    PubMed

    Kwon, Jeong Hyun; Choi, Seungyeop; Jeon, Yongmin; Kim, Hyuncheol; Chang, Ki Soo; Choi, Kyung Cheol

    2017-08-16

    In this study, a new and efficient dielectric-metal-dielectric-based thin-film encapsulation (DMD-TFE) with an inserted Ag thin film is proposed to guarantee the reliability of flexible displays by improving the barrier properties, mechanical flexibility, and heat dissipation, which are considered to be essential requirements for organic light-emitting diode (OLED) encapsulation. The DMD-TFE, which is composed of Al2O3, Ag, and a silica nanoparticle-embedded sol-gel hybrid nanocomposite, shows a water vapor transmission rate of 8.70 × 10(-6) g/m(2)/day and good mechanical reliability at a bending radius of 30 mm, corresponding to 0.41% strain for 1000 bending cycles. The electrical performance of a thin-film encapsulated phosphorescent organic light-emitting diode (PHOLED) was identical to that of a glass-lid encapsulated PHOLED. The operational lifetimes of the thin-film encapsulated and glass-lid encapsulated PHOLEDs are 832 and 754 h, respectively. After 80 days, the thin-film encapsulated PHOLED did not show performance degradation or dark spots on the cell image in a shelf-lifetime test. Finally, the difference in lifetime of the OLED devices in relation to the presence and thickness of a Ag film was analyzed by applying various TFE structures to fluorescent organic light-emitting diodes (FOLEDs) that could generate high amounts of heat. To demonstrate the difference in heat dissipation effect among the TFE structures, the saturated temperatures of the encapsulated FOLEDs were measured from the back side surface of the glass substrate, and were found to be 67.78, 65.12, 60.44, and 39.67 °C after all encapsulated FOLEDs were operated at an initial luminance of 10 000 cd/m(2) for sufficient heat generation. Furthermore, the operational lifetime tests of the encapsulated FOLED devices showed results that were consistent with the measurements of real-time temperature profiles taken with an infrared camera. A multifunctional hybrid thin-film encapsulation based

  7. Generalized Abelnus relations for an anisotropic thin film of an arbitrary dielectric tensor.

    PubMed

    Cojocaru, E

    1997-05-01

    The extended Jones matrix method is applied to one dielectrically anisotropic, homogeneous thin film at oblique incidence. Standard boundary conditions are imposed on resultant electric- and magnetic-field vectors at interfaces. Thus simple matricial relations are obtained for transmitted and reflected electric-field amplitudes at the two interfaces. In the limits of isotropy, they reduce to four well-known Abelès relations, and thus they may be considered as generalized Abelès relations for dielectrically anisotropic thin films. These matricial relations include multiple reflections while dealing with total fields. Thus they provide new insights into the 2 x 2 extended Jones matrix formalism.

  8. Piezoelectric actuated micro-resonators based on the growth of diamond on aluminum nitride thin films.

    PubMed

    Hees, J; Heidrich, N; Pletschen, W; Sah, R E; Wolfer, M; Williams, O A; Lebedev, V; Nebel, C E; Ambacher, O

    2013-01-18

    Unimorph heterostructures based on piezoelectric aluminum nitride (AlN) and diamond thin films are highly desirable for applications in micro- and nanoelectromechanical systems. In this paper, we present a new approach to combine thin conductive boron-doped as well as insulating nanocrystalline diamond (NCD) with sputtered AlN films without the need for any buffer layers between AlN and NCD or polishing steps. The zeta potentials of differently treated nanodiamond (ND) particles in aqueous colloids are adjusted to the zeta potential of AlN in water. Thereby, the nucleation density for the initial growth of diamond on AlN can be varied from very low (10(8) cm(-2)), in the case of hydrogen-treated ND seeding particles, to very high values of 10(11) cm(-2) for oxidized ND particles. Our approach yielding high nucleation densities allows the growth of very thin NCD films on AlN with thicknesses as low as 40 nm for applications such as microelectromechanical beam resonators. Fabricated piezo-actuated micro-resonators exhibit enhanced mechanical properties due to the incorporation of boron-doped NCD films. Highly boron-doped NCD thin films which replace the metal top electrode offer Young's moduli of more than 1000 GPa.

  9. Solution-Processed Rare-Earth Oxide Thin Films for Alternative Gate Dielectric Application.

    PubMed

    Zhuang, Jiaqing; Sun, Qi-Jun; Zhou, Ye; Han, Su-Ting; Zhou, Li; Yan, Yan; Peng, Haiyan; Venkatesh, Shishir; Wu, Wei; Li, Robert K Y; Roy, V A L

    2016-11-16

    Previous investigations on rare-earth oxides (REOs) reveal their high possibility as dielectric films in electronic devices, while complicated physical methods impede their developments and applications. Herein, we report a facile route to fabricate 16 REOs thin insulating films through a general solution process and their applications in low-voltage thin-film transistors as dielectrics. The formation and properties of REOs thin films are analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD), spectroscopic ellipsometry, water contact angle measurement, X-ray photoemission spectroscopy (XPS), and electrical characterizations, respectively. Ultrasmooth, amorphous, and hydrophilic REO films with thickness around 10 nm have been obtained through a combined spin-coating and postannealing method. The compositional analysis results reveal the formation of RE hydrocarbonates on the surface and silicates at the interface of REOs films annealed on Si substrate. The dielectric properties of REO films are investigated by characterizing capacitors with a Si/Ln2O3/Au (Ln = La, Gd, and Er) structure. The observed low leakage current densities and large areal capacitances indicate these REO films can be employed as alternative gate dielectrics in transistors. Thus, we have successfully fabricated a series of low-voltage organic thin-film transistors based on such sol-gel derived REO films to demonstrate their application in electronics. The optimization of REOs dielectrics in transistors through further surface modification has also been studied. The current study provides a simple solution process approach to fabricate varieties of REOs insulating films, and the results reveal their promising applications as alternative gate dielectrics in thin-film transistors.

  10. AlN and Al oxy-nitride gate dielectrics for reliable gate stacks on Ge and InGaAs channels

    NASA Astrophysics Data System (ADS)

    Guo, Y.; Li, H.; Robertson, J.

    2016-05-01

    AlN and Al oxy-nitride dielectric layers are proposed instead of Al2O3 as a component of the gate dielectric stacks on higher mobility channels in metal oxide field effect transistors to improve their positive bias stress instability reliability. It is calculated that the gap states of nitrogen vacancies in AlN lie further away in energy from the semiconductor band gap than those of oxygen vacancies in Al2O3, and thus AlN might be less susceptible to charge trapping and have a better reliability performance. The unfavourable defect energy level distribution in amorphous Al2O3 is attributed to its larger coordination disorder compared to the more symmetrically bonded AlN. Al oxy-nitride is also predicted to have less tendency for charge trapping.

  11. AlN and Al oxy-nitride gate dielectrics for reliable gate stacks on Ge and InGaAs channels

    SciTech Connect

    Guo, Y.; Li, H.; Robertson, J.

    2016-05-28

    AlN and Al oxy-nitride dielectric layers are proposed instead of Al{sub 2}O{sub 3} as a component of the gate dielectric stacks on higher mobility channels in metal oxide field effect transistors to improve their positive bias stress instability reliability. It is calculated that the gap states of nitrogen vacancies in AlN lie further away in energy from the semiconductor band gap than those of oxygen vacancies in Al{sub 2}O{sub 3}, and thus AlN might be less susceptible to charge trapping and have a better reliability performance. The unfavourable defect energy level distribution in amorphous Al{sub 2}O{sub 3} is attributed to its larger coordination disorder compared to the more symmetrically bonded AlN. Al oxy-nitride is also predicted to have less tendency for charge trapping.

  12. Broadband dielectric spectroscopy of BiFeO3 thin film up to Ku band frequency

    NASA Astrophysics Data System (ADS)

    Upadhyay, R. B.; Pandya, N. C.; Joshi, U. S.

    2017-06-01

    BiFeO3 (BFO) thin film nano-structures were grown by pulsed laser deposition (PLD) and their structural and dielectric responses were investigated over a broad frequency band of 10 kHz  <  f  <  15 GHz. An on-chip reflection measurement technique was used, followed by S-parameter based dielectric property extraction for microwave evaluation. The leakage current behaviour was investigated under applied electric field up to 500 kV cm-1. The phase pure polycrystalline film exhibited low leakage current and a very high dielectric constant of 169.785 at 10 MHz and 149 at 15 GHz. The dielectric losses of the film were low. Both dielectric permittivity and loss tangents were found to be nearly frequency non-dispersive over the investigation range and no dielectric relaxation was observed up to 15 GHz. These findings demonstrate that a BFO film with such properties is found to be suitable for tuneable thin film bulk acoustic wave resonators (TFBARs), microwave absorbers and tuneable microwave devices at room temperature.

  13. Dielectric relaxation of barium strontium titanate and application to thin films for DRAM capacitors

    NASA Astrophysics Data System (ADS)

    Baniecki, John David

    This thesis examines the issues associated with incorporating the high dielectric constant material Barium Strontium Titanate (BSTO) in to the storage capacitor of a dynamic random access memory (DRAM). The research is focused on two areas: characterizing and understanding the factors that control charge retention in BSTO thin films and modifying the electrical properties using ion implantation. The dielectric relaxation of BSTO thin films deposited by metal-organic chemical vapor deposition (MOCVD) is investigated in the time and frequency domains. It is shown that the frequency dispersion of the complex capacitance of BSTO thin films can be understood in terms of a power-law frequency dependence from 1mHz to 20GHz. From the correspondence between the time and frequency domain measurements, it is concluded that the power-law relaxation currents extend back to the nano second regime of DRAM operation. The temperature, field, and annealing dependence of the dielectric relaxation currents are also investigated and mechanisms for the observed power law relaxation are explored. An equivalent circuit model of a high dielectric constant thin film capacitor is developed based on the electrical measurements and implemented in PSPICE. Excellent agreement is found between the experimental and simulated electrical characteristics showing the utility of the equivalent circuit model in simulating the electrical properties of high dielectric constant thin films. Using the equivalent circuit model, it is shown that the greatest charge loss due to dielectric relaxation occurs during the first read after a refresh time following a write to the opposite logic state for a capacitor that has been written to the same logic state for a long time (opposite state write charge loss). A theoretical closed form expression that is a function of three material parameters is developed which estimates the opposite state write charge loss due to dielectric relaxation. Using the closed form

  14. Designing hybrid gate dielectric for fully printing high-performance carbon nanotube thin film transistors.

    PubMed

    Li, Qian; Li, Shilong; Yang, Dehua; Su, Wei; Wang, Yanchun; Zhou, Weiya; Liu, Huaping; Xie, Sishen

    2017-08-23

    The electrical characteristics of carbon nanotube (CNT) thin-film transistors (TFTs) strongly depend on the properties of the gate dielectric that is in direct contact with the semiconducting CNT channel materials. Here, we systematically investigated the dielectric effects on the electrical characteristics of fully printed semiconducting CNT-TFTs by introducing the organic dielectrics of poly(methyl methacrylate) (PMMA) and Octadecyltrichlorosilane (OTS) to modify SiO2 dielectric. The results showed that the organic-modified SiO2 dielectric formed a favorable interface for the efficient charge transport in s-SWCNT-TFTs. Compared to single-layer SiO2 dielectric, the use of organic-inorganic hybrid bilayer dielectrics dramatically improved the performances of SWCNT-TFTs such as mobility, threshold voltage, hysteresis and On/Off ratio due to the suppress of charge scattering, gate leakage current and charge trapping. The transport mechanism is related that the dielectric with few charge trapping provided efficient percolation pathways for charge carriers, while reduced the charge scattering. High density of charge traps which could directly act as physical transport barriers and significantly restrict the charge carrier transport and, thus, result in decreased mobile carriers and low device performance. Moreover, the gate leakage phenomenon is caused by conduction through charge traps. So, as a component of TFTs, the gate dielectric is of crucial importance to the manufacture of high quality TFTs from the aspects of affecting the gate leakage current and device operation voltage, as well as the charge carrier transport. Interestingly, the OTS-modified SiO2 allows to directly print horizontally aligned CNT film, and the corresponding devices exhibited a higher mobility than that of the devices with the hybrid PMMA/SiO2 dielectric although the thickness of OTS layer is only ~2.5 nm. Our present result may provide key guidance for the further development of printed

  15. Unintentional carbide formation evidenced during high-vacuum magnetron sputtering of transition metal nitride thin films

    NASA Astrophysics Data System (ADS)

    Greczynski, G.; Mráz, S.; Hultman, L.; Schneider, J. M.

    2016-11-01

    Carbide signatures are ubiquitous in the surface analyses of industrially sputter-deposited transition metal nitride thin films grown with carbon-less source materials in typical high-vacuum systems. We use high-energy-resolution photoelectron spectroscopy to reveal details of carbon temporal chemical state evolution, from carbide formed during film growth to adventitious carbon adsorbed upon contact with air. Using in-situ grown Al capping layers that protect the as-deposited transition metal nitride surfaces from oxidation, it is shown that the carbide forms during film growth rather than as a result of post deposition atmosphere exposure. The XPS signature of carbides is masked by the presence of adventitious carbon contamination, appearing as soon as samples are exposed to atmosphere, and eventually disappears after one week-long storage in lab atmosphere. The concentration of carbon assigned to carbide species varies from 0.28 at% for ZrN sample, to 0.25 and 0.11 at% for TiN and HfN, respectively. These findings are relevant for numerous applications, as unintentionally formed impurity phases may dramatically alter catalytic activity, charge transport and mechanical properties by offsetting the onset of thermally-induced phase transitions. Therefore, the chemical state of C impurities in PVD-grown films should be carefully investigated.

  16. Investigation on the production of copper nitride (copper azide) thin films and their nanostructures

    NASA Astrophysics Data System (ADS)

    Lotfi-Kaljahi, Amir; Savaloni, Hadi

    2013-01-01

    Copper thin films of 80-nm thickness were deposited on glass substrate using electron beam deposition at two different deposition angles of 0° and 40°, and they were post-annealed under flow of nitrogen at different temperatures. The structure of the films was analyzed using X-ray diffraction, atomic force microscope, and scanning electron microscope. Investigation on the copper nitride phase formation showed that this phase was not formed in the samples produced at 0°, while those prepared at oblique angle of 40° clearly showed the formation of copper azide phase. This is related to the porosity of the film structure, hence increased surface area for the reaction of nitrogen with copper atoms. Therefore, this is a simple method for preparation of copper nitride films that are not usually formed due to low reactivity of copper (as transition metal) with nitrogen. The results showed that the crystallite size (coherently diffracting domains), grain size, and surface roughness increase with annealing temperature.

  17. Thermal stability of tungsten sub-nitride thin film prepared by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Zhang, X. X.; Wu, Y. Z.; Mu, B.; Qiao, L.; Li, W. X.; Li, J. J.; Wang, P.

    2017-03-01

    Tungsten sub-nitride thin films deposited on silicon samples by reactive magnetron sputtering were used as a model system to study the phase stability and microstructural evolution during thermal treatments. XRD, SEM&FIB, XPS, RBS and TDS were applied to investigate the stability of tungsten nitride films after heating up to 1473 K in vacuum. At the given experimental parameters a 920 nm thick crystalline film with a tungsten and nitrogen stoichiometry of 2:1 were achieved. The results showed that no phase and microstructure change occurred due to W2N film annealing in vacuum up to 973 K. Heating up to 1073 K led to a partial decomposition of the W2N phase and the formation of a W enrichment layer at the surface. Increasing the annealing time at the same temperature, the further decomposition of the W2N phase was negligible. The complete decomposition of W2N film happened as the temperature reached up to 1473 K.

  18. Transition-metal-nitride-based thin films as novel energy harvesting materials.

    PubMed

    Eklund, Per; Kerdsongpanya, Sit; Alling, Björn

    2016-05-14

    The last few years have seen a rise in the interest in early transition-metal and rare-earth nitrides, primarily based on ScN and CrN, for energy harvesting by thermoelectricity and piezoelectricity. This is because of a number of important advances, among those the discoveries of exceptionally high piezoelectric coupling coefficient in (Sc,Al)N alloys and of high thermoelectric power factors of ScN-based and CrN-based thin films. These materials also constitute well-defined model systems for investigating thermodynamics of mixing for alloying and nanostructural design for optimization of phase stability and band structure. These features have implications for and can be used for tailoring of thermoelectric and piezoelectric properties. In this highlight article, we review the ScN- and CrN-based transition-metal nitrides for thermoelectrics, and drawing parallels with piezoelectricity. We further discuss these materials as a models systems for general strategies for tailoring of thermoelectric properties by integrated theoretical-experimental approaches.

  19. Transition-metal-nitride-based thin films as novel energy harvesting materials

    PubMed Central

    Kerdsongpanya, Sit; Alling, Björn

    2016-01-01

    The last few years have seen a rise in the interest in early transition-metal and rare-earth nitrides, primarily based on ScN and CrN, for energy harvesting by thermoelectricity and piezoelectricity. This is because of a number of important advances, among those the discoveries of exceptionally high piezoelectric coupling coefficient in (Sc,Al)N alloys and of high thermoelectric power factors of ScN-based and CrN-based thin films. These materials also constitute well-defined model systems for investigating thermodynamics of mixing for alloying and nanostructural design for optimization of phase stability and band structure. These features have implications for and can be used for tailoring of thermoelectric and piezoelectric properties. In this highlight article, we review the ScN- and CrN-based transition-metal nitrides for thermoelectrics, and drawing parallels with piezoelectricity. We further discuss these materials as a models systems for general strategies for tailoring of thermoelectric properties by integrated theoretical–experimental approaches. PMID:27358737

  20. Substrate-dependent thermal conductivity of aluminum nitride thin-films processed at low temperature

    SciTech Connect

    Belkerk, B. E.; Bensalem, S.; Soussou, A.; Carette, M.; Djouadi, M. A.; Scudeller, Y.; Al Brithen, H.

    2014-12-01

    In this paper, we report on investigation concerning the substrate-dependent thermal conductivity (k) of Aluminum Nitride (AlN) thin-films processed at low temperature by reactive magnetron sputtering. The thermal conductivity of AlN films grown at low temperature (<200 °C) on single-crystal silicon (Si) and amorphous silicon nitride (SiN) with thicknesses ranging from 100 nm to 4000 nm was measured with the transient hot-strip technique. The k values for AlN films on SiN were found significantly lower than those on Silicon consistently with their microstructures revealed by X-ray diffraction, high resolution scanning electron microscopy, and transmission electron microscopy. The change in k was due to the thermal boundary resistance found to be equal to 10 × 10{sup −9} Km{sup 2}W{sup −1} on SiN against 3.5 × 10{sup −9} Km{sup 2}W{sup −1} on Si. However, the intrinsic thermal conductivity was determined with a value as high as 200 Wm{sup −1}K{sup −1} whatever the substrate.

  1. The effect of the applied electric field on laser-induced damage of dielectric thin films

    NASA Astrophysics Data System (ADS)

    Wu, Shenjiang; Su, Junhong; Li, Dangjuan; Xu, Junqi; Kar, Satyananda; Ge, Jinman

    2017-01-01

    Laser-induced damage threshold (LIDT) in optical materials plays an important role in laser-matter interaction. The anti-laser ability of dielectric films are very important for the application in optical windows. In this paper, HfO2 and SiO2 dielectric thin films with thicknesses of about 240 nm and with good infrared characteristics are deposited by the vacuum thermal evaporation technique. The laser with peak density of 11 J cm-2 is used to irradiate the dielectric thin films. The laser damage morphologies under different laser radiation densities and with or without external electrical fields are studied. The results indicate that the electron density excited by laser has a directly relationship with the absorption coefficient; the increasing electric field reduces the laser energy density, and decreases the optical absorption in the center of laser irradiation region, hence the laser damage area decreases.

  2. Properties of dielectric dead layers for SrTiO3 thin films on Pt electrodes

    NASA Astrophysics Data System (ADS)

    Finstrom, Nicholas H.; Cagnon, Joel; Stemmer, Susanne

    2007-02-01

    Dielectric measurements as a function of temperature were used to characterize the properties of the dielectric dead layers in parallel-plate capacitors with differently textured SrTiO3 thin films and Pt electrodes. The apparent thickness dependence of the permittivity was described with low-permittivity passive (dead) layers at the interfaces connected in series with the bulk of the SrTiO3 film. Interfacial capacitance densities changed with the film microstructure and were weakly temperature dependent. Estimates of the dielectric dead layer thickness and permittivity were limited by the film surface roughness (˜5nm ). The consequences for the possible origins of dielectric dead layers that have been proposed in the literature are discussed.

  3. Microstructure of Thin Films

    DTIC Science & Technology

    1990-02-07

    study of Ion Assisted deposition (IAD) with different materials: metals , Al, Ag, and dielectrics, nitrides, fluorides and oxides. Some additional...optical thin films. The materials studied by ion -assisted deposition has ranged over metals , especially silver and aluminum, and dielectrics, especially... Ion -assisted deposition of metals It was of interest to us to determine if the great benefits of io-assisted deposition in the fabrication of

  4. Electron transfer reactions for image and image-derived states in dielectric thin films.

    PubMed

    Jensen, E T; Sanche, L

    2008-08-21

    We have studied the cross section for electron trapping that occurs at the surfaces and interfaces of a variety of thin dielectric films (n-octane, methanol, n-butanol, and difluoromethane) that are grown on Kr buffer films. When such films are bombarded with electrons of very low incident energies (E less, similar 300 meV), charging cross sections up to the order of 10(-14) cm(2) are measured for submonolayer quantities of a variety of coadsorbed molecules: CH(3)I, CH(3)Br, CH(3)Cl, and CO(2). These huge cross sections are ascribed to the formation of image states at the dielectric film interfaces, which trap incoming electrons and, via coupling to the adsorbate electron affinity levels, dramatically enhance the capture probability. We have also shown that thin film dielectric layer structures can be created which display image-derived states, such as a "quantum well" in a sandwich structure with two "electron barrier" layers surrounding a Kr and adsorbate spacer film. These phenomena are shown to be of a general nature, occurring for a wide variety of molecular thin films, and depend on the dielectric constant and electron affinity of the selected species. We also report the absolute cross section for dissociative electron attachment of submonolayer CH(3)I adsorbed on Kr thin films.

  5. Review of Cernox™ (Zirconium Oxy-Nitride) Thin-Film Resistance Temperature Sensors

    NASA Astrophysics Data System (ADS)

    Courts, S. Scott; Swinehart, Philip R.

    2003-09-01

    Cernox™ resistance thermometers were commercially introduced in 1993. The Cernox™ temperature-sensing element is fabricated from zirconium reactively sputtered in a nitrogen-oxygen atmosphere. The resulting thin film is comprised of conducting zirconium nitride embedded within a zirconium oxide nonconducting matrix. This material has a negative temperature coefficient of resistance making it useful as a temperature sensor. The ratio of conducting to nonconducting material can be varied to tailor the sensor to a given temperature range. A single device can be fabricated for use from below 0.3 K to 420 K. Cernox™ temperature sensors possess many attributes desirable in a temperature sensor including high sensitivity, excellent short-term and long-term stability, small physical size, fast thermal response and small calibration shifts when exposed to magnetic fields or ionizing radiation. This paper presents a review of Cernox™ temperature sensors with regard to their physical, thermometric and operational properties and environmental effects.

  6. Investigation of hexagonal boron nitride as an atomically thin corrosion passivation coating in aqueous solution.

    PubMed

    Zhang, Jing; Yang, Yingchao; Lou, Jun

    2016-09-09

    Hexagonal boron nitride (h-BN) atomic layers were utilized as a passivation coating in this study. A large-area continuous h-BN thin film was grown on nickel foil using a chemical vapor deposition method and then transferred onto sputtered copper as a corrosion passivation coating. The corrosion passivation performance in a Na2SO4 solution of bare and coated copper was investigated by electrochemical methods including cyclic voltammetry (CV), Tafel polarization and electrochemical impedance spectroscopy (EIS). CV and Tafel analysis indicate that the h-BN coating could effectively suppress the anodic dissolution of copper. The EIS fitting result suggests that defects are the dominant leakage source on h-BN films, and improved anti-corrosion performances could be achieved by further passivating these defects.

  7. Impact of sputter deposition parameters on molybdenum nitride thin film properties

    NASA Astrophysics Data System (ADS)

    Stöber, L.; Konrath, J. P.; Krivec, S.; Patocka, F.; Schwarz, S.; Bittner, A.; Schneider, M.; Schmid, U.

    2015-07-01

    Molybdenum and molybdenum nitride thin films are presented, which are deposited by reactive dc magnetron sputtering. The influence of deposition parameters, especially the amount of nitrogen during film synthesization, to mechanical and electrical properties is investigated. The crystallographic phase and lattice constants are determined by x-ray diffraction analyses. Further information on the microstructure as well as on the biaxial film stress are gained from techniques such as transmission electron microscopy, scanning electron microscopy and the wafer bow. Furthermore, the film resistivity and the temperature coefficient of resistance are measured by the van der Pauw technique starting from room temperature up to 300 °C. Independent of the investigated physical quantity, a dominant dependence on the sputtering gas nitrogen content is observed compared to other deposition parameters such as the plasma power or the sputtering gas pressure in the deposition chamber.

  8. Mechanical properties of atomically thin boron nitride and the role of interlayer interactions

    PubMed Central

    Falin, Aleksey; Cai, Qiran; Santos, Elton J. G.; Scullion, Declan; Qian, Dong; Zhang, Rui; Yang, Zhi; Huang, Shaoming; Watanabe, Kenji; Taniguchi, Takashi; Barnett, Matthew R.; Chen, Ying; Ruoff, Rodney S.; Li, Lu Hua

    2017-01-01

    Atomically thin boron nitride (BN) nanosheets are important two-dimensional nanomaterials with many unique properties distinct from those of graphene, but investigation into their mechanical properties remains incomplete. Here we report that high-quality single-crystalline mono- and few-layer BN nanosheets are one of the strongest electrically insulating materials. More intriguingly, few-layer BN shows mechanical behaviours quite different from those of few-layer graphene under indentation. In striking contrast to graphene, whose strength decreases by more than 30% when the number of layers increases from 1 to 8, the mechanical strength of BN nanosheets is not sensitive to increasing thickness. We attribute this difference to the distinct interlayer interactions and hence sliding tendencies in these two materials under indentation. The significantly better interlayer integrity of BN nanosheets makes them a more attractive candidate than graphene for several applications, for example, as mechanical reinforcements. PMID:28639613

  9. Utilizing boron nitride sheets as thin supports for high resolution imaging of nanocrystals.

    PubMed

    Wu, Yimin A; Kirkland, Angus I; Schäffel, Franziska; Porfyrakis, Kyriakos; Young, Neil P; Briggs, G Andrew D; Warner, Jamie H

    2011-05-13

    We demonstrate the use of thin BN sheets as supports for imaging nanocrystals using low voltage (80 kV) aberration-corrected high resolution transmission electron microscopy. This provides an alternative to the previously utilized 2D crystal supports of graphene and graphene oxide. A simple chemical exfoliation method is applied to get few layer boron nitride (BN) sheets with micrometer-sized dimensions. This generic approach of using BN sheets as supports is shown by depositing Mn doped ZnSe nanocrystals directly onto the BN sheets and resolving the atomic structure from both the ZnSe nanocrystals and the BN support. Phase contrast images reveal moiré patterns of interference between the beams diffracted by the nanocrystals and the BN substrate that are used to determine the relative orientation of the nanocrystals with respect to the BN sheets and interference lattice planes. Double diffraction is observed and has been analyzed.

  10. Mechanical properties of atomically thin boron nitride and the role of interlayer interactions

    NASA Astrophysics Data System (ADS)

    Falin, Aleksey; Cai, Qiran; Santos, Elton J. G.; Scullion, Declan; Qian, Dong; Zhang, Rui; Yang, Zhi; Huang, Shaoming; Watanabe, Kenji; Taniguchi, Takashi; Barnett, Matthew R.; Chen, Ying; Ruoff, Rodney S.; Li, Lu Hua

    2017-06-01

    Atomically thin boron nitride (BN) nanosheets are important two-dimensional nanomaterials with many unique properties distinct from those of graphene, but investigation into their mechanical properties remains incomplete. Here we report that high-quality single-crystalline mono- and few-layer BN nanosheets are one of the strongest electrically insulating materials. More intriguingly, few-layer BN shows mechanical behaviours quite different from those of few-layer graphene under indentation. In striking contrast to graphene, whose strength decreases by more than 30% when the number of layers increases from 1 to 8, the mechanical strength of BN nanosheets is not sensitive to increasing thickness. We attribute this difference to the distinct interlayer interactions and hence sliding tendencies in these two materials under indentation. The significantly better interlayer integrity of BN nanosheets makes them a more attractive candidate than graphene for several applications, for example, as mechanical reinforcements.

  11. Tunable phonon polaritons in atomically thin van der Waals crystals of boron nitride.

    PubMed

    Dai, S; Fei, Z; Ma, Q; Rodin, A S; Wagner, M; McLeod, A S; Liu, M K; Gannett, W; Regan, W; Watanabe, K; Taniguchi, T; Thiemens, M; Dominguez, G; Castro Neto, A H; Zettl, A; Keilmann, F; Jarillo-Herrero, P; Fogler, M M; Basov, D N

    2014-03-07

    van der Waals heterostructures assembled from atomically thin crystalline layers of diverse two-dimensional solids are emerging as a new paradigm in the physics of materials. We used infrared nanoimaging to study the properties of surface phonon polaritons in a representative van der Waals crystal, hexagonal boron nitride. We launched, detected, and imaged the polaritonic waves in real space and altered their wavelength by varying the number of crystal layers in our specimens. The measured dispersion of polaritonic waves was shown to be governed by the crystal thickness according to a scaling law that persists down to a few atomic layers. Our results are likely to hold true in other polar van der Waals crystals and may lead to new functionalities.

  12. Stoichiometry and thickness dependence of superconducting properties of niobium nitride thin films

    SciTech Connect

    Beebe, Melissa R. Beringer, Douglas B.; Burton, Matthew C.; Yang, Kaida; Lukaszew, R. Alejandra

    2016-03-15

    The current technology used in linear particle accelerators is based on superconducting radio frequency (SRF) cavities fabricated from bulk niobium (Nb), which have smaller surface resistance and therefore dissipate less energy than traditional nonsuperconducting copper cavities. Using bulk Nb for the cavities has several advantages, which are discussed elsewhere; however, such SRF cavities have a material-dependent accelerating gradient limit. In order to overcome this fundamental limit, a multilayered coating has been proposed using layers of insulating and superconducting material applied to the interior surface of the cavity. The key to this multilayered model is to use superconducting thin films to exploit the potential field enhancement when these films are thinner than their London penetration depth. Such field enhancement has been demonstrated in MgB{sub 2} thin films; here, the authors consider films of another type-II superconductor, niobium nitride (NbN). The authors present their work correlating stoichiometry and superconducting properties in NbN thin films and discuss the thickness dependence of their superconducting properties, which is important for their potential use in the proposed multilayer structure. While there are some previous studies on the relationship between stoichiometry and critical temperature T{sub C}, the authors are the first to report on the correlation between stoichiometry and the lower critical field H{sub C1}.

  13. High temperature performance of sputter-deposited piezoelectric aluminum nitride thin films

    NASA Astrophysics Data System (ADS)

    Gillinger, M.; Schneider, M.; Bittner, A.; Nicolay, P.; Schmid, U.

    2015-05-01

    Aluminum nitride (AlN) is a promising material for sensor applications in harsh environments such as turbine exhausts or thermal power plants due to its piezoelectric properties, good thermal match to silicon and high temperature stability. Typically, the usage of piezoelectric materials in high temperature is limited by the Curie-temperature, the increase of the leakage current as well as by enhanced diffusion effects in the materials. In order to exploit the high temperature potential of AlN thin films, post deposition annealing experiments up to 1000°C in both oxygen and nitrogen gas atmospheres for 2 h were performed. X-ray diffraction measurements indicate that the thin films are chemically stable in a pure oxygen atmosphere for 2 h at annealing temperatures of up to 900°C. After a 2 h annealing step at 1000°C in pure oxygen. However, a 100 nm thin AlN film is completely oxidized. In contrast, the layer is stable up to 1000°C in pure nitrogen atmosphere. The surface topology changes significantly at annealing temperatures above 800°C independent of annealing atmosphere. The surface roughness is increased by about one order of magnitude compared to the "as deposited" state. This is predominantly attributed to recrystallization processes occurring during high temperature loading. Up to an annealing temperature of 700°C, a Poole-Frenkel conduction mechanism dominates the leakage current characteristics. Above, a mixture of different leakage current mechanisms is observed.

  14. Work functions of hafnium nitride thin films as emitter material for field emitter arrays

    SciTech Connect

    Gotoh, Yasuhito Fujiwara, Sho; Tsuji, Hiroshi

    2016-05-15

    The work functions of hafnium nitride thin films prepared by radio-frequency magnetron sputtering were investigated in vacuum, before and after surface cleaning processes, with a view of improving the properties of as-fabricated field emitter arrays comprising hafnium nitride emitters. The measurement of the work function was first performed for the as-deposited films and then for films subjected to surface cleaning process, either thermal treatment or ion bombardment. Thermal treatment at a maximum temperature of 300 °C reduced the work function by 0.7 eV. Once the film was heated, the work function maintained the reduced value, even after cooling to room temperature. A little change in the work function was observed for the second and third thermal treatments. The ion bombardment was conducted by exposing the sample to a thin plasma for different sample bias conditions and processing times. When the sample was biased at −10 V, the work function decreased by 0.6 eV. The work function reduction became saturated in the early stage of the ion bombardment. When the sample was biased at −50 V, the work function exhibited different behaviors, that is, first it decreased rapidly and then increased in response to the increase in processing time. The lowest attainable work function was found to be 4.00 eV. It should be noted that none of the work function values reported in this paper were obtained using surfaces that were demonstrated to be free from oxygen contamination. The present results suggest that the current–voltage characteristics of a field emitter array can be improved by a factor of 25–50 by the examined postprocesses.

  15. Optical and surface characterization of amorphous boron nitride thin films for use as blood compatible coatings

    NASA Astrophysics Data System (ADS)

    Lousinian, S.; Kalfagiannis, N.; Logothetidis, S.

    2009-10-01

    The aim of this work is the investigation of the haemocompatibility properties of homogeneous and amorphous boron nitride (a-BN) thin films, through the adsorption of two basic blood plasma proteins, human serum albumin (HSA) and fibrinogen (Fib). The a-BN thin films were grown onto c-Si(100) substrates under different values of substrate bias voltage, employing the radio frequency (RF) magnetron sputtering technique. For the consideration of the optical, compositional and structural properties of the films, Spectroscopic Ellipsometry (SE) in the Vis-UV spectral region was used, while for the study of surface topography and surface charge distribution as well as of the wetting properties of the a-BN thin films, Atomic Force Microscopy (AFM), Electric Force Microscopy (EFM) and Contact Angle measurements were additionally employed. The properties of the thin films were correlated with their haemocompatibility, through the estimation of the ratio of HSA/Fib surface concentration. The sp 3 content of the samples does not seem to correlate with the haemocompatibility of the a-BN thin films. However, the surface properties determine the thrombogenicity potential of the studied samples. More precisely, the a-BN films with a less negatively charged surface exhibit the smallest possibility of clot formation, possibly due to the interactions between the charged chains of the Fib molecules and the a-BN surface, while slight changes in the surface roughness do not affect their haemocompatibility properties. The wetting properties determine the thickness of the adsorbed Fib as well as the ratio of HSA/Fib surface concentration.

  16. Amorphous Boron Nitride: A Universal, Ultrathin Dielectric for 2D Nanoelectronics (Postprint)

    DTIC Science & Technology

    2015-03-21

    single crystal h-BN. 15. SUBJECT TERMS Nanoelectronics; 2D materials; dielectrics; transistor gate barriers; environmental passivation layers; boron...than previously reported chemical vapor depos- ited h -BN and nearing single crystal h -BN. DOI: 10.1002/adfm.201505455 N. R. Glavin, Dr. M. L...see Table 1 ). The amorphous material possesses a density similar to the crystal - line phases, and retains much of the valued chemical inert- ness and

  17. Parametric formulation of the dielectric function of palladium and palladium hydride thin films.

    PubMed

    Vargas, William E; Azofeifa, Daniel E; Clark, Neville; Solis, Hugo; Montealegre, Felipe; Cambronero, Michael

    2014-08-20

    A parametric description of the dielectric function of Pd thin films with thicknesses between 10 and 30 nm is reported. These films were grown at room temperature on amorphous quartz substrates by electron beam evaporation, with a base pressure of 7.0×10(-7)  mbar. By using nonpolarized normal incident light, transmission spectra were measured for wavelengths between 240 and 1050 nm. Inversion of the spectra by means of a projected gradient method enables us to obtain the mean dielectric function of the Pd grains in the films. We follow the Brendel-Bormann model to describe the frequency dependence of the dielectric function, with the plasma frequency, collision frequency, and screening factor as parameters in the free electron term. The contributions of bound electrons and their interband transitions, described in terms of Lorentz oscillators, involve the resonance frequencies, decay times, strengths, and Gaussian widths as parameters of the model. All these parameters have been optimized from the Pd grains' dielectric function, which fits the transmission spectra. A similar procedure was followed for Pd films exposed to a hydrogen atmosphere close to one bar. Thus, the dielectric functions of palladium and palladium hydride can easily be calculated through spectral ranges covering near-ultraviolet, visible, and near-infrared wavelengths. This can be used to model the behavior of nano-sized structures in which palladium particles or thin films are exposed to hydrogen pressures close to one bar.

  18. Thin film transistors with anodic gate dielectrics and chemical bath deposited active layers

    NASA Astrophysics Data System (ADS)

    Gan, Feng Yuan; Shih, Ishiang

    2002-07-01

    Thin film transistors (TFTs) with an anodic dielectric layer and chemical bath deposited active layer have been fabricated on glass substrates. The effects of anodization conditions on the quality of the anodic dielectric were investigated by measuring the breakdown electric field and leakage current density of the metal-insulator-metal capacitors fabricated. Using the anodic gate dielectric, preliminary thin film transistors with CdS and CdSe films formed by a chemical bath deposition method were fabricated and evaluated. Results of electrical measurements carried out on the CdSe-TFTs with Al2O3 and Ta2O5 gate dielectrics showed field effect mobilities of 3.4 and 0.67 cm2/V s and threshold voltages of 3.2 and 8.2 V, respectively. Field effect mobilities of 0.2 and 2 cm2/V s and threshold voltages of 4.3 and 5.2 V were observed for CdS-TFTs, again with Al2O3 and Ta2O5 gate dielectrics. The mobilities obtained from the present TFTs fabricated on glass substrates are smaller than that on similar TFTs fabricated on thermally grown gate oxides on Si substrates in our previous work. copyright 2002 American Vacuum Society.

  19. Microwave Characterization of Low-k Dielectric Thin Films using a Coplanar Waveguide

    NASA Astrophysics Data System (ADS)

    Radican, Kevin P.; Koeck, Deborah C.; Geerts, Wilhelmus; Spencer, Gregory; Donnelly, David; Galloway, Heather C.

    2003-03-01

    As microelectronic logic devices increase in speed the RC time delay is becoming of greater concern. One remedy is the use of low-k dielectrics along with less resistive metals such as Cu in back end processing. We have demonstrated a method of forming coplanar waveguides on low-k dielectric materials deposited on SiC/Si wafers. These thin films are prepared by the usual semiconductor industry methods. Then, the dielectric properties of the low-k dielectric thin films on wafers were measured at microwave frequencies using coplanar waveguide test structures. Several OSG low k materials were investigated before and after chemical mechanical planarization processing which involves placing the dielectrics in a liquid abrasive slurry. We will report on the details of the fabrication of the waveguide structures using argon laser beam lithography, magnetron sputter deposition, and reactive plasma etching. We will also report on the electrical changes observed due to the chemical processing. Electrical measurements were taken using an Agilent network analyzer, and Cascade Microtech probe station.

  20. Scattering from thin dielectric straps surrounding a perfectly conducting structure

    NASA Technical Reports Server (NTRS)

    Al-Hekail, Zeyad; Gupta, Inder J.

    1989-01-01

    A method to calculate the electromagnetic scattered fields from a dielectric strap wrapped around convex, conducting structure is presented. A moment method technique is used to find the current excited within the strap by the incident plane wave. Then, Uniform Geometrical Theory of Diffraction (UTD) is used to compute the fields scattered by the strap. Reasonable agreement was obtained between the computed and the measured results. The results found in this study are useful in evaluating straps as a target support structure for scattering measurements.

  1. The Propagation of Electromagnetic Waves in Thin Dielectric Slabs.

    DTIC Science & Technology

    1988-05-01

    Continue on reverse if recessary, and identify by block number) This report precents the solutions of Maxwell’s equations for the TE and TM modes of...field versus distance from slab center for two even and two odd TM modes .... 25 5. Electric field for TE even mode and magnetic field for TM even mode...34 vi1and/or ’it Special 6MEN Figures 6. Electric field versus distance from slab center for a slab of 0.35 [ tm thickness and dielectric coefficients of

  2. Polymer dielectric materials for organic thin-film transistors: Interfacial control and development for printable electronics

    NASA Astrophysics Data System (ADS)

    Kim, Choongik

    Organic thin-film transistors (OTFTs) have been extensively studied for organic electronics. In these devices, organic semiconductor-dielectric interface characteristics play a critical role in influencing OTFT operation and performance. This study begins with exploring how the physicochemical characteristics of the polymer gate dielectric affects the thin-film growth mode, microstructure, and OTFT performance parameters of pentacene films deposited on bilayer polymer (top)-SiO2 (bottom) dielectrics. Pentacene growth mode varies considerably with dielectric substrate, and correlations are established between pentacene film deposition temperature, the thin-film to bulk microstructural phase transition, and OTFT device performance. Furthermore, the primary influence of the polymer dielectric layer glass transition temperature on pentacene film microstructure and OTFT response is shown for the first time. Following the first study, the influence of the polymer gate dielectric viscoelastic properties on overlying organic semiconductor film growth, film microstructure, and TFT response are investigated in detail. From the knowledge that nanoscopically-confined thin polymer films exhibit glass transition temperatures that deviate substantially from those of the corresponding bulk materials, pentacene (p-channel) and cyanoperylene (n-channel) films grown on polymer gate dielectrics at temperatures well-below their bulk glass transition temperatures (Tg(b)) have been shown to exhibit morphological/microstructural transitions and dramatic OTFT performance discontinuities at well-defined temperatures (defined as the polymer "surface glass transition temperature," or Tg(s)). These transitions are characteristic of the particular polymer architecture and independent of film thickness or overall film cooperative chain dynamics. Furthermore, by analyzing the pentacene films grown on UV-curable polymer dielectrics with different curing times (hence, different degrees of

  3. Dielectric properties of barium strontium titanate (BST) thin films and phase shifters based on BST thin films

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaoyuan

    In recent years, barium strontium titanate (abbreviated as BST) thin films have attracted extensive interest. Ferroelectric/dielectric behavior of BST is influenced by a number of structural factors, such as lattice tetragonality, defects, ratio of barium to strontium, grain size and etc. In this work several key issues regarding BST thin films have been studied. First, a clear correlation between lattice tetragonality and ferroelectric and dielectric behaviors has been established. The studied material was Ba 0.7Sr0.3TiO3. Grown on substrates like (LaAlO 3)0.3(Sr2AlTaO6)0.7, LaAlO 3, MgAl2O4, BST thin films were found to have distorted lattices. This distorted lattice structure leads to the enhanced in-plane dielectric and ferroelectric properties. The formation mechanism of the lattice distortion was studied in a model system consisting of a SrTiO 3 (film)/SiTiO3 (substrate) homostructure. Among several parameters, deposition pressure was identified to be the critical factors that determined the lattice parameters of the perovskite oxides. Secondly, a phenomenological model was developed to interpret the strain effect on the in-plane dielectric properties of BST thin films with different thickness. The theoretical modeling involved the grouping of strain into biaxial and hydrostatic components, the use of the Landau-Ginsburg-Devonshire formalism and mathematical calculations related to the elastic Gibbs free energy. The calculations confirmed that the ferroelectric transition temperature (Curie temperature) and dielectric constant decrease with the decreasing of film thickness. Thirdly, The heterostructure, SrTiO3/Si, was first prepared by laser molecular-beam epitaxy using an ultra-thin Sr layer as the buffer layer. X-ray diffraction measurements indicated that SrTiO3 was well crystallized and epitaxially aligned with Si. Cross-sectional observations by TEM and X-ray reflectivity measurements revealed that the SrTiO3/Si interface was sharp, smooth and fully

  4. Synthesis and Characterization of Hexagonal Boron Nitride as a Gate Dielectric

    PubMed Central

    Jang, Sung Kyu; Youn, Jiyoun; Song, Young Jae; Lee, Sungjoo

    2016-01-01

    Two different growth modes of large-area hexagonal boron nitride (h-BN) film, a conventional chemical vapor deposition (CVD) growth mode and a high-pressure CVD growth mode, were compared as a function of the precursor partial pressure. Conventional self-limited CVD growth was obtained below a critical partial pressure of the borazine precursor, whereas a thick h-BN layer (thicker than a critical thickness of 10 nm) was grown beyond a critical partial pressure. An interesting coincidence of a critical thickness of 10 nm was identified in both the CVD growth behavior and in the breakdown electric field strength and leakage current mechanism, indicating that the electrical properties of the CVD h-BN film depended significantly on the film growth mode and the resultant film quality. PMID:27458024

  5. High-dielectric-constant ferroelectric thin film and bulk ceramic capacitors for power electronics.

    SciTech Connect

    Auciello, O. H.; Baldo, P.; Baumann, P.; Erck, R. A.; Giumarra, J.; Im, J.; Kaufman, D. Y.; Lanagan, M. T.; Pan, M. J.; Streiffer, S. K.; Zebrowski, J.

    1999-08-10

    Significant effort is presently focused on reducing the size and weight of power electronic modules. To achieve these goals in high-power capacitors, alternative materials and fabrication processes are needed. Thin film (<0.5 {micro}m) and bulk capacitors that use perovskite-based ferroelectric dielectrics are promising alternative technologies. Ferroelectrics possess high dielectric constants, thus offering substantial increases in volumetric capacitance. In thin film form, these materials display low loss and high breakdown strength. The unique properties of some of these materials, such as a nonlinear dielectric response or a high energy-storage capacity accompanying a phase change, can be exploited for power electronic capacitors. Prototype capacitors of two such materials, (Ba,Sr)TiO{sub 3} and PbZrO{sub 3}, have been fabricated in both thin film and bulk ceramic form. The influence of fabrication conditions on dielectric properties has been studied. Initial studies have demonstrated the viability of perovskite ferroelectrics for next-generation capacitor components.

  6. Method of stress and measurement modes for research of thin dielectric films of MIS structures

    NASA Astrophysics Data System (ADS)

    Andreev, Vladimir V.; Maslovsky, Vladimir M.; Andreev, Dmitrii V.; Stolyarov, Alexander A.

    2016-12-01

    The paper proposes a new method of stress and measurement modes for research of thin dielectric films of MIS structures. The method realizes injection of the most part of charge into gate dielectric in one of stress modes: either current owing through dielectric is constant or voltage applied to gate is constant. In order to acquire an additional information about changing of charge state of MIS structure, the stress condition is interrupted in certain time ranges and during these time ranges the mode, in which structure is, is the mode of measurement. In measurement mode, changing of electric fields at interfaces between dielectric and semiconductor is monitored. By using these data, density of charge, which is accumulated in gate dielectric, and its centroid are calculated. Besides, by using these data, one studies processes of generation and relaxation of charge in dielectric. In order to raise precision of the method and reduce an influence of switching effects in measurement mode, density of measurement current should be much lower than density of stress current.

  7. Thermally driven sign switch of static dielectric constant of VO2 thin film

    NASA Astrophysics Data System (ADS)

    Kana Kana, J. B.; Vignaud, G.; Gibaud, A.; Maaza, M.

    2016-04-01

    Smart multifunctional materials exhibiting phase transition and tunable optical and/electrical properties provide a new direction towards engineering switchable devices. Specifically, the reversible, tunable and sign switch dielectric constants via external temperature stimuli observed in vanadium dioxide (VO2) make it a candidate of choice for tunable and switchable technologies devices. Here we report new aspect of the metal-insulator transition (MIT) through the sign switch of the static dielectric constant εS of pure VO2. As it is shown, the static dielectric constant showed an abrupt change from positive at T < 70 °C to negative at T > 70 °C. εS > 0 confirms the insulating phase where charges are localized while εS < 0 confirms the metallic phase of VO2 where charges are delocalized. We report for the first time the tunability of the dielectric constant from a negative sign for the static dielectric constant of VO2 thin film rarely found in real physical systems. We also demonstrate the tunability and switchability of the real and imaginary part of the dielectric constant (ε) via external temperature stimuli. More specifically, the real (ε) and Imaginary (ε) showed an abrupt thermal hysteresis which clearly confirms the phase transition.

  8. Graphene-based thin film supercapacitor with graphene oxide as dielectric spacer

    NASA Astrophysics Data System (ADS)

    Liu, Jinzhang; Galpaya, Dilini; Notarianni, Marco; Yan, Cheng; Motta, Nunzio

    2013-08-01

    Thin film supercapacitors are produced by using electrochemically exfoliated graphene (G) and wet-chemically produced graphene oxide (GO). Either G/GO/G stacked film or sole GO film are sandwiched by two Au films to make devices, where GO is the dielectric spacer. The addition of graphene film can increase the capacitance about two times, compared to the simple Au electrode. It is found that the GO film has very high dielectric constant, accounting for the high capacitance. AC measurement reveals that the relative permittivity of GO is in the order of 104 within the frequency range of 0.1-70 Hz.

  9. Oxide Thin-Film Transistors Fabricated Using Biodegradable Gate Dielectric Layer of Chicken Albumen

    NASA Astrophysics Data System (ADS)

    Jeon, Da-Bin; Bak, Jun-Yong; Yoon, Sung-Min

    2013-12-01

    An oxide thin-film transistor (TFT) using chicken albumen as gate dielectric on paper substrate was demonstrated. Chicken albumen, which was directly extracted from chicken egg white, was deposited as gate dielectric layer. An In-Ga-Zn-O was chosen as an active channel. The TFT feasibilities were successfully confirmed, in which channel mobility and subthreshold slope of the TFT were 6.48 cm2 V-1 s-1 and 1.28 V/s, respectively. This is the first report on the device configuration combining the biodegradable gate insulator and oxide semiconducting channel.

  10. The structure study of thin semiconductor and dielectric films by diffraction of synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Yurjev, G. S.; Fainer, N. I.; Maximovskiy, E. A.; Kosinova, M. L.; Sheromov, M. A.; Rumyantsev, Yu. M.

    1998-02-01

    The structure of semiconductor and dielectric thin (100-300 nm) films was studied by diffraction of synchrotron radiation. The diffraction experiments were performed at both the station "Anomalous scattering" of the storage ring synchrotron facility VEPP-3 and DRON-4 diffractometer. The structure of CdS thin films grown on fused silica, single Si(100) and InP(100) substrates was investigated. The structure of Cu 2S thin films grown on fused silica, single Si(100) substrates and CdS/Si(100)-heterostructure was studied. The structure study was performed on Si 3N 4 films grown on GaAs(100) substrates. The structure of thin BN layers grown on single Si(100) substrates was studied. It was established that structural parameters of above-mentioned thin films coincide on the parameters of JCPDS International Centre for Diffraction Data.

  11. Atomic-Resolution Observations of Semi-Crystalline IntegranularThin Films in Silicon Nitride

    SciTech Connect

    Ziegler, Alexander; Idrobo, Juan C.; Cinibulk, Michael K.; Kisielowski, Christian; Browning, Nigel D.; Ritchie, Robert O.

    2005-08-01

    The thin intergranular phase in a silicon nitride (Si3N4)ceramic, which has been regarded for decades as having an entirely amorphous morphology, is shown to have a semi-crystalline structure. Using two different but complementary high-resolution electron microscopy methods, the intergranular atomic structure was directly imaged at the atomic level. These high-resolution images show that the atomic arrangement of the dopand element cerium takes very periodic positions not only along the interface between the intergranular phase and the Si3N4 matrix grains, but it arranges in a semi-crystalline structure that spans the entire width of the intergranular phase between two adjacent matrix grains, in principle connecting the two separate matrix grains. The result will have implications on the approach of understanding the materials properties of ceramics, most significantly on the mechanical properties and the associated computational modeling of the atomic structure of the thin intergranular phase in Si3N4 ceramics.

  12. Near-infrared electroluminescence at room temperature from neodymium-doped gallium nitride thin films

    SciTech Connect

    Kim, Joo Han; Holloway, Paul H.

    2004-09-06

    Strong near-infrared (NIR) electroluminescence (EL) at room temperature from neodymium (Nd)-doped gallium nitride (GaN) thin films is reported. The Nd-doped GaN films were grown by radio-frequency planar magnetron cosputtering of separate GaN and metallic Nd targets in a pure nitrogen ambient. X-ray diffraction data did not identify the presence of any secondary phases and revealed that the Nd-doped GaN films had a highly textured wurtzite crystal structure with the c-axis normal to the surface of the film. The EL devices were fabricated with a thin-film multilayered structure of Al/Nd-doped GaN/Al{sub 2}O{sub 3}-TiO{sub 2}/indium-tin oxide and tested at room temperate. Three distinct NIR EL emission peaks were observed from the devices at 905, 1082, and 1364 nm, arising from the radiative relaxation of the {sup 4}F{sub 3sol2} excited-state energy level to the {sup 4}I{sub 9sol2}, {sup 4}I{sub 11sol2}, and {sup 4}I{sub 13sol2} levels of the Nd{sup 3+} ion, respectively. The threshold voltage for all the three emission peaks was {approx}150 V. The external power efficiency of the fabricated EL devices was {approx}1x10{sup -5} measured at 40 V above the threshold voltage.

  13. High Temperature Annealing Studies on the Piezoelectric Properties of Thin Aluminum Nitride Films

    SciTech Connect

    Farrell, R.; Pagan, V.R.; Kabulski, A.; Kuchibhatla, S.; Harman, J.; Kasarla, K.R.; Rodak, L.E.; Hensel, J.P.; Famouri, P.; Korakakis, D.

    2008-01-01

    A Rapid Thermal Annealing (RTA) system was used to anneal sputtered and MOVPE-grown Aluminum Nitride (AlN) thin films at temperatures up to 1000°C in ambient and controlled environments. According to Energy Dispersive X-Ray Analysis (EDAX), the films annealed in an ambient environment rapidly oxidize after five minutes at 1000°C. Below 1000°C the films oxidized linearly as a function of annealing temperature which is consistent with what has been reported in literature [1]. Laser Doppler Vibrometry (LDV) was used to measure the piezoelectric coefficient, d33, of these films. Films annealed in an ambient environment had a weak piezoelectric response indicating that oxidation on the surface of the film reduces the value of d33. A high temperature furnace has been built that is capable of taking in-situ measurements of the piezoelectric response of AlN films. In-situ d33 measurements are recorded up to 300°C for both sputtered and MOVPE-grown AlN thin films. The measured piezoelectric response appears to increase with temperature up to 300°C possibly due to stress in the film.

  14. Thin-walled boron nitride microtubes exhibiting intense band-edge UV emission at room temperature

    NASA Astrophysics Data System (ADS)

    Huang, Yang; Bando, Yoshio; Tang, Chengchun; Zhi, Chunyi; Terao, Takeshi; Dierre, Benjamin; Sekiguchi, Takashi; Golberg, Dmitri

    2009-02-01

    Boron nitride (BN) microtubes were synthesized in a vertical induction furnace using Li2CO3 and B reactants. Their structures and morphologies were investigated using x-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive x-ray spectroscopy. The microtubes have diameters of 1-3 µm, lengths of up to hundreds of micrometers, and well-structured ultrathin walls only ~50 nm thick. A mechanism combining the vapor-liquid-solid (VLS) and template self-sacrificing processes is proposed to explain the formation of these novel one-dimensional microstructures, in which the Li2O-B2O3 eutectic reaction plays an important role. Cathodoluminescence studies show that even at room temperature the thin-walled BN microtubes can possess an intense band-edge emission at ~216.5 nm, which is distinct compared with other BN nanostructures. The study suggests that the thin-walled BN microtubes should be promising for constructing compact deep UV devices and find potential applications in microreactors and microfluidic and drug delivery systems.

  15. Epitaxial growth and physical properties of ternary nitride thin films by polymer-assisted deposition

    SciTech Connect

    Enriquez, Erik M.; Zhang, Yingying; Chen, Aiping; Bi, Zhenxing; Wang, Yongqiang; Fu, Engang; Harrell, Zachary John; Lu, Xujie; Dowden, Paul Charles; Wang, Haiyan; Chen, Chonglin; Jia, Quanxi

    2016-08-26

    Epitaxial layered ternary metal-nitride FeMoN2, (Fe0.33 Mo0.67)MoN2, CoMoN2, and FeWN2 thin films have been grown on c-plane sapphire substrates by polymer-assisted deposition. The ABN2 layer sits on top of the oxygen sublattices of the substrate with three possible matching configurations due to the significantly reduced lattice mismatch. The doping composition and elements affect not only the out-of-plane lattice parameters but also the temperature-dependent electrical properties. These films have resistivity in the range of 0.1–1 mΩ·cm, showing tunable metallic or semiconducting behaviors by adjusting the composition. A modified parallel connection channel model has been used to analyze the grain boundary and Coulomb blockade effect on the electrical properties. Furthermore, the growth of the high crystallinity layered epitaxial thin films provides an avenue to study the composition-structure-property relationship in ABN2 materials through A and B-site substitution.

  16. Epitaxial growth and physical properties of ternary nitride thin films by polymer-assisted deposition

    DOE PAGES

    Enriquez, Erik M.; Zhang, Yingying; Chen, Aiping; ...

    2016-08-26

    Epitaxial layered ternary metal-nitride FeMoN2, (Fe0.33 Mo0.67)MoN2, CoMoN2, and FeWN2 thin films have been grown on c-plane sapphire substrates by polymer-assisted deposition. The ABN2 layer sits on top of the oxygen sublattices of the substrate with three possible matching configurations due to the significantly reduced lattice mismatch. The doping composition and elements affect not only the out-of-plane lattice parameters but also the temperature-dependent electrical properties. These films have resistivity in the range of 0.1–1 mΩ·cm, showing tunable metallic or semiconducting behaviors by adjusting the composition. A modified parallel connection channel model has been used to analyze the grain boundary andmore » Coulomb blockade effect on the electrical properties. Furthermore, the growth of the high crystallinity layered epitaxial thin films provides an avenue to study the composition-structure-property relationship in ABN2 materials through A and B-site substitution.« less

  17. Epitaxial growth and physical properties of ternary nitride thin films by polymer-assisted deposition

    SciTech Connect

    Enriquez, Erik M.; Zhang, Yingying; Chen, Aiping; Bi, Zhenxing; Wang, Yongqiang; Fu, Engang; Harrell, Zachary John; Lu, Xujie; Dowden, Paul Charles; Wang, Haiyan; Chen, Chonglin; Jia, Quanxi

    2016-08-26

    Epitaxial layered ternary metal-nitride FeMoN2, (Fe0.33 Mo0.67)MoN2, CoMoN2, and FeWN2 thin films have been grown on c-plane sapphire substrates by polymer-assisted deposition. The ABN2 layer sits on top of the oxygen sublattices of the substrate with three possible matching configurations due to the significantly reduced lattice mismatch. The doping composition and elements affect not only the out-of-plane lattice parameters but also the temperature-dependent electrical properties. These films have resistivity in the range of 0.1–1 mΩ·cm, showing tunable metallic or semiconducting behaviors by adjusting the composition. A modified parallel connection channel model has been used to analyze the grain boundary and Coulomb blockade effect on the electrical properties. Furthermore, the growth of the high crystallinity layered epitaxial thin films provides an avenue to study the composition-structure-property relationship in ABN2 materials through A and B-site substitution.

  18. High Temperature Annealing Studies on the Piezoelectric Properties of Thin Aluminum Nitride Films

    SciTech Connect

    R. Farrell; V. R. Pagan; A. Kabulski; Sridhar Kuchibhatl; J. Harman; K. R. Kasarla; L. E. Rodak; P. Famouri; J. Peter Hensel; D. Korakakis

    2008-05-01

    A Rapid Thermal Annealing (RTA) system was used to anneal sputtered and MOVPE grown Aluminum Nitride (AlN) thin films at temperatures up to 1000°C in ambient and controlled environments. According to Energy Dispersive X-Ray Analysis (EDAX), the films annealed in an ambient environment rapidly oxidize after five minutes at 1000°C. Below 1000°C the films oxidized linearly as a function of annealing temperature which is consistent with what has been reported in literature [1]. Laser Doppler Vibrometry (LDV) was used to measure the piezoelectric coefficient, d33, of these films. Films annealed in an ambient environment had a weak piezoelectric response indicating that oxidation on the surface of the film reduces the value of d33. A high temperature furnace has been built that is capable of taking in-situ measurements of the piezoelectric response of AlN films. In-situ d33 measurements are recorded up to 300°C for both sputtered and MOVPE-grown AlN thin films. The measured piezoelectric response appears to increase with temperature up to 300°C possibly due to stress in the film.

  19. Resistive switching phenomena of tungsten nitride thin films with excellent CMOS compatibility

    SciTech Connect

    Hong, Seok Man; Kim, Hee-Dong; An, Ho-Myoung; Kim, Tae Geun

    2013-12-15

    Graphical abstract: - Highlights: • The resistive switching characteristics of WN{sub x} thin films. • Excellent CMOS compatibility WN{sub x} films as a resistive switching material. • Resistive switching mechanism revealed trap-controlled space charge limited conduction. • Good endurance and retention properties over 10{sup 5} cycles, and 10{sup 5} s, respectively - Abstract: We report the resistive switching (RS) characteristics of tungsten nitride (WN{sub x}) thin films with excellent complementary metal-oxide-semiconductor (CMOS) compatibility. A Ti/WN{sub x}/Pt memory cell clearly shows bipolar RS behaviors at a low voltage of approximately ±2.2 V. The dominant conduction mechanisms at low and high resistance states were verified by Ohmic behavior and trap-controlled space-charge-limited conduction, respectively. A conducting filament model by a redox reaction explains the RS behavior in WN{sub x} films. We also demonstrate the memory characteristics during pulse operation, including a high endurance over >10{sup 5} cycles and a long retention time of >10{sup 5} s.

  20. Dielectric Scattering Patterns for Efficient Light Trapping in Thin-Film Solar Cells.

    PubMed

    van Lare, Claire; Lenzmann, Frank; Verschuuren, Marc A; Polman, Albert

    2015-08-12

    We demonstrate an effective light trapping geometry for thin-film solar cells that is composed of dielectric light scattering nanocavities at the interface between the metal back contact and the semiconductor absorber layer. The geometry is based on resonant Mie scattering. It avoids the Ohmic losses found in metallic (plasmonic) nanopatterns, and the dielectric scatterers are well compatible with nearly all types of thin-film solar cells, including cells produced using high temperature processes. The external quantum efficiency of thin-film a-Si:H solar cells grown on top of a nanopatterned Al-doped ZnO, made using soft imprint lithography, is strongly enhanced in the 550-800 nm spectral band by the dielectric nanoscatterers. Numerical simulations are in good agreement with experimental data and show that resonant light scattering from both the AZO nanostructures and the embedded Si nanostructures are important. The results are generic and can be applied on nearly all thin-film solar cells.

  1. Monitoring Dielectric Thin-Film Production on Product Wafers Using Infrared Emission Spectroscopy

    SciTech Connect

    NIEMCZYK,THOMAS M.; ZHANG,SONGBIAO; HAALAND,DAVID M.

    2000-12-18

    Monitoring of dielectric thin-film production in the microelectronics industry is generally accomplished by depositing a representative film on a monitor wafer and determining the film properties off line. One of the most important dielectric thin films in the manufacture of integrated circuits is borophosphosilicate glass (BPSG). The critical properties of BPSG thin films are the boron content, phosphorus content and film thickness. We have completed an experimental study that demonstrates that infrared emission spectroscopy coupled with multivariate analysis can be used to simultaneous y determine these properties directly from the spectra of product wafers, thus eliminating the need of producing monitor wafers. In addition, infrared emission data can be used to simultaneously determine the film temperature, which is an important film production parameter. The infrared data required to make these determinations can be collected on a time scale that is much faster than the film deposition time, hence infrared emission is an ideal candidate for an in-situ process monitor for dielectric thin-film production.

  2. Effective method to study the thickness-dependent dielectric functions of nanometal thin film.

    PubMed

    Hu, Er-Tao; Cai, Qing-Yuan; Zhang, Rong-Jun; Wei, Yan-Feng; Zhou, Wen-Chao; Wang, Song-You; Zheng, Yu-Xiang; Wei, Wei; Chen, Liang-Yao

    2016-11-01

    A new method for measuring the dielectric functions change with the thickness of nanometal thin films was proposed. To confirm the accuracy and reliability of the method, a nano-thin wedge-shaped gold (Au) film with continuously varied thicknesses was designed and prepared on K9 glass by direct-current-sputtering (DC-sputtering). The thicknesses and the dielectric functions in the wavelength range of 300-1100 nm of the nano-thin Au films were obtained by fitting the ellipsometric parameters with the Drude and critical points model. Results show that while the real part of the dielectric function (ϵ1) changes marginally with increasing film thickness, the imaginary part (ϵ2) decreases drastically with the film thickness, approaching a stable value when the film thickness increases up to about 42 nm. This method is particularly useful in the study of thickness-dependent optical properties of nano-thin film.

  3. Investigation of high-k yttrium copper titanate thin films as alternative gate dielectrics

    NASA Astrophysics Data System (ADS)

    Grazia Monteduro, Anna; Ameer, Zoobia; Rizzato, Silvia; Martino, Maurizio; Caricato, Anna Paola; Tasco, Vittorianna; Chaitanya Lekshmi, Indira; Hazarika, Abhijit; Choudhury, Debraj; Sarma, D. D.; Maruccio, Giuseppe

    2016-10-01

    Nearly amorphous high-k yttrium copper titanate thin films deposited by laser ablation were investigated in both metal-oxide-semiconductor (MOS) and metal-insulator-metal (MIM) junctions in order to assess the potentialities of this material as a gate oxide. The trend of dielectric parameters with film deposition shows a wide tunability for the dielectric constant and AC conductivity, with a remarkably high dielectric constant value of up to 95 for the thick films and conductivity as low as 6  ×  10-10 S cm-1 for the thin films deposited at high oxygen pressure. The AC conductivity analysis points out a decrease in the conductivity, indicating the formation of a blocking interface layer, probably due to partial oxidation of the thin films during cool-down in an oxygen atmosphere. Topography and surface potential characterizations highlight differences in the thin film microstructure as a function of the deposition conditions; these differences seem to affect their electrical properties.

  4. Structural and dielectric study of parylene C thin films

    NASA Astrophysics Data System (ADS)

    Kahouli, A.; Sylvestre, A.; Ortega, L.; Jomni, F.; Yangui, B.; Maillard, M.; Berge, B.; Robert, J.-C.; Legrand, J.

    2009-04-01

    α, β, and γ relaxation mechanisms have been identified in semicrystalline (45% of crystallinity) parylene-C (-H2C-C6H3Cl-CH2-)n films. C-Cl bonds induce the β-relaxation and explain increase in the dielectric constant as the frequency decreases in usual temperatures of operation for devices incorporating parylene-C. At cryogenic temperature (<-20 °C), γ-relaxation is assigned to the local motions of phenyl groups. Both β and γ relaxation processes obey an Arrhenius law with activation energy Ea(β)=91.7 kJ/mole and Ea(γ)=8.68 kJ/mole. α-relaxation associated with cooperative segmental motions of the (-H2C-∅-CH2-)n chains is observed with a peak at 10-2 Hz for T =80 °C and follows a Vogel-Fulcher-Tamman-Hesse law.

  5. Nanomechanical probing of thin-film dielectric elastomer transducers

    NASA Astrophysics Data System (ADS)

    Osmani, Bekim; Seifi, Saman; Park, Harold S.; Leung, Vanessa; Töpper, Tino; Müller, Bert

    2017-08-01

    Dielectric elastomer transducers (DETs) have attracted interest as generators, actuators, sensors, and even as self-sensing actuators for applications in medicine, soft robotics, and microfluidics. Their performance crucially depends on the elastic properties of the electrode-elastomer sandwich structure. The compressive displacement of a single-layer DET can be easily measured using atomic force microscopy (AFM) in the contact mode. While polymers used as dielectric elastomers are known to exhibit significant mechanical stiffening for large strains, their mechanical properties when subjected to voltages are not well understood. To examine this effect, we measured the depths of 400 nanoindentations as a function of the applied electric field using a spherical AFM probe with a radius of (522 ± 4) nm. Employing a field as low as 20 V/μm, the indentation depths increased by 42% at a load of 100 nN with respect to the field-free condition, implying an electromechanically driven elastic softening of the DET. This at-a-glance surprising experimental result agrees with related nonlinear, dynamic finite element model simulations. Furthermore, the pull-off forces rose from (23.0 ± 0.4) to (49.0 ± 0.7) nN implying a nanoindentation imprint after unloading. This embossing effect is explained by the remaining charges at the indentation site. The root-mean-square roughness of the Au electrode raised by 11% upon increasing the field from zero to 12 V/μm, demonstrating that the electrode's morphology change is an undervalued factor in the fabrication of DET structures.

  6. Characterization of capture cross sections of interface states in dielectric/III-nitride heterojunction structures

    NASA Astrophysics Data System (ADS)

    Matys, M.; Stoklas, R.; Kuzmik, J.; Adamowicz, B.; Yatabe, Z.; Hashizume, T.

    2016-05-01

    We performed, for the first time, quantitative characterization of electron capture cross sections σ of the interface states at dielectric/III-N heterojunction interfaces. We developed a new method, which is based on the photo-assisted capacitance-voltage measurements using photon energies below the semiconductor band gap. The analysis was carried out for AlGaN/GaN metal-insulator-semiconductor heterojunction (MISH) structures with Al2O3, SiO2, or SiN films as insulator deposited on the AlGaN layers with Al content (x) varying over a wide range of values. Additionally, we also investigated an Al2O3/InAlN/GaN MISH structure. Prior to insulator deposition, the AlGaN and InAlN surfaces were subjected to different treatments. We found that σ for all these structures lies in the range between 5 × 10 - 19 and 10 - 16 cm2. Furthermore, we revealed that σ for dielectric/AlxGa1-xN interfaces increases with increasing x. We showed that both the multiphonon-emission and cascade processes can explain the obtained results.

  7. Free-Space Time-Domain Method for Measuring Thin Film Dielectric Properties

    DOEpatents

    Li, Ming; Zhang, Xi-Cheng; Cho, Gyu Cheon

    2000-05-02

    A non-contact method for determining the index of refraction or dielectric constant of a thin film on a substrate at a desired frequency in the GHz to THz range having a corresponding wavelength larger than the thickness of the thin film (which may be only a few microns). The method comprises impinging the desired-frequency beam in free space upon the thin film on the substrate and measuring the measured phase change and the measured field reflectance from the reflected beam for a plurality of incident angles over a range of angles that includes the Brewster's angle for the thin film. The index of refraction for the thin film is determined by applying Fresnel equations to iteratively calculate a calculated phase change and a calculated field reflectance at each of the plurality of incident angles, and selecting the index of refraction that provides the best mathematical curve fit with both the dataset of measured phase changes and the dataset of measured field reflectances for each incident angle. The dielectric constant for the thin film can be calculated as the index of refraction squared.

  8. Interferometric sensing platform with dielectric nanostructured thin films.

    PubMed

    Celo, D; Post, E; Summers, M; Smy, T; Brett, M J; Albert, J

    2009-04-13

    A new interferometer-based optical sensing platform with nanostructured thin films of ZrO2 or TiO2 as sensing environment has been developed. With the application of an IC compatible Si(3)N(4) waveguide technology, Mach-Zehnder interferometer devices have been fabricated. The application of the glancing angle deposition technique allowed fabrication of nanostructured thin films as the optical sensing environment. Sensing ability of fabricated devices has been demonstrated through the refractive index measurement of a known gas. The transmission spectra and time response measurements have demonstrated a maximum phase shift of Delta phi=pi/10 and a |Delta P(out)|=0.65 dBm. Devices with TiO2 film on the sensing region performed much better than devices with ZrO2, with sensitivity twice as high.

  9. Integration of metal-organic frameworks into an electrochemical dielectric thin film for electronic applications

    PubMed Central

    Li, Wei-Jin; Liu, Juan; Sun, Zhi-Hua; Liu, Tian-Fu; Lü, Jian; Gao, Shui-Ying; He, Chao; Cao, Rong; Luo, Jun-Hua

    2016-01-01

    The integration of porous metal-organic frameworks onto the surface of materials, for use as functional devices, is currently emerging as a promising approach for gas sensing and flexible displays. However, research focused on potential applications in electronic devices is in its infancy. Here we present a facile strategy by which interpenetrated, crystalline metal-organic framework films are deposited onto conductive metal-plate anodes via in situ temperature-controlled electrochemical assembly. The nanostructure of the surface as well as the thickness and uniformity of the film are well controlled. More importantly, the resulting films exhibit enhanced dielectric properties compared to traditional inorganic or organic gate dielectrics. This study demonstrates the successful implementation of the rational design of metal-organic framework thin films on conductive supports with high-performance dielectric properties. PMID:27282348

  10. Terahertz antireflection coating enabled by a subwavelength metallic mesh capped with a thin dielectric film

    SciTech Connect

    Huang, Li; Chen, Hou -Tong; Zeng, Beibei; Chang, Chun -Chieh

    2016-03-30

    Metamaterials/metasurfaces have enabled unprecedented manipulation of electromagnetic waves. Here we present a new design of metasurface structure functioning as antireflection coatings. The structure consists of a subwavelength metallic mesh capped with a thin dielectric layer on top of a substrate. By tailoring the geometric parameters of the metallic mesh and the refractive index and thickness of the capping dielectric film, reflection from the substrate can be completely eliminated at a specific frequency. Compared to traditional methods such as coatings with single- or multi-layer dielectric films, the metasurface antireflection coatings are much thinner and the requirement of index matching is largely lifted. Here, this approach is particularly suitable for antireflection coatings in the technically challenging terahertz frequency range and is also applicable in other frequency regimes.

  11. A high-K ferroelectric relaxor terpolymer as a gate dielectric for organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Wu, Shan; Shao, Ming; Burlingame, Quinn; Chen, Xiangzhong; Lin, Minren; Xiao, Kai; Zhang, Q. M.

    2013-01-01

    Poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) is a ferroelectric terpolymer relaxor with a static dielectric constant of 50, which was developed using defect modification to eliminate remnant polarization in the normal ferroelectric PVDF. In this work, this solution processable terpolymer was used as the gate insulator in bottom gated organic thin-film transistors with a pentacene semiconductor layer. Due to the high dielectric constant of P(VDF-TrFE-CFE), a large capacitive coupling between the gate and channel can be achieved which causes a high charge concentration at the interface of the semiconductor and dielectric layers. In this device, an on/off ratio of 104 and a low minimum operation gate voltage (5-10 V) were attained.

  12. Integration of metal-organic frameworks into an electrochemical dielectric thin film for electronic applications

    NASA Astrophysics Data System (ADS)

    Li, Wei-Jin; Liu, Juan; Sun, Zhi-Hua; Liu, Tian-Fu; Lü, Jian; Gao, Shui-Ying; He, Chao; Cao, Rong; Luo, Jun-Hua

    2016-06-01

    The integration of porous metal-organic frameworks onto the surface of materials, for use as functional devices, is currently emerging as a promising approach for gas sensing and flexible displays. However, research focused on potential applications in electronic devices is in its infancy. Here we present a facile strategy by which interpenetrated, crystalline metal-organic framework films are deposited onto conductive metal-plate anodes via in situ temperature-controlled electrochemical assembly. The nanostructure of the surface as well as the thickness and uniformity of the film are well controlled. More importantly, the resulting films exhibit enhanced dielectric properties compared to traditional inorganic or organic gate dielectrics. This study demonstrates the successful implementation of the rational design of metal-organic framework thin films on conductive supports with high-performance dielectric properties.

  13. Dielectric dilatometry on thin Teflon-PTFE films prepared by pulsed-laser deposition

    NASA Astrophysics Data System (ADS)

    Schwoediauer, Reinhard; Bauer-Gogonea, Simona; Bauer, Stefan; Heitz, J.; Arenholz, Enno; Baeuerle, Dieter

    1999-12-01

    Polytetrafluoroethylene (Teflon PTFE) films were grown by pulsed-laser deposition (PLD). Films prepared by ablation from press-sintered targets are found to be highly crystalline, with spherulite sizes adjustable over more than one order in magnitude by suitable thermal annealing. As revealed by dielectric dilatometry, PLD-PTFE films show characteristics remarkably similar to those of conventional PTFE, i.e. the same structural first-order phase transitions. Dielectric losses are low and indicate no tendency to film oxidation. PLD-PTFE films additionally show an excellent charge-stability, comparable and even superior to commercially available Teflon-PTFE foils. PLD-PTFE enlarges the family of Teflon materials and may thus become interesting for potential miniaturized electret devices. Furthermore, dielectric dilatometry provides an elegant means for the determination of the coefficient of thermal expansion in thin nonpolar films.

  14. Terahertz antireflection coating enabled by a subwavelength metallic mesh capped with a thin dielectric film

    DOE PAGES

    Huang, Li; Chen, Hou -Tong; Zeng, Beibei; ...

    2016-03-30

    Metamaterials/metasurfaces have enabled unprecedented manipulation of electromagnetic waves. Here we present a new design of metasurface structure functioning as antireflection coatings. The structure consists of a subwavelength metallic mesh capped with a thin dielectric layer on top of a substrate. By tailoring the geometric parameters of the metallic mesh and the refractive index and thickness of the capping dielectric film, reflection from the substrate can be completely eliminated at a specific frequency. Compared to traditional methods such as coatings with single- or multi-layer dielectric films, the metasurface antireflection coatings are much thinner and the requirement of index matching is largelymore » lifted. Here, this approach is particularly suitable for antireflection coatings in the technically challenging terahertz frequency range and is also applicable in other frequency regimes.« less

  15. Morphology, Structural and Dielectric Properties of Vacuum Evaporated V2O5 Thin Films

    NASA Astrophysics Data System (ADS)

    Sengodan, R.; Shekar, B. Chandar; Sathish, S.

    Vanadium pentoxide (V2O5) thin films were deposited on well cleaned glass substrate using evaporation technique under the pressure of 10-5 Torr. The thickness of the films was measured by the multiple beam interferometry technique and cross checked by using capacitance method. Metal-Insulator-Metal (MIM) structure was fabricated by using suitable masks to study dielectric properties. The dielectric properties were studied by employing LCR meter in the frequency range 12 Hz to 100 kHz for various temperatures. The temperature co- efficient of permittivity (TCP), temperature co-efficient of capacitance (TCC) and dielectric constant (ɛ) were calculated. The activation energy was calculated and found to be very low. The activation energy was found to be increasing with increase in frequency. The obtained low value of activation energy suggested that the hopping conduction may be due to electrons rather than ions.

  16. Thermally conductive, dielectric PCM-boron nitride nanosheet composites for efficient electronic system thermal management.

    PubMed

    Yang, Zhi; Zhou, Lihui; Luo, Wei; Wan, Jiayu; Dai, Jiaqi; Han, Xiaogang; Fu, Kun; Henderson, Doug; Yang, Bao; Hu, Liangbing

    2016-11-24

    Phase change materials (PCMs) possessing ideal properties, such as superior mass specific heat of fusion, low cost, light weight, excellent thermal stability as well as isothermal phase change behavior, have drawn considerable attention for thermal management systems. Currently, the low thermal conductivity of PCMs (usually less than 1 W mK(-1)) greatly limits their heat dissipation performance in thermal management applications. Hexagonal boron nitride (h-BN) is a two-dimensional material known for its excellent thermally conductive and electrically insulating properties, which make it a promising candidate to be used in electronic systems for thermal management. In this work, a composite, consisting of h-BN nanosheets (BNNSs) and commercialized paraffin wax was developed, which inherits high thermally conductive and electrically insulating properties from BNNSs and substantial heat of fusion from paraffin wax. With the help of BNNSs, the thermal conductivity of wax-BNNS composites reaches 3.47 W mK(-1), which exhibits a 12-time enhancement compared to that of pristine wax (0.29 W mK(-1)). Moreover, an 11.3-13.3 MV m(-1) breakdown voltage of wax-BNNS composites was achieved, which shows further improved electrical insulating properties. Simultaneously enhanced thermally conductive and electrically insulating properties of wax-BNNS composites demonstrate their promising application for thermal management in electronic systems.

  17. Effect of hydrogen addition on the deposition of titanium nitride thin films in nitrogen added argon magnetron plasma

    NASA Astrophysics Data System (ADS)

    Saikia, P.; Bhuyan, H.; Diaz-Droguett, D. E.; Guzman, F.; Mändl, S.; Saikia, B. K.; Favre, M.; Maze, J. R.; Wyndham, E.

    2016-06-01

    The properties and performance of thin films deposited by plasma assisted processes are closely related to their manufacturing techniques and processes. The objective of the current study is to investigate the modification of plasma parameters occurring during hydrogen addition in N2  +  Ar magnetron plasma used for titanium nitride thin film deposition, and to correlate the measured properties of the deposited thin film with the bulk plasma parameters of the magnetron discharge. From the Langmuir probe measurements, it was observed that the addition of hydrogen led to a decrease of electron density from 8.6 to 6.2  ×  (1014 m-3) and a corresponding increase of electron temperature from 6.30 to 6.74 eV. The optical emission spectroscopy study reveals that with addition of hydrogen, the density of argon ions decreases. The various positive ion species involving hydrogen are found to increase with increase of hydrogen partial pressure in the chamber. The thin films deposited were characterized using standard surface diagnostic tools such as x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), x-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Although it was possible to deposit thin films of titanium nitride with hydrogen addition in nitrogen added argon magnetron plasma, the quality of the thin films deteriorates with higher hydrogen partial pressures.

  18. Exfoliation of crystalline 2D carbon nitride: thin sheets, scrolls and bundles via mechanical and chemical routes.

    PubMed

    Bojdys, Michael J; Severin, Nikolai; Rabe, Jürgen P; Cooper, Andrew I; Thomas, Arne; Antonietti, Markus

    2013-05-27

    The carbon nitride poly(triazine imide) with intercalated bromide ions is a layered, graphitic material of 2D covalently bonded molecular sheets with an exceptionally large gallery height of 3.52 Å due to the intercalated bromide anions. The material can be cleaved both mechanically and chemically into thin sheets and scrolls analogous to the carbon-only systems graphite and graphene. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Thin-film composite materials as a dielectric layer for flexible metal-insulator-metal capacitors.

    PubMed

    Tiwari, Jitendra N; Meena, Jagan Singh; Wu, Chung-Shu; Tiwari, Rajanish N; Chu, Min-Ching; Chang, Feng-Chih; Ko, Fu-Hsiang

    2010-09-24

    A new organic-organic nanoscale composite thin-film (NCTF) dielectric has been synthesized by solution deposition of 1-bromoadamantane and triblock copolymer (Pluronic P123, BASF, EO20-PO70-EO20), in which the precursor solution has been achieved with organic additives. We have used a sol-gel process to make a metal-insulator-metal capacitor (MIM) comprising a nanoscale (10 nm-thick) thin-film on a flexible polyimide (PI) substrate at room temperature. Scanning electron microscope and atomic force microscope revealed that the deposited NCTFs were crack-free, uniform, highly resistant to moisture absorption, and well adhered on the Au-Cr/PI. The electrical properties of 1-bromoadamantane-P123 NCTF were characterized by dielectric constant, capacitance, and leakage current measurements. The 1-bromoadamantane-P123 NCTF on the PI substrate showed a low leakage current density of 5.5 x 10(-11) A cm(-2) and good capacitance of 2.4 fF at 1 MHz. In addition, the calculated dielectric constant of 1-bromoadamantane-P123 NCTF was 1.9, making them suitable candidates for use in future flexible electronic devices as a stable intermetal dielectric. The electrical insulating properties of 1-bromoadamantane-P123 NCTF have been improved due to the optimized dipole moments of the van der Waals interactions.

  20. In situ atomic layer nitridation on the top and down regions of the amorphous and crystalline high-K gate dielectrics

    NASA Astrophysics Data System (ADS)

    Tsai, Meng-Chen; Lee, Min-Hung; Kuo, Chin-Lung; Lin, Hsin-Chih; Chen, Miin-Jang

    2016-11-01

    Amorphous and crystalline ZrO2 gate dielectrics treated with in situ atomic layer nitridation on the top and down regions (top and down nitridation, abbreviated as TN and DN) were investigated. In a comparison between the as-deposited amorphous DN and TN samples, the DN sample has a lower leakage current density (Jg) of ∼7 × 10-4 A/cm2 with a similar capacitance equivalent thickness (CET) of ∼1.53 nm, attributed to the formation of SiOxNy in the interfacial layer (IL). The post-metallization annealing (PMA) leads to the transformation of ZrO2 from the amorphous to the crystalline tetragonal/cubic phase, resulting in an increment of the dielectric constant. The PMA-treated TN sample exhibits a lower CET of 1.22 nm along with a similar Jg of ∼1.4 × 10-5 A/cm2 as compared with the PMA-treated DN sample, which can be ascribed to the suppression of IL regrowth. The result reveals that the nitrogen engineering in the top and down regions has a significant impact on the electrical characteristics of amorphous and crystalline ZrO2 gate dielectrics, and the nitrogen incorporation at the top of crystalline ZrO2 is an effective approach to scale the CET and Jg, as well as to improve the reliability.

  1. A dielectric elastomer actuator thin membrane rotary motor

    NASA Astrophysics Data System (ADS)

    Anderson, Iain A.; Calius, Emilio P.; Gisby, Todd; Hale, Thom; McKay, Thomas; O'Brien, Benjamin; Walbran, Scott

    2009-03-01

    We describe a low profile and lightweight membrane rotary motor based on the dielectric elastomer actuator (DEA). In this motor phased actuation of electroded sectors of the motor membrane imparts orbital motion to a central gear that meshes with the rotor. Two motors were fabricated: a three phase and four phase with three electroded sectors (120°/sector) and four sectors (90°/sector) respectively. Square segments of 3M VHB4905 tape were stretched equibiaxially to 16 times their original area and each was attached to a rigid circular frame. Electroded sectors were actuated with square wave voltages up to 2.5kV. Torque/power characteristics were measured. Contactless orbiter displacements, measured with the rotor removed, were compared with simulation data calculated using a finite element model. A measured specific power of approximately 8mW/g (based on the DEA membrane weight), on one motor compares well with another motor technology. When the mass of the frame was included a peak specific power of 0.022mW/g was calculated. We expect that motor performance can be substantially improved by using a multilayer DEA configuration, enabling the delivery of direct drive high torques at low speeds for a range of applications. The motor is inherently scalable, flexible, flat, silent in operation, amenable to deposition-based manufacturing approaches, and uses relatively inexpensive materials.

  2. High frequency scattering from a thin lossless dielectric slab. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Burgener, K. W.

    1979-01-01

    A solution for scattering from a thin dielectric slab is developed based on geometrical optics and the geometrical theory of diffraction with the intention of developing a model for a windshield of a small private aircraft for incorporation in an aircraft antenna code. Results of the theory are compared with experimental measurements and moment method calculations showing good agreement. Application of the solution is also addressed.

  3. Organic/Inorganic Nano-hybrids with High Dielectric Constant for Organic Thin Film Transistor Applications.

    PubMed

    Yu, Yang-Yen; Jiang, Ai-Hua; Lee, Wen-Ya

    2016-12-01

    The organic material soluble polyimide (PI) and organic-inorganic hybrid PI-barium titanate (BaTiO3) nanoparticle dielectric materials (IBX, where X is the concentration of BaTiO3 nanoparticles in a PI matrix) were successfully synthesized through a sol-gel process. The effects of various BaTiO3 contents on the hybrid film performance and performance optimization were investigated. Furthermore, pentacene-based organic thin film transistors (OTFTs) with PI-BaTiO3/polymethylmethacrylate or cyclic olefin copolymer (COC)-modified gate dielectrics were fabricated and examined. The hybrid materials showed effective dispersion of BaTiO3 nanoparticles in the PI matrix and favorable thermal properties. X-ray diffraction patterns revealed that the BaTiO3 nanoparticles had a perovskite structure. The hybrid films exhibited high formability and planarity. The IBX hybrid dielectric films exhibited tunable insulating properties such as the dielectric constant value and capacitance in ranges of 4.0-8.6 and 9.2-17.5 nF cm(-2), respectively. Adding the modified layer caused the decrease of dielectric constant values and capacitances. The modified dielectric layer without cross-linking displayed a hydrophobic surface. The electrical characteristics of the pentacene-based OTFTs were enhanced after the surface modification. The optimal condition for the dielectric layer was 10 wt% hybrid film with the COC-modified layer; moreover, the device exhibited a threshold voltage of 0.12 V, field-effect mobility of 4.32 × 10(-1) cm(2) V(-1) s(-1), and on/off current of 8.4 × 10(7).

  4. Organic/Inorganic Nano-hybrids with High Dielectric Constant for Organic Thin Film Transistor Applications

    NASA Astrophysics Data System (ADS)

    Yu, Yang-Yen; Jiang, Ai-Hua; Lee, Wen-Ya

    2016-11-01

    The organic material soluble polyimide (PI) and organic-inorganic hybrid PI-barium titanate (BaTiO3) nanoparticle dielectric materials (IBX, where X is the concentration of BaTiO3 nanoparticles in a PI matrix) were successfully synthesized through a sol-gel process. The effects of various BaTiO3 contents on the hybrid film performance and performance optimization were investigated. Furthermore, pentacene-based organic thin film transistors (OTFTs) with PI-BaTiO3/polymethylmethacrylate or cyclic olefin copolymer (COC)-modified gate dielectrics were fabricated and examined. The hybrid materials showed effective dispersion of BaTiO3 nanoparticles in the PI matrix and favorable thermal properties. X-ray diffraction patterns revealed that the BaTiO3 nanoparticles had a perovskite structure. The hybrid films exhibited high formability and planarity. The IBX hybrid dielectric films exhibited tunable insulating properties such as the dielectric constant value and capacitance in ranges of 4.0-8.6 and 9.2-17.5 nF cm-2, respectively. Adding the modified layer caused the decrease of dielectric constant values and capacitances. The modified dielectric layer without cross-linking displayed a hydrophobic surface. The electrical characteristics of the pentacene-based OTFTs were enhanced after the surface modification. The optimal condition for the dielectric layer was 10 wt% hybrid film with the COC-modified layer; moreover, the device exhibited a threshold voltage of 0.12 V, field-effect mobility of 4.32 × 10-1 cm2 V-1 s-1, and on/off current of 8.4 × 107.

  5. Effect of longitudinal electric field on capillary instability of a thin axisymmetric layer of liquid dielectric coating a dielectric fiber

    NASA Astrophysics Data System (ADS)

    Korovin, V. M.

    2016-12-01

    The flow of a viscous dielectric liquid surrounded with a gas is investigated in the process of capillary disintegration of a thin axisymmetric liquid layer on an undeformable cylindrical dielectric fiber in a uniform electric field is investigated. An asymptotic analysis of the system of equations and hydrodynamic boundary conditions written with allowance for surface ponderomotive forces is carried out for the case when the average thickness of the layer is much smaller than the radius of the fiber cross section. The problem of the transition of the liquid configuration from the state of a stationary cylindrical layer to the hydrodynamic state in the form of a regular sequence of drops is formulated. In this formulation, a nonlinear parabolic equation that describes the evolution of the local thickness of the layer on the time interval to the instant of drop formation is derived. The effect of the key parameters on the capillary instability is analyzed based on the linearized version of the resultant equation and the linearized electrostatic problem of calculating the field perturbations.

  6. Tailoring plasmonic properties of metal nanoparticle-embedded dielectric thin films: the sandwich method of preparation

    NASA Astrophysics Data System (ADS)

    Laha, Ranjit; Malar, P.; Osipowicz, Thomas; Kasiviswanathan, S.

    2017-09-01

    Tailoring of plasmonic properties of metal nanoparticle-embedded dielectric thin films are very crucial for many thin film-based applications. We, herein, investigate the various ways of tuning the plasmonic positions of gold nanoparticles (AuNPs)-embedded indium oxide thin films (Au:IO) through a sequence-specific sandwich method. The sandwich method is a four-step process involving deposition of In2O3 film by magnetron sputtering in first and fourth steps, thermal evaporation of Au on to In2O3 film in second and annealing of Au/In2O3 film in the third step. The Au:IO films were characterized by x-ray diffraction, spectrophotometry and transmission electron microscopy. The size and shape of the embedded nanoparticles were found from Rutherford back-scattering spectrometry. Based on dynamic Maxwell Garnett theory, the observed plasmon resonance position was ascribed to the oblate shape of AuNPs formed in sandwich method. Finally, through experimental data, it was shown that the plasmon resonance position of Au:IO thin films can be tuned by 125 nm. The method shown here can be used to tune the plasmon resonance position over the entire range of visible region for the thin films made from other combinations of metal-dielectric pair.

  7. Optical properties of dielectric thin films including quantum dots

    NASA Astrophysics Data System (ADS)

    Flory, F.; Chen, Y. J.; Lee, C. C.; Escoubas, L.; Simon, J. J.; Torchio, P.; Le Rouzo, J.; Vedraine, S.; Derbal-Habak, Hassina; Ackermann, Jorg; Shupyk, Ivan; Didane, Yahia

    2010-08-01

    Depending on the minimum size of their micro/nano structure, thin films can exhibit very different behaviors and optical properties. From optical waveguides down to artificial anisotropy, through diffractive optics and photonic crystals, the application changes when decreasing the minimum feature size. Rigorous electromagnetic theory can be used to model most of the components but when the size is of a few nanometers, quantum theory has also to be used. These materials including quantum structures are of particular interest for other applications, in particular for solar cells, because of their luminescent and electronic properties. We show that the properties of electrons in multiple quantum wells can be easily modeled with a formalism similar to that used for multilayer waveguides. The effects of different parameters, in particular coupling between wells and well thickness dispersion, on possible discrete energy levels or energy band of electrons and on electron wave functions is given. When such quantum confinement appears the spectral absorption and the extinction coefficient dispersion with wavelength is modified. The dispersion of the real part of the refractive index can then be deduced from the Kramers- Krönig relations. Associated with homogenization theory this approach gives a new model of refractive index for thin films including quantum dots. Absorption spectra of samples composed of ZnO quantum dots in PMMA layers are in preparation are given.

  8. Optical properties of dielectric thin films including quantum dots.

    PubMed

    Flory, François; Chen, Yu-Jen; Lee, Cheng-Chung; Escoubas, Ludovic; Simon, Jean-Jacques; Torchio, Philippe; Le Rouzo, Judikaël; Vedraine, Sylvain; Derbal-Habak, Hassina; Shupyk, Ivan; Didane, Yahia; Ackermann, Jörg

    2011-03-20

    Depending on the minimum size of their micro/nanostructure, thin films can exhibit very different behaviors and optical properties. From optical waveguides down to artificial anisotropy, through diffractive optics and photonic crystals, the application changes when decreasing the minimum feature size. Rigorous electromagnetic theory can be used to model most of the components, but, when the size is a few nanometers, quantum theory also has to be used. The materials, including quantum structures, are of particular interest for many applications, in particular for solar cells because of their luminescent and electronic properties. We show that the properties of electrons in periodic and nonperiodic multiple quantum well structures can be easily modeled with a formalism similar to that used for multilayer waveguides. The effects of different parameters, in particular the coupling between wells and well thickness dispersion, on possible discrete energy levels or the energy band of electrons and on electron wave functions are given. When such quantum confinement appears, the spectral absorption and extinction coefficient dispersion with wavelength are modified. The dispersion of the real part of the refractive index can be deduced from the Kramers-Kronig relations. Associated with homogenization theory, this approach gives a new model of the refractive index for thin films including quantum dots. The bandgap of ZnO quantum dots in solution obtained from the absorption spectrum is in good agreement with our calculation.

  9. Investigation of electron mobility and saturation velocity limits in gallium nitride using uniaxial dielectric continuum model

    NASA Astrophysics Data System (ADS)

    Park, K.; Stroscio, M. A.; Bayram, C.

    2017-06-01

    Here we introduce a uniaxial dielectric continuum model with temperature-dependent phonon mode frequencies to study temperature- and orientation-dependent polar-optical-phonon limited electron mobility and saturation velocity in uniaxial semiconductors. The formalism for calculating electron scattering rates, momentum relaxation rates, and rate of energy change as a function of the electron kinetic energy and incident electron angle with respect to the c-axis are presented and evaluated numerically. Electron-longitudinal-optical-phonon interactions are shown to depend weakly on the electron incident angle, whereas the electron-transverse-optical-phonon interactions around the emission threshold energy are observed to depend strongest on the electron incident angle when varied from π/4 to π/2 (with respect to the c-axis). We provide electron mobility and saturation velocity limits in different GaN crystal orientations as a function of temperature and electron concentration. At room temperature and for an electron density of 5 × 1018 cm-3, electron mobility limit of ˜3200 cm2/V s and electron saturation velocity limit of 3.15 × 107 cm/s are calculated. Both GaN electron mobility and saturation velocity are observed to be governed by the longitudinal-optical-phonon interaction, and their directional anisotropy is shown to vary less than 5% as the electron incident angle with respect to the c-axis is varied from 0 to π/2. Overall, we develop a theoretical formalism for calculating anisotropic properties of uniaxial wurtzite semiconductors.

  10. Adhesion, friction, and wear of plasma-deposited thin silicon nitride films at temperatures to 700 C

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Pouch, J. J.; Alterovitz, S. A.; Pantic, D. M.; Johnson, G. A.

    1988-01-01

    The adhesion, friction, and wear behavior of silicon nitride films deposited by low- and high-frequency plasmas (30 kHz and 13.56 MHz) at various temperatures to 700 C in vacuum were examined. The results of the investigation indicated that the Si/N ratios were much greater for the films deposited at 13.56 MHz than for those deposited at 30 kHz. Amorphous silicon was present in both low- and high-frequency plasma-deposited silicon nitride films. However, more amorphous silicon occurred in the films deposited at 13.56 MHz than in those deposited at 30 kHz. Temperature significantly influenced adhesion, friction, and wear of the silicon nitride films. Wear occurred in the contact area at high temperature. The wear correlated with the increase in adhesion and friction for the low- and high-frequency plasma-deposited films above 600 and 500 C, respectively. The low- and high-frequency plasma-deposited thin silicon nitride films exhibited a capability for lubrication (low adhesion and friction) in vacuum at temperatures to 500 and 400 C, respectively.

  11. Correlation between bonding structure and microstructure in fullerenelike carbon nitride thin films

    SciTech Connect

    Gago, R.; Abendroth, B.; Moeller, W.; Jimenez, I.; Neidhardt, J.; Hultman, L.; Caretti, I.

    2005-03-15

    The bonding structure of highly ordered fullerenelike (FL) carbon nitride (CN{sub x}) thin films has been assessed by x-ray absorption near-edge spectroscopy (XANES). Samples with different degrees of FL character have been analyzed to discern spectral signatures related to the FL microstructure. The XANES spectra of FL-CN{sub x} films resemble that of graphitic CN{sub x}, evidencing the sp{sup 2} hybridization of both C and N atoms. The FL structure is achieved with the promotion of N in threefold positions over pyridinelike and cyanidelike bonding environments. In addition, the relative {pi}{sup *}/{sigma}* XANES intensity ratio at the C(1s) edge is independent of the FL character, while it decreases {approx}40% at the N(1s) edge with the formation of FL arrangements. This result indicates that there is no appreciable introduction of C-sp{sup 3} hybrids with the development of FL structures and, additionally, that a different spatial localization of {pi} electrons at C and N sites takes place in curved graphitic structures. The latter has implications for the elastic properties of graphene sheets and could, as such, explain the outstanding elastic properties of FL-CN{sub x}.

  12. Enhanced Field Emission from a Carbon Nanotube Array Coated with a Hexagonal Boron Nitride Thin Film.

    PubMed

    Yang, Xiaoxia; Li, Zhenjun; He, Feng; Liu, Mingju; Bai, Bing; Liu, Wei; Qiu, Xiaohui; Zhou, Hang; Li, Chi; Dai, Qing

    2015-08-12

    A high-quality field emission electron source made of a highly ordered array of carbon nanotubes (CNTs) coated with a thin film of hexagonal boron nitride (h-BN) is fabricated using a simple and scalable method. This method offers the benefit of reproducibility, as well as the simplicity, safety, and low cost inherent in using B(2)O(3) as the boron precursor. Results measured using h-BN-coated CNT arrays are compared with uncoated control arrays. The optimal thickness of the h-BN film is found to be 3 nm. As a result of the incorporation of h-BN, the turn-on field is found to decrease from 4.11 to 1.36 V μm(-1), which can be explained by the significantly lower emission barrier that is achieved due to the negative electron affinity of h-BN. Meanwhile, the total emission current is observed to increase from 1.6 to 3.7 mA, due to a mechanism that limits the self-current of any individual emitting tip. This phenomenon also leads to improved emission stability and uniformity. In addition, the lifetime of the arrays is improved as well. The h-BN-coated CNT array-based field emitters proposed in this work may open new paths for the development of future high-performance vacuum electronic devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Cubic boron nitride thin film growth by boron and nitrogen ion implantation

    SciTech Connect

    Eyhusen, S.; Ronning, C.; Hofsaess, H.

    2005-08-01

    Cubic boron nitride (c-BN) thin films were deposited on silicon substrates using mass separated ion beam deposition (MSIBD). In order to investigate the influence of the ion energy on the growth of c-BN films, {sup 11}B{sup +} and {sup 14}N{sup +} ions were implanted into c-BN with ion energies ranging from 5 keV to 43 keV and substrate temperatures (T{sub S}) from room temperature (RT) to 250 deg. C. A systematic study on the interplay of E{sub ion} and T{sub S} has revealed a characteristic energy-dependent temperature threshold for c-BN growth. This behavior is explained by dynamic annealing of defects caused by a penetrating ion in a collision cascade. In this picture, the suppression of defect accumulation that is crucial for maintaining cubic phase formation is attributed to temperature-driven back diffusion and subsequent annihilation of B and N interstitial recoils. The model is confirmed by analyzing the depth profile of implanted, isotopically pure {sup 10}B, and its application for both c-BN nucleation and growth is discussed.

  14. Superconducting energy scales and anomalous dissipative conductivity in thin films of molybdenum nitride

    SciTech Connect

    Simmendinger, Julian; Pracht, Uwe S.; Daschke, Lena; Proslier, Thomas; Klug, Jeffrey A.; Dressel, Martin; Scheffler, Marc

    2016-08-01

    We report investigations of molybdenum nitride (MoN) thin films with different thickness and disorder and with superconducting transition temperature 9.89K >= T-c >= 2.78 K. Using terahertz frequency-domain spectroscopy we explore the normal and superconducting charge carrier dynamics for frequencies covering the range from 3 to 38 cm(-1) (0.1 to 1.1 THz). The superconducting energy scales, i.e., the critical temperature T-c, the pairing energy Delta, and the superfluid stiffness J, and the superfluid density n(s) can be well described within the Bardeen-Cooper-Schrieffer theory for conventional superconductors. At the same time, we find an anomalously large dissipative conductivity, which cannot be explained by thermally excited quasiparticles, but rather by a temperature-dependent normal-conducting fraction, persisting deep into the superconducting state. Our results on this disordered system constrain the regime, where discernible effects stemming from the disorder-induced superconductor-insulator transition possibly become relevant, to MoN films with a transition temperature lower than at least 2.78 K.

  15. Alternative process for thin layer etching: Application to nitride spacer etching stopping on silicon germanium

    SciTech Connect

    Posseme, N. Pollet, O.; Barnola, S.

    2014-08-04

    Silicon nitride spacer etching realization is considered today as one of the most challenging of the etch process for the new devices realization. For this step, the atomic etch precision to stop on silicon or silicon germanium with a perfect anisotropy (no foot formation) is required. The situation is that none of the current plasma technologies can meet all these requirements. To overcome these issues and meet the highly complex requirements imposed by device fabrication processes, we recently proposed an alternative etching process to the current plasma etch chemistries. This process is based on thin film modification by light ions implantation followed by a selective removal of the modified layer with respect to the non-modified material. In this Letter, we demonstrate the benefit of this alternative etch method in term of film damage control (silicon germanium recess obtained is less than 6 A), anisotropy (no foot formation), and its compatibility with other integration steps like epitaxial. The etch mechanisms of this approach are also addressed.

  16. Surface cleaning procedures for thin films of indium gallium nitride grown on sapphire

    NASA Astrophysics Data System (ADS)

    Douglass, K.; Hunt, S.; Teplyakov, A.; Opila, R. L.

    2010-12-01

    Surface preparation procedures for indium gallium nitride (InGaN) thin films were analyzed for their effectiveness for carbon and oxide removal as well as for the resulting surface roughness. Aqua regia (3:1 mixture of concentrated hydrochloric acid and concentrated nitric acid, AR), hydrofluoric acid (HF), hydrochloric acid (HCl), piranha solution (1:1 mixture of sulfuric acid and 30% H 2O 2) and 1:9 ammonium sulfide:tert-butanol were all used along with high temperature anneals to remove surface contamination. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were utilized to study the extent of surface contamination and surface roughness, respectively. The ammonium sulfide treatment provided the best overall removal of oxygen and carbon. Annealing over 700 °C after a treatment showed an even further improvement in surface contamination removal. The piranha treatment resulted in the lowest residual carbon, while the ammonium sulfide treatment leads to the lowest residual oxygen. AFM data showed that all the treatments decreased the surface roughness (with respect to as-grown specimens) with HCl, HF, (NH 4) 2S and RCA procedures giving the best RMS values (˜0.5-0.8 nm).

  17. Photochemical functionalization of gallium nitride thin films with molecular and biomolecular layers.

    PubMed

    Kim, Heesuk; Colavita, Paula E; Metz, Kevin M; Nichols, Beth M; Sun, Bin; Uhlrich, John; Wang, Xiaoyu; Kuech, Thomas F; Hamers, Robert J

    2006-09-12

    We demonstrate that photochemical functionalization can be used to functionalize and photopattern the surface of gallium nitride crystalline thin films with well-defined molecular and biomolecular layers. GaN(0001) surfaces exposed to a hydrogen plasma will react with organic molecules bearing an alkene (C=C) group when illuminated with 254 nm light. Using a bifunctional molecule with an alkene group at one end and a protected amine group at the other, this process can be used to link the alkene group to the surface, leaving the protected amine exposed. Using a simple contact mask, we demonstrate the ability to directly pattern the spatial distribution of these protected amine groups on the surface with a lateral resolution of <12 mum. After deprotection of the amines, single-stranded DNA oligonucleotides were linked to the surface using a bifunctional cross-linker. Measurements using fluorescently labeled complementary and noncomplementary sequences show that the DNA-modified GaN surfaces exhibit excellent selectivity, while repeated cycles of hybridization and denaturation in urea show good stability. These results demonstrate that photochemical functionalization can be used as an attractive starting point for interfacing molecular and biomolecular systems with GaN and other compound semiconductors.

  18. Superconducting energy scales and anomalous dissipative conductivity in thin films of molybdenum nitride

    NASA Astrophysics Data System (ADS)

    Simmendinger, Julian; Pracht, Uwe S.; Daschke, Lena; Proslier, Thomas; Klug, Jeffrey A.; Dressel, Martin; Scheffler, Marc

    2016-08-01

    We report investigations of molybdenum nitride (MoN) thin films with different thickness and disorder and with superconducting transition temperature 9.89 K ≥Tc≥2.78 K . Using terahertz frequency-domain spectroscopy we explore the normal and superconducting charge carrier dynamics for frequencies covering the range from 3 to 38 cm-1 (0.1 to 1.1 THz). The superconducting energy scales, i.e., the critical temperature Tc, the pairing energy Δ , and the superfluid stiffness J , and the superfluid density ns can be well described within the Bardeen-Cooper-Schrieffer theory for conventional superconductors. At the same time, we find an anomalously large dissipative conductivity, which cannot be explained by thermally excited quasiparticles, but rather by a temperature-dependent normal-conducting fraction, persisting deep into the superconducting state. Our results on this disordered system constrain the regime, where discernible effects stemming from the disorder-induced superconductor-insulator transition possibly become relevant, to MoN films with a transition temperature lower than at least 2.78 K.

  19. Mechanistic, surface chemistry, and growth studies of novel precursors for aluminum nitride thin films

    NASA Astrophysics Data System (ADS)

    Robinson, David Walter

    One of the primary techniques for thin film deposition used in the fabrication of microelectronic and optoelectronic devices is chemical vapor deposition (CVD). In CVD, nutrient elements for film growth are transported in the gas phase to the growth surface where a complex series of chemical reactions occurs. The selection of the chemicals and process parameters determines the properties of the film that will be obtained. Aluminum nitride (AlN) is a direct wide bandgap material with excellent physical properties making it useful for a wide variety of solid state device applications. This research focused on (1) screening novel chemicals as viable sources for vapor phase deposition of AlN by investigating their adsorption and decomposition behavior on technologically important substrates, (2) developing growth strategies from these results, (3) implementing the growth strategies, and (4) characterizing the thin films that were deposited. Surface chemistry investigations of four potential AlN CVD sources were conducted. The sources were bis[amidobis(trimethylsilyl)aluminum] (BABTMSA), 1,1-dimethylhydrazine (DMHy), ammonia (NH3), and dimethylethylamine alane (DMEAA). BABTMSA, a potential single source precursor, did not have adsorption properties that allowed for facile decomposition to AlN. DMHy, NH3, and DMEAA all showed adsorption and decomposition behavior on Si(100) under certain conditions that was promising for AIN deposition. A growth strategy was developed for the deposition of AlN thin films at low temperature with minimal impurities employing a temperature modulated atomic layer growth (ALG) process using DMHy and DMEAA precursors. The growth strategy was implemented and investigated. The deposition proceeded primarily through the dehydrogenation of AlHyNHx species where regeneration of these species occurred in each cycle. This was also found to be the primary mechanism for ALG of AlN using DMEAA and NH3 and similar processing conditions. The low

  20. Poly-crystalline thin-film by aluminum induced crystallization on aluminum nitride substrate

    NASA Astrophysics Data System (ADS)

    Bhopal, Muhammad Fahad; Lee, Doo Won; Lee, Soo Hong

    2016-09-01

    Thin-film polycrystalline silicon ( pc-Si) on foreign (non-silicon) substrates has been researched by various research groups for the production of photovoltaic cells. High quality pc-Si deposition on foreign substrates with superior optical properties is considered to be the main hurdle in cell fabrication. Metal induced crystallization (MIC) is one of the renowned techniques used to produce this quality of material. In the current study, an aluminum induced crystallization (AIC) method was adopted to produce pc-Si thin-film on aluminum nitride (AlN) substrate by a seed layer approach. Aluminum and a-Si layer were deposited using an e-beam evaporator. Various annealing conditions were used in order to investigate the AIC grown pc-Si seed layers for process optimization. The effect of thermal annealing on grain size, defects preferentially crystallographic orientation of the grains were analyzed. Surface morphology was studied using an optical microscope. Poly-silicon film with a crystallinity fraction between 95-100% and an FWHM between 5-6 cm-1 is achievable at low temperatures and for short time intervals. A grain size of about 10 micron can be obtained at a low deposition rate on an AIN substrate. Similarly, Focused ion beam (FIB) also showed that at 425 °C sample B and at 400 °C sample A were fully crystallized. The crystalline quality of pc-Si was evaluated using μ-Raman spectroscopy as a function of annealed conditions and Grazing incidence X-ray diffraction (GIXRD) was used to determine the phase direction of the pc-Si layer. The current study implicates that a poly-silicon layer with good crystallographic orientation and crystallinity fraction is achievable on AIN substrate at low temperatures and short time frames.

  1. All-amorphous-oxide transparent, flexible thin-film transistors. Efficacy of bilayer gate dielectrics.

    PubMed

    Liu, Jun; Buchholz, D Bruce; Hennek, Jonathan W; Chang, Robert P H; Facchetti, Antonio; Marks, Tobin J

    2010-09-01

    Optically transparent and mechanically flexible thin-film transistors (TF-TFTs) composed exclusively of amorphous metal oxide films are fabricated on plastic substrates by combining an amorphous Ta(2)O(5)/SiO(x) bilayer transparent oxide insulator (TOI) gate dielectric with an amorphous zinc-indium-tin oxide (a-ZITO) transparent oxide semiconductor (TOS) channel and a-ZITO transparent oxide conductor (TOC) electrodes. The bilayer gate dielectric is fabricated by the post-cross-linking of vapor-deposited hexachlorodisiloxane-derived films to form thin SiO(x) layers (v-SiO(x)) on amorphous Ta(2)O(5) (a-Ta(2)O(5)) films grown by ion-assisted deposition at room temperature. The a-Ta(2)O(5)/v-SiO(x) bilayer TOI dielectric integrates the large capacitance of the high dielectric constant a-Ta(2)O(5) layer with the excellent dielectric/semiconductor interfacial compatibility of the v-SiO(x) layer in a-ZITO TOS-based TF-TFTs. These all-amorphous-oxide TF-TFTs, having a channel length and width of 100 and 2000 microm, respectively, perform far better than a-Ta(2)O(5)-only devices and exhibit saturation-regime field-effect mobilities of approximately 20 cm(2)/V x s, on-currents >10(-4) A, and current on-off ratios >10(5). These TFTs operate at low voltages (approximately 4.0 V) and exhibit good visible-region optical transparency and excellent mechanical flexibility.

  2. Textured ferroelectric thin films: Synthesis, characterization, and influence of compositional grading on the dielectric behavior

    NASA Astrophysics Data System (ADS)

    El-Naggar, Mohamed Y.

    This dissertation focuses on two topics concerning the connections between structure and property in ferroelectric thin films. First, the synthesis of highly oriented ferroelectric thin films is addressed, where the texture is needed to generate high strains that rely on electromechanical domain switching. The ferroelectric films are integrated with oxide electrodes onto single crystal MgO and Si substrates using biaxially-textured MgO as buffer layers. The second topic focuses on modeling the dielectric behavior of compositionally graded ferroelectrics. The functional ferroelectric PbxBa1- xTiO3 films are deposited by metalorganic chemical vapor deposition (MOCVD). SrRuO3, grown by pulsed laser deposition (PLD), is a lattice-matching electrode. Both the ferroelectric and oxide electrode layers are found to inherit the biaxial texture of the underlying MgO template, which can be deposited by ion beam assisted deposition (IBAD) directly on Si-based substrates. In addition, we demonstrated control of the ferroelectric film stoichiometry using a spectroscopic control loop that monitors the ultraviolet spectra of the gas-phase MOCVD precursors during growth. Detailed studies of the microstructural details of these films will be presented. The second topic of this thesis explores the dielectric behavior of functionally graded ferroelectric thin films. Homogenous ferroelectrics offer the possibility of engineering a tunable dielectric response for components in microwave circuits. However, this approach often leads to an undesired temperature sensitivity. Compositionally-graded BaxSr1- xTO3 ferroelectric films have been explored as a means of redressing this sensitivity, but experimental observations vary depending on geometry and other details. A continuum model is presented to calculate the capacitive response of graded ferroelectric films with realistic electrode geometries by accurately accounting for the polarization distribution and long-range electrostatic

  3. Microstructural and Electrical Characterization of Silicon Carbide and Aluminum Nitride Thin Films Grown by Gas-Source Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Kern, Richard Scott

    1996-08-01

    Monocrystalline thin films, multilayered heterostructures and solid solutions of silicon carbide (SiC) and aluminum nitride (AlN) have been grown on alpha(6H) -SiC(0001) substrates by gas-source molecular beam epitaxy. Growth mechanisms, defect formation, donor and acceptor doping, metal-insulator-semiconductor diodes, pseudomorphic heterostructures and solid solutions in these materials have been studied. Monocrystalline films of beta(3C) -SiC(111) and alpha(6H)-SiC(0001) have been controllably deposited on the silicon face of 6H-SiC(0001) substrates. Polytype control was achieved via changes in the substrate orientation, substrate temperature and gas phase chemistry. Step flow growth was achieved on vicinal substrates at growth temperatures of at least 1350^circC using the SiH _4-rm C_2H_4 -H_2 system. Step bunching, cubic SiC nucleation and double positioning boundaries were observed at all temperatures when H_2 was removed from the system or the growth was performed at below 1350^circC. In both cases, growth rate was strongly dependent on temperature. Films doped using either a NH_3/H _2 mixture or pure N_2 were n-type; Al, p-type. Uniform, controllable doping levels between 10^{15} and 10^{19} cm ^{-3} were achieved for both polytypes. The measured mobility in the undoped 6H polytype, 434 cm ^2 V^{-1} s ^{-1}, is the highest reported in this polytype. Monocrystalline AlN was deposited using aluminum evaporated from a modified MBE effusion cell and either activated nitrogen derived from a compact electron cyclotron resonance plasma source or ammonia. Growth using each of the nitrogen sources was optimized with respect to substrate temperature, reactant flux and system pressure. In general, very thin films (<=q50 A) grown on vicinal 6H-SiC had a higher defect density than those grown on nominally on-axis substrates due to defect formation at or near the steps on the SiC surface. Full-width half maximum (FWHM) values of the (0002)_ {AlN} X-ray diffraction Bragg

  4. Thin dielectric film thickness determination by advanced transmission electron microscopy

    SciTech Connect

    Diebold, A.C.; Foran, B.; Kisielowski, C.; Muller, D.; Pennycook, S.; Principe, E.; Stemmer, S.

    2003-09-01

    High Resolution Transmission Electron Microscopy (HR-TEM) has been used as the ultimate method of thickness measurement for thin films. The appearance of phase contrast interference patterns in HR-TEM images has long been confused as the appearance of a crystal lattice by non-specialists. Relatively easy to interpret crystal lattice images are now directly observed with the introduction of annular dark field detectors for scanning TEM (STEM). With the recent development of reliable lattice image processing software that creates crystal structure images from phase contrast data, HR-TEM can also provide crystal lattice images. The resolution of both methods was steadily improved reaching now into the sub Angstrom region. Improvements in electron lens and image analysis software are increasing the spatial resolution of both methods. Optimum resolution for STEM requires that the probe beam be highly localized. In STEM, beam localization is enhanced by selection of the correct aperture. When STEM measurement is done using a highly localized probe beam, HR-TEM and STEM measurement of the thickness of silicon oxynitride films agree within experimental error. In this paper, the optimum conditions for HR-TEM and STEM measurement are discussed along with a method for repeatable film thickness determination. The impact of sample thickness is also discussed. The key result in this paper is the proposal of a reproducible method for film thickness determination.

  5. Optically activated sub-millimeter dielectric relaxation in amorphous thin film silicon at room temperature

    SciTech Connect

    Rahman, Rezwanur; Ohno, Tim R.; Taylor, P. C.; Scales, John A.

    2014-05-05

    Knowing the frequency-dependent photo-induced complex conductivity of thin films is useful in the design of photovoltaics and other semi-conductor devices. For example, annealing in the far-infrared could in principle be tailored to the specific dielectric properties of a particular sample. The frequency dependence of the conductivity (whether dark or photo-induced) also gives insight into the effective dimensionality of thin films (via the phonon density of states) as well as the presence (or absence) of free carriers, dopants, defects, etc. Ultimately, our goal is to make low-noise, phase-sensitive room temperature measurements of the frequency-dependent conductivity of thin films from microwave frequencies into the far-infrared; covering, the frequency range from ionic and dipole relaxation to atomic and electronic processes. To this end, we have developed a high-Q (quality factor) open cavity resonator capable of resolving the complex conductivity of sub-micron films in the range of 100–350 GHz (0.1–0.35 THz, or 0.4–1 meV). In this paper, we use a low-power green laser to excite bound charges in high-resistivity amorphous silicon thin film. Even at room temperature, we can resolve both the dark conductivity and photo-induced changes associated with dielectric relaxation and possibly some small portion of free carriers.

  6. Deposition of magnesium nitride thin films on stainless steel-304 substrates by using a plasma focus device

    NASA Astrophysics Data System (ADS)

    Ramezani, Amir Hoshang; Habibi, Maryam; Ghoranneviss, Mahmood

    2014-08-01

    In this research, for the first time, we synthesize magnesium nitride thin films on 304-type stainless steel substrates using a Mather-type (2 kJ) plasma focus (PF) device. The films of magnesium nitride are coated with different number of focus shots (like 15, 25 and 35) at a distance of 8 cm from the anode tip and at 0° angular position with respect to the anode axis. For investigation of the structural properties and surface morphology of magnesium nitride films, we utilized the X-ray diffractometer (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis, respectively. Also, the elemental composition is characterized by energy-dispersive X-ray (EDX) analysis. Furthermore, Vicker's microhardness is used to study the mechanical properties of the deposited films. The results show that the degree of crystallinity of deposited thin films (from XRD), the average size of particles and surface roughness (from AFM), crystalline growth of structures (from SEM) and the hardness values of the films depend on the number of focus shots. The EDX analysis demonstrates the existence of the elemental composition of magnesium in the deposited samples.

  7. Effect of radio-frequency electric power applied to a boron nitride unbalanced magnetron sputter target on the deposition of cubic boron nitride thin film

    NASA Astrophysics Data System (ADS)

    Ko, Ji-Sun; Park, Jong-Keuk; Lee, Wook-Seong; Huh, Joo-Youl; Baik, Young-Joon

    2013-11-01

    Cubic boron nitride (c-BN) films were deposited by an unbalanced magnetron sputtering method. A (100) Si wafer with a nanocrystalline diamond thin film as a surface coating layer or that without it was used as a substrate. The target power was varied from 100 to 400 W. A boron nitride target was used, which was connected to a radio frequency power supply. High frequency power connected to a substrate holder was used for self-biasing. The deposition pressure was 0.27 MPa with a flow of Ar (18 sccm) — N2 (2 sccm) mixed gas. The existence of threshold bias voltages for c-BN formation and resputtering were observed irrespective of target power. The bias voltage window for c-BN formation broadened with increased target power. The deposition rate decreased with enhanced bias voltage and decreased target power. Residual stresses of the films did not vary noticeably with target power within the target power range of c-BN formation. A parameter space for c-BN formation according to the target power and the bias voltage, as two variables, was suggested.

  8. Visualization of dielectric constant-electric field-temperature phase maps for imprinted relaxor ferroelectric thin films

    SciTech Connect

    Frederick, J. C.; Kim, T. H.; Maeng, W.; Brewer, A. A.; Podkaminer, J. P.; Saenrang, W.; Vaithyanathan, V.; Schlom, D. G.; Li, F.; Chen, L.-Q.; Trolier-McKinstry, S.; Rzchowski, M. S.; Eom, C. B.

    2016-03-28

    The dielectric phase transition behavior of imprinted lead magnesium niobate–lead titanate relaxor ferroelectric thin films was mapped as a function of temperature and dc bias. To compensate for the presence of internal fields, an external electric bias was applied while measuring dielectric responses. The constructed three-dimensional dielectric maps provide insight into the dielectric behaviors of relaxor ferroelectric films as well as the temperature stability of the imprint. The transition temperature and diffuseness of the dielectric response correlate with crystallographic disorder resulting from strain and defects in the films grown on strontium titanate and silicon substrates; the latter was shown to induce a greater degree of disorder in the film as well as a dielectric response lower in magnitude and more diffuse in nature over the same temperature region. Strong and stable imprint was exhibited in both films and can be utilized to enhance the operational stability of piezoelectric devices through domain self-poling.

  9. Ultra-thin ohmic contacts for p-type nitride light emitting devices

    DOEpatents

    Raffetto, Mark [Raleigh, NC; Bharathan, Jayesh [Cary, NC; Haberern, Kevin [Cary, NC; Bergmann, Michael [Chapel Hill, NC; Emerson, David [Chapel Hill, NC; Ibbetson, James [Santa Barbara, CA; Li, Ting [Ventura, CA

    2012-01-03

    A semiconductor based Light Emitting Device (LED) can include a p-type nitride layer and a metal ohmic contact, on the p-type nitride layer. The metal ohmic contact can have an average thickness of less than about 25 .ANG. and a specific contact resistivity less than about 10.sup.-3 ohm-cm.sup.2.

  10. Galvanic corrosion of structural non-stoichiometric silicon nitride thin films and its implications on reliability of microelectromechanical devices

    SciTech Connect

    Broas, M. Mattila, T. T.; Paulasto-Kröckel, M.; Liu, X.; Ge, Y.

    2015-06-28

    This paper describes a reliability assessment and failure analysis of a poly-Si/non-stoichiometric silicon nitride thin film composite structure. A set of poly-Si/SiN{sub x} thin film structures were exposed to a mixed flowing gas (MFG) environment, which simulates outdoor environments, for 90 days, and an elevated temperature and humidity (85 °C/95% R.H.) test for 140 days. The mechanical integrity of the thin films was observed to degrade during exposure to the chemically reactive atmospheres. The degree of degradation was analyzed with nanoindentation tests. Statistical analysis of the forces required to initiate a fracture in the thin films indicated degradation due to the exposure to the MFG environment in the SiN{sub x} part of the films. Scanning electron microscopy revealed a porous-like reaction layer on top of SiN{sub x}. The morphology of the reaction layer resembled that of galvanically corroded poly-Si. Transmission electron microscopy further clarified the microstructure of the reaction layer which had a complex multi-phase structure extending to depths of ∼100 nm. Furthermore, the layer was oxidized two times deeper in a 90 days MFG-tested sample compared to an untested reference. The formation of the layer is proposed to be caused by galvanic corrosion of elemental silicon in non-stoichiometric silicon nitride during hydrofluoric acid etching. The degradation is proposed to be due uncontrolled oxidation of the films during the stress tests.

  11. Zirconium doped TiO2 thin films: A promising dielectric layer

    NASA Astrophysics Data System (ADS)

    Kumar, Arvind; Mondal, Sandip; Rao, K. S. R. Koteswara

    2016-05-01

    In the present work, we have fabricated the zirconium doped TiO2 thin (ZTO) films from a facile spin - coating method. The addition of Zirconium in TiO2 offers conduction band offset to Si and consequently decreased the leakage current density by approximately two orders as compared to pure TiO2 thin (TO) films. The ZTO thin film shows a high dielectric constant 27 with a very low leakage current density ˜10-8 A/cm2. The oxide capacitate, flat band voltage and change in flat band voltage are 172 pF, -1.19 V and 54 mV. The AFM analysis confirmed the compact and pore free flat surface. The RMS surface roughness is found to be 1.5 Å. The ellipsometry analysis also verified the fact with a high refractive index 2.21.

  12. Zirconium doped TiO{sub 2} thin films: A promising dielectric layer

    SciTech Connect

    Kumar, Arvind; Mondal, Sandip Rao, K. S. R. Koteswara

    2016-05-06

    In the present work, we have fabricated the zirconium doped TiO{sub 2} thin (ZTO) films from a facile spin – coating method. The addition of Zirconium in TiO{sub 2} offers conduction band offset to Si and consequently decreased the leakage current density by approximately two orders as compared to pure TiO{sub 2} thin (TO) films. The ZTO thin film shows a high dielectric constant 27 with a very low leakage current density ∼10{sup −8} A/cm{sup 2}. The oxide capacitate, flat band voltage and change in flat band voltage are 172 pF, -1.19 V and 54 mV. The AFM analysis confirmed the compact and pore free flat surface. The RMS surface roughness is found to be 1.5 Å. The ellipsometry analysis also verified the fact with a high refractive index 2.21.

  13. Structure, composition and microwave dielectric properties of bismuth zinc niobate pyrochlore thin films

    NASA Astrophysics Data System (ADS)

    Wang, Zhao; Ren, Wei; Zhan, Xuelei; Shi, Peng; Wu, Xiaoqing

    2014-11-01

    (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 (BZN) pyrochlore thin films were deposited onto both Pt/TiO2/SiO2/Si and polycrystalline alumina substrates using pulsed laser deposition technique and then post-annealed using rapid thermal processing. The deposition temperature varies from 300 °C to 600 °C, and all the BZN films showed cubic pyrochlore structure after annealing at 650 °C for 30 min in air. The influence of the substrate associated with crystal structure is significant in the as-deposited films and disappears after post-annealing. The dielectric properties as a function of frequency up to the microwave frequency in both films were measured by LCR meter and split-post dielectric resonator technique. It is found that the BZN film deposited at 400 °C and post-annealed at 650 °C shows excellent dielectric properties with low loss in the microwave frequency range. This result indicates that the BZN thin film is a potential microwave material.

  14. Investigation of structural, optical, electrical and dielectric properties of catalytic sprayed hausmannite thin film

    SciTech Connect

    Larbi, T.; Ouni, B.; Boukhachem, A.; Boubaker, K. Amlouk, M.

    2014-12-15

    Hausmannite Mn{sub 3}O{sub 4} thin film have been synthesized using spray pyrolysis method. These films are characterized using X-ray diffraction (XRD), atomic force microscope AFM, UV–vis–NIR spectroscopy and impedance spectroscopy. XRD study confirms the tetragonal structure of the as-deposited films with lattice parameters, a = 5.1822 Å and c = 9.4563 Å and a grain size of about 56 nm. UV–vis–NIR spectroscopy was further used to estimate optical constants such as extinction coefficient, refractive index, band gap and Urbach energy. Moreover, impedance spectroscopy analysis was employed to estimate electrical and dielectrical properties of the sprayed thin films. The activation energy values deduced from DC conductivity and relaxation frequency were almost the same, revealing that the transport phenomena is thermally activated by hopping between localized states. The AC conductivity is found to be proportional to ω{sup s}. The temperature dependence of the AC conductivity and the frequency exponent, s was reasonably well interpreted in terms of the correlated barrier-hopping CBH model. The dielectric properties were sensitive to temperature and frequency. The study of the electrical modulus indicated that the charge carrier was localized. Experimental results concerning optical constants as Urbach energy, dielectric constant, electric modulus and AC and DC conductivity were discussed in terms of the hopping model as suggested by Elliott.

  15. Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

    SciTech Connect

    Esro, M.; Adamopoulos, G.; Mazzocco, R.; Kolosov, O.; Krier, A.; Vourlias, G.; Milne, W. I.

    2015-05-18

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (La{sub x}Al{sub 1−x}O{sub y}) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the La{sub x}Al{sub 1−x}O{sub y} films and devices as a function of the lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As-deposited LaAlO{sub y} dielectrics exhibit a wide band gap (∼6.18 eV), high dielectric constant (k ∼ 16), low roughness (∼1.9 nm), and very low leakage currents (<3 nA/cm{sup 2}). TFTs employing solution processed LaAlO{sub y} gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (∼10 V), high on/off current modulation ratio of >10{sup 6}, subthreshold swing of ∼650 mV dec{sup −1}, and electron mobility of ∼12 cm{sup 2} V{sup −1} s{sup −1}.

  16. Temperature Dependence of Dielectric and Ferroelectric Properties of BiFeO3 Thin Films

    SciTech Connect

    Biegalski, Michael D; Jang, J H; Bark, C; Eom, Professor Chang-Beom

    2009-01-01

    Multiferroic materials, with their potential for novel devices and sensors, have spurred an immense amount of research. The most concentrated effort has been on BiFeO3 thin films due to their high N el temperature and high ferroelectric transition temperature. Most studies on BiFeO3 films suffer from electrical leakage, requiring the measurement of dielectric or ferroelectric properties to be conducted at low temperatures. In this work we show that room-temperature leakage is not intrinsic to BiFeO3. Results are shown for highly insulating films, including the temperature dependence (10K to 300K) of the dielectric properties, ferroelectric P-E loops, and leakage current. This data shows very little temperature change in the dielectric constant with a TCC of 0.38 K-1, and dielectric losses below 0.005. The remanent polarization similarly showed no temperature dependence within the error of the measurement with a Pr of 67 1 C/cm2. The leakage current remains below 3x10-4(A/cm2) at 100 kV/cm. This work proves that BiFeO3 does not intrinsically have high leakage, and validates the extrapolation of the properties of BiFeO3 films measured at low temperatures to room temperatures.

  17. Comparative study on nitridation and oxidation plasma interface treatment for AlGaN/GaN MIS-HEMTs with AlN gate dielectric

    NASA Astrophysics Data System (ADS)

    Zhu, Jie-Jie; Ma, Xiao-Hua; Hou, Bin; Chen, Li-Xiang; Zhu, Qing; Hao, Yue

    2017-02-01

    This paper demonstrated the comparative study on interface engineering of AlN/AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) by using plasma interface pre-treatment in various ambient gases. The 15 nm AlN gate dielectric grown by plasma-enhanced atomic layer deposition significantly suppressed the gate leakage current by about two orders of magnitude and increased the peak field-effect mobility by more than 50%. NH3/N2 nitridation plasma treatment (NPT) was used to remove the 3 nm poor-quality interfacial oxide layer and N2O/N2 oxidation plasma treatment (OPT) to improve the quality of interfacial layer, both resulting in improved dielectric/barrier interface quality, positive threshold voltage (V th) shift larger than 0.9 V, and negligible dispersion. In comparison, however, NPT led to further decrease in interface charges by 3.38 × 1012 cm‑2 and an extra positive V th shift of 1.3 V. Analysis with fat field-effect transistors showed that NPT resulted in better sub-threshold characteristics and transconductance linearity for MIS-HEMTs compared with OPT. The comparative study suggested that direct removing the poor interfacial oxide layer by nitridation plasma was superior to improving the quality of interfacial layer by oxidation plasma for the interface engineering of GaN-based MIS-HEMTs.

  18. Development of dielectric barrier discharge plasma processing apparatus for mass spectrometry and thin film deposition

    NASA Astrophysics Data System (ADS)

    Majumdar, Abhijit; Hippler, Rainer

    2007-07-01

    Cost effective and a very simple dielectric barrier discharge plasma processing apparatus for thin film deposition and mass spectroscopic analysis of organic gas mixture has been described. The interesting features of the apparatus are the construction of the dielectric electrodes made of aluminum oxide or alumina (Al2O3) and glass and the generation of high ignition voltage from the spark plug transformer taken from car. Metal capacitor is introduced in between ground and oscilloscope to measure the executing power during the discharge and the average electron density in the plasma region. The organic polymer films have been deposited on Si (100) substrate using several organic gas compositions. The experimental setup provides a unique drainage system from the reaction chamber controlled by a membrane pump to suck out and remove the poisonous gases or residuals (cyanogens, H-CN, CHxNH2, etc.) which have been produced during the discharge of CH4/N2 mixture.

  19. Organic Thin-Film Transistors Fabricated on Plastic Substrates with a Polymeric Gate Dielectrics

    NASA Astrophysics Data System (ADS)

    Lee, Jung Hun; Kim, Seong Hyun; Kim, Gi Heon; Lim, Sang Chul; Jang, Jin; Zyung, Taehyoung

    2003-05-01

    An organic thin-film transistor using pentacene as an active layer was fabricated on plastic substrate. An organic layer such as thermal curable polymer (JSS-362, Japan Synthetic Rubber (JSR)) was used as the gate dielectrics. The JSS-362 may act not only as a dielectric layer but also as a surface smoothing layer. From the electrical measurement, typical ID-VD characteristics of the field-effect transistor (FET) were observed. The field effect mobility μ was calculated to be 0.12 cm2\\cdotV-1\\cdots-1, while the threshold voltage VT was approximately -15 V. The on/off ratio was above 104 when VG was scanned from -75 V to +0 V.

  20. Low temperature dielectric relaxation and charged defects in ferroelectric thin films

    SciTech Connect

    Artemenko, A.; Payan, S.; Rousseau, A.; Arveux, E.; Maglione, M.; Levasseur, D.; Guegan, G.

    2013-04-15

    We report a dielectric relaxation in BaTiO{sub 3}-based ferroelectric thin films of different composition and with several growth modes: sputtering (with and without magnetron) and sol-gel. The relaxation was observed at cryogenic temperatures (T < 100 K) for frequencies from 100 Hz up to 10 MHz. This relaxation activation energy is always lower than 200 meV and is very similar to the relaxation that we reported in the parent bulk perovskites. Based on our Electron Paramagnetic Resonance (EPR) investigation, we ascribe this dielectric relaxation to the hopping of electrons among Ti{sup 3+}-V(O) charged defects. Being dependent on the growth process and on the amount of oxygen vacancies, this relaxation can be a useful probe of defects in actual integrated capacitors with no need for specific shaping.

  1. Development of dielectric barrier discharge plasma processing apparatus for mass spectrometry and thin film deposition.

    PubMed

    Majumdar, Abhijit; Hippler, Rainer

    2007-07-01

    Cost effective and a very simple dielectric barrier discharge plasma processing apparatus for thin film deposition and mass spectroscopic analysis of organic gas mixture has been described. The interesting features of the apparatus are the construction of the dielectric electrodes made of aluminum oxide or alumina (Al(2)O(3)) and glass and the generation of high ignition voltage from the spark plug transformer taken from car. Metal capacitor is introduced in between ground and oscilloscope to measure the executing power during the discharge and the average electron density in the plasma region. The organic polymer films have been deposited on Si (100) substrate using several organic gas compositions. The experimental setup provides a unique drainage system from the reaction chamber controlled by a membrane pump to suck out and remove the poisonous gases or residuals (cyanogens, H-CN, CH(x)NH(2), etc.) which have been produced during the discharge of CH(4)N(2) mixture.

  2. Low temperature dielectric relaxation and charged defects in ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Artemenko, A.; Payan, S.; Rousseau, A.; Levasseur, D.; Arveux, E.; Guegan, G.; Maglione, M.

    2013-04-01

    We report a dielectric relaxation in BaTiO3-based ferroelectric thin films of different composition and with several growth modes: sputtering (with and without magnetron) and sol-gel. The relaxation was observed at cryogenic temperatures (T < 100 K) for frequencies from 100 Hz up to 10 MHz. This relaxation activation energy is always lower than 200 meV and is very similar to the relaxation that we reported in the parent bulk perovskites. Based on our Electron Paramagnetic Resonance (EPR) investigation, we ascribe this dielectric relaxation to the hopping of electrons among Ti3+-V(O) charged defects. Being dependent on the growth process and on the amount of oxygen vacancies, this relaxation can be a useful probe of defects in actual integrated capacitors with no need for specific shaping.

  3. Low-temperature CVD of iron, cobalt, and nickel nitride thin films from bis[di(tert-butyl)amido]metal(II) precursors and ammonia

    SciTech Connect

    Cloud, Andrew N.; Abelson, John R.; Davis, Luke M.; Girolami, Gregory S.

    2014-03-15

    Thin films of late transition metal nitrides (where the metal is iron, cobalt, or nickel) are grown by low-pressure metalorganic chemical vapor deposition from bis[di(tert-butyl)amido]metal(II) precursors and ammonia. These metal nitrides are known to have useful mechanical and magnetic properties, but there are few thin film growth techniques to produce them based on a single precursor family. The authors report the deposition of metal nitride thin films below 300 °C from three recently synthesized M[N(t-Bu){sub 2}]{sub 2} precursors, where M = Fe, Co, and Ni, with growth onset as low as room temperature. Metal-rich phases are obtained with constant nitrogen content from growth onset to 200 °C over a range of feedstock partial pressures. Carbon contamination in the films is minimal for iron and cobalt nitride, but similar to the nitrogen concentration for nickel nitride. X-ray photoelectron spectroscopy indicates that the incorporated nitrogen is present as metal nitride, even for films grown at the reaction onset temperature. Deposition rates of up to 18 nm/min are observed. The film morphologies, growth rates, and compositions are consistent with a gas-phase transamination reaction that produces precursor species with high sticking coefficients and low surface mobilities.

  4. Surface-sensitive UHV dielectric studies of nanoscale organic thin films: Adsorption, crystallization, and sublimation

    NASA Astrophysics Data System (ADS)

    Underwood, Jason M.

    Nanoscale systems are small collections of atoms or molecules, which as a result of their limited extent, show measurable thermodynamic deviations from bulk samples of the same species. The deviations may result from purely finite-size effects, or may be due to an increased significance of the interaction between the nanoscale system and its container. Ultra-thin (<100 nm) films of organic molecules adsorbed on surfaces afford unique opportunities to study the interplay of forces relevant to nanoscale physics. This thesis describes the development of a novel ultra-high vacuum apparatus to study the behavior of adsorbed polar molecules via dielectric spectroscopy (UHV-DS). Ultra-thin films are grown and characterized in-situ. The use of interdigitated electrode capacitors and a ratio-transformer bridge technique yields resolutions of ˜1 aF and ˜10-5 ppm in the capacitance and loss tangent, respectively. Typical sensitivity is 10 aF per monolayer at 80 K. Results are given for studies on water, methanol, and Cp* (a synthetic molecular rotor). The desorption event in the dielectric spectra is correlated with thermal desorption spectroscopy. During growth of methanol films, we observe partial crystallization for temperatures above ≳ 100 K. Crystallization is also observed upon heating glassy films grown at 80 K. Finally, we discuss UHV-DS as a probe for solid thin-film vapor pressure measurements, and show that our data on methanol compare favorably with those in the literature.

  5. Structural, Optical, and Dielectric Properties of Azure B Thin Films and Impact of Thermal Annealing

    NASA Astrophysics Data System (ADS)

    Zeyada, H. M.; Zidan, H. M.; Abdelghany, A. M.; Abbas, I.

    2017-03-01

    Thin films of azure B (AB) have been prepared by thermal evaporation. Structural, optical, and dielectric characteristics of as-prepared and annealed samples were studied. AB is polycrystalline in as-synthesized powder form. Detailed x-ray diffraction studies showed amorphous structure for pristine and annealed films. Fourier-transform infrared vibrational spectroscopy indicated minor changes in molecular bonds of AB thin films either after deposition or after thermal annealing. Optical transmittance and reflection spectra of prepared thin films were studied at nearly normal light incidence in the spectral range from 200 nm to 2500 nm, showing marked changes without new peaks. Annealing increased the absorption coefficient and decreased the optical bandgap. Onset and optical energy gaps of pristine films were found to obey indirect allowed transition with values of 1.10 eV and 2.64 eV, respectively. Annealing decreased the onset and optical energy gaps to 1.0 eV and 2.57 eV, respectively. The dispersion parameters before and after annealing are discussed in terms of a single-oscillator model. The spectra of the dielectric constants (ɛ 1, ɛ 2) were found to depend on the annealing temperature in addition to the incident photon energy.

  6. Structural and optical characterization of pure Si-rich nitride thin films

    PubMed Central

    2013-01-01

    The specific dependence of the Si content on the structural and optical properties of O- and H-free Si-rich nitride (SiNx>1.33) thin films deposited by magnetron sputtering is investigated. A semiempirical relation between the composition and the refractive index was found. In the absence of Si-H, N-H, and Si-O vibration modes in the FTIR spectra, the transverse and longitudinal optical (TO-LO) Si-N stretching pair modes could be unambiguously identified using the Berreman effect. With increasing Si content, the LO and the TO bands shifted to lower wavenumbers, and the LO band intensity dropped suggesting that the films became more disordered. Besides, the LO and the TO bands shifted to higher wavenumbers with increasing annealing temperature which may result from the phase separation between Si nanoparticles (Si-np) and the host medium. Indeed, XRD and Raman measurements showed that crystalline Si-np formed upon 1100°C annealing but only for SiNx<0.8. Besides, quantum confinement effects on the Raman peaks of crystalline Si-np, which were observed by HRTEM, were evidenced for Si-np average sizes between 3 and 6 nm. A contrario, visible photoluminescence (PL) was only observed for SiNx>0.9, demonstrating that this PL is not originating from confined states in crystalline Si-np. As an additional proof, the PL was quenched while crystalline Si-np could be formed by laser annealing. Besides, the PL cannot be explained neither by defect states in the bandgap nor by tail to tail recombination. The PL properties of SiNx>0.9 could be then due to a size effect of Si-np but having an amorphous phase. PMID:23324447

  7. Decoupled front/back dielectric textures for flat ultra-thin c-Si solar cells.

    PubMed

    Isabella, Olindo; Vismara, Robin; Ingenito, Andrea; Rezaei, Nasim; Zeman, M

    2016-03-21

    The optical analysis of optically-textured and electrically-flat ultra-thin crystalline silicon (c-Si) slabs is presented. These slabs were endowed with decoupled front titanium-dioxide (TiO2) / back silicon-dioxide (SiO2) dielectric textures and were studied as function of two types of back reflectors: standard silver (Ag) and dielectric modulated distributed Bragg reflector (MDBR). The optical performance of such systems was compared to that of state-of-the-art flat c-Si slabs endowed with so-called front Mie resonators and to those of similar optical systems still endowed with the same back reflectors and decoupled front/back texturing but based on textured c-Si and dielectric coatings (front TiO2 and back SiO2). Our optimized front dielectric textured design on 2-µm thick flat c-Si slab with MDBR resulted in more photo-generated current density in c-Si with respect to the same optical system but featuring state-of-the-art Mie resonators ( + 6.4%), mainly due to an improved light in-coupling between 400 and 700 nm and light scattering between 700 and 1050 nm. On the other hand, the adoption of textured dielectric layers resulted in less photo-generated current density in c-Si up to -20.6% with respect to textured c-Si, depending on the type of back reflector taken into account.

  8. Analysis of high-kappa dielectric thin films with time-of-flight medium energy backscattering

    NASA Astrophysics Data System (ADS)

    Geil, Robert D.

    Time-of-flight medium backscattering (TOF-MEBS) is a powerful analytical technique for characterizing high-kappa dielectric thin films and their interface with Si. The amount of information that can be obtained from backscattering experiments can be maximized by carefully choosing a detailed thin film model for simulations and by implementing an experimental configuration that optimizes depth resolution. This thesis presents four main studies. In the first study a thin film model for simulating backscattering spectra is developed and used to extract interfacial information from thin dielectric films. A sufficient film model was found to consist of three layers: (1) dielectric material; (2) interfacial silicate; and (3) substrate. In the next study, the influence of multiple scattering and surface roughness on the shape of backscattering spectra was evaluated by generating spectra using Monte Carlo simulations. For TOF-MEBS analysis of thin (˜50 A) ZrO 2 films on Si, multiple scattering and surface roughness were found to have a negligible influence on the shape of a backscattering spectrum. The third study presents calculations and measurements of the energy and depth resolution of the TOF-MEBS system, and the experimental configuration for optimizing depth resolution was determined. For the analysis of thin films (˜50 A), the depth resolution of the TOF-MEBS system can be improved by operating at a beam energy around 150 keV and by using a glancing tilt angle (˜54°). However, if the angle is too glancing, multiple scattering and surface roughness can significantly degrade depth resolution and distort the shape of the backscattering spectrum. ZrO2 films deposited on H-terminated Si and native Si oxide surfaces were characterized with TOF-MEBS for the final study. The deposition surface was found to significantly affect the physical and chemical properties of MOCVD ZrO2 films and their interface with Si. ZrO2 films deposited on H-terminated Si are low in density

  9. Detection of embedded ultra-subwavelength-thin dielectric features using elongated photonic nanojets.

    PubMed

    Ruiz, César Méndez; Simpson, Jamesina J

    2010-08-02

    Photonic nanojets have been previously shown (both theoretically and experimentally) to be highly sensitive to the presence of an ultra-subwavelength nanoscale particle within the nanojet. In the present work, photonic nanojets elongated by almost an order of magnitude (relative to the latest previously published work) are found to possess another key characteristic: they are sensitive to the presence of ultra-subwavelength nanoscale thin features embedded within a dielectric object. This additional characteristic of photonic nanojets is demonstrated through comparisons between fundamentally different 3-D and corresponding 1-D full Maxwell's equations finite-difference time-domain (FDTD) models.

  10. Dielectric barrier discharge ionization in characterization of organic compounds separated on thin-layer chromatography plates.

    PubMed

    Cegłowski, Michał; Smoluch, Marek; Babij, Michał; Gotszalk, Teodor; Silberring, Jerzy; Schroeder, Grzegorz

    2014-01-01

    A new method for on-spot detection and characterization of organic compounds resolved on thin layer chromatography (TLC) plates has been proposed. This method combines TLC with dielectric barrier discharge ionization (DBDI), which produces stable low-temperature plasma. At first, the compounds were separated on TLC plates and then their mass spectra were directly obtained with no additional sample preparation. To obtain good quality spectra the center of a particular TLC spot was heated from the bottom to increase volatility of the compound. MS/MS analyses were also performed to additionally characterize all analytes. The detection limit of proposed method was estimated to be 100 ng/spot of compound.

  11. Electromagnetic scattering and absorption by thin walled dielectric cylinders with application to ice crystals

    NASA Technical Reports Server (NTRS)

    Senior, T. B. A.; Weil, H.

    1977-01-01

    Important in the atmospheric heat balance are the reflection, transmission, and absorption of visible and infrared radiation by clouds and polluted atmospheres. Integral equations are derived to evaluate the scattering and absorption of electromagnetic radiation from thin cylindrical dielectric shells of arbitrary cross section when irradiated by a plane wave of any polarization incident in a plane perpendicular to the generators. Application of the method to infinitely long hexagonal cylinders has yielded numerical scattering and absorption data which simulate columnar sheath ice crystals. It is found that the numerical procedures are economical for cylinders having perimeters less than approximately fifteen free-space wavelengths.

  12. Temperature-dependent dielectric functions in atomically thin graphene, silicene, and arsenene

    SciTech Connect

    Yang, J. Y.; Liu, L. H.

    2015-08-31

    The dielectric functions of atomically thin graphene, silicene, and arsenene have been investigated as a function of temperature. With zero energy gap, more carriers in graphene and silicene are thermally excited as temperature increases and intraband transition strengthens, resulting in the strengthened absorption peak. Yet with large energy gap, interband transition dominates optical absorption of arsenene but it reduces as lattice vibration enhances, inducing the redshift and decreased absorption peak. To validate the theoretical method, the calculated optical constants of isolated graphene are compared with ellipsometry results and demonstrate good agreement.

  13. Sequential lateral solidification of silicon thin films on low-k dielectrics for low temperature integration

    SciTech Connect

    Carta, Fabio Hlaing, Htay; Kymissis, Ioannis; Gates, Stephen M.; Edelstein, Daniel C.; Limanov, Alexander B.; Im, James S.

    2014-12-15

    We present the excimer laser crystallization of amorphous silicon on a low dielectric constant (low-k) insulator for very large scale integration monolithic 3D integration and demonstrate that low dielectric constant materials are suitable substrates for 3D integration through laser crystallization of silicon thin films. We crystallized 100 nm amorphous silicon on top of SiO{sub 2} and SiCOH (low-k) dielectrics, at different material thicknesses (1 μm, 0.75 μm, and 0.5 μm). The amorphous silicon crystallization on low-k dielectric requires 35% less laser energy than on an SiO{sub 2} dielectric. This difference is related to the thermal conductivity of the two materials, in agreement with one dimensional simulations of the crystallization process. We analyzed the morphology of the material through defect-enhanced microscopy, Raman spectroscopy, and X-ray diffraction analysis. SEM micrographs show that polycrystalline silicon is characterized by micron-long grains with an average width of 543 nm for the SiO{sub 2} sample and 570 nm for the low-k samples. Comparison of the Raman spectra does not show any major difference in film quality for the two different dielectrics, and polycrystalline silicon peaks are closely placed around 517 cm{sup −1}. From X-ray diffraction analysis, the material crystallized on SiO{sub 2} shows a preferential (111) crystal orientation. In the SiCOH case, the 111 peak strength decreases dramatically and samples do not show preferential crystal orientation. A 1D finite element method simulation of the crystallization process on a back end of line structure shows that copper (Cu) damascene interconnects reach a temperature of 70 °C or lower with a 0.5 μm dielectric layer between the Cu and the molten Si layer, a favorable condition for monolithic 3D integration.

  14. Synthesis and selected micro-mechanical properties of titanium nitride thin films by the pyrolysis of tetrakis titanium in ammonia

    SciTech Connect

    Bae, Y.W.; Lee, W.Y.; Besmann, T.M.; Blau, P.J.; Riester, L.

    1994-12-31

    Thin films of titanium nitride were chemical vapor deposited on (100)-oriented single-crystal silicon substrates from tetrakis (dimethylamino) titanium, Ti((CH{sub 3}){sub 2}N){sub 4}, and ammonia gas mixtures in a cold-wall reactor at 623 K and 655 Pa. The films were characterized by Auger electron spectroscopy, X-ray diffraction, and transmission electron spectroscopy. The nano-scale hardness of the film, measured by nanoindentation, was 12.7 {plus_minus} 0.6 GPa. The average kinetic friction coefficient against unlubricated, type 440C stainless steel was determined using a computer-controlled friction microprobe to be {approximately}0.43.

  15. Low-temperature chemical vapor depostion of ruthenium and manganese nitride thin films

    NASA Astrophysics Data System (ADS)

    Lazarz, Teresa S.

    Materials and thin film processing development has been and remains key to continuing to make ever smaller, or miniaturized, microelectronic devices. In order to continue miniaturization, conformal, low-temperature deposition of new electronic materials is needed. Two techniques capable of conformality have emerged: chemical vapor deposition (CVD) and atomic layer deposition (ALD). Here, two processes for deposition of materials which could be useful in microelectronics, but for which no low-temperature, conformal process has been established as commercializable, are presented. One is ruthenium, intended for use in interconnects and in dynamic random access memory electrodes, a known material for use in microelectronics but for which a more conformal, yet fast process than previously demonstrated is required. The other is manganese nitride, which could be used as active magnetic layers in devices or as a dopant in materials for spintronics, which is not yet established as a desired material in part due to the lack of any previously known CVD or ALD process for deposition. A unique challenge arises in trying to grow impurity-free films of a catalyst. Ruthenium metal activates C-H and C-C bonds, which aids C-H and C-C bond scission. This creates a potential catalytic decomposition path for all metal-organic CVD precursors that is likely to lead to significant carbon incorporation. Metallic ruthenium films can be grown by chemical vapor deposition from the organometallic precursor tricarbonyl(1,3-cyclohexadiene)ruthenium(0). This precursor is a highly volatile liquid, easy to synthesize and handle, and capable of delivering at least 0.26 Torr partial pressure at room temperature without the use of a carrier gas. Because the precursor is a liquid, the vaporization rate is not subject to the problem of diminishing surface area that occurs with solid precursors. CVD proceeds readily for substrate temperatures ≥ 200°C. The growth rates are high, up to 24 nm/min, which

  16. Low-voltage and hysteresis-free organic thin-film transistors employing solution-processed hybrid bilayer gate dielectrics

    SciTech Connect

    Ha, Tae-Jun

    2014-07-28

    This study presents a promising approach to realize low-voltage (<3 V) organic thin-film transistors (OTFTs) exhibiting improved electrical and optical stability. Such device performance results from the use of solution-processed hybrid bilayer gate dielectrics consisting of zirconium dioxide (high-k dielectric) and amorphous fluoropolymer, CYTOP{sup ®} (low-k dielectric). Employing a very thin amorphous fluoropolymer film reduces interfacial defect-states by repelling water molecules and other aqueous chemicals from an organic semiconductor active layer due to the hydrophobic surface-property. The chemically clean interface, stemming from decrease in density of trap states improves all the key device properties such as field-effect mobility, threshold voltage, and sub-threshold swing. Furthermore, degradation by electrical bias-stress and photo-induced hysteresis were suppressed in OTFTs employing hybrid bilayer gate dielectrics.

  17. Nanocomposites of polyimide and mixed oxide nanoparticles for high performance nanohybrid gate dielectrics in flexible thin film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Ju Hyun; Hwang, Byeong-Ung; Kim, Do-Il; Kim, Jin Soo; Seol, Young Gug; Kim, Tae Woong; Lee, Nae-Eung

    2017-05-01

    Organic gate dielectrics in thin film transistors (TFTs) for flexible display have advantages of high flexibility yet have the disadvantage of low dielectric constant (low- k). To supplement low- k characteristics of organic gate dielectrics, an organic/inorganic nanocomposite insulator loaded with high- k inorganic oxide nanoparticles (NPs) has been investigated but high loading of high- k NPs in polymer matrix is essential. Herein, compositing of over-coated polyimide (PI) on self-assembled (SA) layer of mixed HfO2 and ZrO2 NPs as inorganic fillers was used to make dielectric constant higher and leakage characteristics lower. A flexible TFT with lower the threshold voltage and high current on/off ratio could be fabricated by using the hybrid gate dielectric structure of the nanocomposite with SA layer of mixed NPs on ultrathin atomic-layer deposited Al2O3. [Figure not available: see fulltext.

  18. Nanocomposites of polyimide and mixed oxide nanoparticles for high performance nanohybrid gate dielectrics in flexible thin film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Ju Hyun; Hwang, Byeong-Ung; Kim, Do-Il; Kim, Jin Soo; Seol, Young Gug; Kim, Tae Woong; Lee, Nae-Eung

    2017-01-01

    Organic gate dielectrics in thin film transistors (TFTs) for flexible display have advantages of high flexibility yet have the disadvantage of low dielectric constant (low-k). To supplement low-k characteristics of organic gate dielectrics, an organic/inorganic nanocomposite insulator loaded with high-k inorganic oxide nanoparticles (NPs) has been investigated but high loading of high-k NPs in polymer matrix is essential. Herein, compositing of over-coated polyimide (PI) on self-assembled (SA) layer of mixed HfO2 and ZrO2 NPs as inorganic fillers was used to make dielectric constant higher and leakage characteristics lower. A flexible TFT with lower the threshold voltage and high current on/off ratio could be fabricated by using the hybrid gate dielectric structure of the nanocomposite with SA layer of mixed NPs on ultrathin atomic-layer deposited Al2O3.

  19. Dynamics of poly(vinyl methyl ketone) thin films studied by local dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Casalini, R.; Labardi, M.; Roland, C. M.

    2017-05-01

    Local dielectric spectroscopy, which entails measuring the change in resonance frequency of the conducting tip of an atomic force microscope to determine the complex permittivity of a sample with high spatial (lateral) resolution, was employed to characterize the dynamics of thin films of poly(vinyl methyl ketone) (PVMK) having different substrate and top surface layers. A free surface yields the usual speeding up of the segmental dynamics, corresponding to a glass transition suppression of 6.5° for 18 nm film thickness. This result is unaffected by the presence of a glassy, compatible polymer, poly-4-vinyl phenol (PVPh), between the metal substrate and the PVMK. However, covering the top surface with a thin layer of the PVPh suppresses the dynamics. The speeding up of PVMK segmental motions observed for a free surface is absent due to interfacial interactions of the PVMK with the glass layer, an effect not seen when the top layer is an incompatible polymer.

  20. Yttrium scandate thin film as alternative high-permittivity dielectric for germanium gate stack formation

    SciTech Connect

    Lu, Cimang Lee, Choong Hyun; Nishimura, Tomonori; Toriumi, Akira

    2015-08-17

    We investigated yttrium scandate (YScO{sub 3}) as an alternative high-permittivity (k) dielectric thin film for Ge gate stack formation. Significant enhancement of k-value is reported in YScO{sub 3} comparing to both of its binary compounds, Y{sub 2}O{sub 3} and Sc{sub 2}O{sub 3}, without any cost of interface properties. It suggests a feasible approach to a design of promising high-k dielectrics for Ge gate stack, namely, the formation of high-k ternary oxide out of two medium-k binary oxides. Aggressive scaling of equivalent oxide thickness (EOT) with promising interface properties is presented by using YScO{sub 3} as high-k dielectric and yttrium-doped GeO{sub 2} (Y-GeO{sub 2}) as interfacial layer, for a demonstration of high-k gate stack on Ge. In addition, we demonstrate Ge n-MOSFET performance showing the peak electron mobility over 1000 cm{sup 2}/V s in sub-nm EOT region by YScO{sub 3}/Y-GeO{sub 2}/Ge gate stack.

  1. Experimental and computational study of plasma bullet reignition behind a thin dielectric slab

    NASA Astrophysics Data System (ADS)

    Ranieri, Pietro; Babaeva, Natalia; Foster, John

    2013-09-01

    Ionization waves (IWs) propagating through plasma jets and helium channels are often observed as luminous fronts of the IWs and conventionally termed as plasma bullets. The preliminary experiments show that if a thin dielectric slab is placed in the helium channel as an obstacle for the bullet propagation, the discharge may reignite below the slab. This process is perceived as though the bullets propagate through the obstacle. The goal of this work is to find conditions under which the bullet can reignite behind the dielectric. The experimental setup consists of a corona discharge, with a single metal electrode, within a quartz tube. We study the influence of the dielectric constant, thickness and the length of the mica slab on the plasma jet behavior. We show that after the impact on the mica surface, the bullet partially reflects from the surface and plasma spreads along the surface. Depending on the location of the mica relative to the tube exit, its capacitance and opacity to photoionizing radiation, a second bullet can emerge below the slab. The computational model used in this work, nonPDPSIM, is a plasma hydrodynamics model in which continuity, momentum and energy equations are solved for charged and neutral species with solution of Poisson's equation for the electric potential.

  2. Thickness dependence of the dielectric properties of thermally evaporated Sb2Te3 thin films

    NASA Astrophysics Data System (ADS)

    Ulutas, K.; Deger, D.; Yakut, S.

    2013-03-01

    Sb2Te3 thin films of different thickness (23 - 350 nm) were prepared by thermal evaporation technique. The thickness dependence of the ac conductivity and dielectric properties of the Sb2Te3 films have been investigated in the frequency range 10 Hz- 100 kHz and within the temperature range 293-373K. Both the dielectric constant epsilon1 and dielectric loss factor epsilon2 were found to depend on frequency, temperature and film thickness. The frequency and temperature dependence of ac conductivity (σac(ω)) has also been determined. The ac conductivity of our samples satisfies the well known ac power law; i.e., σac(ω) propto ωs where s<1 and independent of the film thickness. The temperature dependence of ac conductivity and parameter s is reasonably well interpreted by the correlated barrier hopping (CBH) model. The activation energies were evaluated for various thicknesses. The temperature coefficient of the capacitance (TCC) and permitivity (TCP) were determined as a function of the film thickness. The microstructure of the samples were analyzed using X-ray diffraction (XRD). This results are discussed on the base of the differences in their morphologies and thicknesses. The tendency for amorphization of the crystalline phases becomes evident as the film thickness increases.

  3. Thickness dependent electronic structure and morphology of rubrene thin films on metal, semiconductor, and dielectric substrates

    NASA Astrophysics Data System (ADS)

    Sinha, Sumona; Mukherjee, M.

    2013-08-01

    The evolution of the electronic structure and morphology of rubrene thin films on noble-metal, semiconductor and dielectric substrates have been investigated as a function of thickness of deposited films by using photoelectron spectroscopy and atomic force microscopy. The clean polycrystalline Au and Ag were used as noble-metals, whereas, H passivated and SiO2 coated Si (100) were used as semiconductors and dielectric substrates. Discussion and comparison on interface dipole, energy level alignment, and surface morphology for the four cases are presented. The formation of dipole at metallic interfaces is found to occur due to push back effect. S parameter obtained from the variation of barrier height with the change of work function of the contacting metal indicates moderately weak interaction between rubrene and the metal substrates. The thickness dependent energy level alignment of the physisorbed rubrene films on different substrates is explained by a dielectric model in terms of electrostatic screening of photo-holes or photoemission final state relaxation energy. Films on all the substrates are found to grow following Stranski-Krastnov type growth mode and are more ordered at higher coverage.

  4. Tb2O3 thin films: An alternative candidate for high-k dielectric applications

    NASA Astrophysics Data System (ADS)

    Gray, Nathan W.; Prestgard, Megan C.; Tiwari, Ashutosh

    2014-12-01

    We are reporting the growth and structural, optical, and dielectric properties of Tb2O3, a relatively unexplored high-k dielectric material. A pulsed-laser deposition technique was used to grow Tb2O3 thin-films on four different substrates: Si(100), SrTiO3(100), LaAlO3(100), and MgO(100). High-resolution X-ray diffraction and transmission electron microscopy results confirmed that film growth in an oxygen-rich (10-1 Torr) environment yields nearly single-crystal C-phase films, while a low-oxygen (10-6 Torr) environment growth results in the formation of monoclinic polycrystalline B-phase films. Optical transmission measurements showed that the bandgap of Tb2O3 is direct in nature with a value of 2.8 eV and 3.4 eV for the cubic and monoclinic phases, respectively. By measuring the capacitance of test devices, quite high dielectric constants of 13.5 and 24.9 were obtained for the B- and C-phase Tb2O3 films, respectively.

  5. Optimal structure of light trapping in thin-film solar cells: dielectric nanoparticles or multilayer antireflection coatings?

    PubMed

    Zhao, Yongxiang; Chen, Fei; Shen, Qiang; Zhang, Lianmeng

    2014-08-10

    Recent research has found an alternative way to enhance light trapping of thin-film solar cells by using dielectric nanoparticles deposited on the cell surface. To improve the performance of light trapping, a systematic study on the influence of dielectric nanoparticles on enhancement efficiency is performed in this paper. We prove that the optimal dielectric nanoparticles are substantially equivalent to the multilayer antireflection coatings (ARCs) with a "low-high-low" dielectric constant profile. Moreover, it is demonstrated that the use of a simple two-layer SiO2/SiC ARC can reach 34.15% enhancement, which has exceeded the ideal limit of 32% of nanoparticles structure including plasmonic Ag nanoparticles, dielectric SiC, and TiO2 nanoparticles. That means the optimal multilayer ARCs structure is obviously superior to the optimal dielectric nanoparticles structure, and the deposition of a simple two-layer SiO2/SiC structure on top of a thin-film silicon solar cell can significantly enhance photoelectron generation and hence, result in superior performance of thin-film solar cells.

  6. Plasma deposition of low dielectric constant (k=2.2{approx}2.4) Boron Nitride on methylsilsesquioxane-based nanoporous films

    SciTech Connect

    Liu Jun; Loh, K.P.; Lin Ming; Foo, Y.L.; Wang, W.D.; Chi, D.Z.

    2004-12-01

    The growth of low dielectric constant (k) Boron Nitride (BN) film on silicon as well as methylsilsesquioxane-based nanoporous films (LKD-5109) using plasma-discharged borazine was investigated. BN films were grown using microwave plasma (2.45 GHz) or radio-frequency (rf) atom beam deposition (13.56 MHz) on LKD-5109 in order to evaluate the compatibility of the two plasma processes with the physical integrity of the nanoporous films. Capacitance-voltage measurements were used to characterize the dielectric constants of the films on silicon and BN-integrated LKD (k{sub eff}{approx_equal}2.4). The composition and phases of the films were studied using cross-section transmission electron microscopy and electron-energy-loss spectroscopy. Although the microwave plasma process could produce BC{sub x}N films with a k value of 2.2, the process was not compatible with the nanoporous LKD substrate due to the ion-induced damage of the films. We found that only the rf atom beam deposition process, which was characterized by low-energy neutral fluxes, maintained the dielectric property of the BN-integrated LKD stack at an overall value of 2.4. In addition, the deposited BN films can act as an effective copper diffusion barrier on the LKD and can be lithographically processed to form trench patterns.

  7. Visible and near infrared emitting thin film electroluminescent gallium nitride doped with rare earths

    NASA Astrophysics Data System (ADS)

    Kim, Joo Han

    Visible and near-infrared (NIR) light-emitting thin-film electroluminescent gallium nitride (GaN) doped with rare earth (RE) elements was studied. The rare-earth-doped GaN thin films were prepared by radio frequency (RF) planar magnetron co-sputtering of separate targets consisting of a GaN compound target and a metallic rare earth target in a pure nitrogen atmosphere. The luminescence of rare-earth-doped GaN was shown to be a strong function of its structure and properties, and growth parameters affected the structure and properties of the GaN host films. A phase transition from the thermodynamically stable wurtzite to the metastable zinc-blende structure at room temperature in GaN host films was observed upon increasing the impact energy of the bombarding species, thereby increasing the compressive stress in the GaN film. The switch from wurtzite to zinc-blende GaN occurred at a compressive internal stress of ˜1 GPa. The internal compressive stress above this threshold value apparently stabilizes the zinc-blende GaN phase at room temperature. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) showed that the impact by hyperthermal species yielded a highly condensed fibrous GaN microstructure with a smooth surface morphology due to annihilation of porosity by knock-on and bombardment-induced adatom mobility. X-ray diffraction and texture analyses showed that the GaN films deposited at a low pressure had a predominant cubic phase with a preferred crystallographic orientation of the [111] direction perpendicular to the surface of the film. X-ray rocking curve data revealed that cubic GaN films grown with a lower growth rate exhibited a more highly [111]-textured structure. Alternating-current thin-film electroluminescent (ACTFEL) devices were fabricated based on GaN doped with rare earth (RE) elements. Visible electroluminescent light emission peaks at 475 (blue), 530 (green), and 614 nm (red) were demonstrated at room temperature

  8. Solution-processed high-k magnesium oxide dielectrics for low-voltage oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Jiang, Guixia; Liu, Ao; Liu, Guoxia; Zhu, Chundan; Meng, You; Shin, Byoungchul; Fortunato, Elvira; Martins, Rodrigo; Shan, Fukai

    2016-10-01

    Solution-processed metal-oxide thin films with high dielectric constants (k) have been extensively studied for low-cost and high-performance thin-film transistors (TFTs). In this report, MgO dielectric films were fabricated using the spin-coating method. The MgO dielectric films annealed at various temperatures (300, 400, 500, and 600 °C) were characterized by using thermogravimetric analysis, optical spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and atomic-force microscopy. The electrical measurements indicate that the insulating properties of MgO thin films are improved with an increase in annealing temperature. In order to clarify the potential application of MgO thin films as gate dielectrics in TFTs, solution-derived In2O3 channel layers were separately fabricated on various MgO dielectric layers. The optimized In2O3/MgO TFT exhibited an electron mobility of 5.48 cm2/V s, an on/off current ratio of 107, and a subthreshold swing of 0.33 V/dec at a low operation voltage of 6 V. This work represents a great step toward the development of portable and low-power consumption electronics.

  9. Dielectric properties of hydrogen-incorporated chemical vapor deposited diamond thin films.

    SciTech Connect

    Liu, C.; Xiao, X.; Wang, J.; Shi, B.; Auciello, O.; Carlisle, J. A.; Carpick, R.; Adiga, V.; Univ. of Wisconsin at Madison; Univ. of Pennsylvania

    2007-01-01

    Diamond thin films with a broad range of microstructures from a ultrananocrystalline diamond (UNCD) form developed at Argonne National Laboratory to a microcrystalline diamond (MCD) form have been grown with different hydrogen percentages in the Ar/CH{sub 4} gas mixture used in the microwave plasma enhanced chemical vapor deposition (CVD) process. The dielectric properties of the CVD diamond thin films have been studied using impedance and dc measurements on metal-diamond-metal test structures. Close correlations have been observed between the hydrogen content in the bulk of the diamond films, measured by elastic recoil detection (ERD), and their electrical conductivity and capacitance-frequency (C-f) behaviors. Addition of hydrogen gas in the Ar/CH{sub 4} gas mixture used to grow the diamond films appears to have two main effects depending on the film microstructure, namely, (a) in the UNCD films, hydrogen incorporates into the atomically abrupt grain boundaries satisfying sp{sup 2} carbon dangling bonds, resulting in increased resistivity, and (b) in MCD, atomic hydrogen produced in the plasma etches preferentially the graphitic phase codepositing with the diamond phase, resulting in the statistical survival and growth of large diamond grains and dominance of the diamond phase, and thus having significant impact on the dielectric properties of these films.

  10. The dielectric studies on sol-gel routed molybdenum oxide thin film

    NASA Astrophysics Data System (ADS)

    Arasu, P. Adal; Williams, R. Victor

    The influence of temperature on the dielectric properties of sol-gel routed spin-coated molybdenum trioxide (MoO3) thin film has been investigated. Prepared films were annealed at temperatures 250∘C, 350∘C and 400∘C. The phase transformation from amorphous to α-orthorhombic phase with preferential orientation (0 2 2) has been found by XRD for the film annealed above 250∘C. The vibration modes of α-orthorhombic MoO3 have been examined by Raman spectrum. The predominant Raman’s band of α-orthorhombic MoO3 thin film has been found at the frequency range 1000-600cm-1. Using the UV-Vis spectrum, the band gap of the film is found to be 3.3-3.8eV. The surface morphology of the MoO3 films has been examined by scanning electron microscope. The AC conductivity measurement of the MoO3 film has been carried out in the frequency range 10-106 Hz. The frequency dependence of the impedance has been plotted in the complex plane. The variation of the capacitance and dielectric constant of MoO3 film with respect to temperature and frequency has been analyzed. Tunability of capacitance and figure of merit of the film are also determined.

  11. Dielectric relaxation and polaronic conduction in epitaxial BaFe12O19 hexaferrite thin film

    NASA Astrophysics Data System (ADS)

    Tang, Rujun; Zhou, Hao; Zhao, Run; Jian, Jie; Wang, Han; Huang, Jijie; Fan, Meng; Zhang, Wei; Wang, Haiyan; Yang, Hao

    2016-03-01

    The dielectric properties of epitaxial BaFe12O19 hexaferrite thin film have been investigated as a function of frequency (50 Hz  -  2 MHz) and temperature (100-375 K). The frequency dependent permittivity, impedance ({{Z}\\prime \\prime} ) and modulus ({{M}\\prime \\prime} ) spectra show that the dielectric responses of BaFe12O19 thin film are thermally activated. The activation energy of BaFe12O19 film (E a) is much smaller than that of the polycrystalline bulk BaFe12O19. In addition, E a increases with increasing temperature and there is a distribution of relaxation time in the sample. The scaling behavior of {{Z}\\prime \\prime} and {{M}\\prime \\prime} spectra of the sample further suggest that the distribution of relaxation time is temperature independent at low temperatures (<250 K) and temperature dependent at high temperatures. The temperature dependent dc conductivity shows that small polaron hopping is the most probable conduction mechanism for BaFe12O19 film.

  12. Optical and microwave dielectric properties of pulsed laser deposited Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} thin film

    SciTech Connect

    Joseph, Andrews; Goud, J. Pundareekam; Raju, K. C. James; Emani, Sivanagi Reddy

    2016-05-23

    Optical properties of pulsed laser deposited (PLD) sodium bismuth titanate thin films (NBT), are investigated at wavelengths of 190-2500 nm. Microwave dielectric properties were investigated using the Split Post Dielectric Resonator (SPDR) technique. At 10 GHz, the NBT films have a dielectric constant of 205 and loss tangent of 0.0373 at room temperature. The optical spectra analysis reveals that NBT thin films have an optical band gap E{sub g}=3.55 eV and it has a dielectric constant of 3.37 at 1000 nm with dielectric loss of 0.299. Hence, NBT is a promising candidate for photonic device applications.

  13. Spreading of Thin Droplets of Perfect and Leaky Dielectric Liquids on Inclined Surfaces.

    PubMed

    Corbett, Andrew; Kumar, Satish

    2016-07-05

    The spreading of droplets may be influenced by electric fields, a situation that is relevant to applications such as coating, printing, and microfluidics. In this work we study the effects of an electric field on the gravity-driven spreading of two-dimensional droplets down an inclined plane. We consider both perfect and leaky dielectric liquids, as well as perfectly and partially wetting systems. In addition to the effects of electric fields, we examine the use of thermocapillary forces to suppress the growth of the capillary ridge near the droplet front. Lubrication theory is applied to generate a set of coupled partial differential equations for interfacial height and charge, which are then solved numerically with a finite-difference method. Electric fields increase the height of the capillary ridge in both perfect and leaky dielectric droplets due to electrostatic pressure gradients that drive liquid into the ridge. In leaky dielectrics, large interfacial charge gradients in the contact-line region create shear stresses that also enhance ridge growth and the formation of trailing minor ridges. The coalescence of these ridges can significantly affect the long-time thinning rate of leaky dielectric droplets. In partially wetting liquids, electric fields promote the splitting of smaller droplets from the primary droplet near the receding contact line due to the interplay between electrostatic forces and disjoining pressure. Cooling from below and heating from above generates thermocapillary forces that counteract the effects of electric fields and suppress the growth of the capillary ridge. The results of this work have important implications for manipulating the spreading of droplets down inclined surfaces.

  14. Phase sensitive molecular dynamics of self-assembly glycolipid thin films: A dielectric spectroscopy investigation

    NASA Astrophysics Data System (ADS)

    Velayutham, T. S.; Ng, B. K.; Gan, W. C.; Majid, W. H. Abd.; Hashim, R.; Zahid, N. I.; Chaiprapa, Jitrin

    2014-08-01

    Glycolipid, found commonly in membranes, is also a liquid crystal material which can self-assemble without the presence of a solvent. Here, the dielectric and conductivity properties of three synthetic glycolipid thin films in different thermotropic liquid crystal phases were investigated over a frequency and temperature range of (10-2-106 Hz) and (303-463 K), respectively. The observed relaxation processes distinguish between the different phases (smectic A, columnar/hexagonal, and bicontinuous cubic Q) and the glycolipid molecular structures. Large dielectric responses were observed in the columnar and bicontinuous cubic phases of the longer branched alkyl chain glycolipids. Glycolipids with the shortest branched alkyl chain experience the most restricted self-assembly dynamic process over the broad temperature range studied compared to the longer ones. A high frequency dielectric absorption (Process I) was observed in all samples. This is related to the dynamics of the hydrogen bond network from the sugar group. An additional low-frequency mechanism (Process II) with a large dielectric strength was observed due to the internal dynamics of the self-assembly organization. Phase sensitive domain heterogeneity in the bicontinuous cubic phase was related to the diffusion of charge carriers. The microscopic features of charge hopping were modelled using the random walk scheme, and two charge carrier hopping lengths were estimated for two glycolipid systems. For Process I, the hopping length is comparable to the hydrogen bond and is related to the dynamics of the hydrogen bond network. Additionally, that for Process II is comparable to the bilayer spacing, hence confirming that this low-frequency mechanism is associated with the internal dynamics within the phase.

  15. Surface/interface analysis and optical properties of RF sputter-deposited nanocrystalline titanium nitride thin films

    NASA Astrophysics Data System (ADS)

    White, N.; Campbell, A. L.; Grant, J. T.; Pachter, R.; Eyink, K.; Jakubiak, R.; Martinez, G.; Ramana, C. V.

    2014-02-01

    Titanium nitride (TiNx) thin films were grown by radio-frequency (RF) magnetron sputter deposition by varying the nitrogen content in the reactive gas mixture over a wide range. The effect of nitrogen gas flow rate on the surface and interface morphology, chemical composition and optical properties of TiN thin films was studied employing atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). Analysis of the optical properties probed with SE has shown that films deposited at low (0-5 sccm) nitrogen flow rates have the highest absorption at energies <2 eV. It was also shown that Lorentz oscillators with energy positions lower than 2 eV can be distinguished from the Drude oscillator function during parameter fitting. AFM imaging analysis indicates that the roughness decreases and plateaus at approximately 1.5 nm with the introduction of a small N2 flow rate, remaining consistent thereafter. SEM cross-sectional imaging analysis indicates the dense, columnar structure for the films grown at lower nitrogen flow rates. XPS analysis of atomic composition and the chemical states indicate that the atomic composition remained nearly constant while the chemical states varied significantly among the samples as a function of N2 flow rate. XPS analyses confirm the presence of TiNx, TiO2 and TiOxNy. These process-property relationships derived could be useful for defining and expanding the range of optical and electronic applications of titanium nitrides and (oxy)nitrides.

  16. Three-dimensional kinetic Monte Carlo simulations of cubic transition metal nitride thin film growth

    NASA Astrophysics Data System (ADS)

    Nita, F.; Mastail, C.; Abadias, G.

    2016-02-01

    A three-dimensional kinetic Monte Carlo (KMC) model has been developed and used to simulate the microstructure and growth morphology of cubic transition metal nitride (TMN) thin films deposited by reactive magnetron sputtering. Results are presented for the case of stoichiometric TiN, chosen as a representative TMN prototype. The model is based on a NaCl-type rigid lattice and includes deposition and diffusion events for both N and Ti species. It is capable of reproducing voids and overhangs, as well as surface faceting. Simulations were carried out assuming a uniform flux of incoming particles approaching the surface at normal incidence. The ballistic deposition model is parametrized with an interaction parameter r0 that mimics the capture distance at which incoming particles may stick on the surface, equivalently to a surface trapping mechanism. Two diffusion models are implemented, based on the different ways to compute the site-dependent activation energy for hopping atoms. The influence of temperature (300-500 K), deposition flux (0.1-100 monolayers/s), and interaction parameter r0 (1.5-6.0 Å) on the obtained growth morphology are presented. Microstructures ranging from highly porous, [001]-oriented straight columns with smooth top surface to rough columns emerging with different crystallographic facets are reproduced, depending on kinetic restrictions, deposited energy (seemingly captured by r0), and shadowing effect. The development of facets is a direct consequence of the diffusion model which includes an intrinsic (minimum energy-based) diffusion anisotropy, although no crystallographic diffusion anisotropy was explicitly taken into account at this stage. The time-dependent morphological evolution is analyzed quantitatively to extract the growth exponent β and roughness exponent α , as indicators of kinetic roughening behavior. For dense TiN films, values of α ≈0.7 and β =0.24 are obtained in good agreement with existing experimental data. At this

  17. Propagation of surface waves and waveguide modes guided by a dielectric slab inserted in a sculptured nematic thin film

    NASA Astrophysics Data System (ADS)

    Faryad, Muhammad; Lakhtakia, Akhlesh

    2011-01-01

    Wave propagation guided by a dielectric slab inserted in a sculptured nematic thin film (SNTF) was studied theoretically. Two types of guided waves can be identified: (i) surface (Dyakonov-Tamm) waves guided by one or both of the two planar interfaces of the dielectric slab and the SNTF, and (ii) waveguide modes in the dielectric waveguide formed by the slab with the SNTF as the cladding. As the thickness of the dielectric slab is increased, the number of waveguide modes increases. If the slab thickness is less than twice the e-folding distance into the dielectric slab, the Dyakonov-Tamm waves propagate coupled to both interfaces; the coupling decreases and eventually vanishes as the slab thickness increases, so that Dyakonov-Tamm waves are guided by the individual dielectric-SNTF interfaces independently. The chosen structure supports the propagation of Dyakonov-Tamm waves in all directions, in contrast to the restricted range of propagation supported by a single SNTF-dielectric interface. Propagation of both Dyakonov-Tamm waves and waveguide modes should occur in practice with negligible attenuation, in contrast to that of surface-plasmon-polariton waves that are guided when the dielectric slab is replaced by a metal slab.

  18. Propagation of surface waves and waveguide modes guided by a dielectric slab inserted in a sculptured nematic thin film

    SciTech Connect

    Faryad, Muhammad; Lakhtakia, Akhlesh

    2011-01-15

    Wave propagation guided by a dielectric slab inserted in a sculptured nematic thin film (SNTF) was studied theoretically. Two types of guided waves can be identified: (i) surface (Dyakonov-Tamm) waves guided by one or both of the two planar interfaces of the dielectric slab and the SNTF, and (ii) waveguide modes in the dielectric waveguide formed by the slab with the SNTF as the cladding. As the thickness of the dielectric slab is increased, the number of waveguide modes increases. If the slab thickness is less than twice the e-folding distance into the dielectric slab, the Dyakonov-Tamm waves propagate coupled to both interfaces; the coupling decreases and eventually vanishes as the slab thickness increases, so that Dyakonov-Tamm waves are guided by the individual dielectric-SNTF interfaces independently. The chosen structure supports the propagation of Dyakonov-Tamm waves in all directions, in contrast to the restricted range of propagation supported by a single SNTF-dielectric interface. Propagation of both Dyakonov-Tamm waves and waveguide modes should occur in practice with negligible attenuation, in contrast to that of surface-plasmon-polariton waves that are guided when the dielectric slab is replaced by a metal slab.

  19. Nonlinear dielectric thin films for high-power electric storage with energy density comparable with electrochemical supercapacitors.

    PubMed

    Yao, Kui; Chen, Shuting; Rahimabady, Mojtaba; Mirshekarloo, Meysam Sharifzadeh; Yu, Shuhui; Tay, Francis Eng Hock; Sritharan, Thirumany; Lu, Li

    2011-09-01

    Although batteries possess high energy storage density, their output power is limited by the slow movement of charge carriers, and thus capacitors are often required to deliver high power output. Dielectric capacitors have high power density with fast discharge rate, but their energy density is typically much lower than electrochemical supercapacitors. Increasing the energy density of dielectric materials is highly desired to extend their applications in many emerging power system applications. In this paper, we review the mechanisms and major characteristics of electric energy storage with electrochemical supercapacitors and dielectric capacitors. Three types of in-house-produced ferroic nonlinear dielectric thin film materials with high energy density are described, including (Pb(0.97)La(0.02))(Zr(0.90)Sn(0.05)Ti(0.05))O(3) (PLZST) antiferroelectric ceramic thin films, Pb(Zn(1/3)Nb(2/3))O(3-)Pb(Mg(1/3)Nb(2/3))O(3-)PbTiO(3) (PZN-PMN-PT) relaxor ferroelectric ceramic thin films, and poly(vinylidene fluoride) (PVDF)-based polymer blend thin films. The results showed that these thin film materials are promising for electric storage with outstandingly high power density and fairly high energy density, comparable with electrochemical supercapacitors.

  20. Epitaxy of highly ordered organic semiconductor crystallite networks supported by hexagonal boron nitride

    PubMed Central

    Matković, Aleksandar; Genser, Jakob; Lüftner, Daniel; Kratzer, Markus; Gajić, Radoš; Puschnig, Peter; Teichert, Christian

    2016-01-01

    This study focuses on hexagonal boron nitride as an ultra-thin van der Waals dielectric substrate for the epitaxial growth of highly ordered crystalline networks of the organic semiconductor parahexaphenyl. Atomic force microscopy based morphology analysis combined with density functional theory simulations reveal their epitaxial relation. As a consequence, needle-like crystallites of parahexaphenyl grow with their long axes oriented five degrees off the hexagonal boron nitride zigzag directions. In addition, by tuning the deposition temperature and the thickness of hexagonal boron nitride, ordered networks of needle-like crystallites as long as several tens of micrometers can be obtained. A deeper understanding of the organic crystallites growth and ordering at ultra-thin van der Waals dielectric substrates will lead to grain boundary-free organic field effect devices, limited only by the intrinsic properties of the organic semiconductors. PMID:27929042

  1. Proof of damage-free selective removal of thin dielectric coatings on silicon wafers by irradiation with femtosecond laser pulses

    SciTech Connect

    Rublack, Tino; Muchow, Markus; Schade, Martin; Leipner, Hartmut S.; Seifert, Gerhard

    2012-07-15

    The microstructural impact of selective femtosecond laser ablation of thin dielectric layers from monocrystalline silicon wafers was investigated. Various spots opened by 280 fs laser pulses at {lambda} = 1.03 {mu}m wavelength and 50 fs pulses at 800 nm, respectively, were analyzed in detail using Raman and transmission electron microscopy. The results show clearly that the thin dielectric films can be removed without any detectable modification of the Si crystal structure in the opened area. In contrast, in adjacent regions corresponding to laser fluence slightly below the breaking threshold, a thin layer of amorphous silicon with a maximum thickness of about 50 nm is found at the Si/SiO{sub 2} interface after laser irradiation. More than one pulse on the same position, however, causes structural modification of the silicon after thin film ablation in any case.

  2. Interfacial effects in oxide-polymer laminar composite thin film dielectrics for capacitor applications

    NASA Astrophysics Data System (ADS)

    Tewari, Pratyush

    Continuous increase in the density of active components on microelectronic chip/circuit board requires development of new capacitors with smaller size, weight and cost. Miniaturization in the size of capacitors demands development of high energy density dielectric materials, which are the core of parallel plate capacitors. Nano composite dielectrics comprising high polarizibility oxide fillers randomly dispersed in high breakdown strength polymer matrix are considered as a potential high energy density materials for capacitor applications. Large interfacial volume, generated due to introduction of nano fillers in polymer matrix, might have significant positive contribution towards energy storage in nano composites. However, percolation issues associated with nano fillers and generation of large interfacial volume in nano composites, where complex electric field distribution overlaps with interfacialy modified polymer lead to unclear understanding of polymer-filler interfacial interactions in nano composites. Hence, in the current work laminar composite double layered dielectric structures, which provide relatively simple local field distribution at the interface and ideal series connectivity between oxide and polymer, are used as a model system to understand polymer-oxide interfacial interactions. Interfacial effects are reported for both low permittivity (SiO2-Parylene C) and medium permittivity (ZrO2-P(VDF-TrFE)) laminar composite dielectrics. Pyrolytic vapor decomposition polymerization process was used to grow Parylene C thin films on gold and thermally grown SiO2 surfaces. Enhancement in crystallite dimension with post deposition annealing treatments of Parylene C thin films was found to reduce dielectric loss tangent and hence enhance its dielectric properties. Electric field and temperature dependant leakage current analysis suggested hopping as dominant conduction mechanism in Parylene C thin films. Parylene C thin films in laminar composites showed

  3. Deposition and characterization of titanium dioxide and hafnium dioxide thin films for high dielectric applications

    NASA Astrophysics Data System (ADS)

    Yoon, Meeyoung

    The industry's demand for higher integrated circuit density and performance has forced the gate dielectric layer thickness to decrease rapidly. The use of conventional SiO2 films as gate oxide is reaching its limit due to the rapid increase in tunneling current. Therefore, a need for a high dielectric material to produce large oxide capacitance and low leakage current has emerged. Metal-oxides such as titanium dioxide (TiO2) and hafnium dioxide (HfO2) are attractive candidates for gate dielectrics due to their electrical and physical properties suitable for high dielectric applications. MOCVD of TiO2 using titanium isopropoxide (TTIP) precursor on p-type Si(100) has been studied. Insertion of a TiO x buffer layer, formed by depositing metallic Ti followed by oxidation, at the TiO2/Si interface has reduced the carbon contamination in the TiO2 film. Elemental Ti films, analyzed by in-situ AES, were found to grow according to Stranski-Krastanov mode on Si(100). Carbon-free, stoichiometric TiO2 films were successfully produced on Si(100) without any parasitic SiO2 layers at the TiO 2/Si interface. Electron-beam deposition of HfO2 films on Si(100) has also been investigated in this work. HfO2 films are formed by depositing elemental Hf on Si(100) and then oxidizing it either in O2 or O 3. XPS results reveal that with oxidation Hf(4f) peak shifts +3.45eV with 02 and +3.65eV with O3 oxidation. LEED and AFM studies show that the initially ordered crystalline Hf becomes disordered after oxidation. The thermodynamic stability of HfO2 films on Si has been studied using a unique test-bed structure of Hf/O3/Si. Post-Oxidation of Layer Deposition (POLD) has been employed to produce HfO2 films with a desired thickness. XPS results indicate that stoichiometric HfO 2 films were successfully produced using the POLD process. The investigation of the growth and thin film properties of TiO 2 and HfO2 using oxygen and ozone has laid a foundation for the application of these metal

  4. Terahertz dielectric response of ferroelectric Ba(x)Sr(1-x)TiO3 thin films.

    PubMed

    Kang, Seung Beom; Kwak, Min Hwan; Choi, Muhan; Kim, Sungil; Kim, Taeyong; Cha, Eun Jong; Kang, Kwang Yong

    2011-11-01

    Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films varies with the films compositions. Among the compositions of Ba(x)Sr(1-x)TiO(3) films with different Ba/Sr ratios, Ba(0.6)Sr(0.4)TiO(3) has the highest dielectric constants and the shortest dielectric relaxation time.

  5. Fabrication of water-stable organic transistors using crystalline rubrene thin-film and polymer-treated dielectric (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Kim, Jaejoon; Lee, Hyoek Moo; Cho, Sung Oh

    2015-10-01

    For the real application of organic electronics, stable operation of electronic devices in humid or aqueous condition is essential and desirable. However, most of organic semiconductors were very weak to the oxygen or water and especially, cannot be operated well in aqueous condition without an encapsulation. Here, we present water-stable organic thin-film transistors with highly crystallized rubrene and polymer-treated dielectrics. These high water-stability could be achieved by two factors. First, rubrene, a well-known p-type semiconducting material, showed high air and water stability after the crystallization of `abrupt heating'. By the fabrication and aqueous operation of rubrene thin film transistor, we could show the water stability of crystallized thin-film rubrene. Such high environmental stability is attributed to the fact that rubrene has comparatively low HOMO level of -5.4 eV and large bandgap energy of 3.2 eV and that the rubrene thin-film is composed of well-interconnected orthorhombic rubrene crystals. Second, the polymer-treatment of dielectrics can enhance long-term water stability of fabricated rubrene thin-film transistor. By the complete immersion test of transistors, we could characterize the increase of water-stability after the treatment of dielectrics with cross-linked polymer. For this purpose, polystyrene is cross-linked by electron irradiation and the water penetration into semiconductor/dielectric interface was decreased due to the decreased surface energy of polymer dielectric compared to the SiO₂. The fabricated rubrene thin-film transistors showed a field-effect mobility of ~0.5 cm2V-1s-1 and long-term stability under ambient and aqueous conditions. Also, we investigated their potential applications in chemical or bio sensors.

  6. Tantalum oxide thin films for high-k dielectric applications: Crystallization, anisotropy and three dimensional imaging

    NASA Astrophysics Data System (ADS)

    Min, Kyunghoon

    2004-12-01

    High dielectric constant (high-k) materials have been drawing much attention for applications such as gate oxides for transistors and dynamic random access memory (DRAM) capacitors. Tantalum pentoxide (Ta2O5) is a possible replacement because of its relatively high dielectric constant and process compatibility. The microstructure of Ta2O5 thin films, deposited on Si substrates by atomic layer deposition, was investigated primarily using transmission electron microscopy (TEM). The kinetics of the crystallization and evolution of a complicated subgrain structure were studied by in-situ TEM heating experiments carried out at nominal temperatures of 790°C, 820°C and 850°C. It was found that the crystallization behavior could be modeled by a standard kinetic approach, using the Avrami equation, and differences from conventional bulk behavior are discussed. The growth and overall crystallization activation energies extracted from the in-situ TEM results were 4.2 eV and 6.3 eV, respectively. The tantalum oxide films used in this study were found to have two predominant crystallographic orientations. In order to evaluate the possible anisotropic properties of the two types of grains, micro-capacitors were fabricated on each type using a combination of a focused ion beam machine (FIB) and the TEM. Plan-view TEM samples were prepared to identify and locate grain orientations followed by electron beam assisted chemical vapor deposition of a Pt top electrode using the local deposition capability of the FIB. Electrical measurement of the micro-capacitors was carried out using a micromanipulator inside the FIB. The dielectric properties of the two types of grains were directly compared from the measurements. A further application of FIB combined with TEM allows novel specimen preparation for electron tomography. Accordingly, we can address the three dimensional imaging of Ta2O5 thin films deposited on hemi-spherical grain silicon (HSG) structures. The post-shaped sample

  7. Radiation and Internal Charging Environments for Thin Dielectrics in Interplanetary Space

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Parker, Linda Neergaard; Altstatt, Richard L.

    2004-01-01

    Spacecraft designs using solar sails for propulsion or thin membranes to shade instruments from the sun to achieve cryogenic operating temperatures are being considered for a number of missions in the next decades. A common feature of these designs are thin dielectric materials that will be exposed to the solar wind, solar energetic particle events, and the distant magnetotail plasma environments encountered by spacecraft in orbit about the Earth-Sun L2 point. This paper will discuss the relevant radiation and internal charging environments developed to support spacecraft design for both total dose radiation effects as well as dose rate dependent phenomenon, such as internal charging in the solar wind and distant magnetotail environments. We will describe the development of radiation and internal charging environment models based on nearly a complete solar cycle of Ulysses solar wind plasma measurements over a complete range of heliocentric latitudes and the early years of the Geotail mission where distant magnetotail plasma environments were sampled beyond X(sub GSE) = -100 Re to nearly L2 (X(sub GSE) -236 Re). Example applications of the environment models are shown to demonstrate the radiation and internal charging environments of thin materials exposed to the interplanetary space plasma environments.

  8. Temperature dependent dielectric and ferroelectric studies of BiFeO3 thin film

    NASA Astrophysics Data System (ADS)

    Gaur, Anand P. S.; Barik, Sujit K.; Katiyar, Ram S.

    2013-03-01

    Although BiFeO3 (BFO) has received a lot of interest due to its good multiferroic properties at room temperature, high leakage current limit its usage for practical applications. Recently, it is found that these properties in thin films can be different due to strain effect induced by substrate, preparation conditions and electrode effects, etc. In this context, we have studied the temperature dependence of polarization and dielectric properties of BFO thin film by varying the bottom electrode thickness and using different electrodes. The strain dependent ferroelectric switching behaviors have also been investigated with a traditional ferroelectric tester and switching spectroscopy piezoresponse force microscopy (SS-PFM), respectively. We used pulsed laser deposition to fabricate thin films of BFO using Si (100) substrate and SrTiO3(STO) as buffer layer with different bottom electrodes such as SrRuO3(SRO), LaNiO3(LNO) and Pt/Si. The thickness of STO layer is kept fixed around 70 nm and the thicknesses of BFO and electrode layer were varied from 70 nm to 200nm. The layers were grown under optimized conditions and polycrystalline nature is found from room temperature XRD. A large enhancement of polarization is found while using LNO electrode and also with reducing the thickness of BFO layer. The remnant polarization and cohesivity also shows large increase with increaisng temperature, although leakage current increases significantly. NSF

  9. Controlling the optical scattering of plasmonic nanoparticles using a thin dielectric layer

    NASA Astrophysics Data System (ADS)

    Powell, A. W.; Wincott, M. B.; Watt, A. A. R.; Assender, H. E.; Smith, J. M.

    2013-05-01

    The effect of a thin dielectric film on the plasmonic behaviour of metal nanoparticles (MNPs) above a high refractive index substrate is explored. Using finite-difference time domain simulations, the optical properties of Ag nanoparticles are investigated as a function of film thickness, refractive index, and particle position within the film. We demonstrate that the addition of a film around a MNP at the air interface of a high-index substrate, where nairthin-film solar cells. We show that the inclusion of a thin film can increase the fraction of radiation coupled into the substrate by up to 30% for solar wavelengths. Additional potential benefits of the film structure, such as greater tunability of scattering resonances, an increase in path length of light in the substrate, and some control over the emission pattern are demonstrated. MNPs in a film are found to produce a more finely structured emission pattern than particles at a simple interface, showing potential for this research to be applied to optical nanoantennae.

  10. Design and characterization of terahertz-absorbing nano-laminates of dielectric and metal thin films

    SciTech Connect

    Bolakis, Christos; Grbovic, Dragoslav; Lavrik, Nickolay V; Karunasiri, Gamani

    2010-01-01

    A terahertz-absorbing thin-film stack, containing a dielectric Bragg reflector and a thin chromium metal film, was fabricated on a silicon substrate for applications in bi-material terahertz (THz) sensors. The Bragg reflector is to be used for optical readout of sensor deformation under THz illumination. The THz absorption characteristics of the thin-film composite were measured using Fourier transform infrared spectroscopy. The absorption of the structure was calculated both analytically and by finite element modeling and the two approaches agreed well. Finite element modeling provides a convenient way to extract the amount of power dissipation in each layer and is used to quantify the THz absorption in the multi-layer stack. The calculation and the model were verified by experimentally characterizing the multi-layer stack in the 3-5 THz range. The measured and simulated absorption characteristics show a reasonably good agreement. It was found that the composite film absorbed about 20% of the incident THz power. The model was used to optimize the thickness of the chromium film for achieving high THz absorption and found that about 50% absorption can be achieved when film thickness is around 9 nm.

  11. Electrical properties of nanoscale metallic thin films on dielectric elastomer at various strain rates

    NASA Astrophysics Data System (ADS)

    Faisal, Md. Shahnewaz Sabit; Ye, Zhihang; Chen, Zheng; Asmatulu, Ramazan

    2015-04-01

    Dielectric elastomers (DEs) have significant applications in artificial muscle and other biomedical equipment and device fabrications. Metallic thin films by thin film transfer and sputter coating techniques can provide conductive surfaces on the DE samples, and can be used as electrodes for the actuators and other biomedical sensing devices. In the present study, 3M VHB 4910 tape was used as a DE for the coating and electrical characterization tests. A 150 nm thickness of gold was coated on the DE surfaces by sputter coating under vacuum with different pre-strains, ranging from 0 to 100%. Some of the thin films were transferred to the surface of the DEs. Sputter coating, and direct transferring gold leaf coating methods were studied and the results were analyzed in detail in terms of the strain rates and electrical resistivity changes. Initial studies indicated that the metallic surfaces remain conductive even though the DE films were considerably elongated. The coated DEs can be used as artificial muscle by applying electrical stimulation through the conductive surfaces. This study may provide great benefits to the readers, researchers, as well as companies involved in manufacturing of artificial muscles and actuators using smart materials.

  12. Effect of high-power laser radiation on characteristics of thin silicon nitride films

    SciTech Connect

    Roizin, Y.O.; Khuan, K.S.

    1986-09-01

    High-power laser radiation is used in microelectronic technology for purposes such as annealing radiation defects in MOS structures after ion implantation. This paper considers accumulated changes in electrical characteristics of metal-nitride-oxide-semiconductor (MNOS) structures under the action of neodymium laser pulses with an energy density below the visible damage threshold. The experimental results obtained are interpreted.

  13. Use of cermet thin film resistors with nitride passivated metal insulator field effect transistor

    NASA Technical Reports Server (NTRS)

    Brown, G. A.; Harrap, V.

    1971-01-01

    Film deposition of cermet resistors on same chip with metal nitride oxide silicon field effect transistors permits protection of contamination sensitive active devices from contaminants produced in cermet deposition and definition processes. Additional advantages include lower cost, greater reliability, and space savings.

  14. Group III-nitride thin films grown using MBE and bismuth

    DOEpatents

    Kisielowski, Christian K.; Rubin, Michael

    2000-01-01

    The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

  15. Group III-nitride thin films grown using MBE and bismuth

    DOEpatents

    Kisielowski, Christian K.; Rubin, Michael

    2002-01-01

    The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

  16. Cross-linking effect on dielectric properties of polypropylene thin films and applications in electric energy storage

    NASA Astrophysics Data System (ADS)

    Yuan, Xuepei; Chung, T. C. Mike

    2011-02-01

    A family of cross-linked polypropylene (x-PP) thin film dielectrics is systematically studied to understand the cross-linking effect on the dielectric properties. Evidently, the butylstyrene (BSt) cross-linkers increase both the dielectric constant (ɛ) and breakdown strength (E), without increasing energy loss. An x-PP dielectric, with 3.65 mol % BSt cross-linkers, exhibits a ɛ ˜3, which is independent of a wide range of temperatures and frequencies, slim D-E hysteresis loops, high breakdown strength (E=650 MV/m), narrow breakdown distribution, and reliable energy storage capacity >5 J/cm3 (double that of state-of-the-art biaxially oriented polypropylene capacitors), without showing any increase in energy loss.

  17. The Relationship Between Chemical Structure and Dielectric Properties of Plasma-Enhanced Chemical Vapor Deposited Polymer Thin Films (Postprint)

    DTIC Science & Technology

    2007-01-01

    Materials Sci & Tech Applications, LLC) N. Venkatasubramanian and John T. Grant (University of Dayton) Kurt Eyink, Jesse Enlow, and Timothy J. Bunning...structure and dielectric properties of plasma-enhanced chemical vapor deposited polymer thin films Hao Jiang b,⁎, Lianggou Hong b, N. Venkatasubramanian c

  18. Shift and elimination of microwave Fabry-Perot resonances in a dielectric covered with a thin metal layer

    NASA Astrophysics Data System (ADS)

    Ragulis, Paulius; Simniškis, Rimantas; Kancleris, Žilvinas

    2015-04-01

    In this paper, we consider a plane electromagnetic wave incident onto a dielectric plate, which has one surface covered with a thin layer of metal. An oblique incident angle was considered for the TE (s polarization in optic) and TM (p polarization) plane waves. The thin metal layer is treated as an infinitesimal thickness. It was characterized by a surface conductivity and accounted for by a tangential magnetic field component step induced by the current flow in the metal layer. Compact expressions, which describe the reflection, transmission and absorption in a dielectric plate covered with a thin layer of metal, have been obtained. It was shown that by choosing the appropriate surface conductivity, the Fabry-Perot transmission resonances can be shifted to the position where the maximum reflection is observed in the case of an uncovered dielectric. On the other hand, the elimination of the Fabry-Perot resonances can be also achieved by choosing a proper metal surface conductivity. Measurements of the reflection from the glass covered with a thin layer of metal have been performed in a wide microwave frequency range (2-12 GHz) revealing a large difference in the measured reflection coefficient from the dielectric and metalized surfaces. The measured results fit well with those calculated by employing analytical expressions obtained in this paper.

  19. Low-voltage bendable pentacene thin-film transistor with stainless steel substrate and polystyrene-coated hafnium silicate dielectric.

    PubMed

    Yun, Dong-Jin; Lee, Seunghyup; Yong, Kijung; Rhee, Shi-Woo

    2012-04-01

    The hafnium silicate and aluminum oxide high-k dielectrics were deposited on stainless steel substrate using atomic layer deposition process and octadecyltrichlorosilane (OTS) and polystyrene (PS) were treated improve crystallinity of pentacene grown on them. Besides, the effects of the pentacene deposition condition on the morphologies, crystallinities and electrical properties of pentacene were characterized. Therefore, the surface treatment condition on dielectric and pentacene deposition conditions were optimized. The pentacene grown on polystyrene coated high-k dielectric at low deposition rate and temperature (0.2-0.3 Å/s and R.T.) showed the largest grain size (0.8-1.0 μm) and highest crystallinity among pentacenes deposited various deposition conditions, and the pentacene TFT with polystyrene coated high-k dielectric showed excellent device-performance. To decrease threshold voltage of pentacene TFT, the polystyrene-thickness on high-k dielectric was controlled using different concentration of polystyrene solution. As the polystyrene-thickness on hafnium silicate decreases, the dielectric constant of polystyrene/hafnium silicate increases, while the crystallinity of pentacene grown on polystyrene/hafnium silicate did not change. Using low-thickness polystyrene coated hafnium silicate dielectric, the high-performance and low voltage operating (<5 V) pentacene thin film transistor (μ: ~2 cm(2)/(V s), on/off ratio, >1 × 10(4)) and complementary inverter (DC gains, ~20) could be fabricated.

  20. Temperature dependence of the dielectric function of laser deposited YBCO thin film at 3392nm

    SciTech Connect

    Walmsley, D.G.; Bade, T.; McCafferty, P.G.; Rea, C.; Dawson, P.; Wallace, R.J.; Bowman, R.M.

    1996-12-31

    The authors have excited surface plasmons in an YBCO thin film at different temperatures using attenuated total reflection of light. The 300nm thick c-axis film was fabricated using pulsed laser deposition onto an MgO (100) substrate with 248nm KrF excimer radiation. Critical temperature of the film was 89.6K and its roughness, as shown by atomic force microscopy, 20nm rms, without droplets over areas of 10 {micro}m x 10{micro}m. The sample was mounted in Otto geometry on a cooled stage which allowed the temperature to be varied between 300K and 70K. An infrared HeNe laser at 3,392nm was used to excite the surface plasmons. The dielectric function of the film was determined between room temperature and 80K. The imaginary part of the dielectric function decreased substantially with reduction in temperature. Results obtained were: {var_epsilon}{sub r} = {minus}24.1 + 0.0013T and {var_epsilon}{sub i} = 7.7 + 0.067T where T is the temperature in kelvin. The ratio {var_epsilon}{sub i}{sup 300}/{var_epsilon}{sub i}{sup 80} at 2.13 is less than the resistance ratio R{sup 300}/R{sup 80} at 2.81. An explanation is offered in terms of two temperature independent mechanisms operative at optical frequencies: enhanced Rayleigh scattering of surface plasmons at grain boundaries and intraband/interband transitions. The real part of the dielectric function, {var_epsilon}{sub r}, was found to be only slightly temperature dependent. It was, however, highly sample dependent when comparison was made with the results of other films, a feature attributed to surface and grain boundary contamination.

  1. Thin-dielectric-layer engineering for 3D nanostructure integration using an innovative planarization approach.

    PubMed

    Guerfi, Y; Doucet, J B; Larrieu, G

    2015-10-23

    Three-dimensional (3D) nanostructures are emerging as promising building blocks for a large spectrum of applications. One critical issue in integration regards mastering the thin, flat, and chemically stable insulating layer that must be implemented on the nanostructure network in order to build striking nano-architectures. In this letter, we report an innovative method for nanoscale planarization on 3D nanostructures by using hydrogen silesquioxane as a spin-on-glass (SOG) dielectric material. To decouple the thickness of the final layer from the height of the nanostructure, we propose to embed the nanowire network in the insulator layer by exploiting the planarizing properties of the SOG approach. To achieve the desired dielectric thickness, the structure is chemically etched back with a highly diluted solution to control the etch rate precisely. The roughness of the top surface was less than 2 nm. There were no surface defects and the planarity was excellent, even in the vicinity of the nanowires. This newly developed process was used to realize a multilevel stack architecture with sub-deca-nanometer-range layer thickness.

  2. Development of dielectric barrier discharge plasma processing apparatus for mass spectrometry and thin film deposition

    SciTech Connect

    Majumdar, Abhijit; Hippler, Rainer

    2007-07-15

    Cost effective and a very simple dielectric barrier discharge plasma processing apparatus for thin film deposition and mass spectroscopic analysis of organic gas mixture has been described. The interesting features of the apparatus are the construction of the dielectric electrodes made of aluminum oxide or alumina (Al{sub 2}O{sub 3}) and glass and the generation of high ignition voltage from the spark plug transformer taken from car. Metal capacitor is introduced in between ground and oscilloscope to measure the executing power during the discharge and the average electron density in the plasma region. The organic polymer films have been deposited on Si (100) substrate using several organic gas compositions. The experimental setup provides a unique drainage system from the reaction chamber controlled by a membrane pump to suck out and remove the poisonous gases or residuals (cyanogens, H-CN, CH{sub x}NH{sub 2}, etc.) which have been produced during the discharge of CH{sub 4}/N{sub 2} mixture.

  3. Single frequency correction based on three-element model for thin dielectric MOS capacitor

    NASA Astrophysics Data System (ADS)

    Zhang, Xizhen; Zhu, Huichao; Cheng, Chuanhui; Yu, Tao; Zhang, Daming; Zhong, Hua; Li, Xiangping; Cheng, Yi; Xu, Xuesong; Cheng, Lihong; Sun, Jiashi; Chen, Baojiu

    2017-03-01

    For super thin dielectric MOS capacitor, capacitance extraction by using two-element model is erroneous. Three-element model, considering parasitic parameters of parallel resistance Rp and series resistance Rs, is necessary. In this paper, we develop a single frequency correction method by combining capacitance-voltage (C-V) and current-voltage (I-V) data. By equating impedances of three-element model with that of two-element model, we obtain two characteristic equations. By using a differential resistance dV/dI, we obtain the third equation. Consequently, three real parameters for the capacitance C, the Rp and the Rs are solved. As an application example of Al/HfO2/n-Si MOS, we demonstrate physically reasonable values for all three real parameters. Furthermore, dielectric loss tangent tan δ is calculated as 0.005-0.022 at 1.5 V. A simplified expression of measured capacitance Cm about the C, the Rp, the Rs and angular frequency ω has been deduced. A constraint condition for large ratio Cm/C suggests the reduction of the ratio Rs/Rp and Rs. Considering suitable values for tan δ and ratio of Cm/C, applicable frequency range is from 15 kHz to 1.1-2.1 MHz.

  4. Thickness effect on the dielectric, ferroelectric, and piezoelectric properties of ferroelectric lead zirconate titanate thin films

    NASA Astrophysics Data System (ADS)

    Pérez de la Cruz, J.; Joanni, E.; Vilarinho, P. M.; Kholkin, A. L.

    2010-12-01

    Lead zirconate titanate (PbZr0.52Ti0.48O3-PZT) thin films with different thicknesses were deposited on Pt(111)/Ti/SiO2/Si substrates by a sol-gel method. Single perovskite phase with (111)-texture was obtained in the thinnest films, whereas with the increase in thickness the films changed to a highly (100)-oriented state. An increase in the mean grain size as the film thickness increased was also observed. Dielectric, ferroelectric, and piezoelectric properties were analyzed as a function of the film thickness and explained based on film orientation, grain size, domain structure, domain wall motion, and nonswitching interface layers. Both serial and parallel capacitor models were used to analyze the influence of the nonswitching interface layer in the dielectric properties and the effect of substrate clamping in the microscopic piezoelectric response as the film thickness decreased. The scanning force microscopy technique was used to study the effect of thickness on the microscopic piezoresponse. Significant differences between the macroscopic and microscopic electrical properties of the films were observed. Those differences can be assigned to changes in the nonswitching film-electrode layer and domain structure.

  5. Fundamental performance limits of carbon nanotube thin-film transistors achieved using hybrid molecular dielectrics.

    PubMed

    Sangwan, Vinod K; Ortiz, Rocio Ponce; Alaboson, Justice M P; Emery, Jonathan D; Bedzyk, Michael J; Lauhon, Lincoln J; Marks, Tobin J; Hersam, Mark C

    2012-08-28

    In the past decade, semiconducting carbon nanotube thin films have been recognized as contending materials for wide-ranging applications in electronics, energy, and sensing. In particular, improvements in large-area flexible electronics have been achieved through independent advances in postgrowth processing to resolve metallic versus semiconducting carbon nanotube heterogeneity, in improved gate dielectrics, and in self-assembly processes. Moreover, controlled tuning of specific device components has afforded fundamental probes of the trade-offs between materials properties and device performance metrics. Nevertheless, carbon nanotube transistor performance suitable for real-world applications awaits understanding-based progress in the integration of independently pioneered device components. We achieve this here by integrating high-purity semiconducting carbon nanotube films with a custom-designed hybrid inorganic-organic gate dielectric. This synergistic combination of materials circumvents conventional design trade-offs, resulting in concurrent advances in several transistor performance metrics such as transconductance (6.5 μS/μm), intrinsic field-effect mobility (147 cm(2)/(V s)), subthreshold swing (150 mV/decade), and on/off ratio (5 × 10(5)), while also achieving hysteresis-free operation in ambient conditions.

  6. Thin-dielectric-layer engineering for 3D nanostructure integration using an innovative planarization approach

    NASA Astrophysics Data System (ADS)

    Guerfi, Y.; Doucet, J. B.; Larrieu, G.

    2015-10-01

    Three-dimensional (3D) nanostructures are emerging as promising building blocks for a large spectrum of applications. One critical issue in integration regards mastering the thin, flat, and chemically stable insulating layer that must be implemented on the nanostructure network in order to build striking nano-architectures. In this letter, we report an innovative method for nanoscale planarization on 3D nanostructures by using hydrogen silesquioxane as a spin-on-glass (SOG) dielectric material. To decouple the thickness of the final layer from the height of the nanostructure, we propose to embed the nanowire network in the insulator layer by exploiting the planarizing properties of the SOG approach. To achieve the desired dielectric thickness, the structure is chemically etched back with a highly diluted solution to control the etch rate precisely. The roughness of the top surface was less than 2 nm. There were no surface defects and the planarity was excellent, even in the vicinity of the nanowires. This newly developed process was used to realize a multilevel stack architecture with sub-deca-nanometer-range layer thickness.

  7. Dielectric Barrier Discharge Ionization in Characterization of Organic Compounds Separated on Thin-Layer Chromatography Plates

    PubMed Central

    Cegłowski, Michał; Smoluch, Marek; Babij, Michał; Gotszalk, Teodor; Silberring, Jerzy; Schroeder, Grzegorz

    2014-01-01

    A new method for on-spot detection and characterization of organic compounds resolved on thin layer chromatography (TLC) plates has been proposed. This method combines TLC with dielectric barrier discharge ionization (DBDI), which produces stable low-temperature plasma. At first, the compounds were separated on TLC plates and then their mass spectra were directly obtained with no additional sample preparation. To obtain good quality spectra the center of a particular TLC spot was heated from the bottom to increase volatility of the compound. MS/MS analyses were also performed to additionally characterize all analytes. The detection limit of proposed method was estimated to be 100 ng/spot of compound. PMID:25170762

  8. Metalorganic chemical vapor deposition of indium nitride and indium gallium nitride thin films and nanostructures for electronic and photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Mangum, Joshua L.

    Single and multi-junction InxGa1-xN solar cell devices were modeled in one dimension using MEDICI device simulation software to assess the potential of InxGa1-xN-based solar cells. Cell efficiencies of 16 and 27.4%, under AM0 illumination were predicted for a single and a 5-junction InxGa1-xN solar cell, respectively. Phase separation of InxGa1-xN alloys is determined to have little to no negative effects on the solar cell efficiency. InxGa1-xN alloys were grown by MOCVD over the entire compositional range (0 ≤ x ≤ 1) and phase separation was analyzed with respect to substrate material and growth temperature. A low deposition temperature of 530°C was used to produce metastable InxGa1-xN/c-Al 2O3 thin films over the entire compositional range, which was demonstrated for the first time by MOCVD. The use of higher deposition temperature and closely lattice matched substrates resulted in phase separated films. Substrates with a larger lattice mismatch (c-Al2O3 ) introduce strain in InxGa1-xN which helps to stabilize the film, however, at the expense of crystalline quality. Growth of InN nanowires by MOCVD was controlled without the use of templates or catalysts by varying the inlet flow pattern, N/In ratio, growth temperature, and substrate material. A VLS growth mechanism is proposed, however, a VS growth mechanism can be achieved at high N/In ratios. SEM and TEM analysis revealed a core-shell nanowire structure with a single crystal InN core and a poly-crystalline In2O3 shell. Nanowire growth occurs along the [0002] direction with diameters and lengths ranging from 100 to 300 nm and 10 to 40 mum, respectively for a 1 hr growth. H-MOCVD growth of InN nano- and microrods occurred on different substrates and the nanorod structure was studied by TEM. The polarity of the substrate directly affected the nanorod tip shape and prismatic stacking faults are suggested as the cause for the flower-like growth habit. Variation of growth parameters, such as temperature, N

  9. Millimeter Wave Sensor For On-Line Inspection Of Thin Sheet Dielectrics

    DOEpatents

    Bakhtiari, Sasan; Gopalsami, Nachappa; Raptis, Apostolos C.

    1999-03-23

    A millimeter wave sensor is provided for non-destructive inspection of thin sheet dielectric materials. The millimeter wave sensor includes a Gunn diode oscillator (GDO) source generating a mill meter wave electromagnetic energy signal having a single frequency. A heater is coupled to the GDO source for stabilizing the single frequency. A small size antenna is coupled to the GDO source for transmitting the millimeter wave electromagnetic energy signal to a sample material and for receiving a reflected millimeter wave electromagnetic energy signal from the sample material. Ferrite circulator isolators coupled between the GDO source and the antenna separate the millimeter wave electromagnetic energy signal into transmitted and received electromagnetic energy signal components and a detector detects change in both amplitude and phase of the transmitted and received electromagnetic energy signal components. A millimeter wave sensor is provided for non-destructive inspection of thin sheet dielectric materials. The millimeter wave sensor includes a Gunn diode oscillator (GDO) source generating a mill meter wave electromagnetic energy signal having a single frequency. A heater is coupled to the GDO source for stabilizing the single frequency. A small size antenna is coupled to the GDO source for transmitting the millimeter wave electromagnetic energy signal to a sample material and for receiving a reflected millimeter wave electromagnetic energy signal from the sample material. Ferrite circulator isolators coupled between the GDO source and the antenna separate the millimeter wave electromagnetic energy signal into transmitted and received electromagnetic energy signal components and a detector detects change in both amplitude and phase of the transmitted and received electromagnetic energy signal components.

  10. Least-squares electromagnetic analysis of thin dielectrics using surface equivalence

    NASA Astrophysics Data System (ADS)

    Shieh, Kuen-Wey

    2000-10-01

    In this thesis, the motivation was to study the applicability and test the limits of analytical formulations using surface equivalence, in dealing with the scattering problem of a thin dielectric slab of finite extent. In this application of the surface equivalence principle, the unknowns, equivalent surface electric and magnetic currents, are established using the method of moments. Described herein, in order to solve for the unknowns, are four new numerical techniques called LSM, CLSM, CLSM+RCA and CWLSM+RCA, employed to deal with the radar cross section (RCS) of electromagnetic wave scattering from thin dielectric slabs, for different thicknesses in three dimensions. The designations, LSM, CLSM, CLSM+RCA and CWLSM+RCA stand for least squares method, constrained least squares method, constrained least squares method plus ring current approximation and constrained weighted least squares method plus ring current approximation, respectively. The least squares method is utilized in the new numerical techniques, providing a better solution in the null region of the RCS than the combined field integral equation (CFIE). The new numerical techniques employ surface distributions of equivalent currents, thus in principle requiring less computer memory than those employing volume distributions of current density. Moreover, there is no need to worry about how nearly perfect should be the absorbing boundary condition (ABC) that is used in the finite difference time domain technique (FDTD). Further, in this work, the importance of the equivalent surface currents flowing on the edge of a thin slab (which are referred to as `ring currents') has been identified. The new techniques also show fast convergence for the particularly challenging case of edge-on wave incidence, even when the slab is as thin as 0.001 λ0 (λ0 is wavelength in free space). In particular, the CLSM+RCA and CWLSM+RCA analyses have been validated by experiments for the case of backward RCS, these experiments

  11. Superconducting structure with layers of niobium nitride and aluminum nitride

    DOEpatents

    Murduck, J.M.; Lepetre, Y.J.; Schuller, I.K.; Ketterson, J.B.

    1989-07-04

    A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources. 8 figs.

  12. Superconducting structure with layers of niobium nitride and aluminum nitride

    DOEpatents

    Murduck, James M.; Lepetre, Yves J.; Schuller, Ivan K.; Ketterson, John B.

    1989-01-01

    A superconducting structure is formed by depositing alternate layers of aluminum nitride and niobium nitride on a substrate. Deposition methods include dc magnetron reactive sputtering, rf magnetron reactive sputtering, thin-film diffusion, chemical vapor deposition, and ion-beam deposition. Structures have been built with layers of niobium nitride and aluminum nitride having thicknesses in a range of 20 to 350 Angstroms. Best results have been achieved with films of niobium nitride deposited to a thickness of approximately 70 Angstroms and aluminum nitride deposited to a thickness of approximately 20 Angstroms. Such films of niobium nitride separated by a single layer of aluminum nitride are useful in forming Josephson junctions. Structures of 30 or more alternating layers of niobium nitride and aluminum nitride are useful when deposited on fixed substrates or flexible strips to form bulk superconductors for carrying electric current. They are also adaptable as voltage-controlled microwave energy sources.

  13. High-Permittivity Thin Dielectric Padding Improves Fresh Blood Imaging of Femoral Arteries at 3T

    PubMed Central

    Lindley, Marc D; Kim, Daniel; Morrell, Glen; Heilbrun, Marta E; Storey, Pippa; Hanrahan, Christopher J; Lee, Vivian S

    2014-01-01

    Objectives Fresh blood imaging (FBI) is a useful non-contrast magnetic resonance angiography (NC-MRA) method for assessment of peripheral arterial disease (PAD), particularly in patients with poor renal function. Compared with 1.5T, 3T enables higher signal to noise ratio (SNR) and/or spatio-temporal resolution in FBI, as demonstrated successfully for the calf station. However, FBI of the thigh station at 3T has been reported to suffer from signal void in the common femoral artery of one thigh only due to the radial symmetry in transmit radio-frequency field (B1+) variation. We sought to increase the femoral arterial signal attenuated by B1+ variation in FBI at 3T using high permittivity dielectric padding. Materials and Methods We performed FBI of the thigh station in 13 human subjects at 3T to compare the following 3 settings: no padding, commercially available thick (~ 5 cm) dielectric padding, and high-permittivity thin (~2 cm) dielectric padding. B1+ mapping was also performed in the common femoral arteries to characterize the radial symmetry in B1+ variation and quantify the improvement in B1+ excitation. We characterized the impact of radial symmetry in B1+ variation on the FBI signal and FBI MRA of the right common femoral artery using quantitative (i.e., contrast-to-noise ratio (CNR)) and qualitative (i.e., conspicuity) analyses. Results The radial symmetry in B1+ variation attenuates signal in the right common femoral artery, which can be partially improved with commercial padding and improved further with high permittivity padding. Averaging the results over 13 subjects, the B1+, CNR and conspicuity scores in the right common femoral artery were significantly better with high-permittivity padding than with commercial padding and baseline (p<0.001). Conclusions Our study shows that high-permittivity dielectric padding can be used to increase the femoral arterial signal attenuated by B1+ variation in FBI at 3T. PMID:25329606

  14. Theory and practical considerations of multilayer dielectric thin-film stacks in Ag-coated hollow waveguides.

    PubMed

    Bledt, Carlos M; Melzer, Jeffrey E; Harrington, James A

    2014-02-01

    This analysis explores the theory and design of dielectric multilayer reflection-enhancing thin film stacks based on high and low refractive index alternating layers of cadmium sulfide (CdS) and lead sulfide (PbS) on silver (Ag)-coated hollow glass waveguides (HGWs) for low loss transmission at midinfrared wavelengths. The fundamentals for determining propagation losses in such multilayer thin-film-coated Ag hollow waveguides is thoroughly discussed, and forms the basis for further theoretical analysis presented in this study. The effects on propagation loss resulting from several key parameters of these multilayer thin film stacks is further explored in order to bridge the gap between results predicted through calculation under ideal conditions and deviations from such ideal models that often arise in practice. In particular, the effects on loss due to the number of dielectric thin film layers deposited, deviation from ideal individual layer thicknesses, and surface roughness related scattering losses are presented and thoroughly investigated. Through such extensive theoretical analysis the level of understanding of the underlying loss mechanisms of multilayer thin-film Ag-coated HGWs is greatly advanced, considerably increasing the potential practical development of next-generation ultralow-loss mid-IR Ag/multilayer dielectric-coated HGWs.

  15. Magnetostrictive iron gallium thin films grown onto antiferromagnetic manganese nitride: Structure and magnetism

    NASA Astrophysics Data System (ADS)

    Mandru, Andrada-Oana; Corbett, Joseph P.; Richard, Andrea L.; Gallagher, James; Meng, Keng-Yuan; Ingram, David C.; Yang, Fengyuan; Smith, Arthur R.

    2016-10-01

    We report structural and magnetic properties of magnetostrictive Fe100 -xGax (x ≈ 15) alloys when deposited onto antiferromagnetic manganese nitride and non-magnetic magnesium oxide substrates. From X-ray diffraction measurements, we find that the FeGa films are single crystalline. Scanning tunneling microscopy imaging reveals that the surface morphologies are dictated by the growth temperature, composition, and substrate. The magnetic properties can be tailored by the substrate, as found by magnetic force microscopy imaging and vibrating sample magnetometry measurements. In addition to pronounced tetragonal deformations, depositing FeGa onto manganese nitride leads to the formation of stripe-like magnetic domain patterns and to the appearance of perpendicular magnetic anisotropy.

  16. Single-crystal cubic boron nitride thin films grown by ion-beam-assisted molecular beam epitaxy

    SciTech Connect

    Hirama, Kazuyuki Taniyasu, Yoshitaka; Karimoto, Shin-ichi; Krockenberger, Yoshiharu; Yamamoto, Hideki

    2014-03-03

    We investigated the formation of cubic boron nitride (c-BN) thin films on diamond (001) and (111) substrates by ion-beam-assisted molecular beam epitaxy (MBE). The metastable c-BN (sp{sup 3}-bonded BN) phase can be epitaxially grown as a result of the interplay between competitive phase formation and selective etching. We show that a proper adjustment of acceleration voltage for N{sub 2}{sup +} and Ar{sup +} ions is a key to selectively discriminate non-sp{sup 3} BN phases. At low acceleration voltage values, the sp{sup 2}-bonded BN is dominantly formed, while at high acceleration voltages, etching dominates irrespective of the bonding characteristics of BN.

  17. Influence of laser pulse frequency on the microstructure of aluminum nitride thin films synthesized by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Antonova, K.; Duta, L.; Szekeres, A.; Stan, G. E.; Mihailescu, I. N.; Anastasescu, M.; Stroescu, H.; Gartner, M.

    2017-02-01

    Aluminum Nitride (AlN) thin films were synthesized on Si (100) wafers at 450 °C by pulsed laser deposition. A polycrystalline AlN target was multipulsed irradiated in a nitrogen ambient, at different laser pulse repetition rate. Grazing Incidence X-Ray Diffraction and Atomic Force Microscopy analyses evidenced nanocrystallites with a hexagonal lattice in the amorphous AlN matrix. The thickness and optical constants of the layers were determined by infrared spectroscopic ellipsometry. The optical properties were studied by Fourier Transform Infrared reflectance spectroscopy in polarised oblique incidence radiation. Berreman effect was observed around the longitudinal phonon modes of the crystalline AlN component. Angular dependence of the A1LO mode frequency was analysed and connected to the orientation of the particles' optical axis to the substrate surface normal. The role of the laser pulse frequency on the layers' properties is discussed on this basis.

  18. Low temperature plasma-enhanced atomic layer deposition of thin vanadium nitride layers for copper diffusion barriers

    SciTech Connect

    Rampelberg, Geert; Devloo-Casier, Kilian; Deduytsche, Davy; Detavernier, Christophe; Blasco, Nicolas

    2013-03-18

    Thin vanadium nitride (VN) layers were grown by atomic layer deposition using tetrakis(ethylmethylamino)vanadium and NH{sub 3} plasma at deposition temperatures between 70 Degree-Sign C and 150 Degree-Sign C on silicon substrates and polymer foil. X-ray photoelectron spectroscopy revealed a composition close to stoichiometric VN, while x-ray diffraction showed the {delta}-VN crystal structure. The resistivity was as low as 200 {mu}{Omega} cm for the as deposited films and further reduced to 143 {mu}{Omega} cm and 93 {mu}{Omega} cm by annealing in N{sub 2} and H{sub 2}/He/N{sub 2}, respectively. A 5 nm VN layer proved to be effective as a diffusion barrier for copper up to a temperature of 720 Degree-Sign C.

  19. Preparation of ultra-thin hexagonal boron nitride nanoplates for cancer cell imaging and neurotransmitter sensing.

    PubMed

    Nurunnabi, Md; Nafiujjaman, Md; Lee, Sang-Joon; Park, In-Kyu; Huh, Kang Moo; Lee, Yong-Kyu

    2016-04-26

    A facile and convenient process was optimized for preparing water-soluble hydroxyl-functionalized hexagonal boron nitride (hBN-OH) from hBN. The hBN-OH (2-3 nm thickness) contains ∼40% oxygen and exhibits blue emission with a quantum yield of approximately 36%. The hBN-OH could be used for imaging cells and for the in vitro detection of biomolecules through electrochemical analysis.

  20. A mixed solution-processed gate dielectric for zinc-tin oxide thin-film transistor and its MIS capacitance

    PubMed Central

    Kim, Hunho; Kwack, Young-Jin; Yun, Eui-Jung; Choi, Woon-Seop

    2016-01-01

    Solution-processed gate dielectrics were fabricated with the combined ZrO2 and Al2O3 (ZAO) in the form of mixed and stacked types for oxide thin film transistors (TFTs). ZAO thin films prepared with double coatings for solid gate dielectrics were characterized by analytical tools. For the first time, the capacitance of the oxide semiconductor was extracted from the capacitance-voltage properties of the zinc-tin oxide (ZTO) TFTs with the combined ZAO dielectrics by using the proposed metal-insulator-semiconductor (MIS) structure model. The capacitance evolution of the semiconductor from the TFT model structure described well the threshold voltage shift observed in the ZTO TFT with the ZAO (1:2) gate dielectric. The electrical properties of the ZTO TFT with a ZAO (1:2) gate dielectric showed low voltage driving with a field effect mobility of 37.01 cm2/Vs, a threshold voltage of 2.00 V, an on-to-off current ratio of 1.46 × 105, and a subthreshold slope of 0.10 V/dec. PMID:27641430

  1. Full range dielectric characteristics of calcium copper titanate thin films prepared by continuous composition-spread sputtering.

    PubMed

    Kang, Hyo Min; Baek, Seung-Hyub; Song, Jong Han; Cho, Yong Soo; Choi, Ji-Won

    2014-09-08

    Perovskite CaCu3Ti4O12 has drawn a great deal of attention for various electronic applications due to its giant dielectric property as well as a strong stability in a wide range of temperature. In this paper, we use an off-axis continuous composition-spread (CCS) sputtering method to investigate the full range dielectric characteristics of calcium copper titanate thin films. The film compositions are continuously distributed by deposition from two targets of CaTiO3 and CuTiO3. A slightly Ca-deficient, Cu- and Ti-rich film, which has a 0.9:3.2:4.3 ratio for Ca:Cu:Ti, demonstrated the best performance by showing a dielectric constant of 781 at 100 kHz. On the other hand, all other films far away from the CaCu3Ti4O12 composition showed suppressed dielectric properties. Analyses by X-ray photon spectroscopy, micro-Raman microscopy, transmission electron microscopy, and Rutherford backscattering spectroscopy reveal that there are three possible origins for such superior performance at off stoichiometric thin films: (1) bulk doping by excessive Cu and Ti ions, (2) chemically modified grain boundary, and (3) the lowered electrode-sample interface resistance. Our result will provide a new insight into engineering the dielectric properties using off-stoichiometric synthesis.

  2. Effect of substitution group on dielectric properties of 4H-pyrano [3, 2-c] quinoline derivatives thin films

    NASA Astrophysics Data System (ADS)

    H, M. Zeyada; F, M. El-Taweel; M, M. El-Nahass; M, M. El-Shabaan

    2016-07-01

    The AC electrical conductivity and dielectrical properties of 2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3, 2-c]quinoline-3-carbonitrile (Ph-HPQ) and 2-amino-4-(2-chlorophenyl)-6-ethyl-5-oxo-5,6-dihydro-4H-pyrano [3, 2-c] quinoline-3-carbonitrile (Ch-HPQ) thin films were determined in the frequency range of 0.5 kHz-5 MHz and the temperature range of 290-443 K. The AC electrical conduction of both compounds in thin film form is governed by the correlated barrier hopping (CBH) mechanism. Some parameters such as the barrier height, the maximum barrier height, the density of charges, and the hopping distance were determined as functions of temperature and frequency. The phenoxyphenyl group has a greater influence on those parameters than the chlorophenyl group. The AC activation energies were determined at different frequencies and temperatures. The dielectric behaviors of Ph-HPQ and Ch-HPQ were investigated using the impedance spectroscopy technique. The impedance data are presented in Nyquist diagrams for different temperatures. The Ch-HPQ films have higher impedance than the Ph-HPQ films. The real dielectric constant and dielectric loss show a remarkable dependence on the frequency and temperature. The Ph-HPQ has higher dielectric constants than the Ch-HPQ.

  3. Spurious phenomena occurring during current measurement on ultra-thin dielectric layers: From electro-thermal effects to surface damage

    SciTech Connect

    Grandfond, A.; Gautier, B.; Militaru, L.; Albertini, D.; Descamps-Mandine, A.

    2014-04-07

    In this paper, the conduction properties of dielectric ultra-thin layers are studied using atomic force microscopy. Especially, the conductive-atomic force microscope allows to measure the leakage current at the nanoscale and to study the degradation mechanisms locally. Nonetheless, the dielectric layer seems to be damaged by a technique's specific phenomenon: hillocks appear when a positive tip bias is applied on different dielectrics. In this paper, the formation of these hillocks is studied. Contrary to what is observed during the dielectric breakdown, the conductivity is reduced after hillocks formation which occurs after the dielectric breakdown. Moreover, we have observed the formation of cavities in the silicon substrate linked to the formation of hillocks, which is not compatible with a swelling process (as dielectric breakdown induced epitaxy). We propose that these results may be explained by an electro-thermal effect due to the large dissipated energy, maybe combined with the oxidation of the substrate. Finally, the interdependence of measurements is demonstrated during serial acquisition.

  4. A uniform GTD analysis of the EM diffraction by a thin dielectric/ferrite half-plane and related configurations

    NASA Technical Reports Server (NTRS)

    Rojas, Roberto G.

    1985-01-01

    A uniform geometrical theory of diffraction (UTD) solution is developed for the problem of the diffraction by a thin dielectric/ferrite half plane when it is excited by a plane, cylindrical, or surface wave field. Both transverse electric and transverse magnetic cases are considered. The solution of this problem is synthesized from the solutions to the related problems of EM diffraction by configurations involving perfectly conducting electric and magnetic walls covered by a dielectric/ferrite half-plane of one half the thickness of the original half-plane.

  5. A study on the ESD damage of a silicon oxy-nitride hard mask on the chromium surface of PSM blank

    NASA Astrophysics Data System (ADS)

    Moon, Songbae; Kim, Heebom; Shin, Inkyun; Jeon, Chanuk

    2013-09-01

    A thin silicon oxy-nitride hard mask on the PSM blank is needed for the feature patterning with the size smaller than 70 nm. It is a good material for hard mask. However, the electrical property of silicon oxy-nitride with the thickness smaller than 10 nm causes the chromium surface damage during the mask processes. From the measurement of the surface damage, we figure out that the chromium surface damage is originated from the charging and the dielectric breakdown phenomena. In our present work, two types of silicon oxy-nitride film with the thicknesses of 5 nm and 12 nm are tested for verifying optimal mask fabrication processes. We find that the occurrence of ESD damage is related to the thickness of silicon oxy-nitride hard mask and mask fabrication process conditions. The optimal fabrication process condition for silicon oxy-nitride thin film hard mask, in which break-down never occurs, is discussed.

  6. Deposition and characterization of zirconium nitride (ZrN) thin films by reactive magnetron sputtering with linear gas ion source and bias voltage

    SciTech Connect

    Kavitha, A.; Kannan, R.; Subramanian, N. Sankara; Loganathan, S.

    2014-04-24

    Zirconium nitride thin films have been prepared on stainless steel substrate (304L grade) by reactive cylindrical magnetron sputtering method with Gas Ion Source (GIS) and bias voltage using optimized coating parameters. The structure and surface morphologies of the ZrN films were characterized using X-ray diffraction, atomic microscopy and scanning electron microscopy. The adhesion property of ZrN thin film has been increased due to the GIS. The coating exhibits better adhesion strength up to 10 N whereas the ZrN thin film with bias voltage exhibits adhesion up to 500 mN.

  7. Dielectric and piezoelectric properties of (110) oriented Pb(Zr1-x Ti x )O3 thin films

    NASA Astrophysics Data System (ADS)

    Jian-Hua, Qiu; Zhi-Hui, Chen; Xiu-Qin, Wang; Ning-Yi, Yuan; Jian-Ning, Ding

    2016-05-01

    A phenomenological Landau-Devonshire theory is developed to investigate the ferroelectric, dielectric, and piezoelectric properties of (110) oriented Pb(Zr1-x Ti x )O3 (x = 0.4, 0.5, 0.6, and 0.7) thin films. At room temperature, the tetragonal a 1 phase, the orthorhombic a 2 c phase, the triclinic γ 1 phase, and the triclinic γ 2 phase are stable. The appearance of the negative polarization component P 2 in the a 2 c phase and the γ 1 phase is attributed to the nonlinear coupling terms in the thermodynamic potential. The γ phase of the Pb(Zr1-x Ti x )O3 thin films has better dielectric and piezoelectric properties than the a 2 c phase and the a 1 phase. The largest dielectric and piezoelectric coefficients are obtained in the Pb(Zr0.5Ti0.5)O3 thin film. The piezoelectric coefficient of 110-150 pm/V is obtained in the (110) oriented Pb(Zr0.5Ti0.5)O3 thin film, and the Pb(Zr0.3Ti0.7)O3 thin film has the remnant polarization and relative dielectric constant of 50 μC/cm2 and 100, respectively, which are in agreement with the experimental measurements reported in the literature. Project supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions, China, the Research Fund of Jiangsu Province Cultivation Base for State Key Laboratory of Photovoltaic Science and Technology, China, Major Projects of Natural Science Research in Jiangsu Province, China (Grant No. 15KJA43002), and Qing Lan Project of Education Department of Jiangsu Province, China.

  8. Nanosecond laser-induced nanostructuring of thin metal layers and dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Lorenz, P.; Klöppel, M.; Ehrhardt, M.; Zimmer, K.; Schwaller, P.

    2015-03-01

    Nanostructuring of dielectric surfaces has a widespread field of applications. In this work the recently introduced laser method validates this novel concept for complex nanostructuring of dielectric surfaces. This concept combines the mechanism of self-assembly of metal films due to laser irradiation with the concept of laser-assisted transfer of these patterns into the underlying material. The present work focuses on pattern formation in fused silica near the border of the laser spot, where distorted nested ring-like patterns were found in contrast to concentric ring patterns at homogeneous laser irradiation. For the experiments a lateral homogeneous spot of a KrF excimer laser (λ = 248 nm) and a Gaussian beam Yb fiber laser (λ = 1064 nm) was used for irradiation of a thin chromium layer onto fused silica resulting in the formation of different ring structures into the fused silica surface. The obtained structures were analysed by AFM and SEM. It is found that the mechanism comprises laser-induced metal film melting, contraction of the molten metal, and successive transfer of the metal hole geometry to the fused silica. Simulations taking into account the heat and the Navier-Stokes equations were compared with the experimental results. A good agreement of simulation results with experimental data was found. These first results demonstrate that the variation of the laser beam profile allows the local control of the melt dynamics which causes changes of the shape and the size of the ring patterns. Hence, a light-controlled self-assembly is feasible.

  9. Uniform Non-stoichiometric Titanium Nitride Thin Films for Improved Kinetic Inductance Detector Arrays

    NASA Astrophysics Data System (ADS)

    Coiffard, G.; Schuster, K.-F.; Driessen, E. F. C.; Pignard, S.; Calvo, M.; Catalano, A.; Goupy, J.; Monfardini, A.

    2016-08-01

    We describe the fabrication of homogeneous sub-stoichiometric titanium nitride films for microwave kinetic inductance detector (KID) arrays. Using a 6'' sputtering target and a homogeneous nitrogen inlet, the variation of the critical temperature over a 2'' wafer was reduced to {<}25 %. Measurements of a 132-pixel KID arrays from these films reveal a sensitivity of 16 kHz/pW in the 100 GHz band, comparable to the best aluminum KIDs. We measured a noise equivalent power of NEP = 3.6× 10^{-15} W/Hz^{1/2}. Finally, we describe possible routes to further improve the performance of these TiN KID arrays.

  10. Microwave dielectric dispersion in a multiferroic Pb(Fe1/2Nb1/2)O3 thin film

    NASA Astrophysics Data System (ADS)

    Sobiestianskas, R.; Peng, W.; Lemée, N.; Karkut, M.; Banys, J.; Holc, J.; Kosec, M.

    2012-03-01

    We present the dielectric dispersion in a Pb(Fe1/2Nb1/2)O3 (PFN) thin film grown on (001) SrTiO3 substrate from 20 MHz to 20 GHz in the temperature range of 270 to 340 K. In the radio frequency region, the hopping charge transport and associated polar nanoregion and/or domain-wall motion contribute to the spectrum. In the microwave region, relaxational dispersion was observed with a dielectric contribution of Δɛ ≈ 600 at room temperature having a characteristic frequency (fm)0.4 = 9.8 . (T-T0) Hz, where T0 is 660 K. It is associated with possible mode-softening behavior, related to the onset of polar nanoregions at T0. The dielectric permittivity shows similarities with 1-dimensional Ising model behaviour.

  11. Effects of high energy x ray and proton irradiation on lead zirconate titanate thin films' dielectric and piezoelectric response

    NASA Astrophysics Data System (ADS)

    Bastani, Y.; Cortés-Peña, A. Y.; Wilson, A. D.; Gerardin, S.; Bagatin, M.; Paccagnella, A.; Bassiri-Gharb, N.

    2013-05-01

    The effects of irradiation by X rays and protons on the dielectric and piezoelectric response of highly (100)-textured polycrystalline Pb(ZrxTi1-x)O3 (PZT) thin films have been studied. Low-field dielectric permittivity, remanent polarization, and piezoelectric d33,f response all degraded with exposure to radiation, for doses higher than 300 krad. At first approximation, the degradation increased at higher radiation doses, and was stronger in samples exposed to X rays, compared to the proton-irradiated ones. Nonlinear and high-field dielectric characterization suggest a radiation-induced reduction of the extrinsic contributions to the response, attributed to increased pinning of the domain walls by the radiation-induced point defects.

  12. Effects of high energy x ray and proton irradiation on lead zirconate titanate thin films' dielectric and piezoelectric response

    SciTech Connect

    Bastani, Y.; Cortes-Pena, A. Y.; Wilson, A. D.; Gerardin, S.; Bagatin, M.; Paccagnella, A.; Bassiri-Gharb, N.

    2013-05-13

    The effects of irradiation by X rays and protons on the dielectric and piezoelectric response of highly (100)-textured polycrystalline Pb(Zr{sub x}Ti{sub 1-x})O{sub 3} (PZT) thin films have been studied. Low-field dielectric permittivity, remanent polarization, and piezoelectric d{sub 33,f} response all degraded with exposure to radiation, for doses higher than 300 krad. At first approximation, the degradation increased at higher radiation doses, and was stronger in samples exposed to X rays, compared to the proton-irradiated ones. Nonlinear and high-field dielectric characterization suggest a radiation-induced reduction of the extrinsic contributions to the response, attributed to increased pinning of the domain walls by the radiation-induced point defects.

  13. Stable dielectric response of low-loss aromatic polythiourea thin films on Pt/SiO2 substrate

    NASA Astrophysics Data System (ADS)

    Eršte, A.; Fulanović, L.; Čoga, L.; Lin, M.; Thakur, Y.; Zhang, Q. M.; Bobnar, V.

    2016-03-01

    We have investigated dielectric properties of aromatic polythiourea (ArPTU, a polar polymer containing high dipolar moments with very low defect levels) thin films that were developed on Pt/SiO2 substrate. The detected response is compared to the response of commercially available polymers, such as high density polyethylene (HDPE) and polypropylene (PP), which are at present used in foil capacitors. Stable values of the dielectric constant ɛ‧≈5 (being twice higher than in HDPE and PP) over broad temperature and frequency ranges and dielectric losses as low as in commercial systems suggest ArPTU as a promising candidate for future use in a variety of applications.

  14. Investigations of thin films on GaAs using the proton resonant scattering technique

    NASA Astrophysics Data System (ADS)

    Yu, Kin Man; Jaklevic, J. M.; Haller, E. E.

    1988-04-01

    We have characterized a number of thermally stable thin film/GaAs systems including thin films of refractory metal suicides and nitrides as well as dielectric films on GaAs substrates using a MeV proton scattering technique. Thin films of tungsten suicides, zirconium nitride and silicon dioxide on GaAs substrates are investigated. The enhanced proton scattering cross sections of nitrogen, silicon and oxygen at their corresponding resonant energies enable us to accurately measure the compositions of these films. The advantages and disadvantages of this technique regarding depth resolution, accessible depth, and mass resolution compared to the conventional Rutherford backscattering spectrometry for thin film analysis are discussed.

  15. Recombination and thin film properties of silicon nitride and amorphous silicon passivated c-Si following ammonia plasma exposure

    SciTech Connect

    Wan, Yimao; Thomson, Andrew F.; Cuevas, Andres; McIntosh, Keith R.

    2015-01-26

    Recombination at silicon nitride (SiN{sub x}) and amorphous silicon (a-Si) passivated crystalline silicon (c-Si) surfaces is shown to increase significantly following an ammonia (NH{sub 3}) plasma exposure at room temperature. The effect of plasma exposure on chemical structure, refractive index, permittivity, and electronic properties of the thin films is also investigated. It is found that the NH{sub 3} plasma exposure causes (i) an increase in the density of Si≡N{sub 3} groups in both SiN{sub x} and a-Si films, (ii) a reduction in refractive index and permittivity, (iii) an increase in the density of defects at the SiN{sub x}/c-Si interface, and (iv) a reduction in the density of positive charge in SiN{sub x}. The changes in recombination and thin film properties are likely due to an insertion of N–H radicals into the bulk of SiN{sub x} or a-Si. It is therefore important for device performance to minimize NH{sub 3} plasma exposure of SiN{sub x} or a-Si passivating films during subsequent fabrication steps.

  16. Recombination and thin film properties of silicon nitride and amorphous silicon passivated c-Si following ammonia plasma exposure

    NASA Astrophysics Data System (ADS)

    Wan, Yimao; McIntosh, Keith R.; Thomson, Andrew F.; Cuevas, Andres

    2015-01-01

    Recombination at silicon nitride (SiNx) and amorphous silicon (a-Si) passivated crystalline silicon (c-Si) surfaces is shown to increase significantly following an ammonia (NH3) plasma exposure at room temperature. The effect of plasma exposure on chemical structure, refractive index, permittivity, and electronic properties of the thin films is also investigated. It is found that the NH3 plasma exposure causes (i) an increase in the density of Si≡N3 groups in both SiNx and a-Si films, (ii) a reduction in refractive index and permittivity, (iii) an increase in the density of defects at the SiNx/c-Si interface, and (iv) a reduction in the density of positive charge in SiNx. The changes in recombination and thin film properties are likely due to an insertion of N-H radicals into the bulk of SiNx or a-Si. It is therefore important for device performance to minimize NH3 plasma exposure of SiNx or a-Si passivating films during subsequent fabrication steps.

  17. Atomically Thin Layers of Graphene and Hexagonal Boron Nitride Made by Solvent Exfoliation of Their Phosphoric Acid Intercalation Compounds.

    PubMed

    Kovtyukhova, Nina I; Perea-López, Nestor; Terrones, Mauricio; Mallouk, Thomas E

    2017-07-25

    The development of scalable and reliable techniques for the production of the atomically thin layers of graphene and hexagonal boron nitride (h-BN) in bulk quantities could make these materials a powerful platform for devices and composites that impact a wide variety of technologies (Nature 2012, 490, 192-200). To date a number of practical exfoliation methods have been reported that are based on sonicating or stirring powdered graphite or h-BN in common solvents. However, the products of these experiments consist mainly of few-layer sheets and contain only a small fraction of monolayers. A possible reason for this is that splitting the crystals into monolayers starts from solvent intercalation, which must overcome the substantial interlayer cohesive energy (120-720 mJ/m(2)) of the van der Waals solids. Here we show that the yield of the atomically thin layers can be increased to near unity when stage-1 intercalation compounds of phosphoric acid are used as starting materials. The exfoliation to predominantly monolayers was achieved by stirring them in medium polarity organic solvents that can form hydrogen bonds. The exfoliation process does not disrupt the sp(2) π-system of graphene and is gentle enough to allow the preparation of graphene and h-BN monolayers that are tens of microns in their lateral dimensions.

  18. Growth and optical characterization of aluminum nitride thin films deposited on silicon by radio-frequency sputtering

    NASA Astrophysics Data System (ADS)

    Dogheche, E.; Rémiens, D.; Boudrioua, A.; Loulergue, J. C.

    1999-03-01

    Highly textured hexagonal aluminum nitride (AlN) thin films were deposited on silicon substrates by radio-frequency magnetron sputtering at a substrate temperature below 400 °C and annealed in the temperature range of 400-450 °C by rapid thermal annealing. The optical and the electro-optical properties have been investigated using the prism-coupling technique. Both ordinary and extraordinary refractive indices (n0=2.0058 and ne=2.0374 at 632.8 nm) were respectively determined from the transverse electric and the transverse magnetic mode excitations. Furthermore, refractive index profiles analysis by using an improved inverse Wentzel-Kramer-Brillouin method reveals a step-like behavior of AlN thin films. The optical losses have been evaluated to be around 7 dB cm-1. The electro-optic coefficient r13 of 0.98 pm/V has been measured from the variation of the shift of guided-modes spectrum as a function of the applied electric field in the experiment.

  19. Atomic layer deposited tungsten nitride thin films as a new lithium-ion battery anode.

    PubMed

    Nandi, Dip K; Sen, Uttam K; Sinha, Soumyadeep; Dhara, Arpan; Mitra, Sagar; Sarkar, Shaibal K

    2015-07-14

    This article demonstrates the atomic layer deposition (ALD) of tungsten nitride using tungsten hexacarbonyl [W(CO)6] and ammonia [NH3] and its use as a lithium-ion battery anode. In situ quartz crystal microbalance (QCM), ellipsometry and X-ray reflectivity (XRR) measurements are carried out to confirm the self-limiting behaviour of the deposition. A saturated growth rate of ca. 0.35 Å per ALD cycle is found within a narrow temperature window of 180-195 °C. In situ Fourier transform infrared (FTIR) vibrational spectroscopy is used to determine the reaction pathways of the surface bound species after each ALD half cycle. The elemental presence and chemical composition is determined by XPS. The as-deposited material is found to be amorphous and crystallized to h-W2N upon annealing at an elevated temperature under an ammonia atmosphere. The as-deposited materials are found to be n-type, conducting with an average carrier concentration of ca. 10(20) at room temperature. Electrochemical studies of the as-deposited films open up the possibility of this material to be used as an anode material in Li-ion batteries. The incorporation of MWCNTs as a scaffold layer further enhances the electrochemical storage capacity of the ALD grown tungsten nitride (WNx). Ex situ XRD analysis confirms the conversion based reaction mechanism of the as-grown material with Li under operation.

  20. Surface enhanced Raman scattering activity of TiN thin film prepared via nitridation of sol-gel derived TiO2 film

    NASA Astrophysics Data System (ADS)

    Dong, Zhanliang; Wei, Hengyong; Chen, Ying; Wang, Ruisheng; Zhao, Junhong; Lin, Jian; Bu, Jinglong; Wei, Yingna; Cui, Yi; Yu, Yun

    2015-10-01

    Surface-enhanced Raman scattering (SERS) is a powerful and non-destructive analytical technique tool for chemical and biological sensing applications. Metal-free SERS substrates have recently been developed by using semiconductor nanostructures. The optical property of TiN film is similar to that of gold. Besides that, its good chemical inertness and thermodynamic stability make TiN thin film an excellent candidate for SERS. In order to investigate its SERS activity, the TiN thin film was successfully prepared via direct nitridation of the sol-gel derived TiO2 thin film on the quartz substrate using ammonia gas as reducing agent. The crystallite structures and morphology of TiN thin film were determined by XRD, RAMAN and FE-SEM. The results show that the thin film obtained is cubic titanium nitride with a lattice parameter of 4.2349 Å. The surface of TiN thin film is rough and with the particles of 50 nm in average sizes. The thickness of TiN thin film is about 130 nm. The TiN thin film displays a surface Plasmon resonance absorption peak at around 476 nm, which can lead to a strong enhancement of the EM field on the interface. The Raman signal of the probe molecule R6G was greatly enhanced through TiN thin film substrates. The enhancement factor is about 4.1×103 and the detection limit achieves 10-6 M for R6G. The TiN thin film substrate also shows a good reproducibility of SERS performance. The results indicate that TiN thin film is an attractive material with potential application in SERS substrates.

  1. Investigations on laser printing of microcapacitors using poly (methyl methacrylate) dielectric thin films for organic electronics applications

    NASA Astrophysics Data System (ADS)

    Constantinescu, Catalin; Rapp, Ludovic; Delaporte, Philippe; Alloncle, Anne-Patricia

    2016-06-01

    Thin solid pixels made of Ag/PMMA stacks have been fabricated by laser-induced forward transfer (LIFT), to be tested as thin film microcapacitors in organic electronics applications. The square-shaped laser-printed pixels have a lateral size of ∼350 μm, and the thickness of the dielectric film was varied between 100 and 1500 nm. The pixels were deposited on electrode structures made by LIFT printing of silver nanoparticles ink and paste. Optimal printing conditions led to the fabrication of microcapacitors with typical capacitance in the pF range, tuned by changing the properties of the multilayered structure (e.g. pixel size and/or thickness of the dielectric). Their stability was also investigated over time. We discuss on the morphological and electrical properties of such laser-printed structures, with respect to the impact resistance of the polymer and its suitability for the LIFT process.

  2. Printable ion-gel gate dielectrics for low-voltage polymer thin-film transistors on plastic.

    PubMed

    Cho, Jeong Ho; Lee, Jiyoul; Xia, Yu; Kim, BongSoo; He, Yiyong; Renn, Michael J; Lodge, Timothy P; Frisbie, C Daniel

    2008-11-01

    An important strategy for realizing flexible electronics is to use solution-processable materials that can be directly printed and integrated into high-performance electronic components on plastic. Although examples of functional inks based on metallic, semiconducting and insulating materials have been developed, enhanced printability and performance is still a challenge. Printable high-capacitance dielectrics that serve as gate insulators in organic thin-film transistors are a particular priority. Solid polymer electrolytes (a salt dissolved in a polymer matrix) have been investigated for this purpose, but they suffer from slow polarization response, limiting transistor speed to less than 100 Hz. Here, we demonstrate that an emerging class of polymer electrolytes known as ion gels can serve as printable, high-capacitance gate insulators in organic thin-film transistors. The specific capacitance exceeds that of conventional ceramic or polymeric gate dielectrics, enabling transistor operation at low voltages with kilohertz switching frequencies.

  3. Effects of annealing conditions on the dielectric properties of solution-processed Al2O3 layers for indium-zinc-tin-oxide thin-film transistors.

    PubMed

    Kim, Yong-Hoon; Kim, Kwang-Ho; Park, Sung Kyu

    2013-11-01

    In this paper, the effects of annealing conditions on the dielectric properties of solution-processed aluminum oxide (Al2O3) layers for indium-zinc-tin-oxide (IZTO) thin-film transistors (TFTs) have been investigated. The dielectric properties of Al2O3 layers such as leakage current density and dielectric strength were largely affected by their annealing conditions. In particular, oxygen partial pressure in rapid thermal annealing, and the temperature profile of hot plate annealing had profound effects on the dielectric properties. From a refractive index analysis, the enhanced dielectric properties of Al2O3 gate dielectrics can be attributed to higher film density depending on the annealing conditions. With the low-temperature-annealed Al2O3 gate dielectric at 350 degrees C, solution-processed IZTO TFTs with a field-effect mobility of approximately 2.2 cm2/Vs were successfully fabricated.

  4. Composite surface-plasmon-polariton waves guided by a thin metal layer sandwiched between a homogeneous isotropic dielectric material and a periodically multilayered isotropic dielectric material

    NASA Astrophysics Data System (ADS)

    Chiadini, Francesco; Fiumara, Vincenzo; Scaglione, Antonio; Lakhtakia, Akhlesh

    2015-01-01

    Multiple p- and s-polarized compound surface-plasmon-polariton (SPP) waves at a fixed frequency can be guided by a structure consisting of a metal layer sandwiched between a homogeneous isotropic dielectric (HID) material and a periodic multilayered isotropic dielectric (PMLID) material. For any thickness of the metal layer, at least one compound SPP wave must exist. It possesses the p-polarization state, and is strongly bound to the metal/HID interface when the metal thickness is large but to both metal/dielectric interfaces when the metal thickness is small. When the metal layer vanishes, this compound SPP wave transmutes into a Tamm wave. Additional compound SPP waves exist, depending on the thickness of the metal layer, the relative permittivity of the HID material, and the period and composition of the PMLID material. Some of these are p-polarized, the others are s-polarized. All of them differ in phase speed, attenuation rate, and field profile, even though all are excitable at the same frequency. The multiplicity and dependence of the number of compound SPP waves on the relative permittivity of the HID material when the metal layer is thin could be useful for optical sensing applications and intrachip plasmonic optical communication.

  5. Temporally and spatially resolved plasma spectroscopy in pulsed laser deposition of ultra-thin boron nitride films

    NASA Astrophysics Data System (ADS)

    Glavin, Nicholas R.; Muratore, Christopher; Jespersen, Michael L.; Hu, Jianjun; Fisher, Timothy S.; Voevodin, Andrey A.

    2015-04-01

    Physical vapor deposition (PVD) has recently been investigated as a viable, alternative growth technique for two-dimensional materials with multiple benefits over other vapor deposition synthesis methods. The high kinetic energies and chemical reactivities of the condensing species formed from PVD processes can facilitate growth over large areas and at reduced substrate temperatures. In this study, chemistry, kinetic energies, time of flight data, and spatial distributions within a PVD plasma plume ablated from a boron nitride (BN) target by a KrF laser at different pressures of nitrogen gas were investigated. Time resolved spectroscopy and wavelength specific imaging were used to identify and track atomic neutral and ionized species including B+, B*, N+, N*, and molecular species including N2*, N2+, and BN. Formation and decay of these species formed both from ablation of the target and from interactions with the background gas were investigated and provided insights into fundamental growth mechanisms of continuous, amorphous boron nitride thin films. The correlation of the plasma diagnostic results with film chemical composition and thickness uniformity studies helped to identify that a predominant mechanism for BN film formation is condensation surface recombination of boron ions and neutral atomic nitrogen species. These species arrive nearly simultaneously to the substrate location, and BN formation occurs microseconds before arrival of majority of N+ ions generated by plume collisions with background molecular nitrogen. The energetic nature and extended dwelling time of incident N+ ions at the substrate location was found to negatively impact resulting BN film stoichiometry and thickness. Growth of stoichiometric films was optimized at enriched concentrations of ionized boron and neutral atomic nitrogen in plasma near the condensation surface, providing few nanometer thick films with 1:1 BN stoichiometry and good thicknesses uniformity over macroscopic areas.

  6. Temporally and spatially resolved plasma spectroscopy in pulsed laser deposition of ultra-thin boron nitride films

    SciTech Connect

    Glavin, Nicholas R. E-mail: andrey.voevodin@us.af.mil; Muratore, Christopher; Jespersen, Michael L.; Hu, Jianjun; Fisher, Timothy S.; Voevodin, Andrey A. E-mail: andrey.voevodin@us.af.mil

    2015-04-28

    Physical vapor deposition (PVD) has recently been investigated as a viable, alternative growth technique for two-dimensional materials with multiple benefits over other vapor deposition synthesis methods. The high kinetic energies and chemical reactivities of the condensing species formed from PVD processes can facilitate growth over large areas and at reduced substrate temperatures. In this study, chemistry, kinetic energies, time of flight data, and spatial distributions within a PVD plasma plume ablated from a boron nitride (BN) target by a KrF laser at different pressures of nitrogen gas were investigated. Time resolved spectroscopy and wavelength specific imaging were used to identify and track atomic neutral and ionized species including B{sup +}, B*, N{sup +}, N*, and molecular species including N{sub 2}*, N{sub 2}{sup +}, and BN. Formation and decay of these species formed both from ablation of the target and from interactions with the background gas were investigated and provided insights into fundamental growth mechanisms of continuous, amorphous boron nitride thin films. The correlation of the plasma diagnostic results with film chemical composition and thickness uniformity studies helped to identify that a predominant mechanism for BN film formation is condensation surface recombination of boron ions and neutral atomic nitrogen species. These species arrive nearly simultaneously to the substrate location, and BN formation occurs microseconds before arrival of majority of N{sup +} ions generated by plume collisions with background molecular nitrogen. The energetic nature and extended dwelling time of incident N{sup +} ions at the substrate location was found to negatively impact resulting BN film stoichiometry and thickness. Growth of stoichiometric films was optimized at enriched concentrations of ionized boron and neutral atomic nitrogen in plasma near the condensation surface, providing few nanometer thick films with 1:1 BN stoichiometry and good

  7. High-Quality Solution-Processed Silicon Oxide Gate Dielectric Applied on Indium Oxide Based Thin-Film Transistors.

    PubMed

    Jaehnike, Felix; Pham, Duy Vu; Anselmann, Ralf; Bock, Claudia; Kunze, Ulrich

    2015-07-01

    A silicon oxide gate dielectric was synthesized by a facile sol-gel reaction and applied to solution-processed indium oxide based thin-film transistors (TFTs). The SiOx sol-gel was spin-coated on highly doped silicon substrates and converted to a dense dielectric film with a smooth surface at a maximum processing temperature of T = 350 °C. The synthesis was systematically improved, so that the solution-processed silicon oxide finally achieved comparable break downfield strength (7 MV/cm) and leakage current densities (<10 nA/cm(2) at 1 MV/cm) to thermally grown silicon dioxide (SiO2). The good quality of the dielectric layer was successfully proven in bottom-gate, bottom-contact metal oxide TFTs and compared to reference TFTs with thermally grown SiO2. Both transistor types have field-effect mobility values as high as 28 cm(2)/(Vs) with an on/off current ratio of 10(8), subthreshold swings of 0.30 and 0.37 V/dec, respectively, and a threshold voltage close to zero. The good device performance could be attributed to the smooth dielectric/semiconductor interface and low interface trap density. Thus, the sol-gel-derived SiO2 is a promising candidate for a high-quality dielectric layer on many substrates and high-performance large-area applications.

  8. Low-voltage organic thin-film transistors based on solution-processed hybrid dielectrics: theoretical and experimental studies

    NASA Astrophysics Data System (ADS)

    Ke, Qiutan; Wu, Qian; Liang, Lijuan; Pei, Yanli; Lu, Xubing; Li, Minmin; Huang, Kairong; Liu, Xuying; Liu, Chuan

    2017-10-01

    In organic thin-film transistors (OTFTs), using high-k dielectrics could increase the accumulated carrier numbers at low operation voltage (i.e. the bulk effect), but may induce extra dipolar disorders to affect the electronic states in organic semiconductors (i.e. the interfacial effect). The two effects are considered together to model charge transport in OTFTs and to give quantitative calculations of the impacts from using high-k dielectrics or hybrid dielectrics, especially the relations between mobility and Fermi-energy, carrier concentrations, or gate-voltage. In experimental studies, zirconium oxide (ZrO2) and yttrium oxide (Y2O3) are fabricated by solution process for high-k dielectrics. The oxide insulating films are modified by low-k polymer layers and the resulting OTFTs show low operation voltage and high performance in ambient test. The highest mobility reaches 2.38 cm2 V‑1 s‑1 for ZrO2 based OTFT and 3.56 cm2 V‑1 s‑1 for Y2O3 based OTFT, and the on/off ratio is 1.4 × 104 for ZrO2 devices and 5.4 × 104 for Y2O3 devices. In general, the trends of experimentally measured mobility are consistent with the theoretical calculations, showing the high-k/low-k hybrid dielectrics mainly improve the carrier mobility in the regime of low carrier density.

  9. ZnO-based thin film transistors employing aluminum titanate gate dielectrics deposited by spray pyrolysis at ambient air.

    PubMed

    Afouxenidis, Dimitrios; Mazzocco, Riccardo; Vourlias, Georgios; Livesley, Peter J; Krier, Anthony; Milne, William I; Kolosov, Oleg; Adamopoulos, George

    2015-04-08

    The replacement of SiO2 gate dielectrics with metal oxides of higher dielectric constant has led to the investigation of a wide range of materials with superior properties compared with SiO2. Despite their attractive properties, these high-k dielectrics are usually manufactured using costly vacuum-based techniques. To overcome this bottleneck, research has focused on the development of alternative deposition methods based on solution-processable metal oxides. Here we report the application of spray pyrolysis for the deposition and investigation of Al2x-1·TixOy dielectrics as a function of the [Ti(4+)]/[Ti(4+)+2·Al(3+)] ratio and their implementation in thin film transistors (TFTs) employing spray-coated ZnO as the active semiconducting channels. The films are studied by UV-visible absorption spectroscopy, spectroscopic ellipsometry, impedance spectroscopy, atomic force microscopy, X-ray diffraction and field-effect measurements. Analyses reveal amorphous Al2x-1·TixOy dielectrics that exhibit a wide band gap (∼4.5 eV), low roughness (∼0.9 nm), high dielectric constant (k ∼ 13), Schottky pinning factor S of ∼0.44 and very low leakage currents (<5 nA/cm(2)). TFTs employing stoichiometric Al2O3·TiO2 gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with low operating voltages (∼10 V), negligible hysteresis, high on/off current modulation ratio of ∼10(6), subthreshold swing (SS) of ∼550 mV/dec and electron mobility of ∼10 cm(2) V(-1) s(-1).

  10. Adsorption and electronic properties of pentacene on thin dielectric decoupling layers

    PubMed Central

    Kabakchiev, Alexander; Kuhnke, Klaus; Kern, Klaus

    2017-01-01

    With the increasing use of thin dielectric decoupling layers to study the electronic properties of organic molecules on metal surfaces, comparative studies are needed in order to generalize findings and formulate practical rules. In this paper we study the adsorption and electronic properties of pentacene deposited onto h-BN/Rh(111) and compare them with those of pentacene deposited onto KCl on various metal surfaces. When deposited onto KCl, the HOMO and LUMO energies of the pentacene molecules scale with the work functions of the combined KCl/metal surface. The magnitude of the variation between the respective KCl/metal systems indicates the degree of interaction of the frontier orbitals with the underlying metal. The results confirm that the so-called IDIS model developed by Willenbockel et al. applies not only to molecular layers on bare metal surfaces, but also to individual molecules on thin electronically decoupling layers. Depositing pentacene onto h-BN/Rh(111) results in significantly different adsorption characteristics, due to the topographic corrugation of the surface as well as the lateral electric fields it presents. These properties are reflected in the divergence from the aforementioned trend for the orbital energies of pentacene deposited onto h-BN/Rh(111), as well as in the different adsorption geometry. Thus, the highly desirable capacity of h-BN to trap molecules comes at the price of enhanced metal–molecule interaction, which decreases the HOMO–LUMO gap of the molecules. In spite of the enhanced interaction, the molecular orbitals are evident in scanning tunnelling spectroscopy (STS) and their shapes can be resolved by spectroscopic mapping. PMID:28900594

  11. Effects of Plasmonic Metal Core -Dielectric Shell Nanoparticles on the Broadband Light Absorption Enhancement in Thin Film Solar Cells.

    PubMed

    Yu, Peng; Yao, Yisen; Wu, Jiang; Niu, Xiaobin; Rogach, Andrey L; Wang, Zhiming

    2017-08-09

    To guide the design of plasmonic solar cells, theoretical investigation of core (metal)-shell (dielectric) nanoparticles for light absorption enhancement in thin film Si solar cells is performed. In contrast to the reported simulations and experimental results that rear-located surface plasmon on bare metallic nanoparticles is preferred, the core-shell nanoparticles demonstrate better performance when surface plasmon is located in front of a solar cell. This has been attributed to the enhanced forward scattering with vanishing backward scattering preserved over a wide spectral range in core-shell nanoparticles. This work provides a concept to achieve enhanced forward scattering with weakened backward scattering in plasmonic thin film solar cells.

  12. Atomic Layer Deposited Thin Films for Dielectrics, Semiconductor Passivation, and Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Xu, Runshen

    Atomic layer deposition (ALD) utilizes sequential precursor gas pulses to deposit one monolayer or sub-monolayer of material per cycle based on its self-limiting surface reaction, which offers advantages, such as precise thickness control, thickness uniformity, and conformality. ALD is a powerful means of fabricating nanoscale features in future nanoelectronics, such as contemporary sub-45 nm metal-oxide-semiconductor field effect transistors, photovoltaic cells, near- and far-infrared detectors, and intermediate temperature solid oxide fuel cells. High dielectric constant, kappa, materials have been recognized to be promising candidates to replace traditional SiO2 and SiON, because they enable good scalability of sub-45 nm MOSFET (metal-oxide-semiconductor field-effect transistor) without inducing additional power consumption and heat dissipation. In addition to high dielectric constant, high-kappa materials must meet a number of other requirements, such as low leakage current, high mobility, good thermal and structure stability with Si to withstand high-temperature source-drain activation annealing. In this thesis, atomic layer deposited Er2O3 doped TiO2 is studied and proposed as a thermally stable amorphous high-kappa dielectric on Si substrate. The stabilization of TiO2 in its amorphous state is found to achieve a high permittivity of 36, a hysteresis voltage of less than 10 mV, and a low leakage current density of 10-8 A/cm-2 at -1 MV/cm. In III-V semiconductors, issues including unsatisfied dangling bonds and native oxides often result in inferior surface quality that yields non-negligible leakage currents and degrades the long-term performance of devices. The traditional means for passivating the surface of III-V semiconductors are based on the use of sulfide solutions; however, that only offers good protection against oxidation for a short-term (i.e., one day). In this work, in order to improve the chemical passivation efficacy of III-V semiconductors

  13. Hole mobility modulation of solution-processed nickel oxide thin-film transistor based on high-k dielectric

    SciTech Connect

    Liu, Ao; Liu, Guoxia E-mail: fukaishan@yahoo.com; Zhu, Huihui; Shan, Fukai E-mail: fukaishan@yahoo.com; Shin, Byoungchul; Fortunato, Elvira; Martins, Rodrigo

    2016-06-06

    Solution-processed p-type oxide semiconductors have recently attracted increasing interests for the applications in low-cost optoelectronic devices and low-power consumption complementary metal-oxide-semiconductor circuits. In this work, p-type nickel oxide (NiO{sub x}) thin films were prepared using low-temperature solution process and integrated as the channel layer in thin-film transistors (TFTs). The electrical properties of NiO{sub x} TFTs, together with the characteristics of NiO{sub x} thin films, were systematically investigated as a function of annealing temperature. By introducing aqueous high-k aluminum oxide (Al{sub 2}O{sub 3}) gate dielectric, the electrical performance of NiO{sub x} TFT was improved significantly compared with those based on SiO{sub 2} dielectric. Particularly, the hole mobility was found to be 60 times enhancement, quantitatively from 0.07 to 4.4 cm{sup 2}/V s, which is mainly beneficial from the high areal capacitance of the Al{sub 2}O{sub 3} dielectric and high-quality NiO{sub x}/Al{sub 2}O{sub 3} interface. This simple solution-based method for producing p-type oxide TFTs is promising for next-generation oxide-based electronic applications.

  14. Aqueous combustion synthesis of aluminum oxide thin films and application as gate dielectric in GZTO solution-based TFTs.

    PubMed

    Branquinho, Rita; Salgueiro, Daniela; Santos, Lídia; Barquinha, Pedro; Pereira, Luís; Martins, Rodrigo; Fortunato, Elvira

    2014-11-26

    Solution processing has been recently considered as an option when trying to reduce the costs associated with deposition under vacuum. In this context, most of the research efforts have been centered in the development of the semiconductors processes nevertheless the development of the most suitable dielectrics for oxide based transistors is as relevant as the semiconductor layer itself. In this work we explore the solution combustion synthesis and report on a completely new and green route for the preparation of amorphous aluminum oxide thin films; introducing water as solvent. Optimized dielectric layers were obtained for a water based precursor solution with 0.1 M concentration and demonstrated high capacitance, 625 nF cm(-2) at 10 kHz, and a permittivity of 7.1. These thin films were successfully applied as gate dielectric in solution processed gallium-zinc-tin oxide (GZTO) thin film transistors (TFTs) yielding good electrical performance such as subthreshold slope of about 0.3 V dec(-1) and mobility above 1.3 cm2 V(-1) s(-1).

  15. Hole mobility modulation of solution-processed nickel oxide thin-film transistor based on high-k dielectric

    NASA Astrophysics Data System (ADS)

    Liu, Ao; Liu, Guoxia; Zhu, Huihui; Shin, Byoungchul; Fortunato, Elvira; Martins, Rodrigo; Shan, Fukai

    2016-06-01

    Solution-processed p-type oxide semiconductors have recently attracted increasing interests for the applications in low-cost optoelectronic devices and low-power consumption complementary metal-oxide-semiconductor circuits. In this work, p-type nickel oxide (NiOx) thin films were prepared using low-temperature solution process and integrated as the channel layer in thin-film transistors (TFTs). The electrical properties of NiOx TFTs, together with the characteristics of NiOx thin films, were systematically investigated as a function of annealing temperature. By introducing aqueous high-k aluminum oxide (Al2O3) gate dielectric, the electrical performance of NiOx TFT was improved significantly compared with those based on SiO2 dielectric. Particularly, the hole mobility was found to be 60 times enhancement, quantitatively from 0.07 to 4.4 cm2/V s, which is mainly beneficial from the high areal capacitance of the Al2O3 dielectric and high-quality NiOx/Al2O3 interface. This simple solution-based method for producing p-type oxide TFTs is promising for next-generation oxide-based electronic applications.

  16. Structure, mechanical properties, and high-temperature stability of nanolayered titanium nitride/titanium diboride and zirconium nitride/zirconium diboride thin films

    NASA Astrophysics Data System (ADS)

    Martin, Keith Joseph

    2001-07-01

    The focus of this research is the deposition, structure, mechanical properties, and high temperature stability of polycrystalline nanolayered thin films. TiN/TiB2 and ZrN/ZrB2 nanolayers were magnetron sputtered with periods (Λ) ranging from 2 to 28 nm. The films were chemically and structurally characterized using Auger electron spectroscopy (AES), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The mechanical properties were characterized using nanoindentation, scratch testing, Rockwell indentation, and substrate curvature measurements. High temperature annealing, 750--1100°C, was used to investigate the thermal stability of the layered structures. As-deposited TiN/TiB2 and ZrN/ZrB2 nanolayers displayed an amorphous structure for the boride layers and a (200) and (111) preferred orientation for TiN and ZrN respectively. Annealing of the coatings was required to crystallize the diboride layers. XRD showed the presence of a mixed orientation (001) and (101) TiB2 and (001) ZrB2. The improved crystallinity raised the nanolayer hardness from a maximum of 38 GPa to 49 GPa for both material systems, a hardness enhancement of ~25% over the rule-of-mixtures value for the constituent materials. Analysis of the annealed TiN/TiB 2 microstructure with TEM revealed a randomly oriented, rotated nanolayer domain structure. The deposition process used allowed for variation of the substrate bias voltage, thereby allowing the production of nanolayered coatings with different amounts of residual stress. Increasing the amount of compressive stress was shown to have a positive effect on hardness, but was detrimental to film/substrate adhesion. The compressive stress of the nanolayered coatings was observed to be as much as 7 times less than the monolithic component materials. The interface structure was assumed to allow for stress relaxation through point defect annihilation and stress compensation. Deposition of a series of nanolayers with differing interface

  17. Electrodeposition of titania and barium titanate thin films for high dielectric applications

    NASA Astrophysics Data System (ADS)

    Roy, Biplab Kumar

    In order to address the requirement of a low-temperature low-cost cost processing for depositing high dielectric constant ceramic films for applications in embedded capacitor and flexible electronics technology, two different chemical bath processes, namely, thermohydrolytic deposition (TD) and cathodic electrodeposition (ED) have been exploited to generate titania thin films. In thermohydrolytic deposition technique, titania films were generated from acidic aqueous solution of titanium chloride on F: SnO2 coated glass and Si substrates by temperature assisted hydrolysis mechanism. On the other hand, in cathodic electrodeposition, in-situ electro-generation of hydroxyl ions triggered a fast deposition of titania on conductive substrates such as copper and F: SnO2 coated glass from peroxotitanium solution at low temperatures (˜0°C). In both techniques, solution compositions affected the morphology and crystallinity of the films. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques have been employed to perform such characterization. As both processes utilized water as solvent, the as-deposited films contained hydroxyl ligand or physically adsorbed water molecules in the titania layer. Besides that, electrodeposited films contained peroxotitanium bonds which were characterized by FTIR studies. Although as-electrodeposited titania films were X-ray amorphous, considerable crystallinity could be generated by heat treatment. The films obtained from both the processes showed v moderately high dielectric constant (ranging from 9-30 at 100 kHz) and high breakdown voltage (0.09-0.15 MV/cm) in electrical measurements. To further improve the dielectric constant, electrodeposited titania films were converted to barium titanate films in high pH barium ion containing solution at 80-90°C. The resultant film contained cubic crystalline barium titanate verified by XRD analysis. Simple low-temperature hydrothermal technique of conversion worked

  18. Thin-film dielectric elastomer sensors to measure the contraction force of smooth muscle cells

    NASA Astrophysics Data System (ADS)

    Araromi, O.; Poulin, A.; Rosset, S.; Favre, M.; Giazzon, M.; Martin-Olmos, C.; Liley, M.; Shea, H.

    2015-04-01

    The development of thin-film dielectric elastomer strain sensors for the characterization of smooth muscle cell (SMC) contraction is presented here. Smooth muscle disorders are an integral part of diseases such as asthma and emphysema. Analytical tools enabling the characterization of SMC function i.e. contractile force and strain, in a low-cost and highly parallelized manner are necessary for toxicology screening and for the development of new and more effective drugs. The main challenge with the design of such tools is the accurate measurement of the extremely low contractile cell forces expected as a result of SMC monolayer contraction (as low as ~ 100 μN). Our approach utilizes ultrathin (~5 μm) and soft elastomer membranes patterned with elastomer-carbon composite electrodes, onto which the SMCs are cultured. The cell contraction induces an in-plane strain in the elastomer membrane, predicted to be in the order 1 %, which can be measured via the change in the membrane capacitance. The cell force can subsequently be deduced knowing the mechanical properties of the elastomer membrane. We discuss the materials and fabrication methods selected for our system and present preliminary results indicating their biocompatibility. We fabricate functional capacitive senor prototypes with good signal stability over the several hours (~ 0.5% variation). We succeed in measuring in-plane strains of 1 % with our fabricated devices with good repeatability and signal to noise ratio.

  19. Quantitative model for near-field scanning microwave microscopy: application to metrology of thin film dielectrics.

    PubMed

    Reznik, Alexander N; Talanov, Vladimir V

    2008-11-01

    We have experimentally verified a recently proposed theoretical model for near-field microwave microscopy of multilayer media. The model addresses a near-field microwave probe as an electrically small antenna with a Gaussian-like current distribution that has a single characteristic length scale on the order of the probe size. Electrodynamic response of an antenna is calculated using Green functions in the form of integral transforms for electric and magnetic fields (both quasistatic and propagating), which are generated by a pointlike dipole. Experimental data were obtained at 4 GHz using a near-field scanning microwave microscope with aperture size of approximately 5 microm for a set of six SiO(2) films with thickness ranging from 0.1 to 1.5 microm. For each sample the probe resonant frequency was both measured and simulated as a function of the tip-sample distance, and good agreement between the theory and experimental data was observed. It was found that the model is capable of determining thin film dielectric constant with accuracy of approximately 5%-7%.

  20. Impact of temperature increments on tunneling barrier height and effective electron mass for plasma nitrided thin SiO{sub 2} layer on a large wafer area

    SciTech Connect

    Aygun, G.; Roeder, G.; Erlbacher, T.; Wolf, M.; Schellenberger, M.; Pfitzner, L.

    2010-10-15

    Thermally grown SiO{sub 2} layers were treated by a plasma nitridation process realized in a vertical furnace. The combination of a pulsed-low frequency plasma and a microwave remote plasma with N{sub 2}/NH{sub 3}/He feed gas mixture was used to nitride the thermally grown SiO{sub 2} gate dielectrics of MIS structures. Temperature dependency of effective masses and the barrier heights for electrons in pure thermally grown SiO{sub 2} as well as plasma nitrided SiO{sub 2} in high electric field by means of Fowler-Nordheim regime was determined. It is frequently seen from the literature that either effective electron mass or barrier height (generally effective electron mass) is assumed to be a constant and, as a result, the second parameter is calculated under the chosen assumption. However, in contrast to general attitude of previous studies, this work does not make any such assumptions for the calculation of neither of these two important parameters of an oxide at temperature ranges from 23 to 110 deg. C for SiO{sub 2}, and 23 to 130 deg. C for nitrided oxide. It is also shown here that both parameters are affected from the temperature changes; respectively, the barrier height decreases while the effective mass increases as a result of elevated temperature in both pure SiO{sub 2} and plasma nitrided SiO{sub 2}. Therefore, one parameter could be miscalculated if the other parameter, i.e., effective mass of electron, was assumed to be a constant with respect to variable physical conditions like changing temperature. Additionally, the barrier heights were calculated just by taking constant effective masses for both types of oxides to be able to compare our results to common literature values.

  1. Cancer cells (MCF-7, Colo-357, and LNCaP) viability on amorphous hydrogenated carbon nitride film deposited by dielectric barrier discharge plasma

    SciTech Connect

    Majumdar, Abhijit; Hippler, Rainer; Ummanni, Ramesh; Walther, Reinhard; Schroeder, Karsten

    2009-08-01

    Atmospheric pressure dielectric barrier discharge plasma in CH{sub 4}/N{sub 2} (1:1) gas mixture has been employed to deposit amorphous hydrogenated carbon nitride (aH-CN{sub x}) film. In vitro studies with three different cancer cell lines were carried out on the coated surfaces. Preliminary biocompatibility and effect of CH{sub 4}/N{sub 2} films have been investigated by measuring cell proliferation. Three different cancer cell (MCF-7, Colo-357, and LNCaP) suspensions have been exposed on the surface of aH-CN{sub x} film to investigate the effect of deposited films on viability of cells. Results from the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2- (4-sulfophenyl)-2H- tetrazolium, inner salt) proliferation assays indicated that the deposited aH-CN{sub x} film is cytotoxic to cancer cell lines. Time course cell viability assay indicated maximum cell death at 24 h after seeding the cells. This effect is dependant on physicochemical and mechanical properties of the deposited films. The deposited film has been characterized by x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results confirm the presence of C-N, Cident toN, C-H{sub x}, C-O, N-O, overlapping NH, and OH bonds in the film.

  2. Cancer cells (MCF-7, Colo-357, and LNCaP) viability on amorphous hydrogenated carbon nitride film deposited by dielectric barrier discharge plasma

    NASA Astrophysics Data System (ADS)

    Majumdar, Abhijit; Ummanni, Ramesh; Schröder, Karsten; Walther, Reinhard; Hippler, Rainer

    2009-08-01

    Atmospheric pressure dielectric barrier discharge plasma in CH4/N2 (1:1) gas mixture has been employed to deposit amorphous hydrogenated carbon nitride (aH-CNx) film. In vitro studies with three different cancer cell lines were carried out on the coated surfaces. Preliminary biocompatibility and effect of CH4/N2 films have been investigated by measuring cell proliferation. Three different cancer cell (MCF-7, Colo-357, and LNCaP) suspensions have been exposed on the surface of aH-CNx film to investigate the effect of deposited films on viability of cells. Results from the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H- tetrazolium, inner salt) proliferation assays indicated that the deposited aH-CNx film is cytotoxic to cancer cell lines. Time course cell viability assay indicated maximum cell death at 24 h after seeding the cells. This effect is dependant on physicochemical and mechanical properties of the deposited films. The deposited film has been characterized by x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results confirm the presence of C-N, C≡N, C-Hx, C-O, N-O, overlapping NH, and OH bonds in the film.

  3. Cytocompatibility of amorphous hydrogenated carbon nitride films deposited by CH4/N2 dielectric barrier discharge plasmas with respect to cell lines

    NASA Astrophysics Data System (ADS)

    Majumdar, Abhijit; Schröder, Karsten; Hippler, Rainer

    2008-10-01

    Special amorphous hydrogenated carbon nitride (a-H-CNx) films have been prepared on glass substrates for the investigation of adhesion and proliferation of different mammalian cell lines. CH4/N2 dielectric barrier discharge plasmas were applied to deposit a-H-CNx coatings at half of the atmospheric pressure. Film quality was modified by varying the CH4:N2 ratio and deposition duration. Chemical composition was determined by x-ray photoelectron spectroscopy and Fourier transformed infrared spectroscopy. The N/C ratio was in the range of 0.20-0.55. A very small surface roughness was verified by atomic force microscopy. Human embryonic kidney (HEK) and rat adrenal pheochromocytoma (PC12) cells were cultivated on the a-H-CNx films to investigate the cytocompatibility of these surfaces. The microscopic images show that both kinds of cells lines were unable to survive. The cells did not adhere to the surfaces, and most of the cells died after certain time spans. Increased amounts of nitrogen in the film induce an accelerated cell death. It is concluded, that the deposited CNx film behaves cytotoxic to HEK and PC12 cell lines.

  4. 1/f noise in thin oxide p-channel metal-nitride-oxide-silicon transistors

    NASA Astrophysics Data System (ADS)

    Maes, Herman E.; Usmani, Sabir H.

    1983-04-01

    The 1/f noise behavior of p-channel metal-nitride-oxide-silicon transistors is presented. Devices with different oxide thicknesses, geometries and different technological treatments were used for this study. It is shown that the noise behavior can be well explained quantitatively with the number fluctuation model developed for MOS transistors. The close correlation between the increase of the noise and of the interface state density after different levels of degradation indeed indicates that the exchange of carriers between the channel and the interface traps lies at the origin of the 1/f noise. The observed degradation in MNOS devices is consistent with a diffusion controlled model for the creation of surface traps but is found to be a saturating effect. The predictions of the mobility fluctuation model are not confirmed in our experiments.

  5. UV-irradiation and thermal-annealing studies in amorphous hydrogenated boron nitride thin films

    SciTech Connect

    Brown, I.M.; Lin, S.; Feldman, B.J.

    1997-07-01

    Both photoproduction and photobleaching of dangling bonds by uv irradiation and thermal annealing were observed by electron spin resonance (ESR) in amorphous hydrogenated boron nitride. A model involving long-range hydrogen diffusion and hydrogen evolution is proposed to account for the ESR spectral line shapes observed after uv irradiation and thermal annealing. A Gaussian distribution of activation energies for the long-range hydrogen diffusion was used to explain the observed decrease in spin susceptibility after thermal annealing. A best fit to the spin susceptibility data gave an average activation energy of 0.0475 eV and a half-width of this Gaussian distribution of 0.027 eV. {copyright} {ital 1997} {ital The American Physical Society}

  6. Anisotropic charge carrier transport in free-standing hexagonal boron nitride thin films

    NASA Astrophysics Data System (ADS)

    Dahal, Rajendra; Ahmed, Kawser; Woei Wu, Jia; Weltz, Adam; Jian-Qiang Lu, James; Danon, Yaron; Bhat, Ishwara B.

    2016-06-01

    The in-plane and out-of-plane mobility-lifetime products of electrons and holes in free-standing hexagonal boron nitride (hBN) films are extracted from current-voltage characteristics of metal-hBN-metal structures measured under external excitations. The in-plane mobility-lifetime products for electrons and holes are ˜2.8 × 10-5 and ˜4.85 × 10-6 cm2/V, measured from lateral carrier collection, whereas the out-of-plane mobility-lifetime products for electrons and holes are ˜5.8 × 10-8 and ˜6.1 × 10-9 cm2/V, measured from vertical carrier collection, respectively. The mobility-lifetime product is a few orders of magnitude higher along the plane than along the out of plane in hBN films.

  7. Thickness Influence on In Vitro Biocompatibility of Titanium Nitride Thin Films Synthesized by Pulsed Laser Deposition

    PubMed Central

    Duta, Liviu; Stan, George E.; Popa, Adrian C.; Husanu, Marius A.; Moga, Sorin; Socol, Marcela; Zgura, Irina; Miculescu, Florin; Urzica, Iuliana; Popescu, Andrei C.; Mihailescu, Ion N.

    2016-01-01

    We report a study on the biocompatibility vs. thickness in the case of titanium nitride (TiN) films synthesized on 410 medical grade stainless steel substrates by pulsed laser deposition. The films were grown in a nitrogen atmosphere, and their in vitro cytotoxicity was assessed according to ISO 10993-5 [1]. Extensive physical-chemical analyses have been carried out on the deposited structures with various thicknesses in order to explain the differences in biological behavior: profilometry, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction and surface energy measurements. XPS revealed the presence of titanium oxynitride beside TiN in amounts that vary with the film thickness. The cytocompatibility of films seems to be influenced by their TiN surface content. The thinner films seem to be more suitable for medical applications, due to the combined high values of bonding strength and superior cytocompatibility. PMID:28787846

  8. Thickness Influence on In Vitro Biocompatibility of Titanium Nitride Thin Films Synthesized by Pulsed Laser Deposition.

    PubMed

    Duta, Liviu; Stan, George E; Popa, Adrian C; Husanu, Marius A; Moga, Sorin; Socol, Marcela; Zgura, Irina; Miculescu, Florin; Urzica, Iuliana; Popescu, Andrei C; Mihailescu, Ion N

    2016-01-13

    We report a study on the biocompatibility vs. thickness in the case of titanium nitride (TiN) films synthesized on 410 medical grade stainless steel substrates by pulsed laser deposition. The films were grown in a nitrogen atmosphere, and their in vitro cytotoxicity was assessed according to ISO 10993-5 [1]. Extensive physical-chemical analyses have been carried out on the deposited structures with various thicknesses in order to explain the differences in biological behavior: profilometry, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction and surface energy measurements. XPS revealed the presence of titanium oxynitride beside TiN in amounts that vary with the film thickness. The cytocompatibility of films seems to be influenced by their TiN surface content. The thinner films seem to be more suitable for medical applications, due to the combined high values of bonding strength and superior cytocompatibility.

  9. Diffusion barrier properties of single- and multilayered quasi-amorphous tantalum nitride thin films against copper penetration

    NASA Astrophysics Data System (ADS)

    Chen, G. S.; Chen, S. T.

    2000-06-01

    Tantalum-related thin films containing different amounts of nitrogen are sputter deposited at different argon-to-nitrogen flow rate ratios on (100) silicon substrates. Using x-ray diffractometry, transmission electron microscopy, composition and resistivity analyses, and bending-beam stress measurement technique, this work examines the impact of varying the nitrogen flow rate, particularly on the crystal structure, composition, resistivity, and residual intrinsic stress of the deposited Ta2N thin films. With an adequate amount of controlled, reactive nitrogen in the sputtering gas, thin films of the tantalum nitride of nominal formula Ta2N are predominantly amorphous and can exist over a range of nitrogen concentrations slightly deviated from stoichiometry. The single-layered quasi-amorphous Ta2N (a-Ta2N) thin films yield intrinsic compressive stresses in the range 3-5 GPa. In addition, the use of the 40-nm-thick a-Ta2N thin films with different nitrogen atomic concentrations (33% and 36%) and layering designs as diffusion barriers between silicon and copper are also evaluated. When subjected to high-temperature annealing, the single-layered a-Ta2N barrier layers degrade primarily by an amorphous-to-crystalline transition of the barrier layers. Crystallization of the single-layered stoichiometric a-Ta2N (Ta67N33) diffusion barriers occurs at temperatures as low as 450 °C. Doing so allows copper to preferentially penetrate through the grain boundaries or thermal-induced microcracks of the crystallized barriers and react with silicon, sequentially forming {111}-facetted pyramidal Cu3Si precipitates and TaSi2 Overdoping nitrogen into the amorphous matrix can dramatically increase the crystallization temperature to 600 °C. This temperature increase slows down the inward diffusion of copper and delays the formation of both silicides. The nitrogen overdoped Ta2N (Ta64N36) diffusion barriers can thus be significantly enhanced so as to yield a failure temperature 100

  10. Frequency-Stable Ionic-Type Hybrid Gate Dielectrics for High Mobility Solution-Processed Metal-Oxide Thin-Film Transistors

    PubMed Central

    Heo, Jae Sang; Choi, Seungbeom; Jo, Jeong-Wan; Kang, Jingu; Park, Ho-Hyun; Kim, Yong-Hoon; Park, Sung Kyu

    2017-01-01

    In this paper, we demonstrate high mobility solution-processed metal-oxide thin-film transistors (TFTs) by using a high-frequency-stable ionic-type hybrid gate dielectric (HGD). The HGD gate dielectric, a blend of sol-gel aluminum oxide (AlOx) and poly(4-vinylphenol) (PVP), exhibited high dielectric constant (ε~8.15) and high-frequency-stable characteristics (1 MHz). Using the ionic-type HGD as a gate dielectric layer, an minimal electron-double-layer (EDL) can be formed at the gate dielectric/InOx interface, enhancing the field-effect mobility of the TFTs. Particularly, using the ionic-type HGD gate dielectrics annealed at 350 °C, InOx TFTs having an average field-effect mobility of 16.1 cm2/Vs were achieved (maximum mobility of 24 cm2/Vs). Furthermore, the ionic-type HGD gate dielectrics can be processed at a low temperature of 150 °C, which may enable their applications in low-thermal-budget plastic and elastomeric substrates. In addition, we systematically studied the operational stability of the InOx TFTs using the HGD gate dielectric, and it was observed that the HGD gate dielectric effectively suppressed the negative threshold voltage shift during the negative-illumination-bias stress possibly owing to the recombination of hole carriers injected in the gate dielectric with the negatively charged ionic species in the HGD gate dielectric. PMID:28772972

  11. Mechanical property changes in porous low-k dielectric thin films during processing

    SciTech Connect

    Stan, G. Gates, R. S.; Kavuri, P.; Torres, J.; Michalak, D.; Ege, C.; Bielefeld, J.; King, S. W.

    2014-10-13

    The design of future generations of Cu-low-k dielectric interconnects with reduced electronic crosstalk often requires engineering materials with an optimal trade off between their dielectric constant and elastic modulus. This is because the benefits associated with the reduction of the dielectric constant by increasing the porosity of materials, for example, can adversely affect their mechanical integrity during processing. By using load-dependent contact-resonance atomic force microscopy, the changes in the elastic modulus of low-k dielectric materials due to processing were accurately measured. These changes were linked to alterations sustained by the structure of low-k dielectric films during processing. A two-phase model was used for quantitative assessments of the elastic modulus changes undergone by the organosilicate skeleton of the structure of porous and pore-filled dielectrics.

  12. Mechanical property changes in porous low-k dielectric thin films during processing

    NASA Astrophysics Data System (ADS)

    Stan, G.; Gates, R. S.; Kavuri, P.; Torres, J.; Michalak, D.; Ege, C.; Bielefeld, J.; King, S. W.

    2014-10-01

    The design of future generations of Cu-low-k dielectric interconnects with reduced electronic crosstalk often requires engineering materials with an optimal trade off between their dielectric constant and elastic modulus. This is because the benefits associated with the reduction of the dielectric constant by increasing the porosity of materials, for example, can adversely affect their mechanical integrity during processing. By using load-dependent contact-resonance atomic force microscopy, the changes in the elastic modulus of low-k dielectric materials due to processing were accurately measured. These changes were linked to alterations sustained by the structure of low-k dielectric films during processing. A two-phase model was used for quantitative assessments of the elastic modulus changes undergone by the organosilicate skeleton of the structure of porous and pore-filled dielectrics.

  13. Room-temperature magneto-dielectric response in multiferroic ZnFe2O4/PMN-PT bilayer thin films

    NASA Astrophysics Data System (ADS)

    Garg, T.; Kulkarni, A. R.; Venkataramani, N.

    2016-08-01

    The magneto-dielectric response in multiferroic ZnFe2O4/PMN-PT bilayer thin films prepared on a glass substrate using RF magnetron sputtering has been investigated in this work. PMN-PT thin films (i.e. PMN-PT/LCMO/Pt/Ti/glass) deposited on glass were used as a substrate for deposition of ZnFe2O4 thin films. ZnFe2O4 thin films were annealed ex situ at different temperatures. Structural, magnetic, ferroelectric, dielectric and magneto-dielectric studies were carried out on these multiferroic bilayer thin films. Structural studies revealed the presence of each layer in its respective single phase. Magnetic and ferroelectric studies revealed the ferromagnetic and ferroelectric behaviors of these bilayers. To quantify the magnetoelectric coupling, the dielectric constant of the bilayer was measured at room temperature as a function of frequency with and without the applied magnetic field. The magneto-dielectric response MD(%) was calculated by finding the relative change in dielectric constant at 1 kHz as a percentage. The observed MD response was correlated with magnetization of the ferrite layer. An MD response of 2.60% was found for a bilayer film annealed at 350 °C. At this particular annealing temperature, the ZnFe2O4 layer also has the highest saturation magnetization of 1900 G.

  14. Maximizing the dielectric response of molecular thin films via quantum chemical design.

    PubMed

    Heitzer, Henry M; Marks, Tobin J; Ratner, Mark A

    2014-12-23

    Developing high-capacitance organic gate dielectrics is critical for advances in electronic circuitry based on unconventional semiconductors. While high-dielectric constant molecular substances are known, the mechanism of dielectric response and the fundamental chemical design principles are not well understood. Using a plane-wave density functional theory formalism, we show that it is possible to map the atomic-scale dielectric profiles of molecule-based materials while capturing important bulk characteristics. For molecular films, this approach reveals how basic materials properties such as surface coverage density, molecular tilt angle, and π-system planarity can dramatically influence dielectric response. Additionally, relatively modest molecular backbone and substituent variations can be employed to substantially enhance film dielectric response. For dense surface coverages and proper molecular alignment, conjugated hydrocarbon chains can achieve dielectric constants of >8.0, more than 3 times that of analogous saturated chains, ∼2.5. However, this conjugation-related dielectric enhancement depends on proper molecular orientation and planarization, with enhancements up to 60% for proper molecular alignment with the applied field and an additional 30% for conformations such as coplanarity in extended π-systems. Conjugation length is not the only determinant of dielectric response, and appended polarizable high-Z substituents can increase molecular film response more than 2-fold, affording estimated capacitances of >9.0 μF/cm2. However, in large π-systems, polar substituent effects are substantially attenuated.

  15. Nonlinear conductivity in silicon nitride

    NASA Astrophysics Data System (ADS)

    Tuncer, Enis

    2017-08-01

    To better comprehend electrical silicon-package interaction in high voltage applications requires full characterization of the electrical properties of dielectric materials employed in wafer and package level design. Not only the packaging but wafer level dielectrics, i.e. passivation layers, would experience high electric fields generated by the voltage applied pads. In addition the interface between the passivation layer and a mold compound might develop space charge because of the mismatch in electrical properties of the materials. In this contribution electrical properties of a thin silicon nitride (Si3N4) dielectric is reported as a function of temperature and electric field. The measured values later analyzed using different temperature dependent exponential expressions and found that the Mott variable range hopping conduction model was successful to express the data. A full temperature/electric field dependency of conductivity is generated. It was found that the conduction in Si3N4 could be expressed like a field ionization or Fowler-Nordheim mechanism.

  16. A novel polysilicon field-enhanced nanowire thin-film transistor with the TiN-hafnia-nitride-vacuum-silicon (THNVAS) structure for nonvolatile memory applications.

    PubMed

    Wu, Chun-Yu; Liao, Ta-Chuan; Liu, Yen-Ting; Yu, Ming H; Cheng, Huang-Chung

    2012-07-01

    A novel poly-Si field-enhanced nanowire (FEN) TFT memory with the TiN-hafnia-nitride-vacuum-silicon (THNVAS) structure fabricated simply via a sidewall spacer formation has been presented. The THNVAS devices with superior memory performance were demonstrated by introducing the hafnia as blocking oxide and the vacuum, the lowest-k in nature, as tunneling layer. According to the simulation results, the memory device with oxide/nitride/vacuum gate dielectric exhibited a higher local electric-field of 4.72 x 10(7) V/cm as compared to 2.55 x 10(7) V/cm for the conventional oxide/nitride/oxide counterpart. In addition, the electric-field of tunneling layer could be further increased to 7.06 x 10(7) V/cm while the blocking oxide was substituted for hafnia. The experimental data showed that THNVAS possessed a greater threshold voltage shift of 3.75 V in 10 ms at V(GS) = 12 V, whereas the shift only 2.5 V for THNOS ones. These considerable improvements for THNVAS devices could be attributed to the evident field enhancement across the vacuum tunneling layer. Furthermore, owing to the empty feature of vacuum tunneling layer, the THNVAS demonstrated much-improved endurance performance and preferable data retention property. Hence, such excellent characteristics of THNVAS will be an attractive nonvolatile memory for future system-on-panel and 3-D Flash applications.

  17. Role of nitrogen doping at the surface of titanium nitride thin films towards capacitive charge storage enhancement

    NASA Astrophysics Data System (ADS)

    Achour, A.; Chaker, M.; Achour, H.; Arman, A.; Islam, M.; Mardani, M.; Boujtita, M.; Le Brizoual, L.; Djouadi, M. A.; Brousse, T.

    2017-08-01

    We recently reported an impressive cycling stability (over 20,000 cycles) of titanium nitride (TiN) electrodes with high specific capacitance. It is anticipated that nitrogen (β-N) doping in the oxidized surface of TiN film plays a crucial role in charge storage mechanism and stability of this material. In this work, we offer an evidence on the effect of β-N doping on improvement in specific capacitance of vacuum annealed TiN thin films. The annealing of the TiN films leads to the diffusion of the excess β-N from sub-surface to oxidized TiN film surface without further oxidation of the electrode surface. We demonstrate an increase in the TiN areal capacitance upon an increase in the amount of β-N dopant. The areal capacitance of the annealed films was enhanced by 3-fold (8.2 mF cm-2 in K2SO4 aqueous electrolyte) without sacrificing the cycling stability of the electrodes after more than 10,000 consecutive charge/discharge cycles.

  18. Structural and magnetic phase transitions in chromium nitride thin films grown by rf nitrogen plasma molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Alam, Khan; Disseler, Steven M.; Ratcliff, William D.; Borchers, Julie A.; Ponce-Pérez, Rodrigo; Cocoletzi, Gregorio H.; Takeuchi, Noboru; Foley, Andrew; Richard, Andrea; Ingram, David C.; Smith, Arthur R.

    2017-09-01

    A magnetostructural phase transition is investigated in single-crystal chromium nitride (CrN) thin films grown by rf plasma molecular beam epitaxy on MgO(001) substrates. While still within the vacuum environment following molecular beam epitaxy growth, in situ low-temperature scanning tunneling microscopy, and in situ variable low-temperature reflection high-energy electron diffraction are applied, revealing an atomically smooth and metallic CrN(001) surface, and an in-plane structural transition from 1 ×1 (primitive CrN unit cell) to √{2 }×√{2 }-R 45∘ with a transition temperature of (278 ±3 ) K, respectively. Ex situ temperature-dependent measurements using neutron diffraction are also performed, looking at the structural peaks and likewise revealing a first-order structural transition along the [111] out-of-plane direction, with transition temperatures of (268 ± 3) K. Turning to the magnetic peaks, neutron diffraction confirms a clear magnetic transition from paramagnetic at room temperature to antiferromagnetic at low temperatures with a sharp, first-order phase transition and a Néel temperature of (270 ±2 ) K or (280 ±2 ) K for two different films. In addition to the experimental measurements of structural and magnetic ordering, we also discuss results from first-principles theoretical calculations which explore various possible magnetostructural models.

  19. Sixfold ring clustering in sp{sup 2}-dominated carbon and carbon nitride thin films: A Raman spectroscopy study

    SciTech Connect

    Abrasonis, G.; Gago, R.; Vinnichenko, M.; Kreissig, U.; Kolitsch, A.; Moeller, W.

    2006-03-15

    The atomic arrangement in sp{sup 2}-dominated carbon (C) and carbon nitride (CN{sub x}) thin films has been studied by Raman spectroscopy as a function of substrate temperature and, in the case of CN{sub x}, different N incorporation routes (growth methods). In this way, materials composing graphitelike, fullerenelike (FL), and paracyanogenlike structures have been compared. The results show that each type of arrangement results in a characteristic set of the Raman spectra parameters, which describe the degree of aromatic clustering, bond length, and angle distortion and order in sixfold structures. In the case of C films, the atomic structure evolves with substrate temperature from a disordered network to nanocrystalline planar graphitic configurations, with a progressive promotion in size and ordering of sixfold ring clusters. Nitrogen incorporation favors the promotion of sixfold rings in highly disordered networks produced at low temperatures, but precludes the formation of extended graphiticlike clusters at elevated substrate temperatures (>700 K). In the latter case, N introduces a high degree of disorder in sixfold ring clusters and enhances the formation of a FL microstructure. The formation and growth of aromatic clusters are discussed in terms of substrate temperature, N incorporation, growth rate, film-forming sources, and concurrent bombardment by hyperthermal particles during growth.

  20. Effect of process parameters on the mechanical properties of carbon nitride thin films synthesized by plasma assisted pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Tabbal, M.; Mérel, P.; Chaker, M.

    We present an investigation of the effect of the process parameters, namely deposition pressure and laser intensity, on the growth and mechanical properties of carbon nitride (CNx) thin films synthesized by plasma assisted pulsed laser deposition. Deposition at high remote plasma pressure (200 mTorr) enhances both growth rate and nitrogen incorporation (up to 40 at.%), but nano-indentation measurements indicate that these films are very soft and have poor mechanical properties. At low remote plasma pressure (0.5 mTorr), the nitrogen content varies from 24 to 16 at.% with increasing laser intensity as the films become much harder and more elastic, with hardness and Young's modulus values reaching 24 GPa and 230 GPa, respectively. These effects are explained in terms of a thermalization of the laser plasma at 200 mTorr and indicate that plasma activation of nitrogen does not provide any particular benefit to the film properties when deposition is performed at high pressure. However, at low pressure, the benefit of plasma activation is evidenced through enhanced nitrogen incorporation in the films while preserving the highly energetic species in the ablation plume. Such conditions lead to the synthesis, at room temperature, of hard and elastic films having properties close to those of fullerene-like CNx.

  1. Control of the stabilization of cubic boron nitride thin films deposited by unbalanced magnetron sputtering and dc pulsed substrate biasing

    NASA Astrophysics Data System (ADS)

    Otano-Rivera, Wilfredo

    The formation of cubic boron nitride (cBN) thin films deposited by unbalanced magnetron sputtering and dc pulsed substrate biasing has been studied. Thin films were deposited at different pressures and negative bias voltages to study the effect of the energetic bombardment on the stabilization conditions of the cubic phase of BN thin films. It is shown that it is possible to clearly define a stabilization window for cBN by controlling the sputtering deposition process parameters of pressure and negative substrate bias. It is also shown that at higher deposition pressures charge exchange and momentum transfer collisions in the plasma sheath reduce the bombardment energy of the particles. These collisional processes result in the use of a higher substrate bias voltages for increasing gas pressures in order to maintain the momentum per arriving boron atom, P/a, imparted to the growing film inside the stabilization window for the cubic phase. The end result is a trend where the substrate bias voltage for the formation of cBN increases negatively as a function of pressure times sheath thickness. A series of films were also deposited on different types of substrates in order to study the effects of chemistry and epitaxy on the nucleation of cBN. It was possible to nucleate the BN cubic phase on a wide variety of substrates. Diamond coated silicon substrates were the only ones that showed a marked effect on the nucleation of the cBN, where the FWHM of the FTIR signal was reduced two-fold as compared to the FTIR signal of films deposited on silicon under similar deposition conditions. The experimental results suggest that there is a threshold energy for the bombarding ions below which it is not possible to nucleate cBN. This result, in combination with the fact that P/a controls the cBN stabilization during the nucleation stage and other reported observations pertinent to the cBN thin film formation, leads to a proposed mechanism for the nucleation and growth stages of cBN.

  2. Localization and pair breaking parameter in superconducting molybdenum nitride thin films.

    PubMed

    Tsuneoka, Takuya; Makise, Kazumasa; Maeda, Sho; Shinozaki, Bunju; Ichikawa, Fusao

    2017-01-11

    We have investigated the superconductor-insulator transition in molybdenum nitride films prepared by deposition onto MgO substrates. It is indicated that the T c depression from [Formula: see text] for thick films with increase of the normal state sheet resistance [Formula: see text] was well explained by the Finkel'stein formula from the localization theory. Present analysis suggests that the superconducting-insulator transition occurs at a critical sheet resistance [Formula: see text]. It is found that the [Formula: see text] above [Formula: see text] shows different characteristics of [Formula: see text] and [Formula: see text] in the regions [Formula: see text] and [Formula: see text], respectively, where [Formula: see text] is the classical residual resistance and A is a constant. The excess conductance [Formula: see text] due to thermal fluctuation has been analyzed by the sum of the Aslamazov-Larkin and Maki-Thompson correction terms with use of the pair breaking parameter [Formula: see text] in the latter term. The sum agrees well with the data, although the experimental results of the [Formula: see text] dependence of [Formula: see text], that is, [Formula: see text] shows the disagreement with a linear relation [Formula: see text] derived from the localization theory.

  3. Spin-dependent processes in silicon-rich silicon-nitride thin film solar cells

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Yun; Paik, Seoyoung; McCamey, Dane; Boehme, Christoph; Hu, Jian; Zhu, Feng; Madan, Arun

    2010-03-01

    Silicon-rich silicon-nitride (SiNx:H) is attracting attention due to its relevance for light emitting diodes, electrolytic devices and solar cells. Charge transport and recombination in this material are key factors for its optoelectronic properties. Since SiNx:H is highly disordered and exhibits weak spin-orbit coupling similar to amorphous silicon (a-Si:H), many of the electronic transitions in this material take place through localized electronic states and are governed by spin-selection rules. Thus, it is possible to study these processes using electrically detected magnetic resonance spectroscopy (EDMR). Using coherent, pulsed EDMR, we observed a variety of qualitatively different spin-dependent processes. We present a mapping of the properties of these processes regarding coupling and defect type and show that the nature of many of these processes is similar to previously studied mechanisms in a-Si:H as they involve a variety of different states (dangling bonds, tails states), with various spin coupling modes (exchange, dipolar coupling). However, in contrast to a-Si:H, many of the transitions between strongly spin-coupled pairs influence the conductivity and hence they do not represent geminate recombination processes.

  4. Ultra-thin superconducting film coated silicon nitride nanowire resonators for low-temperature applications

    NASA Astrophysics Data System (ADS)

    Sebastian, Abhilash; Zhelev, Nikolay; de Alba, Roberto; Parpia, Jeevak

    We demonstrate fabrication of high stress silicon nitride nanowire resonators with a thickness and width of less than 50 nm intended to be used as probes for the study of superfluid 3He. The resonators are fabricated as doubly-clamped wires/beams using a combination of electron-beam lithography and wet/dry etching techniques. We demonstrate the ability to suspend (over a trench of depth ~8 µm) wires with a cross section as small as 30 nm, covered with a 20 nm superconducting film, and having lengths up to 50 µm. Room temperature resonance measurements were carried out by driving the devices using a piezo stage and detecting the motion using an optical interferometer. The results show that metalizing nano-mechanical resonators not only affects their resonant frequencies but significantly reduce their quality factor (Q). The devices are parametrically pumped by modulating the system at twice its fundamental resonant frequency, which results in observed amplification of the signal. The wires show self-oscillation with increasing modulation strength. The fabricated nanowire resonators are intended to be immersed in the superfluid 3He. By tracking the resonant frequency and the Q of the various modes of the wire versus temperature, we aim to probe the superfluid gap structure.

  5. Sub-picowatt resolution calorimetry with niobium nitride thin-film thermometer

    SciTech Connect

    Dechaumphai, Edward; Chen, Renkun

    2014-09-15

    High-resolution calorimetry has many important applications such as probing nanoscale thermal transport and studying the thermodynamics of biological and chemical systems. In this work, we demonstrated a calorimeter with an unprecedentedly high resolution at room temperature using a high-performance resistive thermometry material, niobium nitride (NbN{sub x}). Based on a theoretical analysis, we first showed that the heat flux resolution of a resistive-thermometry based calorimeter depends on the parasitic thermal conductance of the device and the temperature coefficient of resistance (TCR) of the thermometer, when the noise is limited by the Johnson noise. Based on this analysis, we then developed a calorimeter using NbN{sub x} as the thermometry material because it possesses both high TCR (∼0.67%/K) and a low thermal conductivity (k ∼ 1.1 W/m K). This calorimeter, when used with the modulated heating scheme, demonstrated an unprecedentedly high power resolution of 0.26 pW at room temperature. In addition, NbN{sub x} based resistive thermometry can also be extended to cryogenic temperature, where the TCR is shown to be significantly higher.

  6. Dispersion engineering and frequency comb generation in thin silicon nitride concentric microresonators.

    PubMed

    Kim, Sangsik; Han, Kyunghun; Wang, Cong; Jaramillo-Villegas, Jose A; Xue, Xiaoxiao; Bao, Chengying; Xuan, Yi; Leaird, Daniel E; Weiner, Andrew M; Qi, Minghao

    2017-08-29

    Kerr nonlinearity-based frequency combs and solitons have been generated from on-chip microresonators. The initiation of the combs requires global or local anomalous dispersion which leads to many limitations, such as material choice, film thickness, and spectral ranges where combs can be generated, as well as fabrication challenges. Using a concentric racetrack-shaped resonator, we show that such constraints can be lifted and resonator dispersion can be engineered to be anomalous over moderately broad bandwidth. We demonstrate anomalous dispersion in a 300 nm thick silicon nitride film, suitable for semiconductor manufacturing but previously thought to result in waveguides with high normal dispersion. Together with a mode-selective, tapered coupling scheme, we generate coherent mode-locked frequency combs. Our method can realize anomalous dispersion for resonators at almost any wavelength and simultaneously achieve material and process compatibility with semiconductor manufacturing.Kerr frequency comb generation from microresonators requires anomalous dispersion, imposing restrictions on materials and resonator design. Here, Kim et al. propose a concentric racetrack-resonator design where the dispersion can be engineered to be anomalous via resonant mode coupling.

  7. Sub-picowatt resolution calorimetry with niobium nitride thin-film thermometer

    NASA Astrophysics Data System (ADS)

    Dechaumphai, Edward; Chen, Renkun

    2014-09-01

    High-resolution calorimetry has many important applications such as probing nanoscale thermal transport and studying the thermodynamics of biological and chemical systems. In this work, we demonstrated a calorimeter with an unprecedentedly high resolution at room temperature using a high-performance resistive thermometry material, niobium nitride (NbNx). Based on a theoretical analysis, we first showed that the heat flux resolution of a resistive-thermometry based calorimeter depends on the parasitic thermal conductance of the device and the temperature coefficient of resistance (TCR) of the thermometer, when the noise is limited by the Johnson noise. Based on this analysis, we then developed a calorimeter using NbNx as the thermometry material because it possesses both high TCR (˜0.67%/K) and a low thermal conductivity (k ˜ 1.1 W/m K). This calorimeter, when used with the modulated heating scheme, demonstrated an unprecedentedly high power resolution of 0.26 pW at room temperature. In addition, NbNx based resistive thermometry can also be extended to cryogenic temperature, where the TCR is shown to be significantly higher.

  8. The Dielectric Breakdown Model applied to explain various morphologies of deposited metallic structures in thin gap metal electro-deposition

    NASA Astrophysics Data System (ADS)

    Chowdhury, Aditya; Dutta, Dibakar

    2015-06-01

    The phenomenon of metal electro-deposition in thin-gap geometry leads to very interesting and diverse two dimensional morphologies. This varies from dense ramified growth to thin dendritic projections. In this paper, we have proposed a stochastic model that incorporates such diversity. We carried out thin-gap electro-deposition of Copper and Zinc with varying electrolytic concentrations. A well known model, that until this work was used to explain dielectric breakdown patterns, was employed to explain the variation in deposition morphology with concentration. The sole parameter in the model was varied and the numerically obtained patterns was seen to correlate well with those obtained from electro-deposition. A linear relationship between the parameter and molar concentration was established. The established relationship was then analysed and interpreted.

  9. Thin film deposition at atmospheric pressure using dielectric barrier discharges: Advances on three-dimensional porous substrates and functional coatings

    NASA Astrophysics Data System (ADS)

    Fanelli, Fiorenza; Bosso, Piera; Mastrangelo, Anna Maria; Fracassi, Francesco

    2016-07-01

    Surface processing of materials by atmospheric pressure dielectric barrier discharges (DBDs) has experienced significant growth in recent years. Considerable research efforts have been directed for instance to develop a large variety of processes which exploit different DBD electrode geometries for the direct and remote deposition of thin films from precursors in gas, vapor and aerosol form. This article briefly reviews our recent progress in thin film deposition by DBDs with particular focus on process optimization. The following examples are provided: (i) the plasma-enhanced chemical vapor deposition of thin films on an open-cell foam accomplished by igniting the DBD throughout the entire three-dimensional (3D) porous structure of the substrate, (ii) the preparation of hybrid organic/inorganic nanocomposite coatings using an aerosol-assisted process, (iii) the DBD jet deposition of coatings containing carboxylic acid groups and the improvement of their chemical and morphological stability upon immersion in water.

  10. Optical, Dielectric Characterization and Impedance Spectroscopy of Ni-Substituted MgTiO3 Thin Films

    NASA Astrophysics Data System (ADS)

    Gogoi, Pallabi; Srinivas, P.; Sharma, Pramod; Pamu, D.

    2016-02-01

    We report the effects of oxygen mixing percentage (OMP) and annealing temperature on surface morphology, optical, dielectric and electrical properties of (Mg0.95Ni0.05)TiO3 (MNT) thin films deposited onto amorphous SiO2 and platinized silicon (Pt/TiO2/SiO2/Si) substrates by radio frequency (RF) magnetron sputtering. The annealed films exhibited the highest refractive index, 2.05, at 600 nm with an optical bandgap value of 4.33 eV. The metal-insulator-metal (MIM) capacitors of the MNT thin films were fabricated under different OMPs and the dielectric properties were analyzed by using Maxwell-Wagner two-layer theory and Koop's phenomenological theory. MNT films prepared under 50% OMP displayed the highest dielectric constant (11.21) and minimum loss tangent (0.0114) at 1 MHz. The impedance spectroscopy of the films deposited under 50% OMP has been studied. The Nyquist plots of MNT films revealed two semi-circular arcs and is explained on the basis of an equivalent circuit model. The frequency-dependent alternative current (AC) conductivity followed the Jonscher's power law. The activation energies are calculated using the Arrhenius relationship. The hopping frequency of the charged species was calculated, and the correlation between AC and direct current (DC) conduction mechanisms established in accordance with the Barton-Nakajima-Namikawa (BNN) relationship.

  11. 7-Octenyltrichrolosilane/trimethyaluminum hybrid dielectrics fabricated by molecular-atomic layer deposition on ZnO thin film transistors

    NASA Astrophysics Data System (ADS)

    Huang, Jie; Lee, Mingun; Lucero, Antonio T.; Cheng, Lanxia; Ha, Min-Woo; Kim, Jiyoung

    2016-06-01

    We demonstrate the fabrication of 7-octenytrichlorosilane (7-OTS)/trimethylaluminum (TMA) organic-inorganic hybrid films using molecular-atomic layer deposition (MALD). The properties of 7-OTS/TMA hybrid films are extensively investigated using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and electrical measurements. Our results suggest that uniform and smooth amorphous hybrid thin films with excellent insulating properties are obtained using the MALD process. Films have a relatively high dielectric constant of approximately 5.0 and low leakage current density. We fabricate zinc oxide (ZnO) based thin film transistors (TFTs) using 7-OTS/TMA hybrid material as a back gate dielectric with the top ZnO channel layer deposited in-situ via MALD. The ZnO TFTs exhibit a field effect mobility of approximately 0.43 cm2 V-1 s-1, a threshold voltage of approximately 1 V, and an on/off ratio of approximately 103 under low voltage operation (from -3 to 9 V). This work demonstrates an organic-inorganic hybrid gate dielectric material potentially useful in flexible electronics application.

  12. Poly(3-hexylthiophene) thin-film transistors with variable polymer dielectrics for transfer-printed flexible electronics

    NASA Astrophysics Data System (ADS)

    Hines, D. R.; Southard, A.; Fuhrer, M. S.

    2008-07-01

    The fabrication of high quality organic thin-film transistors onto flexible, plastic substrates has been extended to include the polymeric semiconductor material poly(3-hexlythiophene). The transfer printing method is used to easily assemble these devices onto either polyethylene terephthalate (PET) or polycarbonate (PC) substrates. A PC dielectric layer is used in conjunction with the PC substrate while both poly(methyl methacrylate) and polystyrene dielectric layers are used in conjunction with the PET substrate. In all cases the mobility of the transfer-printed devices, 0.019-0.041 cm2/V s, is significantly higher than that of the unprinted reference devices (SiO2 dielectric layer on a Si substrate), 0.007 cm2/V s. The width-normalized contact resistance is also lower for the transfer-printed devices, 0.18 MΩ cm, as compared to that for the reference devices, 0.56 MΩ cm. For the devices reported, the threshold voltage becomes more positive as the polar component of the surface energy of the polymer dielectric material increases. These results illustrate the simplicity, power, and versatility of the transfer printing method for the fabrication of high quality flexible electronics.

  13. Instantaneous Pulsed-Light Cross-Linking of a Polymer Gate Dielectric for Flexible Organic Thin-Film Transistors.

    PubMed

    Kim, Soo Jin; Jang, Mi; Yang, Hee Yeon; Cho, Jinhan; Lim, Ho Sun; Yang, Hoichang; Lim, Jung Ah

    2017-04-05

    We report the instantaneous pulsed-light cross-linking of polymer gate dielectrics on a flexible substrate by using intensely pulsed white light (IPWL) irradiation. Irradiation with IPWL for only 1.8 s of a poly(4-vinylphenol) (PVP) thin film with the cross-linking agent poly(melamine-co-formaldehyde) (PMF) deposited on a plastic substrate was found to yield fully cross-linked PVP films. It was confirmed that the IPWL-cross-linked PVP films have smooth pinhole-free surfaces and exhibit a low leakage current density, organic solvent resistance, and good compatibility with organic semiconductor, and that they can be used as replacements for typical PVP dielectrics that are cross-linked with time and energy intensive thermal heating processes. The synchronization of the IPWL irradiation with substrate transfer was found to enable the preparation of cross-linked PVP films on large area substrates with a highly uniform capacitance. Flexible OTFT based on IPWL-cross-linked PVP dielectrics were found to exhibit good electrical performance that is comparable to that of devices with thermally cross-linked PVP dielectric, as well as excellent deformation stability even at a bending radius of 3 mm.

  14. Tunability of the dielectric function of heavily doped germanium thin films for mid-infrared plasmonics

    NASA Astrophysics Data System (ADS)

    Frigerio, Jacopo; Ballabio, Andrea; Isella, Giovanni; Sakat, Emilie; Pellegrini, Giovanni; Biagioni, Paolo; Bollani, Monica; Napolitani, Enrico; Manganelli, Costanza; Virgilio, Michele; Grupp, Alexander; Fischer, Marco P.; Brida, Daniele; Gallacher, Kevin; Paul, Douglas J.; Baldassarre, Leonetta; Calvani, Paolo; Giliberti, Valeria; Nucara, Alessandro; Ortolani, Michele

    2016-08-01

    Heavily doped semiconductor thin films are very promising for application in mid-infrared plasmonic devices because the real part of their dielectric function is negative and broadly tunable in the 5 to 50 μ m wavelength range at least. In this work, we investigate the electrodynamics of heavily n -type-doped germanium epilayers at infrared frequencies beyond the assumptions of the Drude model. The films are grown on silicon and germanium substrates, are in situ doped with phosphorous in the 1017 to 1019 cm-3 range, then screened plasma frequencies in the 100 to 1200 cm-1 range were observed. We employ infrared spectroscopy, pump-probe spectroscopy, and dc transport measurements to determine the tunability of the plasma frequency. Although no plasmonic structures have been realized in this work, we derive estimates of the decay time of mid-infrared plasmons and of their figures of merit for field confinement and for surface plasmon propagation. The average electron scattering rate increases almost linearly with excitation frequency, in agreement with quantum calculations based on a model of the ellipsoidal Fermi surface at the conduction band minimum of germanium accounting for electron scattering with optical phonons and charged impurities. Instead, we found weak dependence of plasmon losses on neutral impurity density. In films where a transient plasma was generated by optical pumping, we found significant dependence of the energy relaxation times in the few-picosecond range on the static doping level of the film, confirming the key but indirect role played by charged impurities in energy relaxation. Our results indicate that underdamped mid-infrared plasma oscillations are attained in n -type-doped germanium at room temperature.

  15. A comparison of methods for modeling electrically thin dielectric and conducting sheets in the finite-difference time-domain (FDTD) method

    NASA Astrophysics Data System (ADS)

    Maloney, James G.; Smith, Glenn S.

    1993-05-01

    A comparison is made between several different methods that have recently been proposed for efficiently modeling electrically thin material sheets in the finite-difference time-domain (FDTD) method. The test problems used in the comparison are parallel-plate waveguides loaded with electrically thin dielectric (lossless) and conducting sheets for which exact solutions are available.

  16. Cyanoresin, cyanoresin/cellulose triacetate blends for thin film, dielectric capacitors

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S. (Inventor); Lewis, Carol R. (Inventor); Cygan, Peter J. (Inventor); Jow, T. Richard (Inventor)

    1996-01-01

    Non brittle dielectric films are formed by blending a cyanoresin such as cyanoethyl, hydroxyethyl cellulose (CRE) with a compatible, more crystalline resin such as cellulose triacetate. The electrical breakdown strength of the blend is increased by orienting the films by uniaxial or biaxial stretching. Blends of high molecular weight CRE with high molecular weight cyanoethyl cellulose (CRC) provide films with high dielectric constants.

  17. Cyanoresin, cyanoresin/cellulose triacetate blends for thin film, dielectric capacitors

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping (Inventor); Jow, T. Richard (Inventor)

    1993-01-01

    Non-brittle dielectric films are formed by blending a cyanoresin such as cyanoethyl, hydroxyethyl cellulose (CRE) with a compatible, more crystalline resin such as cellulose triacetate. The electrical breakdown strength of the blend is increased by orienting the films by uniaxial or biaxial stretching. Blends of high molecular weight CRE with high molecular weight cyanoethyl cellulose (CRC) provide films with high dielectric constants.

  18. Effect of thermal stresses on the dielectric properties of strontium titanate thin films

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Weiss, C. V.; Alpay, S. P.

    2011-07-01

    We develop a quantitative thermodynamic model to understand the role of thermal stresses on the dielectric permittivity and tunability of (001)-textured polycrystalline monodomain strontium titanate (SrTiO3) films. This methodology is used to compute the dielectric constant and tunability of SrTiO3 films on Si, c-sapphire, LaAlO3, and MgO substrates. Results show that dielectric properties of SrTiO3 depend strongly on the growth/processing temperature TG. For substrates such as MgO that induce compressive in-plane thermal stresses, the dielectric response of SrTiO3 is enhanced. However, for SrTiO3 films on IC-compatible substrates (Si and c-sapphire), thermal stresses can significantly degrade the dielectric permittivity and tunability.

  19. Nanostructured pyronin Y thin films as a new organic semiconductor: Linear/nonlinear optics, band gap and dielectric properties

    NASA Astrophysics Data System (ADS)

    Zahran, H. Y.; Yahia, I. S.; Alamri, F. H.

    2017-05-01

    Pyronin Y dye (PY) is a kind of xanthene derivatives. Thin films of pyronin Y were deposited onto highly cleaned glass substrates using low-cost/spin coating technique. The structure properties of pyronin Y thin films with different thicknesses were investigated by using X-ray diffraction (XRD) and atomic force microscope (AFM). PY thin films for all the studied thicknesses have an amorphous structure supporting the short range order of the grain size. AFM supports the nanostructure with spherical/clusters morphologies of the investigated thin films. The optical constants of pyronin Y thin films for various thicknesses were studied by using UV-vis-NIR spectrophotometer in the wavelength range 350-2500 nm. The transmittance T(λ), reflectance R(λ) spectral and absorbance (abs(λ)) were obtained for all film thicknesses at room temperature and the normal light incident. These films showed a high transmittance in the wide scale wavelengths. For different thicknesses of the studied thin films, the optical band gaps were determined and their values around 2 eV. Real and imaginary dielectric constants, dissipation factor and the nonlinear optical parameters were calculated in the wavelengths to the range 300-2500 nm. The pyronin Y is a new organic semiconductor with a good optical absorption in UV-vis regions and it is suitable for nonlinear optical applications.

  20. Electron energy loss spectroscopy of plasmon resonances in titanium nitride thin films

    SciTech Connect

    Herzing, Andrew A.; Guler, Urcan; Zhou, Xiuli; Norris, Theodore B.; Boltasseva, Alexandra; Shalaev, Vladimir

    2016-04-25

    The plasmon resonance characteristics of refractory TiN thin films were analyzed using electron energy-loss spectroscopy (EELS). A bulk plasmon resonance was observed at 2.81 eV and a weaker surface plasmon resonance peak was detected at 2.05 eV. These findings are compared to finite-difference time-domain simulations based on measured optical data. The calculated values for both the bulk and surface resonances (2.74 eV and 2.15 eV, respectively) show reasonable agreement with those measured via EELS. The amplitude of the experimentally observed surface resonance was weaker than that typically encountered in noble metal nanostructures, and this is discussed in the context of electron density and reduced spatial confinement of the resonance mode in the thin-film geometry.

  1. Localization and pair breaking parameter in superconducting molybdenum nitride thin films

    NASA Astrophysics Data System (ADS)

    Tsuneoka, Takuya; Makise, Kazumasa; Maeda, Sho; Shinozaki, Bunju; Ichikawa, Fusao

    2017-01-01

    We have investigated the superconductor-insulator transition in molybdenum nitride films prepared by deposition onto MgO substrates. It is indicated that the T c depression from ≈ 6.6 \\text{K} for thick films with increase of the normal state sheet resistance R\\text{sq}\\text{N} was well explained by the Finkel’stein formula from the localization theory. Present analysis suggests that the superconducting-insulator transition occurs at a critical sheet resistance {{R}\\text{c}}≈ 2 \\text{k} Ω . It is found that the {{R}\\text{sq}}(T) above {{R}\\text{c}} shows different characteristics of {{R}\\text{sq}}(T)={{R}\\text{sq,0}}-A\\ln T and {{R}\\text{sq}}(T)\\propto \\exp ≤ft[{≤ft({{T}0}/T\\right)}1/2}\\right] in the regions {{R}\\text{c}}\\text{sq}\\text{N}<{{R}\\text{Q}}=h/4{{e}2}≈ 6.45 \\text{k} Ω and R\\text{sq}\\text{N}>{{R}\\text{Q}} , respectively, where {{R}\\text{sq,0}} is the classical residual resistance and A is a constant. The excess conductance {{σ\\prime}{}(T) due to thermal fluctuation has been analyzed by the sum of the Aslamazov-Larkin and Maki-Thompson correction terms with use of the pair breaking parameter δ in the latter term. The sum agrees well with the data, although the experimental results of the R\\text{sq}\\text{N} dependence of δ , that is, δ \\propto {{≤ft(R\\text{sq}\\text{N}\\right)}≈ 1.7} shows the disagreement with a linear relation δ \\propto ≤ft(R\\text{sq}\\text{N}\\right) derived from the localization theory.

  2. Highly Bendable In-Ga-ZnO Thin Film Transistors by Using a Thermally Stable Organic Dielectric Layer

    PubMed Central

    Kumaresan, Yogeenth; Pak, Yusin; Lim, Namsoo; kim, Yonghun; Park, Min-Ji; Yoon, Sung-Min; Youn, Hyoc-Min; Lee, Heon; Lee, Byoung Hun; Jung, Gun Young

    2016-01-01

    Flexible In-Ga-ZnO (IGZO) thin film transistor (TFT) on a polyimide substrate is produced by employing a thermally stable SA7 organic material as the multi-functional barrier and dielectric layers. The IGZO channel layer was sputtered at Ar:O2 gas flow rate of 100:1 sccm and the fabricated TFT exhibited excellent transistor performances with a mobility of 15.67 cm2/Vs, a threshold voltage of 6.4 V and an on/off current ratio of 4.5 × 105. Further, high mechanical stability was achieved by the use of organic/inorganic stacking of dielectric and channel layers. Thus, the IGZO transistor endured unprecedented bending strain up to 3.33% at a bending radius of 1.5 mm with no significant degradation in transistor performances along with a superior reliability up to 1000 cycles. PMID:27876893

  3. High-density carrier-accumulated and electrically stable oxide thin-film transistors from ion-gel gate dielectric

    NASA Astrophysics Data System (ADS)

    Fujii, Mami N.; Ishikawa, Yasuaki; Miwa, Kazumoto; Okada, Hiromi; Uraoka, Yukiharu; Ono, Shimpei

    2015-12-01

    The use of indium-gallium-zinc oxide (IGZO) has paved the way for high-resolution uniform displays or integrated circuits with transparent and flexible devices. However, achieving highly reliable devices that use IGZO for low-temperature processes remains a technological challenge. We propose the use of IGZO thin-film transistors (TFTs) with an ionic-liquid gate dielectric in order to achieve high-density carrier-accumulated IGZO TFTs with high reliability, and we discuss a distinctive mechanism for the degradation of this organic-inorganic hybrid device under long-term electrical stress. Our results demonstrated that an ionic liquid or gel gate dielectric provides highly reliable and low-voltage operation with IGZO TFTs. Furthermore, high-density carrier accumulation helps improve the TFT characteristics and reliability, and it is highly relevant to the electronic phase control of oxide materials and the degradation mechanism for organic-inorganic hybrid devices.

  4. Performance improvement in polymeric thin film transistors using chemically modified both silver bottom contacts and dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Xie, Ying-Tao; Ouyang, Shi-Hong; Wang, Dong-Ping; Zhu, Da-Long; Xu, Xin; Tan, Te; Fong, Hon-Hang

    2015-09-01

    An efficient interface modification is introduced to improve the performance of polymeric thin film transistors. This efficient interface modification is first achieved by 4-fluorothiophenol (4-FTP) self-assembled monolayers (SAM) to chemically treat the silver source-drain (S/D) contacts while the silicon oxide (SiO2) dielectric interface is further primed by either hexamethyldisilazane (HMDS) or octyltrichlorosilane (OTS-C8). Results show that contact resistance is the dominant factor that limits the field effect mobility of the PTDPPTFT4 transistors. With proper surface modification applied to both the dielectric surface and the bottom contacts, the field effect mobilities of the bottom-gate bottom-contact PTDPPTFT4 transistors were significantly improved from 0.15 cm2·V-1·s-1 to 0.91 cm2·V-1·s-1. Project supported by the National Basic Research Program of China (Grant No. 2013CB328803).

  5. In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

    NASA Technical Reports Server (NTRS)

    Singh, R.; Sinha, S.; Hsu, N. J.; Thakur, R. P. S.; Chou, P.; Kumar, A.; Narayan, J.

    1990-01-01

    In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectric having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writting capability, complex device structures like three-terminal hybrid semiconductors/superconductors transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray defraction, electron microscopy, and energy dispersive x-ray analysis are discussed.

  6. In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

    NASA Astrophysics Data System (ADS)

    Singh, R.; Sinha, S.; Hsu, N. J.; Thakur, R. P. S.; Chou, P.; Kumar, A.; Narayan, J.

    1990-04-01

    In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectric having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writting capability, complex device structures like three-terminal hybrid semiconductors/superconductors transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray defraction, electron microscopy, and energy dispersive x-ray analysis are discussed.

  7. High-density carrier-accumulated and electrically stable oxide thin-film transistors from ion-gel gate dielectric

    PubMed Central

    Fujii, Mami N.; Ishikawa, Yasuaki; Miwa, Kazumoto; Okada, Hiromi; Uraoka, Yukiharu; Ono, Shimpei

    2015-01-01

    The use of indium–gallium–zinc oxide (IGZO) has paved the way for high-resolution uniform displays or integrated circuits with transparent and flexible devices. However, achieving highly reliable devices that use IGZO for low-temperature processes remains a technological challenge. We propose the use of IGZO thin-film transistors (TFTs) with an ionic-liquid gate dielectric in order to achieve high-density carrier-accumulated IGZO TFTs with high reliability, and we discuss a distinctive mechanism for the degradation of this organic–inorganic hybrid device under long-term electrical stress. Our results demonstrated that an ionic liquid or gel gate dielectric provides highly reliable and low-voltage operation with IGZO TFTs. Furthermore, high-density carrier accumulation helps improve the TFT characteristics and reliability, and it is highly relevant to the electronic phase control of oxide materials and the degradation mechanism for organic–inorganic hybrid devices. PMID:26677773

  8. Highly Bendable In-Ga-ZnO Thin Film Transistors by Using a Thermally Stable Organic Dielectric Layer

    NASA Astrophysics Data System (ADS)

    Kumaresan, Yogeenth; Pak, Yusin; Lim, Namsoo; Kim, Yonghun; Park, Min-Ji; Yoon, Sung-Min; Youn, Hyoc-Min; Lee, Heon; Lee, Byoung Hun; Jung, Gun Young

    2016-11-01

    Flexible In-Ga-ZnO (IGZO) thin film transistor (TFT) on a polyimide substrate is produced by employing a thermally stable SA7 organic material as the multi-functional barrier and dielectric layers. The IGZO channel layer was sputtered at Ar:O2 gas flow rate of 100:1 sccm and the fabricated TFT exhibited excellent transistor performances with a mobility of 15.67 cm2/Vs, a threshold voltage of 6.4 V and an on/off current ratio of 4.5 × 105. Further, high mechanical stability was achieved by the use of organic/inorganic stacking of dielectric and channel layers. Thus, the IGZO transistor endured unprecedented bending strain up to 3.33% at a bending radius of 1.5 mm with no significant degradation in transistor performances along with a superior reliability up to 1000 cycles.

  9. Polarization and Dielectric Study of Methylammonium Lead Iodide Thin Film to Reveal its Nonferroelectric Nature under Solar Cell Operating Conditions

    SciTech Connect

    Hoque, Md Nadim Ferdous; Yang, Mengjin; Li, Zhen; Islam, Nazifah; Pan, Xuan; Zhu, Kai; Fan, Zhaoyang

    2016-07-08

    Researchers have debated whether methylammonium lead iodide (MAPbI3), with a perovskite crystal structure, is ferroelectric and therefore contributes to the current--voltage hysteresis commonly observed in hybrid perovskite solar cells (PSCs). We thoroughly investigated temperature-dependent polarization, dielectric, and impedance spectroscopies, and we found no evidence of ferroelectric effect in a MAPbI3 thin film at normal operating conditions. Therefore, the effect does not contribute to the hysteresis in PSCs, whereas the large component of ionic migration observed may play a critical role. Our temperature-based polarization and dielectric studies find that MAPbI3 exhibits different electrical behaviors below and above ca. 45 degrees C, suggesting a phase transition around this temperature. In particular, we report the activation energies of ionic migration for the two phases and temperature-dependent permittivity of MAPbI3. This study contributes to the understanding of the material properties and device performance of hybrid perovskites.

  10. In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

    NASA Technical Reports Server (NTRS)

    Singh, R.; Sinha, S.; Hsu, N. J.; Thakur, R. P. S.; Chou, P.; Kumar, A.; Narayan, J.

    1991-01-01

    In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectrics having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writing capability, complex device structures like three terminal hybrid semiconductor/superconductor transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray deffraction, electron microscopy, and energy dispersive x-ray analysis are discussed.

  11. The Effect of Sputtering Parameters and Doping of Copper on Surface Free Energy and Magnetic Properties of Iron and Iron Nitride Nano Thin Films on Polymer Substrate

    PubMed Central

    Khan, Waheed; Wang, Qun; Jin, Xin; Feng, Tangfeng

    2017-01-01

    The objective of this study was to deposit thin films on PET polymer substrate and examine the functional properties systematically. Their properties have been studied as a function of the N2-Ar flow rates, deposition time span and Cu doping. Iron nitride film deposited on both sides exhibits ferromagnetic phases, γ′-Fe4N and ε-Fe3N co-existed, shows negligible magnetic anisotropy. Other samples show the evolution of N-rich (FeN, Fe2N) and N-poor (Fe16N2, Fe3N, Fe4N) phases under different deposition time conditions. XPS analysis and free energy calculations confirmed that co-sputtered Fe-Cu thin films are more stable than layer deposited counterparts. From VSM results it is evident that the dominant phase, changes steadily from the ferromagnetic α-Fe (N) to the paramagnetic ξ-Fe2N with the increase of nitrogen flow rates and the ordering of the nitrogen atoms. Binding energy increases steadily from 733 eV to 740 eV with the increasing thickness of thin films from 74 nm to 94 nm. It was observed that surface energy decreases as the contact angle of glycol increases and changes the thin film surface from polar to nonpolar. TEM images indicate that cubic γ′-Fe4N and ε-Fe3N nano particles oriented in preferred directions dispersed uniformly in the amorphous iron nitride matrix. PMID:28772577

  12. The Effect of Sputtering Parameters and Doping of Copper on Surface Free Energy and Magnetic Properties of Iron and Iron Nitride Nano Thin Films on Polymer Substrate.

    PubMed

    Khan, Waheed; Wang, Qun; Jin, Xin; Feng, Tangfeng

    2017-02-22

    The objective of this study was to deposit thin films on PET polymer substrate and examine the functional properties systematically. Their properties have been studied as a function of the N₂-Ar flow rates, deposition time span and Cu doping. Iron nitride film deposited on both sides exhibits ferromagnetic phases, γ'-Fe₄N and ε-Fe₃N co-existed, shows negligible magnetic anisotropy. Other samples show the evolution of N-rich (FeN, Fe₂N) and N-poor (Fe16N₂, Fe₃N, Fe₄N) phases under different deposition time conditions. XPS analysis and free energy calculations confirmed that co-sputtered Fe-Cu thin films are more stable than layer deposited counterparts. From VSM results it is evident that the dominant phase, changes steadily from the ferromagnetic α-Fe (N) to the paramagnetic ξ-Fe₂N with the increase of nitrogen flow rates and the ordering of the nitrogen atoms. Binding energy increases steadily from 733 eV to 740 eV with the increasing thickness of thin films from 74 nm to 94 nm. It was observed that surface energy decreases as the contact angle of glycol increases and changes the thin film surface from polar to nonpolar. TEM images indicate that cubic γ'-Fe₄N and ε-Fe₃N nano particles oriented in preferred directions dispersed uniformly in the amorphous iron nitride matrix.

  13. Comprehensive dielectric performance of bismuth acceptor doped BaTiO3 based nanocrystal thin film capacitors

    SciTech Connect

    Liu, SY; Zhang, HN; Sviridov, L; Huang, LM; Liu, XH; Samson, J; Akins, D; Li, J; O'Brien, S

    2012-11-07

    We present a novel approach to preparing bismuth acceptor doped barium titanate nanocrystal formulations that can be deposited in conjunction with polymers in order to prepare a thin film nanocomposite dielectric that exhibits desirable capacitor characteristics. Exploring the limits of dielectric function in nanocomposites is an important avenue of materials research, while paying strict attention to the overall device quality, namely permittivity, loss and equivalent series resistance (ESR). Pushing capacitor function to higher frequencies, a desirable goal from an electrical engineering point of view, presents a new set of challenges in terms of minimizing interfacial, space charge and polarization effects within the dielectric. We show the ability to synthesize BaTi0.96Bi0.04O3 or BaTi0.97Bi0.03O3 depending on nominal molar concentrations of bismuth at the onset. The low temperature solvothermal route allows for substitution at the titanium site (strongly supported by Rietveld and Raman analysis). Characterization is performed by XRD with Rietveld refinement, Raman Spectroscopy, SEM and HRTEM. A mechanism is proposed for bismuth acceptor substitution, based on the chemical reaction of the alkoxy-metal precursors involving nucleophilic addition. Dielectric analysis of the nanocrystal thin films is performed by preparing nanocrystal/PVP 2-2 nanocomposites (no annealing) and comparing BaTi0.96Bi0.04O3 and BaTi0.97Bi0.03O3 with undoped BaTiO3. Improvements of up to 25% in capacitance (permittivity) are observed, with lower loss and dramatically improved ESR, all to very high frequency ranges (>10 MHz).

  14. Dielectric, optical and electric studies on nanocrystalline Ba5Nb4O15 thin films deposited by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Anil Kumar, C.; Pamu, D.

    2015-06-01

    We report the fabrication of nanocrystalline Ag/BNO/Pt/Ti/SiO2/Si thin film capacitors by RF magnetron sputtering with different film thicknesses. The effect of Ba5Nb4O15 (BNO) thickness on structural, microstructural, electrical, optical and dielectric properties is investigated for the first time. BNO sputtering target prepared is by mechanochemical synthesis method to eliminate the subordinate phases. As deposited thin films were X-ray amorphous and crystallinity is induced after annealing at 700 °C. Upon annealing, refractive indices of the films enhanced whereas the bandgap is decreased and are in the range of 1.89-2.16 and 4.07-4.24, respectively. With an increase in thickness, the dielectric properties improved substantially, which is described by the representation of a dead layer connected in series with a bulk region of the BNO film. The extracted values of thickness and dielectric constant for the dead layer found to be 15.21 nm and 37.03, correspondingly. The activation energy of the mobile charge carriers obtained using the Arrhenius relation are found to be 0.254, 0.036 and 0.027 eV, for the films with 150, 250 and 450 nm, respectively. The leakage current density found to decrease with thickness and found to be 2.5 × 10-6 A/cm2 at applied voltage of 50 kV/cm. The J-E characteristics of the BNO films show a combined response of grain, grain boundaries and film-electrode interfaces. It is interesting to note that in the negative electric field region, conduction is ohmic in nature whereas in the positive field region BNO films exhibit both ohmic and the space charge-limited current mechanisms. The achieved dielectric, electrical and optical properties make these films suitable for MIC, CMOS and optoelectronic applications.

  15. A K-band Frequency Agile Microstrip Bandpass Filter using a Thin Film HTS/Ferroelectric/dielectric Multilayer Configuration

    NASA Technical Reports Server (NTRS)

    Subramanyam, Guru; VanKeuls, Fred; Miranda, Felix A.

    1998-01-01

    We report on YBa2Cu3O(7-delta) (YBCO) thin film/SrTiO3 (STO) thin film K-band tunable bandpass filters on LaAlO3 (LAO) dielectric substrates. The 2 pole filter has a center frequency of 19 GHz and a 4% bandwidth. Tunability is achieved through the non-linear dc electric field dependence of the relative dielectric constant of STO(epsilon(sub rSTO). A large tunability ((Delta)f/f(sub 0) = (f(sub Vmax) - f(sub 0)/f(sub 0), where f(sub 0) is the center frequency of the filter at no bias and f(sub Vmax) is the center frequency of the filter at the maximum applied bias) of greater than 10% was obtained in YBCO/STO/LAO microstrip bandpass filters operating below 77 K. A center frequency shift of 2.3 GHz (i.e., a tunability factor of approximately 15%) was obtained at a 400 V bipolar dc bias, and 30 K, with minimal degradation in the insertion loss of the filter. This paper addresses design, fabrication and testing of tunable filters based on STO ferroelectric thin films. The performance of the YBCO/STO/LAO filters is compared to that of gold/STO/LAO counterparts.

  16. Enhanced dielectric and piezoelectric responses in Zn1-xMgxO thin films near the phase separation boundary

    DOE PAGES

    Kang, Xiaoyu; Shetty, Smitha; Garten, Lauren; ...

    2017-01-23

    Dielectric and piezoelectric properties for Zn1-xMgxO (ZMO) thin films are reported as a function of MgO composition up to and including the phase separation region. Zn1-xMgxO (0.25 ≤ x ≤ 0.5) thin films with c-axis textures were deposited by pulsed laser deposition on platinized sapphire substrates. The films were phase pure wurtzite for MgO concentrations up to 40%; above that limit, a second phase with rocksalt structure evolves with strong {100} texture. With increasing MgO concentration, the out-of-plane (d33,f) and in-plane (e31,f) piezoelectric coefficients increase by 360% and 290%, respectively. The increase in piezoelectric coefficients is accompanied by a 35%more » increase in relative permittivity. Loss tangent values fall monotonically with increasing MgO concentration, reaching a minimum of 0.001 for x ≥ 0.30, at which point the band gap is reported to be 4 eV. As a result, the enhanced piezoelectric response, the large band gap, and the low dielectric loss make Zn1-xMgxO an interesting candidate for thin film piezoelectric devices, and demonstrate that compositional phase transformations provide opportunities for property engineering.« less

  17. Enhanced dielectric and piezoelectric responses in Zn1-xMgxO thin films near the phase separation boundary

    NASA Astrophysics Data System (ADS)

    Kang, Xiaoyu; Shetty, Smitha; Garten, Lauren; Ihlefeld, Jon F.; Trolier-McKinstry, Susan; Maria, Jon-Paul

    2017-01-01

    Dielectric and piezoelectric properties for Zn1-xMgxO (ZMO) thin films are reported as a function of MgO composition up to and including the phase separation region. Zn1-xMgxO (0.25 ≤ x ≤ 0.5) thin films with c-axis textures were deposited by pulsed laser deposition on platinized sapphire substrates. The films were phase pure wurtzite for MgO concentrations up to 40%; above that limit, a second phase with rocksalt structure evolves with strong {100} texture. With increasing MgO concentration, the out-of-plane (d33,f) and in-plane (e31,f) piezoelectric coefficients increase by 360% and 290%, respectively. The increase in piezoelectric coefficients is accompanied by a 35% increase in relative permittivity. Loss tangent values fall monotonically with increasing MgO concentration, reaching a minimum of 0.001 for x ≥ 0.30, at which point the band gap is reported to be 4 eV. The enhanced piezoelectric response, the large band gap, and the low dielectric loss make Zn1-xMgxO an interesting candidate for thin film piezoelectric devices, and demonstrate that compositional phase transformations provide opportunities for property engineering.

  18. Study of Hf-Ti-O Thin Film as High- k Gate Dielectric and Application for ETSOI MOSFETs

    NASA Astrophysics Data System (ADS)

    Chen, Xiaoqiang; Zhao, Hongbin; Xiong, Yuhua; Wei, Feng; Du, Jun; Tang, Zhaoyun; Tang, Bo; Yan, Jiang

    2016-08-01

    This work focused on the metal-oxide-semiconductor (MOS) capacitor and extremely thin silicon-on-insulator (ETSOI) p-type MOS field-effect transistor ( pMOSFET) with laminated hafnium and titanium oxide (Hf-Ti-O) thin films as gate dielectric. The electrical behavior of the MOS capacitor shows that the capacitor with Hf-Ti-O gate dielectric has high performance with low equivalent oxide thickness (EOT, ~0.77 nm), small hysteresis (Δ V fb, ~4 mV), and gate current density of 0.33 A/cm2 at V g = V fb - 1 V. The dominant conduction mechanism of the Hf-Ti-O thin film (25°C to 125°C) was Schottky emission at lower gate voltage (-0.8 V to -0.2 V) and Fowler-Nordheim (F-N) tunneling at higher gate voltage (<-0.8 V). An ETSOI pMOSFET with 25 nm gate length ( L g) also exhibited good electrical properties with switch ratio of 3.2 × 104, appropriate threshold voltage of -0.16 V, maximum transconductance ( G max) of 2.63 mS, drain-induced barrier lowering of 53 mV/V, and subthreshold swing of 65 mV/dec.

  19. In-situ observation of self-cleansing phenomena during ultra-high vacuum anneal of transition metal nitride thin films: Prospects for non-destructive photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Greczynski, G.; Hultman, L.

    2016-11-01

    Self-cleansing of transition metal nitrides is discovered to take place during ultra-high vacuum annealing of TiN, NbN, and VN thin films. Native oxide layers from air exposure disappear after isothermal anneal at 1000 °C. Also, for TiN, the Ti 2p and N 1s X-ray photoelectron spectra (XPS) recorded after the anneal are identical to those obtained from in-situ grown and analyzed epitaxial TiN(001). These unexpected effects are explained by oxide decomposition in combination with N-replenishing of the nitride during recrystallization. The finding opens up new possibilities for true bonding assignments through non-destructive XPS analyses, thus avoiding artefacts from Ar etching.

  20. Charge trapping/de-trapping in nitrided SiO2 dielectrics and its influence on device reliability

    NASA Astrophysics Data System (ADS)

    Kambour, Kenneth; Hjalmarson, Harold; Nguyen, Duc; Kouhestani, Camron; Devine, Roderick

    2012-02-01

    Field effect devices with insulator gate dielectrics are excellent test vehicles to probe the physics of defects and charge trapping in the insulator/ semiconductor structure. p-channel field effect device reliability under negative bias stressing has been identified to originate from at least two terms: a) charged defect generation at the Si substrate/SiOxNy interface and b) charge trapping at neutral defect pre-cursors in the ``bulk'' of the SiOxNy beyond the interface. Measurements of transistor characteristics enable extraction of the two terms. We report the results of such measurements and demonstrate that short time effects are associated primarily with electric field assisted tunneling of holes from the inversion layer to neutral traps. This is confirmed by bias stressing measurements at different frequencies in the range 1 Hz to 2 MHz. First principles modeling of the tunneling/trapping phenomena is presented. K.Kambour worked under contract FA9453-08-C-0245 with the Air Force Research Laboratory/RVSE. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  1. The electron-phonon relaxation time in thin superconducting titanium nitride films

    SciTech Connect

    Kardakova, A.; Finkel, M.; Kovalyuk, V.; An, P.; Morozov, D.; Dunscombe, C.; Mauskopf, P.; Tarkhov, M.; Klapwijk, T. M.; Goltsman, G.

    2013-12-16

    We report on the direct measurement of the electron-phonon relaxation time, τ{sub eph}, in disordered TiN films. Measured values of τ{sub eph} are from 5.5 ns to 88 ns in the 4.2 to 1.7 K temperature range and consistent with a T{sup −3} temperature dependence. The electronic density of states at the Fermi level N{sub 0} is estimated from measured material parameters. The presented results confirm that thin TiN films are promising candidate-materials for ultrasensitive superconducting detectors.

  2. Structural and dielectric studies of Co doped MgTiO3 thin films fabricated by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Kumar, T. Santhosh; Gogoi, P.; Thota, S.; Pamu, D.

    2014-06-01

    We report the structural, dielectric and leakage current properties of Co doped MgTiO3 thin films deposited on platinized silicon (Pt/TiO2/SiO2/Si) substrates by RF magnetron sputtering. The role of oxygen mixing percentage (OMP) on the growth, morphology, electrical and dielectric properties of the thin films has been investigated. A preferred orientation of grains along (110) direction has been observed with increasing the OMP. Such evolution of the textured growth is explained on the basis of the orientation factor analysis followed the Lotgering model. (Mg1-xCox)TiO3 (x = 0.05) thin films exhibits a maximum relative dielectric permittivity of ɛr = 12.20 and low loss (tan δ ˜ 1.2 × 10-3) over a wide range of frequencies for 75% OMP. The role of electric field frequency (f) and OMP on the ac-conductivity of (Mg0.95Co0.05)TiO3 have been studied. A progressive increase in the activation energy (Ea) and relative permittivity ɛr values have been noticed up to 75% of OMP, beyond which the properties starts deteriorate. The I-V characteristics reveals that the leakage current density decreases from 9.93 × 10-9 to 1.14 × 10-9 A/cm2 for OMP 0% to 75%, respectively for an electric field strength of 250 kV/cm. Our experimental results reveal up to that OMP ≥ 50% the leakage current mechanism is driven by the ohmic conduction, below which it is dominated by the schottky emission.

  3. Synthesis of aluminium indium nitride (AlInN) thin films by stacked elemental layers method

    NASA Astrophysics Data System (ADS)

    Afzal, Naveed; Devarajan, Mutharasu; Ibrahim, Kamarulazizi

    2014-07-01

    AlInN thin films were synthesized on Si substrates by using stacked elemental layers (SEL) technique. Three stacking sequence Al/InN, Al/InN/Al/InN and Al/InN/Al/InN/Al/InN were prepared on Si (1 0 0) substrates by reactive RF sputtering of In target in Ar-N2 and DC sputtering of Al target in Ar atmosphere at room temperature. Annealing of the deposited stacks was carried out at 400 °C for 6 h in a three zone tube furnace. Structural properties of the annealed films were investigated using X-ray diffraction (XRD) whereas the surface analysis of the films was carried out using field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). XRD results show the formation of wurtzite AlInN thin films which become more obvious with increasing the stacked layers. FESEM analysis reveals drops-like polycrystalline films structure with randomly oriented grains whereas the AFM results show a decrease in the surface roughness with increasing stacking sequence. The formation of more prominent AlInN films with increase of stacking layers is attributed to a uniform interaction among the top and bottom Al and InN multilayers as a result of the annealing.

  4. Phase and disorder investigations in boron nitride thin films grown by PECVD

    SciTech Connect

    Depero, L.E.; Sangaletti, L.; Schaffnit, C.; Rossi, F.; Gibson, P.N.

    1996-12-31

    Based on X-ray diffraction and infrared spectroscopy measurements, BN thin films grown by PECVD on silicon substrates have been studied with the aim of identifying the thin film phase. In a set of samples, while the infrared spectra showed characteristic bands of the hexagonal phase, X-ray diffraction patterns only displayed reflections belonging to the cubic BN phase. Therefore, structural models have been developed to explain the apparent inconsistency between the two sets of experimental data. In particular, static disorder effects--which have been introduced in the model starting from the sp{sup 2} hybridization of the ordered hexagonal phase, as suggested by the infra-red spectroscopy results--allowed a consistent interpretation of the X-ray diffraction patterns. For another set of samples, which also showed a characteristic hexagonal signal in the IR data, the XRD pattern could not be indexed with any of the BN phases. In this case, the presence of molecular and ionic phases, associated with impurities, was considered in structural modeling studies.

  5. A Novel K-Band Tunable Microstrip Bandpass Filter Using a Thin Film HTS/Ferroelectric/ Dielectric Configuration

    NASA Technical Reports Server (NTRS)

    Subramanyam, G.; VanKeuls, F.; Miranda, F. A.

    1998-01-01

    We report on YBCO/strontium titanate (STO) thin film K-band tunable bandpass filters on lanthanum aluminate substrates. The 2 pole filters were designed for a center frequency of 19 GHz and 4% bandwidth. Tunability is achieved through the non-linear dc electric field dependence of the relative dielectric constant of STO (epsilon-rSTO). Center frequency shifts greater than 2 GHz were obtained at a 400V bipolar dc bias at temperatures below 77K, with minimum degradation in the insertion loss of the filters.

  6. Impact of forming gas annealing on the dielectric properties of SrBi2Ta2O9 thin films prepared by metalorganic decomposition

    NASA Astrophysics Data System (ADS)

    Wang, Dong-Sheng

    2012-10-01

    SrBi2Ta2O9 (SBT) thin films were prepared on Pt/TiO2/SiO2/Si substrates by metalorganic decomposition method. The dielectric properties of SBT films strongly depend on annealing conditions and annealing time. Compared with films not annealed in forming gas, the relative dielectric constant and the dissipation factor for SBT films annealed at 400 °C decrease by 23.4% and 30.6%, respectively. It implies that the dominant dielectric loss mechanism is related to the degradation of films. Forming gas ambient may have played an important role in the increase of oxygen vacancies in SBT thin films and the degradation of dielectric properties.

  7. Microwave dielectric and optical properties of amorphous and crystalline Ba0.5Sr0.5TiO3 thin films

    NASA Astrophysics Data System (ADS)

    Goud, J. Pundareekam; Joseph, Andrews; Ramakanth, S.; Naidu, Kuna Lakshun; Raju, K. C. James

    2016-05-01

    The thin films of composition Ba0.5Sr0.5TiO3 (BST5) were deposited by Pulsed Laser Deposition technique on amorphous fused silica substrates at room temperature (RT) and at 700°C. The film deposited at RT is amorphous while the other crystallized in cubic structure. The refractive index (n) and optical band gap (Eg) extracted from transmission spectra in the 190 -2500 nm range. Microwave dielectric properties were investigated using the Split Post Dielectric Resonators (SPDR) technique at spot frequencies of 10GHz and 20GHz. The experimental results show that thin films deposited at high temperature (700°C) shows very high dielectric constant for both 10GHz and 20 GHz. These high dielectric constant films can be used in a wide range of applications such as capacitors, non-volatile high speed random access memories, and electro-optic devices.

  8. Improved Dielectric Properties of Heterostructured Ba2.5Sr0.5TiO3 Thin Film Composites for Microwave Dielectric Devices

    NASA Technical Reports Server (NTRS)

    Jain, M.; Majumder, S. B.; Katiyar, R. S.; Bhalla, A. S.; Agrawal, D. C.; Kulkarni, V. N.; VanKeuls, F. W.; Miranda, F. A.; Romanofsky, R. R.; Mueller, C. H.; Fernandez, F.

    2002-01-01

    In the present work we have deposited MgO and Ba(sub 0.5)Sr(sub 0.5)TiO(sub 3)(BST50) thin layers in different sequences to make MgO:BST50 hetero-structured thin films. These films were characterized by X-ray diffraction and Rutherford backscattering technique and found to be highly (100) textured. The figure of merit {(C(sub0)-C(sub v)/(C(sub0-tandelta)} of the hetero-structured films was found to be higher as compared to pure BST50 films measured at 1 MHz frequency with electric field of 25.3 kV/cm. These films were used to make eight element coupled micro-strip phase shifter and characterized in a frequency range of 13-15 GHz. The high frequency figure of merit (kappa factor, defined as the ratio of degree of phase shift per dB loss) measured at around 14 GHz with electric field of 333 kV/cm has been markedly improved (around 64.28 deg/dB for hetero-structured film as compared to 24.65 deg /dB for pure film). Improvement in dielectric properties in a wide frequency range in the MgO:BST are believed to be due to the higher densification of the hetero-structured films.

  9. Aluminum nitride thin film based acoustic wave sensors for biosensing applications

    NASA Astrophysics Data System (ADS)

    Xu, Jianzeng

    In recent years, SAW devices have drawn enormous interest from the analytical assay and sensing business, especially in the biosensing area where highly sensitive, cost efficient and miniaturized sensors are in urgent needs. This dissertation focuses on the development of AIN thin film based SAW devices suitable for biosensing applications. AIN thin films have been synthesized on different orientations of sapphire substrates by a plasma source molecular beam epitaxy system. Surface and structural characterization techniques have been applied to investigate the film quality and the results show that high quality c-plane AIN was epitaxially grown on both c-plane and a-plane sapphire substrates. Complete process flows have been developed for the fabrication of SAW delay line and resonator devices. Important electrical parameters such as the insertion loss, bandwidth, and impedance have been measured to assist the design optimization and derivation the phase velocity, electromechanical coupling coefficient, and temperature coefficient of frequency. On both c-plane and a-plane sapphire substrates, the SAW phase velocities (˜5700 m/s) and electromechanical coupling coefficients (˜0.3%) have been thoroughly mapped out with respect to the propagation direction and film thickness to wavelength ratio. The data are of practical importance for designing AIN-based SAW devices. A higher velocity (>6000 m/s) shear horizontal SAW mode has been discovered only at isolated propagating directions. This mode is especially suitable for aqueous biosensing due to its weak energy coupling to liquid. Much stronger response of the SH-SAW mode has been detected on the c-plane AIN on a-plane sapphire structure than on the c-plane AIN on c-plane sapphire structure, which could be attributed to large anisotropy in a-plane sapphire substrate. Linear frequency-temperature relationship has also been observed for both modes. We further quantify the mass sensitivity of the SAW and SH-SAW by

  10. Reactive magnetron cosputtering of hard and conductive ternary nitride thin films: Ti-Zr-N and Ti-Ta-N

    SciTech Connect

    Abadias, G.; Koutsokeras, L. E.; Dub, S. N.; Tolmachova, G. N.; Debelle, A.; Sauvage, T.; Villechaise, P.

    2010-07-15

    Ternary transition metal nitride thin films, with thickness up to 300 nm, were deposited by dc reactive magnetron cosputtering in Ar-N{sub 2} plasma discharges at 300 deg. C on Si substrates. Two systems were comparatively studied, Ti-Zr-N and Ti-Ta-N, as representative of isostructural and nonisostructural prototypes, with the aim of characterizing their structural, mechanical, and electrical properties. While phase-separated TiN-ZrN and TiN-TaN are the bulk equilibrium states, Ti{sub 1-x}Zr{sub x}N and Ti{sub 1-y}Ta{sub y}N solid solutions with the Na-Cl (B1-type) structure could be stabilized in a large compositional range (up to x=1 and y=0.75, respectively). Substituting Ti atoms by either Zr or Ta atoms led to significant changes in film texture, microstructure, grain size, and surface morphology, as evidenced by x-ray diffraction, x-ray reflectivity, and scanning electron and atomic force microscopies. The ternary Ti{sub 1-y}Ta{sub y}N films exhibited superior mechanical properties to Ti{sub 1-x}Zr{sub x}N films as well as binary compounds, with hardness as high as 42 GPa for y=0.69. All films were metallic, the lowest electrical resistivity {rho}{approx}65 {mu}{Omega} cm being obtained for pure ZrN, while for Ti{sub 1-y}Ta{sub y}N films a minimum was observed at y{approx}0.3. The evolution of the different film properties is discussed based on microstructrural investigations.

  11. Low-temperature ({<=}200 Degree-Sign C) plasma enhanced atomic layer deposition of dense titanium nitride thin films

    SciTech Connect

    Samal, Nigamananda; Du Hui; Luberoff, Russell; Chetry, Krishna; Bubber, Randhir; Hayes, Alan; Devasahayam, Adrian

    2013-01-15

    Titanium nitride (TiN) has been widely used in the semiconductor industry for its diffusion barrier and seed layer properties. However, it has seen limited adoption in other industries in which low temperature (<200 Degree-Sign C) deposition is a requirement. Examples of applications which require low temperature deposition are seed layers for magnetic materials in the data storage (DS) industry and seed and diffusion barrier layers for through-silicon-vias (TSV) in the MEMS industry. This paper describes a low temperature TiN process with appropriate electrical, chemical, and structural properties based on plasma enhanced atomic layer deposition method that is suitable for the DS and MEMS industries. It uses tetrakis-(dimethylamino)-titanium as an organometallic precursor and hydrogen (H{sub 2}) as co-reactant. This process was developed in a Veeco NEXUS Trade-Mark-Sign chemical vapor deposition tool. The tool uses a substrate rf-biased configuration with a grounded gas shower head. In this paper, the complimentary and self-limiting character of this process is demonstrated. The effects of key processing parameters including temperature, pulse time, and plasma power are investigated in terms of growth rate, stress, crystal morphology, chemical, electrical, and optical properties. Stoichiometric thin films with growth rates of 0.4-0.5 A/cycle were achieved. Low electrical resistivity (<300 {mu}{Omega} cm), high mass density (>4 g/cm{sup 3}), low stress (<250 MPa), and >85% step coverage for aspect ratio of 10:1 were realized. Wet chemical etch data show robust chemical stability of the film. The properties of the film have been optimized to satisfy industrial viability as a Ruthenium (Ru) preseed liner in potential data storage and TSV applications.

  12. Correlation between iron self-diffusion and thermal stability in doped iron nitride thin films

    NASA Astrophysics Data System (ADS)

    Tayal, Akhil; Gupta, Mukul; Kumar, D.; Reddy, V. R.; Gupta, Ajay; Amir, S. M.; Korelis, Panagiotis; Stahn, Jochen

    2014-12-01

    Nanocrystalline Fe-X-N thin films (with doping X = 0, 3.1 at. % Al, 1.6 at. % Zr), were deposited using reactive ion beam sputtering. Magnetization study reveals that the deposited films exhibit a perpendicular magnetic anisotropy. Thermal stability of the films was investigated systematically and it was observed that the structural and the magnetic stability gets significantly enhanced with Al doping, whereas Zr doping has only a marginal effect. Fe self-diffusion, obtained using polarized neutron reflectivity, shows a suppression with both additives. A correlation between the thermal stability and the diffusion process gives a direct evidence that the enhancement in the thermal stability is primarily diffusion controlled. A combined picture of diffusion, structural, and magnetic stability has been drawn to understand the obtained results.

  13. Growth kinetics and characterizations of gallium nitride thin films by remote PECVD

    NASA Technical Reports Server (NTRS)

    Choi, S. W.; Bachmann, K. J.; Lucovsky, G.

    1993-01-01

    Thin films of GaN have been deposited at relatively low growth temperatures by remote plasma-enhanced chemical-vapor deposition (RPECVD), using a plasma excited NH3, and trimethylgallium (TMG), injected downstream from the plasma. The activation energy for GaN growth has been tentatively assigned to the dissociation of NH groups as the primary N-atom precursors in the surface reaction with adsorbed TMG, or TMG fragments. At high He flow rates, an abrupt increase in the growth rate is observed and corresponds to a change in the reaction mechanism attributed to the formation of atomic N. XRD reveals an increased tendency to ordered growth in the (0001) direction with increasing growth temperature, He flow rate, and RF plasma power. IR spectra show the fundamental lattice mode of GaN at 530 cm without evidence for vibrational modes of hydrocarbon groups.

  14. Carbon Ion Irradiation Effects on Pulsed Laser Deposited Titanium Nitride Thin Films

    NASA Astrophysics Data System (ADS)

    Mahmood, Khaliq; Bashir, Shazia; Akram, Mahreen; Hayat, Asma; Faizan-Ul-Haq; Saadat, Shahzad

    2015-02-01

    Pulse laser deposited thin films of TiN are irradiated by 1 MeV carbon (C+) ions beam for various doses ranging 0.4 to 2.8 × 1014 ions/cm2. Atomic force microscopy (AFM) analysis reveals the formation of hillocks like structures after ion irradiation. X-ray diffraction (XRD) investigations show that the film crystallinity increases for lower doses ranging from 0.4 to 1.2 × 1014 ions/cm2 and decreases for higher doses (2 to 2.8 × 1014 ions/cm2) of ions. No new bands are identified from Raman spectroscopy. However, a noticeable change in microhardness has been observed. The hillock densities as well as hardness are strongly dependent upon ion dose.

  15. Radiofrequency characteristics of ionized sputtered tantalum nitride thin-film resistor in CMOS device

    NASA Astrophysics Data System (ADS)

    Sul, Woo Suk; Kwon, Soon Hyeong; Choi, Eunmi; Cui, Yinhua; Lee, Kang Won; Shim, Ho Jae; Gao, Yuan; Hahn, Sang June; Pyo, Sung Gyu

    2017-05-01

    We report the analysis of the radiofrequency (RF) characteristics according to the size, area, and shape of TaN thin-film resistor (TFR) layers. As the TFR size increased, its characteristics were degraded with increasing frequency owing to the increased capacitive parasitic components. As the frequency increased from 1 MHz to 10 GHz, the effective resistance decreased by approximately 12.5%, 16.4%, and 37.8% when the resistor widths and lengths were 0.5 × 20, 1 × 40, and 2 × 80 μm, respectively. To optimize the performance of the high-frequency TFR, ensuring RF isolation via sufficient separation from the silicon substrates was crucial. To realize this RF isolation, methods for minimizing the effect of lossy Si substrates by using TFRs with a smaller area or by forming a patterned ground shield should be introduced. [Figure not available: see fulltext.

  16. Growth kinetics and characterizations of gallium nitride thin films by remote PECVD

    NASA Technical Reports Server (NTRS)

    Choi, S. W.; Bachmann, K. J.; Lucovsky, G.

    1993-01-01

    Thin films of GaN have been deposited at relatively low growth temperatures by remote plasma-enhanced chemical-vapor deposition (RPECVD), using a plasma excited NH3, and trimethylgallium (TMG), injected downstream from the plasma. The activation energy for GaN growth has been tentatively assigned to the dissociation of NH groups as the primary N-atom precursors in the surface reaction with adsorbed TMG, or TMG fragments. At high He flow rates, an abrupt increase in the growth rate is observed and corresponds to a change in the reaction mechanism attributed to the formation of atomic N. XRD reveals an increased tendency to ordered growth in the (0001) direction with increasing growth temperature, He flow rate, and RF plasma power. IR spectra show the fundamental lattice mode of GaN at 530 cm without evidence for vibrational modes of hydrocarbon groups.

  17. Correlation between iron self-diffusion and thermal stability in doped iron nitride thin films

    SciTech Connect

    Tayal, Akhil; Gupta, Mukul E-mail: dr.mukul.gupta@gmail.com; Kumar, D.; Reddy, V. R.; Gupta, Ajay; Amir, S. M.; Korelis, Panagiotis; Stahn, Jochen

    2014-12-14

    Nanocrystalline Fe-X-N thin films (with doping X = 0, 3.1 at. % Al, 1.6 at. % Zr), were deposited using reactive ion beam sputtering. Magnetization study reveals that the deposited films exhibit a perpendicular magnetic anisotropy. Thermal stability of the films was investigated systematically and it was observed that the structural and the magnetic stability gets significantly enhanced with Al doping, whereas Zr doping has only a marginal effect. Fe self-diffusion, obtained using polarized neutron reflectivity, shows a suppression with both additives. A correlation between the thermal stability and the diffusion process gives a direct evidence that the enhancement in the thermal stability is primarily diffusion controlled. A combined picture of diffusion, structural, and magnetic stability has been drawn to understand the obtained results.

  18. Interface and stability analysis of Tantalum- and Titanium nitride thin films onto Lithiumniobate

    NASA Astrophysics Data System (ADS)

    Vogel, U.; Oswald, S.; Eckert, J.

    2017-12-01

    Modern surface-acoustic-wave (SAW) devices are characterized by their trend to higher frequencies, power densities and new applications. For this, a shrinking of the dimensions is necessary resulting in an increased power density and temperature within the metallization. To reduce the emerging damaging effects (acustomigration, diffusion etc.) additional barrier layers between substrates and electrodes are necessary, especially for high temperature applications. In this context, we present results of detailed chemical interface analysis of sputtered TaN and TiN thin films as potential barrier layers onto SAW-substrate material (LiNbO3) with respect to their temporal (up to 8 h) and thermal stability up to 600 °C in vacuum. We report good stability of both systems. The main technique for analysis was non-destructive and surface sensitive angle-resolved X-ray photoelectron spectroscopy (AR-XPS).

  19. Development and evaluation of gallium nitride-based thin films for x-ray dosimetry.

    PubMed

    Hofstetter, Markus; Howgate, John; Sharp, Ian D; Stutzmann, Martin; Thalhammer, Stefan

    2011-06-07

    X-ray radiation plays an important role in medical procedures ranging from diagnostics to therapeutics. Due to the harm such ionizing radiation can cause, it has become common practice to closely monitor the dosages received by patients. To this end, precise online dosimeters have been developed with the dual objectives of monitoring radiation in the region of interest and improving therapeutic methods. In this work, we evaluate GaN thin film high electron mobility heterostructures with sub-mm(2) detection areas as x-ray radiation detectors. Devices were tested using 40-300 kV Bremsstrahlung x-ray sources. We find that the photoconductive device response exhibits a large gain, is almost independent of the angle of irradiation, and is constant to within 2% of the signal throughout this medical diagnostic x-ray range, indicating that these sensors do not require recalibration for geometry or energy. Furthermore, the devices show a high sensitivity to x-ray intensity and can measure in the air kerma rate (free-in-air) range of 1 µGy s(-1) to 10 mGy s(-1) with a signal stability of ±1% and a linear total dose response over time. Medical conditions were simulated by measurements of device responses to irradiation through human torso phantoms. Direct x-ray imaging is demonstrated using the index finger and wrist sections of a human phantom. The results presented here indicate that GaN-based thin film devices exhibit a wide range of properties, which make them promising candidates for dosimetry applications. In addition, with potential detection volumes smaller than 10(-6) cm(3), they are well suited for high-resolution x-ray imaging. Moreover, with additional engineering steps, these devices can be adapted to potentially provide both in vivo biosensing and x-ray dosimetry.

  20. Flexible SiInZnO thin film transistor with organic/inorganic hybrid gate dielectric processed at 150 °C

    NASA Astrophysics Data System (ADS)

    Choi, J. Y.; Kim, S.; Hwang, B.-U.; Lee, N.-E.; Lee, S. Y.

    2016-12-01

    Silicon indium zinc oxide (SIZO) thin film transistors (TFTs) have been fabricated on a flexible polyimide (PI) substrate by using organic/inorganic hybrid gate dielectrics of poly-4vinyl phenol (PVP) and Al2O3. To improve the mechanical stability, Al2O3 has been used as a buffer layer on the flexible substrate. The Al2O3 layer of hybrid gate dielectrics protected the organic gate dielectric and improved mechanical flexibility. The different surface roughness of the gate dielectrics is investigated. The performance of the device with smooth surface roughness was significantly improved. Finally, the electrical characteristics of the TFTs with hybrid gate dielectrics were measured as well as the promising electrical endurance characteristics at the bending radius of 5 mm.

  1. Modeling the electrode geometry of co-planar capacitors for the microwave dielectric characterization of ceramic thin films

    SciTech Connect

    Veber, A. Fabijan, D.; Kunej, S.

    2013-12-14

    This paper describes the influence of co-planar electrode geometry on the measurement accuracy of microwave dielectric properties of sol-gel-derived Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}-NaTaO{sub 3} thin films. The interdigital, co-planar capacitor configurations were prepared with E-beam lithography. A combination of analytical and numerical modelling was used for the optimization of co-planar, interdigital electrode structures for the thin-film characterization. We observed that the number of fingers, their length, as well as the gap between the fingers of the interdigital electrode structure of the co-planar capacitor have a pronounced influence on the accuracy of measurements.

  2. Al capping layers for nondestructive x-ray photoelectron spectroscopy analyses of transition-metal nitride thin films

    SciTech Connect

    Greczynski, Grzegorz Hultman, Lars; Petrov, Ivan; Greene, J. E.

    2015-09-15

    X-ray photoelectron spectroscopy (XPS) compositional analyses of materials that have been air exposed typically require ion etching in order to remove contaminated surface layers. However, the etching step can lead to changes in sample surface and near-surface compositions due to preferential elemental sputter ejection and forward recoil implantation; this is a particular problem for metal/gas compounds and alloys such as nitrides and oxides. Here, the authors use TiN as a model system and compare XPS analysis results from three sets of polycrystalline TiN/Si(001) films deposited by reactive magnetron sputtering in a separate vacuum chamber. The films are either (1) air-exposed for ≤10 min prior to insertion into the ultrahigh-vacuum (UHV) XPS system; (2) air-exposed and subject to ion etching, using different ion energies and beam incidence angles, in the XPS chamber prior to analysis; or (3) Al-capped in-situ in the deposition system prior to air-exposure and loading into the XPS instrument. The authors show that thin, 1.5–6.0 nm, Al capping layers provide effective barriers to oxidation and contamination of TiN surfaces, thus allowing nondestructive acquisition of high-resolution core-level spectra representative of clean samples, and, hence, correct bonding assignments. The Ti 2p and N 1s satellite features, which are sensitive to ion bombardment, exhibit high intensities comparable to those obtained from single-crystal TiN/MgO(001) films grown and analyzed in-situ in a UHV XPS system and there is no indication of Al/TiN interfacial reactions. XPS-determined N/Ti concentrations acquired from Al/TiN samples agree very well with Rutherford backscattering and elastic recoil analysis results while ion-etched air-exposed samples exhibit strong N loss due to preferential resputtering. The intensities and shapes of the Ti 2p and N 1s core level signals from Al/TiN/Si(001) samples do not change following long-term (up to 70 days) exposure to ambient conditions

  3. Induced Charge Electrokinetics Over ``Controllably Contaminated'' Surfaces: The Effects of Dielectric Thin Films and Surface Chemistry on Slip Velocity

    NASA Astrophysics Data System (ADS)

    Pascall, Andrew; Squires, Todd

    2009-11-01

    Microfluidics has renewed interest in utilizing electrokinetics (EK) for transporting fluids on small scales, and has subjected EK theories and understanding to new challenges. For example, induced-charge electro-osmosis (ICEO), a non-linear EK effect in which an externally applied AC electric field both induces and drives a layer of charged fluid near an electrically conductive surface, could provide an on-chip means to drive high pressures with low voltage [1]. Experimental data on ICEO and related phenomena have shown that the standard theory consistently overpredicts slip velocities by up to a factor of 1000[2]. Here we present experiments in which we controllably ``contaminate'' the metallic surface with a thin dielectric film or Au-thiol self assembled monolayer, and derive a theory for ICEO that incorporates both dielectric effects and surface chemistry, which both act to decrease the slip velocity relative to a `clean' metal. Data for over a thousand combinations of electric field strength and frequency, electrolyte composition, dielectric thickness and surface chemistry show essentially unprecedented quantitative agreement with our theory. [1] Squires & Bazant. J. Fluid Mech. 2004 [2] Bazant, et al. arXiv. 0903.4790

  4. Tb{sub 2}O{sub 3} thin films: An alternative candidate for high-k dielectric applications

    SciTech Connect

    Gray, Nathan W.; Prestgard, Megan C.; Tiwari, Ashutosh

    2014-12-01

    We are reporting the growth and structural, optical, and dielectric properties of Tb{sub 2}O{sub 3}, a relatively unexplored high-k dielectric material. A pulsed-laser deposition technique was used to grow Tb{sub 2}O{sub 3} thin-films on four different substrates: Si(100), SrTiO{sub 3}(100), LaAlO{sub 3}(100), and MgO(100). High-resolution X-ray diffraction and transmission electron microscopy results confirmed that film growth in an oxygen-rich (10{sup −1 }Torr) environment yields nearly single-crystal C-phase films, while a low-oxygen (10{sup −6 }Torr) environment growth results in the formation of monoclinic polycrystalline B-phase films. Optical transmission measurements showed that the bandgap of Tb{sub 2}O{sub 3} is direct in nature with a value of 2.8 eV and 3.4 eV for the cubic and monoclinic phases, respectively. By measuring the capacitance of test devices, quite high dielectric constants of 13.5 and 24.9 were obtained for the B- and C-phase Tb{sub 2}O{sub 3} films, respectively.

  5. Contributions to the dielectric losses of textured SrTiO3 thin films with Pt electrodes

    NASA Astrophysics Data System (ADS)

    Lu, Jiwei; Schmidt, Steffen; Ok, Young-Woo; Keane, Sean P.; Stemmer, Susanne

    2005-09-01

    The factors controlling low-frequency (1 MHz) dielectric losses of textured SrTiO3 thin films deposited by radio-frequency magnetron sputtering on platinized sapphire substrates were investigated. In particular, the influence of film texture, phase transformations, applied bias field, temperature, and annealing atmospheres was studied. Films that were (111) textured showed a phase transformation at ~150 K, whereas films that were predominantly (110) oriented did not exhibit a phase transformation in the measured temperature range (100-300 K). Two major contributions to the dielectric losses were identified: a low-temperature loss increase for the (111) oriented film, which could be suppressed by an applied bias field, and a loss peak at ~250 K (at 1 MHz), which was strongly frequency-dependent and likely associated with a relaxing defect. The low-temperature loss mode was related to the appearance of a phase transformation and contributed to the dielectric losses even at temperatures that were more than 100 K above the phase transformation. In contrast to the leakage properties of the films, which were strongly dependent on annealing atmospheres, annealing under reducing conditions had no significant influence on any of the observed loss modes. Possible origins of the different loss contributions were discussed.

  6. Temperature dependence of reliability characteristics for magnetic tunnel junctions with a thin MgO dielectric film

    NASA Astrophysics Data System (ADS)

    Choi, Chul-Min; Oh, Young-Taek; Kim, Kyung-Jun; Park, Jin-Suk; Sukegawa, Hiroaki; Mitani, Seiji; Kim, Sung-Kyu; Lee, Jeong-Yong; Song, Yun-Heub

    2016-07-01

    Temperature dependence of the reliability characteristics of magnetic tunnel junctions (MTJs) with a thin (∼1 nm thick) MgO dielectric film were investigated by numerical analyses based on the E-model, 1/E-model, and power-law voltage V-model, as well as by measuring time-dependent dielectric breakdown (TDDB) degradation. Although the tunneling process giving rise to TDDB is still under debate, the temperature dependence of TDDB was much weaker using the 1/E model than the E-model or power-law model. The TDDB data measured experimentally in CoFeB/MgO/CoFeB MTJ devices also showed rather weak temperature dependence, in good agreement with the numerical results obtained from the 1/E-model considering the self-heating effect in MTJ devices. Moreover, we confirmed by interval voltage stress tests that some degradation in the MgO dielectric layer occurred. Based on our findings, we suggest that to characterize the reliability of MTJs, combined temperature measurements of TDDB and 1/E-model analyses taking the self-heating effect into account should be performed.

  7. Influence of dielectric substrate modification and deposition temperature on structure and morphology of CuPc thin films: X-ray reflectivity and angle dependent NEXAFS study

    NASA Astrophysics Data System (ADS)

    Sinha, Sumona; Wang, C.-H.; Mukherjee, M.

    2017-09-01

    The performances of organic thin film transistor devices are significantly linked with the structural properties at organic semiconductor/dielectric interface. The changes in internal structure, molecular ordering and morphology of 20 nm thick CuPc thin films have been investigated by modifying surface of the dielectric substrate with various organic buffer layers at different deposition temperatures. CuPc films are prepared on bare and modified SiO2 substrates at three deposition temperatures. Dielectric surface modification and deposition temperature modify the CuPc /dielectric interfaces accordingly and growth of subsequent CuPc layer. The internal structure, ordering and morphology of CuPc film strongly depends on the behavior of the dielectric layers at various temperatures as well as the diffusion of CuPc molecules. The XRR results reveal that the thickness and ordering of periodic part of CuPc film is varied with dielectric substrate modification as well as deposition temperature. The periodicity of CuPc molecules in the film is always obtained in its α-form. In addition, the angle dependent NEXAFS data determine the angle of CuPc molecular orientation in the range 64° to 71° in the range of 40° to 120 °C deposition temperature, independent of surface modification. The results pave the way for the design and realization of CuPc based thin film transistor devices.

  8. Low-dielectric-constant fluorinated diamond-like carbon thin films by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Yi, Jeong Woo

    Fluorinated amorphous carbon (a-C:F) thin films are developed for a low dielectric constant interlayer dielectric material from hexafluorobenze (C 6F6) or 1,1,1,2-tetrafluoroethane (FCH2CF 4) as the source gas and argon as the diluent gas in an asymmetric capacitively coupled rf (radio frequency) plasma reactor and an inductively coupled plasma reactor. Effects of input rf power, fluorination, applied bias voltage and post annealing on the properties of a-C:F films are investigated. For depositing a-C:F films from highly diluted C6F6 (3%) and argon (97%) in the capacitively rf plasma reactor at 150 mTorr, the dielectric constant of the film increases from 2.0 to 2.8 as the rf power is increased from 10 W to 70 W, while the optical energy gap decreases from 2.6 eV to 1.9 eV and the transparency in a ultra-violet range is degraded. At input power of 100 W, the deposited film exhibits high residual stress of 40 MPa and easily peeled off by a Scotch tape test. This is due to high self-bias voltage (-230 V) developed at the substrate holder during deposition. When depositing amorphous carbon films from tetrafluoroethane (TFE) and methane in the capacitively coupled plasma reactor, the incorporation of fluorine in the film is increased with increasing TFE fraction in the feed gas mixture. The dielectric constant of the a-C:F film deposited from pure TFE is as low as 2.3, but the film exhibits poor thermal stability while a-C:H (diamond-like carbon) film deposited from pure methane has a dielectric constant of 3.8 and shows good thermal stability up to 400°C. As the TFE content in the feed is increased, the dielectric constant and the refractive index decrease while the transparency of the film is enhanced significantly. When depositing a-C:F films from C6F6 (4 sccm) and Ar (5 sccm) in the inductively coupled rf plasma reactor, the bias voltage (from a separate 100 KHz source) applied to the substrate holder affects the film properties significantly. As the negative bias

  9. Ultrahigh mobility and efficient charge injection in monolayer organic thin-film transistors on boron nitride

    PubMed Central

    He, Daowei; Qiao, Jingsi; Zhang, Linglong; Wang, Junya; Lan, Tu; Qian, Jun; Li, Yun; Shi, Yi; Chai, Yang; Lan, Wei; Ono, Luis K.; Qi, Yabing; Xu, Jian-Bin; Ji, Wei; Wang, Xinran

    2017-01-01

    Organic thin-film transistors (OTFTs) with high mobility and low contact resistance have been actively pursued as building blocks for low-cost organic electronics. In conventional solution-processed or vacuum-deposited OTFTs, due to interfacial defects and traps, the organic film has to reach a certain thickness for efficient charge transport. Using an ultimate monolayer of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) molecules as an OTFT channel, we demonstrate remarkable electrical characteristics, including intrinsic hole mobility over 30 cm2/Vs, Ohmic contact with 100 Ω · cm resistance, and band-like transport down to 150 K. Compared to conventional OTFTs, the main advantage of a monolayer channel is the direct, nondisruptive contact between the charge transport layer and metal leads, a feature that is vital for achieving low contact resistance and current saturation voltage. On the other hand, bilayer and thicker C8-BTBT OTFTs exhibit strong Schottky contact and much higher contact resistance but can be improved by inserting a doped graphene buffer layer. Our results suggest that highly crystalline molecular monolayers are promising form factors to build high-performance OTFTs and investigate device physics. They also allow us to precisely model how the molecular packing changes the transport and contact properties. PMID:28913429

  10. Ultra-high-Q thin-silicon nitride strip-loaded ring resonators.

    PubMed

    Stefan, L; Bernard, M; Guider, R; Pucker, G; Pavesi, L; Ghulinyan, M

    2015-07-15

    We report on the design, fabrication, and characterization of thin Si3N4 ultra-high-quality (UHQ) factor ring resonators monolithically integrated on a silicon chip. The devices are based on a strip-loaded configuration and operate at both near-infrared (NIR) and third-telecom wavelengths. This approach allows us to use a guiding Si3N4 core that is one order of magnitude thinner than what has been reported in the past for obtaining similar device performances. Our strip-loaded devices benefit from the absence of physically etched lateral boundaries to show minute light scattering and, therefore, reducing significantly scattering-related losses. Consequently, UHQs of 3.7×10(6) in the NIR and high-quality factors of up to 9×10(5) in the C-band were measured for the guiding material thickness of 80 nm and 115 nm, respectively. These first results are subject to further improvements that may allow employing strip-loaded resonators in nonlinear frequency conversion or quantum computing schemes within the desired spectral range provided by the material transparency.

  11. Test results for electron beam charging of flexible insulators and composites. [solar array substrates, honeycomb panels, and thin dielectric films

    NASA Technical Reports Server (NTRS)

    Staskus, J. V.; Berkopec, F. D.

    1979-01-01

    Flexible solar-array substrates, graphite-fiber/epoxy - aluminum honeycomb panels, and thin dielectric films were exposed to monoenergetic electron beams ranging in energy from 2 to 20 keV in the Lewis Research Center's geomagnetic-substorm-environment simulation facility to determine surface potentials, dc currents, and surface discharges. The four solar-array substrate samples consisted of Kapton sheet reinforced with fabrics of woven glass or carbon fibers. They represented different construction techniques that might be used to reduce the charge accumulation on the array back surface. Five honeycomb-panel samples were tested, two of which were representative of Voyager antenna materials and had either conductive or nonconductive painted surfaces. A third sample was of Navstar solar-array substrate material. The other two samples were of materials proposed for use on Intelsat V. All the honeycomb-panel samples had graphite-fiber/epoxy composite face sheets. The thin dielectric films were 2.54-micrometer-thick Mylar and 7.62-micrometer-thick Kapton.

  12. Test results for electron beam charging of flexible insulators and composites. [solar array substrates, honeycomb panels, and thin dielectric films

    NASA Technical Reports Server (NTRS)

    Staskus, J. V.; Berkopec, F. D.

    1979-01-01

    Flexible solar-array substrates, graphite-fiber/epoxy - aluminum honeycomb panels, and thin dielectric films were exposed to monoenergetic electron beams ranging in energy from 2 to 20 keV in the Lewis Research Center's geomagnetic-substorm-environment simulation facility to determine surface potentials, dc currents, and surface discharges. The four solar-array substrate samples consisted of Kapton sheet reinforced with fabrics of woven glass or carbon fibers. They represented different construction techniques that might be used to reduce the charge accumulation on the array back surface. Five honeycomb-panel samples were tested, two of which were representative of Voyager antenna materials and had either conductive or nonconductive painted surfaces. A third sample was of Navstar solar-array substrate material. The other two samples were of materials proposed for use on Intelsat V. All the honeycomb-panel samples had graphite-fiber/epoxy composite face sheets. The thin dielectric films were 2.54-micrometer-thick Mylar and 7.62-micrometer-thick Kapton.

  13. Dielectric characterization of Bi3.25La0.75Ti3O12 thin films

    NASA Astrophysics Data System (ADS)

    Wu, Di; Li, Aidong; Ming, Naiben

    2004-05-01

    Dielectric properties of Pt/Bi3.25La0.75Ti3O12(BLaT)/Pt ferroelectric thin film capacitors were studied as functions of frequency (40-106 Hz) and temperature (30-590 °C). BLaT thin films showed a first-order para-ferroelectric transition around 400 °C. Pt/BLaT/Pt capacitors post-annealed in Ar exhibited broadened transition with larger losses, which was interpreted in terms of increased oxygen vacancies. Via complex impedance spectroscopy study, the conduction activation energy of the space charges was determined to be ˜1.1 eV, close to that of oxygen vacancies in perovskite materials. The impedance characteristics of Pt/BLaT/Pt were compared with those of Pt/SrBi2Ta2O9(SBT)/Pt capacitors. The impact of dielectric characteristics on fatigue resistance of BLaT films was briefly discussed in comparison with SBT films.

  14. Room temperature analysis of dielectric function of ZnO-based thin film on fused quartz substrate

    SciTech Connect

    Kurniawan, Robi; Sutjahja, Inge M.; Winata, Toto; Rusydi, Andrivo; Darma, Yudi

    2015-09-30

    A set of sample consist of pure ZnO and Cu-doped ZnO film were grown on fused-quartz substrates using pulsed laser deposition (PLD) technique. Here, we report room temperature spectroscopic ellipsometry analysis (covering energy range of 0.5 to 6.3 eV) of pure ZnO film and Cu doped ZnO film at 8 in at. %. The thickness of pure ZnO and Cu-doped ZnO film using in this study is about 350 nm. To extract the dielectric function of ZnO thin film, multilayer modeling is performed which takes into account reflections at each interface through Fresnel coefficients. This method based on Drude-Lorentz models that connect with Kramers-Kronig relations. The best fitting of Ψ (amplitude ratio) and Δ (phase difference) taken by SE measurement are obtained reasonably well by mean the universal fitting of three different photon incident angles. The imaginary part of dielectric function (ε{sub 2}) show the broad peak at around 3.3 eV assigned as combination of optical band energy edge with excitonic states. The exitonic states could not be observed clearly in this stage. The evolution of extracted dielectric function is observable by introducing 8% Cu as indicated by decreasing of excitonic intensity. This result indicates the screening of excitonic state. This study will bring us to have a good undestanding for the role of Cu impurities for ZnO thin films.

  15. Epitaxial Growth of MOF Thin Film for Modifying the Dielectric Layer in Organic Field-Effect Transistors.

    PubMed

    Gu, Zhi-Gang; Chen, Shan-Ci; Fu, Wen-Qiang; Zheng, Qingdong; Zhang, Jian

    2017-03-01

    Metal-organic framework (MOF) thin films are important in the application of sensors and devices. However, the application of MOF thin films in organic field effect transistors (OFETs) is still a challenge to date. Here, we first use the MOF thin film prepared by a liquid-phase epitaxial (LPE) approach (also called SURMOFs) to modify the SiO2 dielectric layer in the OFETs. After the semiconductive polymer of PTB7-Th (poly[4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b:4,5-b']dithiophene-co-3-fluorothieno[3,4-b]thiophene-2-carboxylate]) was coated on MOF/SiO2 and two electrodes on the semiconducting film were deposited sequentially, MOF-based OFETs were fabricated successfully. By controlling the LPE cycles of SURMOF HKUST-1 (also named Cu3(BTC)2, BTC = 1,3,5-benzenetricarboxylate), the performance of the HKUST-1/SiO2-based OFETs showed high charge mobility and low threshold voltage. This first report on the application of MOF thin film in OFETs will offer an effective approach for designing a new kind of materials for the OFET application.

  16. Nanoindentation study of niobium nitride thin films on niobium fabricated by reactive pulsed laser deposition

    SciTech Connect

    Mamun, Md Abdullah Al; Farha, Ashraf Hassan; Ufuktepe, Yüksel; Elsayed-Ali, Hani E.; Elmustafa, Abdelmageed A.

    2015-03-01

    Nanomechanical and structural properties of NbNx films deposited on single crystal Nb using pulsed laser deposition for different substrate temperature were previously investigated as a function of film/substrate crystal structure (Mamun et al. (2012) [30]). In this study we focus on the effect of laser fluences and background nitrogen pressure on the nanomechanical and structural properties of NbNx films. The crystal structure and surface morphology of the thin films were tested by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. Using nanoindentation, the investigation of the nanomechanical properties revealed that the hardness of the NbNx films was directly influenced by the laser fluence for low background nitrogen pressure, whereas the nanomechanical hardness showed no apparent correlation with laser fluence at high background nitrogen pressure. The NbNx film hardness measured at 30% film thickness increased from 14.0 ± 1.3 to 18.9 ± 2.4 GPa when the laser fluence was increased from 15 to 25 J/cm2 at 10.7 Pa N2 pressure. X-ray diffraction showed NbNx films with peaks that correspond to δ-NbN cubic and β-Nb2N hexagonal phases in addition to the δ'-NbN hexagonal phase. Finally, increasing the laser fluence resulted in NbNx films with larger grain sizes.

  17. Microstructure and Properties of Ultra-Thin Amorphous Silicon Nitride Protective Coating

    SciTech Connect

    Toney, Michael F

    2003-06-25

    The effect of N content on the structure and properties of rf reactively sputtered a-SiN{sub x} has been studied by Rutherford backscattering spectrometry (RBS), x-ray reflectivity (XRR), ellipsometry, and nano-indentation. The N content in the film increased with the N{sub 2} concentration in the sputtering gas until the Si{sub 3}N{sub 4} stoichiometry was reached. The hardness of a-SiN, increased with density, which in turn increased with the N content. The maximum hardness of 25 GPa and density of 3.2 g/cm{sup 3} were attained at the stoichiometric Si{sub 3}N{sub 4} composition. With the application of protective overcoat for magnetic disks in mind, thin a-SiN{sub x} films were deposited on CoPtCr media to examine their coverage, pinhole density, and wear resistance. According to x-ray photoelectron spectroscopy (XPS), the minimum thickness of a-SiN{sub x} required to protect the CoPtCr alloy from oxidation was 10 {angstrom}, which was 10 {angstrom} thinner than that of the reference a-CN{sub x}. A statistic model showed the lower coverage limit of a-SiN{sub x} can be attributed to its high density, which corresponds to 93% bulk density of Si{sub 3}N{sub 4}. Compared with 45 {angstrom} a-CN{sub x} coated disks, 15 {angstrom} a-SiN{sub x} coated disks had lower pinhole defect density and superior wear resistance.

  18. Designing nanoscale constructs from atomic thin sheets of graphene, boron nitride and gold nanoparticles for advanced material applications

    NASA Astrophysics Data System (ADS)

    Jasuja, Kabeer

    2011-12-01

    Nanoscale materials invite immense interest from diverse scientific disciplines as these provide access to precisely understand the physical world at their most fundamental atomic level. In concert with this aim of enhancing our understanding of the fundamental behavior at nanoscale, this dissertation presents research on three nanomaterials: Gold nanoparticles (GNPs), Graphene and ultra-thin Boron Nitride sheets (UTBNSs). The three-fold goals which drive this research are: incorporating mobility in nanoparticle based single-electron junction constructs, developing effective strategies to functionalize graphene with nano-forms of metal, and exfoliating ultrathin sheets of Boron Nitride. Gold nanoparticle based electronic constructs can achieve a new degree of operational freedom if nanoscale mobility is incorporated in their design. We achieved such a nano-electromechanical construct by incorporating elastic polymer molecules between GNPs to form 2-dimensional (2-D) molecular junctions which show a nanoscale reversible motion on applying macro scale forces. This GNP-polymer assembly works like a molecular spring opening avenues to maneuver nano components and store energy at nano-scale. Graphene is the first isolated nanomaterial that displays single-atom thickness. It exhibits quantum confinement that enables it to possess a unique combination of fascinating electronic, optical, and mechanical properties. Modifying the surface of graphene is extremely significant to enable its incorporation into applications of interest. We demonstrated the ability of chemically modified graphene sheets to act as GNP stabilizing templates in solution, and utilized this to process GNP composites of graphene. We discovered that GNPs synthesized by chemical or microwave reduction stabilize on graphene-oxide sheets to form snow-flake morphologies and bare-surfaces respectively. These hybrid nano constructs were extensively studied to understand the effect and nature of GNPs

  19. Dielectric properties of aluminum silver alloy thin films in optical frequency range

    SciTech Connect

    Yang Guang; Sun Jingbo; Zhou Ji

    2011-06-15

    The dielectric properties of direct current (dc) magnetron sputtering aluminum silver alloy films in optical frequency have been quantitatively studied by variable angle spectroscopic ellipsometry. The structure and surface topography of the alloy films were characterized using scanning probe microscopy and x-ray diffraction. The Drude-Lorentz model was used to simulate the dielectric function of Al-Ag alloy films. Meanwhile, the effective medium theory has been utilized for the treatment of surface roughness. We found that the interband transition around 1.5 eV can be shifted through a variable annealing temperature and a changeable silver percentage of Al-Ag alloys.

  20. Single-pulse perforation of thin transparent dielectrics by femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Ganin, Daniil; Lapshin, Konstantin; Obidin, Alexey; Vartapetov, Sergey

    2017-05-01

    The methods of elongation of the effective interaction area (>100 microns) of single femtosecond pulses with transparent dielectrics when focusing in the bulk of material are given. Principal diagrams of transparent materials perforation with single femtosecond laser pulses are proposed. Capability to form cylindrical holes in the transparent dielectrics as a result of material photodegradation subjected to single femtosecond laser pulses was successfully demonstrated. The diameter of through holes made in the polypropylene 50 microns thick film at the energy of femtosecond laser pulses of 5 µJ was 5 µm.