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Sample records for nitride dielectric thin

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    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 HfO2, 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.

  3. 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.

  4. Nanocrystalline-graphene-tailored hexagonal boron nitride thin films.

    PubMed

    Lee, Kang Hyuck; Shin, Hyeon-Jin; Kumar, Brijesh; Kim, Han Sol; Lee, Jinyeong; Bhatia, Ravi; Kim, Sang-Hyeob; Lee, In-Yeal; Lee, Hyo Sug; Kim, Gil-Ho; Yoo, Ji-Beom; Choi, Jae-Young; Kim, Sang-Woo

    2014-10-20

    Unintentionally formed nanocrystalline graphene (nc-G) can act as a useful seed for the large-area synthesis of a hexagonal boron nitride (h-BN) thin film with an atomically flat surface that is comparable to that of exfoliated single-crystal h-BN. A wafer-scale dielectric h-BN thin film was successfully synthesized on a bare sapphire substrate by assistance of nc-G, which prevented structural deformations in a chemical vapor deposition process. The growth mechanism of this nc-G-tailored h-BN thin film was systematically analyzed. This approach provides a novel method for preparing high-quality two-dimensional materials on a large surface. PMID:25204810

  5. Thin dielectric technology and memory devices

    NASA Astrophysics Data System (ADS)

    King, Ya-Chin

    With advances in technology and scaling, silicon Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) based VLSI circuits have remained dominant in data processing and memory applications. Perpetuated by the demand for high-performance and low-cost integrated circuits, the lateral dimensions of the MOSFETs are being aggressively scaled. This in turn demands scaling of the gate oxide thickness as well. Thin gate oxides present both challenges to the modeling and design device of the classical MOSFET and opportunities to explore new device designs and applications. This study investigates the effect of inversion layer quantization on the capacitance and current characteristics of thin-gate-oxide MOS transistors. In addition, this study explores the possibility of employing thin tunnel oxide for new quasi-nonvolatile memory devices. The performance limitation of a thin dielectric floating gate memory device as well as its potential for dynamic memory applications are discussed. An alternative device structure (i.e. charge-trap based memory cells) is examined by the single charge tunneling model governed by Coulomb Blockade theory. Two methods of forming charge storage nodes embedded in the gate dielectric are investigated. The resulting devices are then characterized. The first proposed device contains a charge trapping layer of silicon rich oxide (SRO) for dynamic/non-volatile memory application. This device has a similar structure as a MONOS device with SRO instead of silicon nitride for charge trapping on top of a very thin tunneling oxide (<2nm). Since it uses charge trapped in the oxide to create threshold voltage shift, the SRO memory cell is a non-destructive-read device. A new process of depositing SRO and high temperature oxide (HTO) in a single furnace step is developed to better top the control oxide thickness and improve data retention. This device achieved write and erase speeds comparable to that of a DRAM cell and longer data retention time than

  6. Polyimide thin-film dielectrics on ferroelectrics

    NASA Technical Reports Server (NTRS)

    Galiardi, R. V.

    1977-01-01

    Conducting layers of multi-layered thin-film ferroelectric device, such as is used in liquid crystal/ferroelectric display, can be electrically isolated using thin-film layer of polyimide. Ease of application and high electrical-breakdown strength allow dependable and economical means of providing dielectric for other thin-film microelectronic devices.

  7. 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. PMID:26348822

  8. 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.

  9. Anisotropic Dielectric Breakdown of Hexagonal Boron Nitride Film

    NASA Astrophysics Data System (ADS)

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

    Hexagonal boron nitride (h-BN) is considered as ideal substrate for 2D material devises. However, the reliability of insulating properties of h-BN itself has not been clarified yet. In this study, the anisotropic dielectric breakdown of h-BN is studied. We have found that the dielectric breakdown in c axis direction using a conductive atomic force microscope proceeded in the layer-by-layer manner. The obtained dielectric field strength was ~12 MV/cm, which is comparable to the conventional SiO2. On the other hand, to estimate the dielectric field strength in a direction perpendicular to c axis, voltage is applied to a relatively thick h-BN (10-60 nm) through Cr/Au electrodes fabricated on the h-BN. We realized that the absorbed water on h-BN significantly affect the IV characters and the breakdown voltage. After the adsorbed water was removed by the heating in vacuum, the dielectric field strength was determined to be ~3 MV/cm, which is the same order as that in c axis direction. This value could be increased when we consider the effect of electric field concentration around the metal electrode. Although the large difference in dielectric filed strength for two directions was initially expected due to the highly-anisotropic layered structure with the van der Waals bonding, it was not the case because the sp2 bonding should be broken for dielectric breakdown regardless of its direction. This research was supported by Grants-in-Aid for Scientific Research on Innovative Areas and for Research Activity Start-up by MEXT, Japan.

  10. 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. PMID:26214048

  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. 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.

  13. Magnetoresistance measurements of superconducting molybdenum nitride thin films

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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 Bc2(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.

  14. 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.

  15. A microfabricated sensor for thin dielectric layers.

    PubMed

    Fierlinger, P; DeVoe, R; Flatt, B; Gratta, G; Green, M; Kolkowitz, S; Leport, F; Montero Diez, M; Neilson, R; O'Sullivan, K; Pocar, A; Wodin, J

    2008-04-01

    We describe a sensor for the measurement of thin dielectric layers capable of operation in a variety of environments. The sensor is obtained by microfabricating a capacitor with interleaved aluminum fingers, exposed to the dielectric to be measured. In particular, the device can measure thin layers of solid frozen from a liquid or gaseous medium. Sensitivity to single atomic layers is achievable in many configurations and, by utilizing fast, high sensitivity capacitance readout in a feedback system onto environmental parameters; coatings of few layers can be dynamically maintained. We discuss the design, readout, and calibration of several versions of the device optimized in different ways. We specifically dwell on the case in which atomically thin solid xenon layers are grown and stabilized, in cryogenic conditions, from a liquid xenon bath. PMID:18447546

  16. Thin film dielectric microstrip kinetic inductance detectors

    NASA Astrophysics Data System (ADS)

    Mazin, Benjamin A.; Sank, Daniel; McHugh, Sean; Lucero, Erik A.; Merrill, Andrew; Gao, Jiansong; Pappas, David; Moore, David; Zmuidzinas, Jonas

    2010-03-01

    Microwave kinetic inductance detectors, or MKIDs, are a type of low temperature detector that exhibit intrinsic frequency domain multiplexing at microwave frequencies. We present the first theory and measurements on a MKID based on a microstrip transmission line resonator. A complete characterization of the dielectric loss and noise properties of these resonators is performed, and agrees well with the derived theory. A competitive noise equivalent power of 5×10-17 W Hz-1/2 at 10 Hz has been demonstrated. The resonators exhibit the highest quality factors known in a microstrip resonator with a deposited thin film dielectric.

  17. 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.

  18. 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.

  19. 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

    2016-01-01

    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

  20. 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

  1. Influence of Si/SiO 2 interface properties on electrical performance and breakdown characteristics of ultrathin stacked oxide/nitride dielectric films

    NASA Astrophysics Data System (ADS)

    Lee, Yi-Mu; Wu, Yider

    2008-05-01

    In this work, the influence of Si/SiO 2 interface properties, interface nitridation and remote-plasma-assisted oxidation (RPAO) thickness (<1 nm), on electrical performance and TDDB characteristics of sub-2 nm stacked oxide/nitride gate dielectrics has been investigated using a constant voltage stress (CVS). It is demonstrated that interfacial plasma nitridation improves the breakdown and electrical characteristics. In the case of PMOSFETs stressed in accumulation, interface nitridation suppresses the hole traps at the Si/SiO 2 interface evidenced by less negative Vt shifts. Interface nitridation also retards hole tunneling between the gate and drain, resulting in reduced off-state drain leakage. In addition, the RPAO thickness of stacked gate dielectrics shows a profound effect in device performance and TDDB reliability. Also, it is demonstrated that TDDB characteristics are improved for both PMOS and NMOS devices with the 0.6 nm-RPAO layer using Weibull analysis. The maximum operating voltage is projected to be improved by 0.3 V difference for a 10-year lifetime. However, physical breakdown mechanism and effective defect radius during stress appear to be independent of RPAO thickness from the observation of the Weibull slopes. A correlation between trap generation and dielectric thickness changes based on the C- V distortion and oxide thinning model is presented to clarify the trapping behavior in the RPAO and bulk nitride layer during CVS stress.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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 SiO2/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.

  3. 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.

  4. 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. PMID:24999923

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

    PubMed Central

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

    2014-01-01

    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/cm2. PMID:25280842

  6. 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). PMID:25280842

  7. 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.

  8. Thin films of aluminum nitride and aluminum gallium nitride for cold cathode applications

    NASA Astrophysics Data System (ADS)

    Sowers, A. T.; Christman, J. A.; Bremser, M. D.; Ward, B. L.; Davis, R. F.; Nemanich, R. J.

    1997-10-01

    Cold cathode structures have been fabricated using AlN and graded AlGaN structures (deposited on n-type 6H-SiC) as the thin film emitting layer. The cathodes consist of an aluminum grid layer separated from the nitride layer by a SiO2 layer and etched to form arrays of either 1, 3, or 5 μm holes through which the emitting nitride surface is exposed. After fabrication, a hydrogen plasma exposure was employed to activate the cathodes. Cathode devices with 5 μm holes displayed emission for up to 30 min before failing. Maximum emission currents ranged from 10-100 nA and required grid voltages ranging from 20-110 V. The grid currents were typically 1 to 104 times the collector currents.

  9. 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.

  10. Dielectric properties of KDP filled porous alumina nanocomposite thin films.

    PubMed

    Boni, O; Berger, S

    2001-12-01

    A new concept of a composite dielectric thin film fabrication is presented. The fabrication process consists of two stages. The first stage is anodizing a thin aluminum film to produce a porous alumina film that contains an array of nanometer sized parallel pores. The second stage is filling the pores with a saturated KDP (KH2PO4) liquid solution due to capillary forces. After drying KDP nanocrystals are formed inside the pores. This process results in a formation of a composite dielectric thin film composed of the alumina pores walls as one dielectric material and the KDP nanocrystals inside the pores as another dielectric material. The dielectric permittivity of this composite film is higher than that of the porous alumina film at all applied frequencies. The dielectric enhancement is more pronounced at low frequencies due to an interface polarization mechanism. This fabrication process enables controlling the size, composition, and microstructure of the composite dielectric film constituents and thus changing its dielectric properties over a wide range of values. PMID:12914085

  11. Model for nitridation of nanoscale SiO{sub 2} thin films in pulsed inductively coupled N{sub 2} plasma

    SciTech Connect

    Rauf, Shahid; Lim, Sangwoo; Ventzek, Peter L.G.

    2005-07-15

    As nitration of SiO{sub 2} gate dielectric can increase the film's dielectric constant and reduce boron penetration into the Si channel during ion implantation, plasma nitridation is of considerable interest for the fabrication of semiconductor devices. A coupled plasma equipment-surface physics model is used in conjunction with an experimental analysis of nitrided SiO{sub 2} thin films to understand the mechanism of SiO{sub 2} plasma nitridation. This investigation is conducted in a pulsed inductively coupled N{sub 2} plasma. Computational results show that N atoms and N{sub 2}{sup +} ions are the primary species in the N{sub 2} plasma that contribute to the nitridation of SiO{sub 2} thin film. N atoms adsorb at the SiO{sub 2} surface and diffuse into the bulk film, and most nitrogen near the surface is due to these adsorbed N atoms. N{sub 2}{sup +} ions, on the other hand, penetrate deeper into the SiO{sub 2} film in an ion-implantation-like manner, and these ions are responsible for the observed tail in the nitrogen concentration profile. Nitrogen concentration in the film can be increased by enhancing the plasma source power or the nitridation time. However, once the dielectric surface starts saturating with nitrogen, further nitrogen adsorption is inhibited and nitridation rate tapers off. As the fluxes of atomic N and N{sub 2}{sup +} ions to the wafer decrease with increasing gas pressure, the nitridation rate decreases with gas pressure. For the range of SiO{sub 2} film thickness examined (13-15 A ), the nitrogen transport and reaction properties in the film are film thickness dependent, probably due to the nonuniform density of the initial SiO{sub 2} thin film or to interfacial stresses.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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 SiO2, (2) plasma-enhanced chemical-vapor deposition (PECVD) SiNx, and (3) a PECVD SiOx/SiNx dual-dielectric. X-ray photoelectron and photoluminescence spectroscopy showed the Vo concentration was dependent on the hydrogen concentration of the underlying dielectric film. IGZO films on SiNx (high Vo) and SiO2 (low Vo) had the highest and lowest conductivity, respectively. A PECVD SiOx/SiNx dual-dielectric layer was effective in suppressing hydrogen diffusion from the nitride layer into the IGZO and resulted in higher resistivity films.

  13. Interfacial properties of germanium nitride dielectric layers in germanium

    NASA Astrophysics Data System (ADS)

    Meiners, L. G.

    The first year's effort on this project has been primarily devoted to the design and construction of a low-pressure chemical vapor deposition system for growth of the germanium nitride layers. The gas manifold layout is shown schematically, as is the reactor assembly, and the vacuum pumping assembly. The generator-cavity system is capable of delivering 0-600 W of microwave power at 2.45 GHz. The power generating section has been constructed from components contained in a portable home microwave oven and the cavity was assembled from easily machinable pieces. The cw magnetron source was mounted directly on a cylindrical microwave cavity. The plasma was contained in an on-axis 20-mm o.d. quartz tube. Design tradeoffs and operating information are discussed.

  14. 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.

  15. 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.

  16. Structure and Properties of Epitaxial Dielectrics on gallium nitride

    NASA Astrophysics Data System (ADS)

    Wheeler, Virginia Danielle

    GaN is recognized as a possible material for metal oxide semiconductor field effect transistors (MOSFETs) used in high temperature, high power and high speed electronic applications. However, high gate leakage and low device breakdown voltages limit their use in these applications. The use of high-kappa dielectrics, which have both a high permittivity (ε) and high band gap energy (Eg), can reduce the leakage current density that adversely affects MOS devices. La2O3 and Sc2O 3 are rare earth oxides with a large Eg (6.18 eV and 6.3 eV respectively) and a relatively high ε (27 and 14.1 respectively), which make them good candidates for enhancing MOSFET performance. Epitaxial growth of oxides is a possible approach to reducing leakage current and Fermi level pinning related to a high density of interface states for dielectrics on compound semiconductors. In this work, La2O3 and Sc2O 3 were characterized structurally and electronically as potential epitaxial gate dielectrics for use in GaN based MOSFETs. GaN surface treatments were examined as a means for additional interface passivation and influencing subsequent oxide formation. Potassium persulfate (K2(SO4)2) and potassium hydroxide (KOH) were explored as a way to achieve improved passivation and desired surface termination for GaN films deposited on sapphire substrates by metal organic chemical vapor deposition (MOCVD). X-ray photoelectron spectroscopy (XPS) showed that KOH left a nitrogen-rich interface, while K2(SO 4)2 left a gallium-rich interface, which provides a way to control surface oxide formation. K2(SO4)2 exhibited a shift in the O1s peak indicating the formation of a gallium-rich GaOx at the surface with decreased carbon contaminants. GaO x acts as a passivating layer prior to dielectric deposition, which resulted in an order of magnitude reduction in leakage current, a reduced hysteresis window, and an overall improvement in device performance. Furthermore, K2(SO4)2 resulted in an additional 0.4 eV of

  17. Infrared optical properties of mixed-phase thin films studied by spectroscopic ellipsometry using boron nitride as an example

    NASA Astrophysics Data System (ADS)

    Schubert, M.; Rheinländer, B.; Franke, E.; Neumann, H.; Tiwald, T. E.; Woollam, J. A.; Hahn, J.; Richter, F.

    1997-11-01

    We present a microstructure-dependent anisotropic infrared-optical dielectric function model for mixed-phase polycrystalline material from which we derive the transverse and longitudinal-optical modes observable in thin films. Infrared ellipsometry over the wavelength range from 700 to 3000 cm-1 is then used to determine the phase and microstructure of polycrystalline and multilayered hexagonal and cubic boron nitride thin films deposited by magnetron sputtering onto (100) silicon. The ellipsometric data depend on the thin-film multilayer structure, the layer-phase composition, and the average orientation of the hexagonal grain c axes. In particular, we demonstrate the existence of spectral shifts of longitudinal optical phonons as a function of microstructure, i.e., the average grain crystallographic orientation within the mixed-phase material.

  18. Stress relaxation in Si-rich silicon nitride thin films

    SciTech Connect

    Habermehl, S.

    1998-05-01

    Si-rich silicon nitride thin films have been deposited by low pressure chemical vapor deposition, at 850{degree}C from mixtures of dichlorosilane and ammonia. The films{close_quote} elastic properties have been studied as a function of film composition. Fourier transform infrared spectroscopy and ellipsometric data indicate that the local atomic strain is a strong function of the calculated volume fraction of Si contained in the films. A relationship is observed that shows the strain to be inversely proportional to the cube root of the Si volume fraction. A model that accounts for distortion in Si{endash}Si{sub x}N{sub 4{minus}x} tetrahedra (x=0{endash}4), upon substitution of silicon for nitrogen in the film is applied to the data. The model is shown to be consistent with measurements of intrinsic film stress across a compositional range from stoichiometric silicon nitride, Si{sub 3}N{sub 4}, to nitrogen-free amorphous silicon, a-Si. {copyright} {ital 1998 American Institute of Physics.}

  19. 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.

  20. 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.

  1. Mechanical properties of sputtered silicon nitride thin films

    NASA Astrophysics Data System (ADS)

    Vila, M.; Cáceres, D.; Prieto, C.

    2003-12-01

    Silicon nitride thin films were prepared by reactive sputtering from different sputtering targets and using a range of Ar/N2 sputtering gas mixtures. The hardness and the Young's modulus of the samples were determined by nanoindentation measurements. Depending on the preparation parameters, the obtained values were in the ranges 8-23 and 100-210 GPa, respectively. Additionally, Fourier-transform infrared spectroscopy, Rutherford backscattering spectroscopy, and x-ray diffraction were used to characterize samples with respect to different types of bonding, atomic concentrations, and structure of the films to explain the variation of mechanical properties. The hardness and Young's modulus were determined as a function of film composition and structure and conditions giving the hardest film were found. Additionally, a model that assumes a series coupling of the elastic components, corresponding to the Si-O and Si-N bonds present in the sample has been proposed to explain the observed variations of hardness and Young's modulus.

  2. Characterization of tantalum nitride thin films synthesized by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Zaman, Anna

    Tantalum Nitride is chemically inert, oxidation resistant and hard. TaN finds its application as a protective coating on steel due to their excellent wear properties. It has become a very promising diffusion barrier material in Cu interconnect technology in microelectronics. TaN has not been analyzed as much as other transition metal nitrides like the TiN system because TaN exhibits various stable and metastable phases. The emergence of these phases and the different physical, chemical and mechanical properties depend on the growth technique and deposition conditions. TaN thin films were deposited using the magnetron PVD system in the SaNEL lab. The aim of this study was to identify the effect of processing parameters like N2/Ar ratio, substrate bias and temperature, on the emergence of the different phases present in TaN thin films and the effect of deposition conditions on the mechanical properties of these films. The phases present in the films, deposited at varying conditions were explored via low angle X-Ray Diffraction (XRD), hardness of the films was measured by Nanoindentation and tribological tests were carried out to measure the frictional and wear behavior. It was observed that at high percentage of Nitrogen (10%-25%) the main phase present was FCC TaN and as the nitrogen content was decreased a mixture of phases was present in these films. The hardness of the films increases as we decrease the Nitrogen content, yielding a film with a hardness of 37.1 GPa at 3% N2 with a substrate bias voltage of -100 V.

  3. Spectroscopic studies of refractory and dielectric thin films

    SciTech Connect

    Truong, C.M.

    1993-01-01

    This work demonstrated the application of the techniques and methodology of surface science to investigate the mechanisms of thin film deposition processes on solid surfaces. The synthesis of boron nitride (BN) thin films was studied using X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). In this model system, diborane (B[sub 2]H[sub 6]), ammonia (NH[sub 3]) and hydrazine (N[sub 2]H[sub 4]) were used as precursors to deposit BN thin films on a clean Ru(0001) surface. The result showed that ammonia reaction with diborane yielded only boron-rich boron nitride overlayers. However, stoichiometric BN films in excess of one monolayer could be produced when hydrazine was substituted for ammonia. The effects of oxygen on boron-rich and stoichiometric boron-nitrogen films were also examined. In the second part of this work, high resolution electron energy loss spectroscopy (HREELS) was used to characterize defect centers in MgO and in lithium-doped MgO thin films. The HREELS results showed that MgO thin films grown on Mo(100) were nearly defect-free at temperatures up to 1100 K. HREELS measurements indicated that annealings to higher temperatures induced F-type defect centers in the MgO films. The formation of [Li[sup +]O[sup [minus

  4. Spotting 2D atomic layers on aluminum nitride thin films.

    PubMed

    Chandrasekar, Hareesh; Bharadwaj B, Krishna; Vaidyuala, Kranthi Kumar; Suran, Swathi; Bhat, Navakanta; Varma, Manoj; Srinivasan Raghavan

    2015-10-23

    Substrates for 2D materials are important for tailoring their fundamental properties and realizing device applications. Aluminum nitride (AIN) films on silicon are promising large-area substrates for such devices in view of their high surface phonon energies and reasonably large dielectric constants. In this paper epitaxial layers of AlN on 2″ Si wafers have been investigated as a necessary first step to realize devices from exfoliated or transferred atomic layers. Significant thickness dependent contrast enhancements are both predicted and observed for monolayers of graphene and MoS2 on AlN films as compared to the conventional SiO2 films on silicon, with calculated contrast values approaching 100% for graphene on AlN as compared to 8% for SiO2 at normal incidences. Quantitative estimates of experimentally measured contrast using reflectance spectroscopy show very good agreement with calculated values. Transistors of monolayer graphene on AlN films are demonstrated, indicating the feasibility of complete device fabrication on the identified layers. PMID:26422387

  5. Spotting 2D atomic layers on aluminum nitride thin films

    NASA Astrophysics Data System (ADS)

    Chandrasekar, Hareesh; Bharadwaj B, Krishna; Vaidyuala, Kranthi Kumar; Suran, Swathi; Bhat, Navakanta; Varma, Manoj; Raghavan, Srinivasan

    2015-10-01

    Substrates for 2D materials are important for tailoring their fundamental properties and realizing device applications. Aluminum nitride (AIN) films on silicon are promising large-area substrates for such devices in view of their high surface phonon energies and reasonably large dielectric constants. In this paper epitaxial layers of AlN on 2″ Si wafers have been investigated as a necessary first step to realize devices from exfoliated or transferred atomic layers. Significant thickness dependent contrast enhancements are both predicted and observed for monolayers of graphene and MoS2 on AlN films as compared to the conventional SiO2 films on silicon, with calculated contrast values approaching 100% for graphene on AlN as compared to 8% for SiO2 at normal incidences. Quantitative estimates of experimentally measured contrast using reflectance spectroscopy show very good agreement with calculated values. Transistors of monolayer graphene on AlN films are demonstrated, indicating the feasibility of complete device fabrication on the identified layers.

  6. 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.

  7. Dielectric Engineering of a Boron Nitride/Hafnium Oxide Heterostructure for High-Performance 2D Field Effect Transistors.

    PubMed

    Zou, Xuming; Huang, Chun-Wei; Wang, Lifeng; Yin, Long-Jing; Li, Wenqing; Wang, Jingli; Wu, Bin; Liu, Yunqi; Yao, Qian; Jiang, Changzhong; Wu, Wen-Wei; He, Lin; Chen, Shanshan; Ho, Johnny C; Liao, Lei

    2016-03-01

    A unique design of a hexagonal boron nitride (h-BN)/HfO2 dielectric heterostructure stack is demonstrated, with few-layer h-BN to alleviate the surface optical phonon scattering, followed by high-κ HfO2 deposition to suppress Coulombic impurity scattering so that high-performance top-gated two-dimensional semiconductor transistors are achieved. Furthermore, this dielectric stack can also be extended to GaN-based transistors to enhance their performance. PMID:26762171

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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.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

  10. Impact of oxygen bonding on the atomic structure and photoluminescence properties of Si-rich silicon nitride thin films

    SciTech Connect

    Nguyen, P. D.; Sunding, M. F.; Vestland, L. O.; Finstad, T. G.; Olsen, A.; Kepaptsoglou, D. M.; Ramasse, Q. M.

    2012-10-01

    The atomic structure and optical properties of Si-rich silicon nitride thin films have been for decades the subject of intense research, both theoretically and experimentally. It has been established in particular that modifying the chemical composition of this material (e.g., the Si excess concentration) can lead to dramatic differences in its physical, optical, and electrical properties. The present paper reports on how the incorporation of oxygen into silicon nitride networks influences their chemical bonding and photoluminescence properties. Here, by using a combination of analytical scanning transmission electron microscopy and x-ray photoelectron spectroscopy it is demonstrated that the structure of Si-rich silicon nitride with low O content can be described by the co-existence of Si nanocrystals in a Si{sub 3}N{sub 4} matrix, with occasional localized nano-regions of a Si{sub 2}ON{sub 2} phase, depending on the amount of excess Si. Furthermore, it is shown that the structure of silicon nitride with high O content can be adequately described by a so-called random bonding model, according to which the material consists in bonded networks of randomly distributed tetrahedral SiO{sub x}N{sub 4-x} (where x = 0, 1, 2, 3, and 4). Photoluminescence measurements indicate that the effect of O is to introduce a gap state in the band gap of Si{sub 3}N{sub 4} matrix. When a large amount of O is introduced, on the other hand, the photoluminescence measurements are in agreement with a shifted conduction band minimum in the dielectric. For both cases (high and low O content), Si dangling bonds were found to give rise to the deep level in the band gap of the nitride matrix, causing the dominant emission band in the photoluminescence of the films.

  11. Hysteresis free carbon nanotube thin film transistors comprising hydrophobic dielectrics

    NASA Astrophysics Data System (ADS)

    Lefebvre, J.; Ding, J.; Li, Z.; Cheng, F.; Du, N.; Malenfant, P. R. L.

    2015-12-01

    We present two examples of carbon nanotube network thin film transistors with strongly hydrophobic dielectrics comprising either Teflon-AF or a poly(vinylphenol)/poly(methyl silsesquioxane) (PVP/pMSSQ) blend. In the absence of encapsulation, bottom gated transistors in air ambient show no hysteresis between forward and reverse gate sweep direction. Device threshold gate voltage and On-current present excellent time dependent stability even under dielectric stress. Furthermore, threshold gate voltage for hole conduction is negative upon device encapsulation with PVP/pMSSQ enabling much improved current On/Off ratio at 0 V. This work addresses two major challenges impeding solution based fabrication of relevant thin film transistors with printable single-walled carbon nanotube channels.

  12. Synthesis and characterization of hexagonal boron nitride film as a dielectric layer for graphene devices.

    PubMed

    Kim, Ki Kang; Hsu, Allen; Jia, Xiaoting; Kim, Soo Min; Shi, Yumeng; Dresselhaus, Mildred; Palacios, Tomas; Kong, Jing

    2012-10-23

    Hexagonal boron nitride (h-BN) is a promising material as a dielectric layer or substrate for two-dimensional electronic devices. In this work, we report the synthesis of large-area h-BN film using atmospheric pressure chemical vapor deposition on a copper foil, followed by Cu etching and transfer to a target substrate. The growth rate of h-BN film at a constant temperature is strongly affected by the concentration of borazine as a precursor and the ambient gas condition such as the ratio of hydrogen and nitrogen. h-BN films with different thicknesses can be achieved by controlling the growth time or tuning the growth conditions. Transmission electron microscope characterization reveals that these h-BN films are polycrystalline, and the c-axis of the crystallites points to different directions. The stoichiometry ratio of boron and nitrogen is close to 1:1, obtained by electron energy loss spectroscopy. The dielectric constant of h-BN film obtained by parallel capacitance measurements (25 μm(2) large areas) is 2-4. These CVD-grown h-BN films were integrated as a dielectric layer in top-gated CVD graphene devices, and the mobility of the CVD graphene device (in the few thousands cm(2)/(V·s) range) remains the same before and after device integration. PMID:22970651

  13. 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.

  14. The effect of dielectric properties of sintering additives on microwave sintered silicon nitride ceramics.

    PubMed

    Chockalingam, Sreekumar; George, Jacob; Earl, David; Amarakoon, Vasantha R W

    2008-01-01

    Silicon nitride requires the use of susceptive additives for microwave liquid phase sintering due to the material's low dielectric loss. In this article, we report the effect of complex dielectric properties of two compositions of sintering aids on 2.45 GHz microwave sintered Si3N4 with respect to power absorption, temperature distribution and densification behavior. The temperature dependent dielectric properties were measured from 25 degrees C to 1400 degrees C using a conventional cavity perturbation technique. Finite Difference Time Domain (FDTD) electromagnetic simulations coupled with a thermal solver was used to predict the microwave power absorption and the corresponding temperature evolution inside the samples. The additive with higher dielectric loss (4 wt% MgO, 6 wt% Y2O3 and 2.5 wt% ZrO2) produces a greater sintered density than the lower loss additive (4 wt% MgO and 6 wt% Y2O3) or pure Si3N4. Although microwave loss at temperatures below 600 degrees C is insignificant with or without the additives, the loss begins to increase at higher temperatures when the additives are present and has a strong upward trend above 1000 degrees C. Above 1200 degrees C the sample containing ZrO2 exhibited the greatest loss. Numerical simulations at the peak sintering temperature show greater microwave power absorption and higher temperature in the sample with the highest loss additive. The simulation results correlate to the difference in densification behavior observed. The simulation was also useful because the material temperature was not accurately provided by optical pyrometer measurements of the crucible sample holder. PMID:19227072

  15. Dielectric response of carbon and boron nitride nanotubes from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Kozinsky, Boris; Marzari, Nicola

    2007-03-01

    We present a complete characterization of the dielectric response of isolated single- and multi-wall carbon (CNT) and boron-nitride nanotubes (BNNT) using first-principles calculations and density-functional theory. The longitudinal polarizability of a nanotube is sensitive to the band gap and its radius, and in multi-wall nanotubes and bundles it is trivially given by the sum of the polarizabilities of the constituent tubes. The transverse polarizability of both types of nanotubes is insensitive to band gap and chirality and depends only on the radius. However, the transverse response and screening properties of BNNTs are qualitatively different from those of metallic and semiconducting CNTs. The fundamental differences in electronic properties of the two materials are inherited from the corresponding two-dimensional sheets - graphene and boron-nitride. The screening of the external field in CNTs is stronger than in BNNTs and has a different radius dependence. The transverse response in BNNTs is found to be that of an insulator, while in CNTs it is intermediate between metallic and semiconducting. Our results have practical implications for selective growth of different types of nanotubes using aligning electric fields and for Raman characterization of nanotubes.

  16. 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

  17. 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

    2015-12-01

    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. PMID:26510890

  18. Combinatorial synthesis of thin film libraries for microwave dielectrics

    NASA Astrophysics Data System (ADS)

    Wessler, B.; Jéhanno, V.; Rossner, W.; Maier, W. F.

    2004-02-01

    The short innovation cycles in communication technology require the development and optimization of high-performance dielectrics for passive integration, utilized, e.g., in band pass filters, antennas, or dielectric resonators. Applying combinatorial methods offers the advantage to accelerate the discovery of more efficient microwave dielectrics and to investigate the effects of a variety of dopants on the dielectric properties. In the present study, libraries consisting of chemically diverse thin films are produced by chemical solution deposition. A sol-gel precursor set was developed consisting of precursor solutions for different elements, such as Ba, Ti, W, and Sr, which convert to the corresponding oxides by annealing. These precursor solutions are mixed in various ratios by pipetting robots and are then deposited on structured substrates followed by calcination and sintering. The influence of different parameters on the film quality such as the type of precursor used, their miscibility with each other, the thermal processing, and the technique used to pre-structure the wafer is discussed.

  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. 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.

  1. 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

    2016-01-01

    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 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. PMID:27184121

  2. 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.

  3. Growth of atomically thin hexagonal boron nitride films by diffusion through a metal film and precipitation

    NASA Astrophysics Data System (ADS)

    Suzuki, Satoru; Molto Pallares, Roger; Hibino, Hiroki

    2012-09-01

    Atomically thin hexagonal boron nitride films were grown on both the top and bottom surfaces of a polycrystalline Co or Ni film by annealing a Co (Ni)/amorphous boron nitride/SiO2 structure in vacuum. This method of growing hexagonal boron nitride is much simpler than other methods, such as thermal chemical vapour deposition. B and N atoms diffuse through the metal film, although N is almost completely insoluble in both Co and Ni, and precipitation occurs at the topmost surface. The mass transport is considered to be caused by grain boundary diffusion.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

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

    PubMed

    Al Shakhs, Mohammed; 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. 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

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. Research on titanium nitride thin films deposited by reactive magnetron sputtering for MEMS applications

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Titanium nitride can be used among other materials as diffusion barrier for MEMS (microelectromechanical systems) applications. The aim of this study is to elaborate and to characterize at nanoscale titanium nitride thin films. The thin films were deposited by reactive magnetron sputtering on silicon substrates using a 99.99% purity titanium target. Different deposition parameters were employed. The deposition temperature, deposition time, substrate bias voltage and the presence/absence of a titanium buffer layer are the parameters that were modified. The so-obtained films were then investigated by atomic force microscopy. A significant impact of the deposition parameters on the determined mechanical and tribological characteristics was highlighted. The results showed that the titanium nitride thin films deposited for 20 min at room temperature without the presence of a titanium buffer layer when a negative bias of -90 V was applied to the substrate is characterized by the best tribological and mechanical behavior.

  12. 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.

  13. 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.

  14. Dielectric Function and Electronic Excitations of Functionalized DNA Thin Films

    NASA Astrophysics Data System (ADS)

    Lee, Hosuk; Lee, Hosun; Lee, Jung Eun; Rha Lee, U.; Choi, Dong Hoon

    2010-06-01

    We measure the dielectric functions of organic-soluble, functionalized DNAs bearing functional moieties in the near-infrared, visible, and ultra-violet spectra by using spectroscopic ellipsometry. Natural double-stranded DNA is dissolved in water and reacted with carbazole-based trimethyl ammonium bromide, cetyltrimethylammonium bromide, and chalcone-terminated trimethyl ammonium bromide. The functional DNA products are all precipitated and filtered for washing and drying. We successfully prepare functionalized DNAs that are insoluble in water but soluble in organic solvents. The thin films are fabricated by using the spin coating technique after preparing solutions in either homogeneous or mixed organic solvents. We measure the ultraviolet-visible absorbance spectra of the films. The absorbance spectra show that the optical energy gaps of the functionalized DNAs change little even though the DNAs are connected to the complex molecules by electrostatic interaction. From the measured ellipsometric angles, we estimate the dielectric functions by using parametric optical constant model and layer model analysis. Depending on the nature of the attached complex molecules, the dielectric functions change, new optical structures develop below and above band gaps arising from the side molecules, and the optical energy gaps of the DNAs are altered slightly by weak coupling to the tethered complex molecules.

  15. Orientational relationship between cubic boron nitride and hexagonal boron nitride in a thin film synthesized by ion plating

    NASA Astrophysics Data System (ADS)

    Zhou, Wei-Lie; Ikuhara, Yuichi; Suzuki, Tetsuya

    1995-12-01

    Cubic boron nitride (c-BN) thin films synthesized by the ion-plating method were examined by high-resolution electron microscopy. It was found that the {0002} planes of hexagonal boron nitride (h-BN) at the boundaries of c-BN grains preferred to nucleate almost parallel to {111} planes of c-BN. Cross-sectional observation in the initial stage of growth showed that the c-BN can grow on top of the prismatic planes and the {0001} basal planes of h-BN, keeping the parallelism of the (111)c-BN to (0001)h-BN. A few degrees deviation (˜4°) between h-BN {0002} planes and c-BN {111} planes was frequently found in the film. The nucleation mechanism of c-BN was discussed analogous to that of diamond on graphite.

  16. Valence and conduction band offsets at amorphous hexagonal boron nitride interfaces with silicon network dielectrics

    SciTech Connect

    King, Sean W. Brockman, Justin; Bielefeld, Jeff; French, Marc; Kuhn, Markus; Paquette, Michelle M.; Otto, Joseph W.; Caruso, A. N.; French, Benjamin

    2014-03-10

    To facilitate the design of heterostructure devices employing hexagonal/sp{sup 2} boron nitride, x-ray photoelectron spectroscopy has been utilized in conjunction with prior reflection electron energy loss spectroscopy measurements to determine the valence and conduction band offsets (VBOs and CBOs) present at interfaces formed between amorphous hydrogenated sp{sup 2} boron nitride (a-BN:H) and various low- and high-dielectric-constant (k) amorphous hydrogenated silicon network dielectric materials (a-SiX:H, X = O, N, C). For a-BN:H interfaces formed with wide-band-gap a-SiO{sub 2} and low-k a-SiOC:H materials (E{sub g} ≅ 8.2−8.8 eV), a type I band alignment was observed where the a-BN:H band gap (E{sub g} = 5.5 ± 0.2 eV) was bracketed by a relatively large VBO and CBO of ∼1.9 and 1.2 eV, respectively. Similarly, a type I alignment was observed between a-BN:H and high-k a-SiC:H where the a-SiC:H band gap (E{sub g} = 2.6 ± 0.2 eV) was bracketed by a-BN:H with VBO and CBO of 1.0 ± 0.1 and 1.9 ± 0.2 eV, respectively. The addition of O or N to a-SiC:H was observed to decrease the VBO and increase the CBO with a-BN:H. For high-k a-SiN:H (E{sub g} = 3.3 ± 0.2 eV) interfaces with a-BN:H, a slightly staggered type II band alignment was observed with VBO and CBO of 0.1 ± 0.1 and −2.3 ± 0.2 eV, respectively. The measured a-BN:H VBOs were found to be consistent with those deduced via application of the commutative and transitive rules to VBOs reported for a-BN:H, a-SiC:H, a-SiN:H, and a-SiO{sub 2} interfaces with Si (100)

  17. 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.

  18. 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.

  19. Determination of mechanical properties of PECVD silicon nitride thin films for tunable MEMS Fabry Pérot optical filters

    NASA Astrophysics Data System (ADS)

    Huang, H.; Winchester, K.; Liu, Y.; Hu, X. Z.; Musca, C. A.; Dell, J. M.; Faraone, L.

    2005-03-01

    This paper reports an investigation on techniques for determining elastic modulus and intrinsic stress gradient in plasma-enhanced chemical vapor deposition (PECVD) silicon nitride thin films. The elastic property of the silicon nitride thin films was determined using the nanoindentation method on silicon nitride/silicon bilayer systems. A simple empirical formula was developed to deconvolute the film elastic modulus. The intrinsic stress gradient in the films was determined by using micrometric cantilever beams, cross-membrane structures and mechanical simulation. The deflections of the silicon nitride thin film cantilever beams and cross-membranes caused by in-thickness stress gradients were measured using optical interference microscopy. Finite-element beam models were built to compute the deflection induced by the stress gradient. Matching the deflection computed under a given gradient with that measured experimentally on fabricated samples allows the stress gradient of the PECVD silicon nitride thin films introduced from the fabrication process to be evaluated.

  20. High-Temperature Dielectric Properties of Aluminum Nitride Ceramic for Wireless Passive Sensing Applications

    PubMed Central

    Liu, Jun; Yuan, Yukun; Ren, Zhong; Tan, Qiulin; Xiong, Jijun

    2015-01-01

    The accurate characterization of the temperature-dependent permittivity of aluminum nitride (AlN) ceramic is quite critical to the application of wireless passive sensors for harsh environments. Since the change of the temperature-dependent permittivity will vary the ceramic-based capacitance, which can be converted into the change of the resonant frequency, an LC resonator, based on AlN ceramic, is prepared by the thick film technology. The dielectric properties of AlN ceramic are measured by the wireless coupling method, and discussed within the temperature range of 12 °C (room temperature) to 600 °C. The results show that the extracted relative permittivity of ceramic at room temperature is 2.3% higher than the nominal value of 9, and increases from 9.21 to 10.79, and the quality factor Q is decreased from 29.77 at room temperature to 3.61 at 600 °C within the temperature range. PMID:26370999

  1. 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. PMID:19333330

  2. 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.

  3. Silicon nitride coated silicon thin film on three dimensions current collector for lithium ion battery anode

    NASA Astrophysics Data System (ADS)

    Wu, Cheng-Yu; Chang, Chun-Chi; Duh, Jenq-Gong

    2016-09-01

    Silicon nitride coated silicon (N-Si) has been synthesized by two-step DC sputtering on Cu Micro-cone arrays (CMAs) at ambient temperature. The electrochemical properties of N-Si anodes with various thickness of nitride layer are investigated. From the potential window of 1.2 V-0.05 V, high rate charge-discharge and long cycle test have been executed to investigate the electrochemical performances of various N-Si coated Si-based lithium ion batteries anode materials. Higher specific capacity can be obtained after 200 cycles. The cycling stability is enhanced via thinner nitride layer coating as silicon nitride films are converted to Li3N with covered Si thin films. These N-Si anodes can be cycled under high rates up to 10 C due to low charge transfer resistance resulted from silicon nitride films. This indicates that the combination of silicon nitride and silicon can effectively endure high current and thus enhance the cycling stability. It is expected that N-Si is a potential candidate for batteries that can work effectively under high power.

  4. Dielectric relaxation of thin films of polyamide random copolymers.

    PubMed

    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, T(g), evaluated from the EP process agrees very well with the T(g) 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. PMID:26066192

  5. 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.

  6. Nanoscale electrochemistry using dielectric thin films as solid electrolytes.

    PubMed

    Valov, Ilia; Lu, Wei D

    2016-08-01

    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. PMID:27150952

  7. Dielectric relaxation and defect analysis of Ta2O5 thin films

    NASA Astrophysics Data System (ADS)

    Ezhilvalavan, S.; Shiahn Tsai, Ming; Yuen Tseng, Tseung; Shiahn Tsai, Ming

    2000-05-01

    The presence of defects in thin-film dielectrics often leads to dielectric relaxation as a function of frequency, in which the dielectric constant decreases and the loss tangent increases with increasing frequency. Dielectric relaxation results in charge storage capacity reduction under dynamic random access memory operating conditions. In this work, the dielectric relaxation behaviour of dc reactive sputtered Ta2O5 thin film was investigated. Using dielectric dispersion measurements as a function of frequency (100 Hz≤f≤10 MHz) and temperature (27 °C≤T≤150 °C), we determined the dielectric relaxation and defect quantity of the films and propose an equivalent circuit on the basis of complex capacitance, admittance and impedance spectral studies.

  8. Polarity inversion in aluminum nitride thin films under high sputtering power

    SciTech Connect

    Akiyama, Morito; Kamohara, Toshihiro; Ueno, Naohiro; Sakamoto, Michiru; Kano, Kazuhiko; Teshigahara, Akihiko; Kawahara, Nobuaki

    2007-04-09

    The authors have investigated the influence of sputtering power on the piezoelectric response of aluminum nitride (AlN) thin films prepared on titanium nitride bottom electrodes. The piezoelectric response strongly depends on the sputtering power. The polar inversion was found by piezoresponse force microscopy. The polarity gradually changes from the N polarity to Al polarity with increasing sputtering power. The piezoelectric response of the films changes from -2.7 to +4.3 pC/N with increasing sputtering power from 100 to 500 W. Furthermore, the polarity inversion from the N polarity to Al polarity is observed by increasing sputtering power during growth.

  9. Determination of attenuation lengths and electron escape depths in silicon nitride thin films

    SciTech Connect

    Honggang Hu; Carim, A.H. . Dept. of Materials Science and Engineering)

    1993-11-01

    Amorphous silicon nitride thin films prepared by low pressure chemical vapor deposition have been investigated by x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The attenuation lengths and escape depths of Si 2p photoelectrons with kinetic energy of 1,385 eV from silicon nitride thin films have been calculated. High resolution transmission electron microscopy (HRTEM) has been used to characterize the thin film thickness. The atomic density of Si in the films decreases with increasing film thickness, leading to a longer attenuation length for thicker films ([lambda][degree] [approx] 4.7 nm for films with thickness of t > 5 nm) than for thinner films ([lambda][degree] [approx] 3.6 nm, t < 4 nm). The attenuation length dependence on the film thickness and experimental setup also provides direct experimental evidence that the simple exponential model for electron attenuation may be inaccurate due to elastic scattering effects.

  10. 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.

  11. 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. PMID:23618222

  12. 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.

  13. Influences of low temperature silicon nitride films on the electrical performances of hydrogenated amorphous silicon thin film transistors

    NASA Astrophysics Data System (ADS)

    Huang, Jung-Jie; Liu, Chan-Jui; Lin, Hung-Chien; Tsai, Cheng-Ju; Chen, Yung-Pei; Hu, Guo-Ren; Lee, Cheng-Chung

    2008-12-01

    Influences of silicon nitride (SiNx) films on the electrical performances of hydrogenated amorphous silicon thin film transistors (a-Si : H TFTs) are studied. Relatively low temperature (200 °C) SiNx films are prepared by plasma enhanced chemical vapour deposition at different radio-frequency powers. Results indicate that the SiNx films at a radio-frequency power of 340 W (Power density = 1.96 × 10-1 W cm-2) are near-stoichiometric and have better interface quality. Therefore, a-Si : H TFTs with this SiNx gate dielectric layer have a high field effect mobility and sustain the bias stress. The field effect mobility is 0.59 cm2 V-1 s-1 and the threshold voltage shift after a constant voltage stress (CVS) for 2.8 h is 3.18 V. The electrical degradation mechanism of a-Si : H TFTs is studied from the capacitance-voltage measurement. The degradation of the a-Si : H TFT after CVS is due to the defect generation in the SiNx gate dielectric and a-Si : H active layers. However, when the surface roughness of the SiNx film is poor, the degradation from the a-Si : H/SiNx interface is predominated. Therefore, if the SiNx film is used as a gate dielectric layer to fabricate a-Si : H TFTs, the surface roughness and chemical composition of the SiNx film should be considered simultaneously.

  14. Bismuth pyrochlore-based thin films for dielectric energy storage

    NASA Astrophysics Data System (ADS)

    Michael, Elizabeth K.

    The drive towards the miniaturization of electronic devices has created a need for dielectric materials with large energy storage densities. These materials, which are used in capacitors, are a critical component in many electrical systems. Here, the development of dielectric energy storage materials for pulsed power applications, which require materials with the ability to accumulate a large amount of energy and then deliver it to the system rapidly, is explored. The amount of electrostatic energy that can be stored by a material is a function of the induced polarization and the dielectric breakdown strength of the material. An ideal energy storage dielectric would possess a high relative permittivity, high dielectric breakdown strength, and low loss tangent under high applied electric fields. The bismuth pyrochlores are a compositionally tunable family of materials that meet these requirements. Thin films of cubic pyrochlore bismuth zinc niobate, bismuth zinc tantalate, and bismuth zinc niobate tantalate, were fabricated using a novel solution chemistry based upon the Pechini method. This solution preparation is advantageous because it avoids the use of teratogenic solvents, such as 2-methoxyethanol. Crystalline films fabricated using this solution chemistry had very small grains that were approximately 27 nm in lateral size and 35 nm through the film thickness. Impedance measurements found that the resistivity of the grain boundaries was two orders of magnitude higher than the resistivity of the grain interior. The presence of many resistive grain boundaries impeded conduction through the films, resulting in high breakdown strengths for these materials. In addition to high breakdown strengths, this family of materials exhibited moderate relative permittivities of 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

  15. 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

  16. THE CHARACTERISTIC IMPEDANCE OF RECTANGULAR TRANSMISSION LINES WITH THIN CENTER CONDUCTOR AND AIR DIELECTRIC

    EPA Science Inventory

    The characteristic impedance of large-scale rectangular strip transmission line facilities used for such purposes as EMI susceptibility testing, biological exposures, etc., is discussed. These lines are characterized by a thin center conductor and an air dielectric. Impedance dat...

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

    PubMed

    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

  18. Transverse electric surface mode in atomically thin Boron-Nitride.

    PubMed

    Merano, Michele

    2016-06-01

    The spatial confinement and the propagation length of surface waves in a single-layer two-dimensional atomic crystal are analyzed in terms of its surface susceptibility and its surface conductivity. Based on the values of these macroscopic parameters, extracted from experimental observations, it is confirmed that graphene supports a transverse magnetic nonradiating surface mode in the ultraviolet spectral region while a single-layer hexagonal Boron-Nitride is predicted to support a transverse electric nonradiating surface mode in the visible spectrum. This last mode, at a vacuum wavelength of 633 nm, has a spatial confinement of 15 μm and an intensity-propagation distance greater than 2 cm. PMID:27244441

  19. Transverse electric surface mode in atomically thin Boron–Nitride

    NASA Astrophysics Data System (ADS)

    Merano, Michele

    2016-06-01

    The spatial confinement and the propagation length of surface waves in a single-layer two-dimensional atomic crystal are analysed in term of its surface susceptibility and its surface conductivity. Based on the values of these macroscopic parameters, extracted from experimental observations, it is confirmed that graphene supports a transverse magnetic non-radiating surface mode in the ultraviolet spectral region while a single-layer hexagonal Boron-Nitride is predicted to support a transverse electric non-radiating surface mode in the visible spectrum. This last mode, at a vacuum wavelength of 633 nm, has a spatial confinement of 15 microns and an intensity-propagation distance greater than 2 cm.

  20. Synthesis and characterization of visible emission from rare-earth doped aluminum nitride, gallium nitride and gallium aluminum nitride powders and thin films

    NASA Astrophysics Data System (ADS)

    Tao, Jonathan Huai-Tse

    A three-step solution-based process had been used synthesize powders of GaN, AlN and their alloys. The complete solid solubility and tunable nature of these nitride band gaps in the visible spectrum were the motivation of these studies due to their application in solid state lighting. Energy dispersive X-ray spectroscopy confirmed the reduction in oxygen content for the GaN powders to as low as 4 atom % with an 8 % oxygen to nitrogen ratio. Relative to commercial GaN powders, the bandedge of the powders synthesized by such approach also shifted to higher energy, which indicated fewer defects, as observed from reflectance measurements. Inspired by the use of rare-earth elements as color emitters in fluorescent lamp phosphors, these elements were also used as activators in our nitride material. Visible emission was demonstrated through photoluminescence measurements in AlN powders activated with rare-earth elements Eu3+, Tb3+, Tm3+. These ions showed emission in the red, green and blue regions of the visible spectrum, respectively. Eu3+ and Tb3+ co-activation was also observed in an AlN sample that indicated successful energy transfer from the host to sensitizer, and subsequently to another activator. Tb3+ emission was observed under cathodoluminescence in GaN powders synthesized by the same method, and a concentration study showed no effect of concentration quenching up to 8 atom %. Using the same source powder, a pulsed-laser deposited thin film was fabricated that showed both band gap emission and activator-related emission, suggesting a reduction of defects when the powders were deposited as thin films. Additionally, GaN:Tb3+ films were also fabricated using metallorganic vapor phase epitaxy using precursors with and without oxygen ligands. Tb3+ emission was only observed in the sample fabricated from the precursor with oxygen ligand, suggestion that oxygen may be required for effective rare earth luminescence. Finally, Ga1-xAl xN alloy powders (x=0.5) and Ga1-x

  1. (Ba,Sr)TiO{sub 3} dielectrics: Relationship between bulk and thin film properties

    SciTech Connect

    Kingon, A. I.; Streiffer, S. K.; Parker, C. B.; Stemmer, S.

    1999-12-22

    Thin films of complex perovskites have a number of potentially important applications. Of major scientific and practical concern is the scaling of properties as film dimensions are reduced. This paper describes a satisfactory relationship between bulk and thin film dielectric properties of (Ba,Sr)TiO{sub 3}. Relative contributions of strain, A:B cation stoichiometry, and interface are separated to explain temperature dependent dielectric behavior.

  2. 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.

  3. 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}.

  4. Pulsed DC magnetron sputtered piezoelectric thin film aluminum nitride - Technology and piezoelectric properties

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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 d31 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 d33.

  5. 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}.

  6. Surface scattering mechanisms of tantalum nitride thin film resistor

    PubMed Central

    2014-01-01

    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. PMID:24725295

  7. Investigation of Nonvolatile Memory Effect of Organic Thin-Film Transistors with Triple Dielectric Layers

    NASA Astrophysics Data System (ADS)

    Yu, Hsin-Chieh; Chen, Ying-Chih; Huang, Chun-Yuan; Su, Yan-Kuin

    2012-03-01

    Pentacene thin-film transistor (TFT) memory using poly(2-hydroxyethyl methacrylate) (PHEMA)-based polymer dielectric layers has been developed. The electric performance and memory behaviors of memory TFTs can be significantly improved by using triple polymer dielectric layers consisting of PHEMA/poly(methyl methacrylate) (PMMA)/PHEMA. This can be attributed to the improvement of the channel/dielectric interface. This memory effect is due to the charge storage of the dipolar group or molecules in the dielectric. The devices exhibit a wide memory window (ΔVth, >20 V), switchable channel current, and long retention time.

  8. Thin Dielectric Films Containing Tb3+ Ions For Application In Thin Film Solar Cells

    NASA Astrophysics Data System (ADS)

    Sendova-Vassileva, M.; Baumgartner, K.; Angelov, O.; Holländer, B.; Dimova-Malmovska, D.; Carius, R.

    2010-01-01

    Thin transparent dielectric films containing Tb3+ are developed for application as spectral converters of the solar spectrum in thin film silicon solar cells. The results on the deposition and characterization of thin SiO2 and Al2O3 films containing Tb3+ ions are presented. The films are prepared by RF magnetron co-sputtering, a well established technique for large area coatings. Photoluminescence (PL) is measured at room temperature, using the 488 nm line of an Ar laser and a nitrogen-cooled CCD camera attached to a monochromator. The dependence of the PL intensity on the concentration of Tb in the film is studied. It is found that the intensity exhibits a maximum at about 1 at.%. Annealing studies are performed on SiO2:Tb with two different methods to improve the PL intensity. In both regimes of annealing, the best results for thin SiO2:Tb films are obtained in the temperature range of 650-700° C. After treatment at this temperature the Tb PL increases 2.5-3 times.

  9. Thin Dielectric Films Containing Tb{sup 3+} Ions For Application In Thin Film Solar Cells

    SciTech Connect

    Sendova-Vassileva, M.; Angelov, O.; Dimova-Malmovska, D.; Baumgartner, K.; Carius, R.; Hollaender, B.

    2010-01-21

    Thin transparent dielectric films containing Tb{sup 3+} are developed for application as spectral converters of the solar spectrum in thin film silicon solar cells. The results on the deposition and characterization of thin SiO{sub 2} and Al{sub 2}O{sub 3} films containing Tb{sup 3+} ions are presented. The films are prepared by RF magnetron co-sputtering, a well established technique for large area coatings. Photoluminescence (PL) is measured at room temperature, using the 488 nm line of an Ar laser and a nitrogen-cooled CCD camera attached to a monochromator. The dependence of the PL intensity on the concentration of Tb in the film is studied. It is found that the intensity exhibits a maximum at about 1 at.%. Annealing studies are performed on SiO{sub 2}:Tb with two different methods to improve the PL intensity. In both regimes of annealing, the best results for thin SiO{sub 2}:Tb films are obtained in the temperature range of 650-700 deg. C. After treatment at this temperature the Tb PL increases 2.5-3 times.

  10. Effect of dispersion degree of orientation on dielectric properties of (100)-oriented PST thin film

    NASA Astrophysics Data System (ADS)

    Li, Xiaoting; Hu, Tao; Wang, Biao; Weng, Wenjian; Han, Gaorong; Song, Chenglu; Ma, Ning; Du, Piyi

    2013-12-01

    (100) Oriented (PbxSr1-x)TiO3 (PST) thin films were prepared on indium tin oxide coated glass substrates by sol-gel technique with rapid thermal processing. The dielectric permittivity and tunability of the thin films with different dispersion degrees of orientation were investigated in detail by characterizing the full width at half maximum of their (100) peak based on rocking curves at different annealing temperatures. Influence of orientation dispersion on dielectric properties was exhibited in the tunable dielectric thin films. It shows that the dielectric constant and hence the tunability of the sol-gel derived PST thin films are improved with the decrease in the dispersion degree of orientation of the perovskite phase other than the increase in the content of crystalline phase in the thin films. The dielectric constant (capacitance) and figure of merit of the oriented thin films are 3-6 times and 1 times higher than that of randomly oriented thin film respectively.

  11. 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.

  12. The electrical properties of sulfur-implanted cubic boron nitride thin films

    NASA Astrophysics Data System (ADS)

    Deng, Jin-Xiang; Qin, Yang; Kong, Le; Yang, Xue-Liang; Li, Ting; Zhao, Wei-Ping; Yang, Ping

    2012-04-01

    Cubic boron nitride (c-BN) thin films are deposited on p-type Si wafers using radio frequency (RF) sputtering and then doped by implanting S ions. The implantation energy of the ions is 19 keV, and the implantation dose is between 1015 ions/cm2 and 1016 ions/cm2. The doped c-BN thin films are then annealed at a temperature between 400 °C and 800 °C. The results show that the surface resistivity of doped and annealed c-BN thin films is lowered by two to three orders, and the activation energy of c-BN thin films is 0.18 eV.

  13. Gate bias stress effects due to polymer gate dielectrics in organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Ng, Tse Nga; Daniel, Jürgen H.; Sambandan, Sanjiv; Arias, Ana-Claudia; Chabinyc, Michael L.; Street, Robert A.

    2008-02-01

    The operational stability of organic thin-film transistors (OTFTs) comprising bilayer polymer dielectric of poly(methylsilsesquioxane) (pMSSQ) and either the epoxy resin SU-8 or poly(4-vinyl phenol) was examined. Although not in direct contact with the semiconductor materials, the bottom dielectric layer did affect OTFT stability through water ion movement or charge injection inside the bottom dielectrics. In the comparison between our best polymer dielectric pMSSQ/SU-8 to the silicon oxide dielectric, the result emphasized that, at equal initial charge concentration, polymer dielectrics did not alleviate threshold-voltage shift but did maintain more stable current due to the lower gate capacitance than silicon oxide.

  14. 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.

  15. Influence of argon gas flow on mechanical and electrical properties of sputtered titanium nitride thin films

    NASA Astrophysics Data System (ADS)

    Khojier, Kaykhosrow; Savaloni, Hadi; Shokrai, Ebrahim; Dehghani, Zohreh; Dehnavi, Naser Zare

    2013-07-01

    Titanium nitrides have good mechanical, tribological, electrical, biomedical, and optical properties; therefore, they are used to harden and protect cutting and sliding surfaces, as semiconductor devices, and as a nontoxic exterior for biomedical applications. The dependence of the mechanical and electrical properties of titanium nitride thin films deposited on silicon substrates by direct-current reactive magnetron sputtering technique on argon gas flow (in the range of 8 to 20 sccm) was investigated. The crystallographic structure of the films was studied by X-ray diffraction (XRD), while surface morphology was studied using atomic force microscopy (AFM). Mechanical and electrical properties of these films were investigated by nanoindentation test and a four-point probe instrument, respectively. The XRD patterns showed titanium nitride (TiN) formation with a face-centered cubic structure for all samples. It was also observed that (111) crystallographic direction was the preferred orientation for TiN thin films which became more pronounced with increasing argon gas flow. The AFM images showed a granular structure for TiN layers. The hardness, crystallite/grain size (obtained from XRD and AFM), and surface roughness increased with the flow of argon gas, while elastic modulus and dislocation density in the films decreased. The study on electrical properties showed that the dependence of voltage with current for all samples was linear, and film resistivity was increased with argon gas flow.

  16. Local bonding environment of plasma deposited nitrogen-rich silicon nitride thin films

    NASA Astrophysics Data System (ADS)

    Soh, Martin T. K.; Savvides, N.; Musca, Charles A.; Martyniuk, Mariusz P.; Faraone, Lorenzo

    2005-05-01

    Plasma deposited nitrogen-rich silicon nitride thin films were prepared at temperatures between 80 and 300 °C. The infrared transmission (400-4000cm-1) was measured, and selected absorption bands were quantified through a multiple Lorentzian oscillator parametric analysis. It is observed that the concentration of silicon-centered tetrahedra bonded together through nitrogen atoms increases monotonically with increasing deposition temperature. A qualitative model is presented to highlight the impact of the active adsorption site density on the degree of stepped (ordered) nucleation at the vapor-film interface. The importance of this growth profile, in particular for micro-systems-technology, is discussed in conjunction with measurements of the biaxial modulus and residual stress of the thin films. A mechanism for residual stress controllability is also presented. The atomic concentrations of silicon, nitrogen, and hydrogen in the thin films were calculated using infrared calibration factors derived from the deposition temperature dependent condensation processes. The results for silicon nitride thin films deposited at 300 °C were observed to be similar in composition to silicon diimide. Additional observations of the infrared transmission characteristics are reported, which include the identification of silazane bridge characteristics for the absorption feature around 610cm-1, which is typically associated with Si-H (bending) absorption.

  17. 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. PMID:27251325

  18. 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.

  19. Photoacoustic Evaluation of the Mechanical Properties of Aluminum / Silicon Nitride Double-Layer Thin Films

    NASA Astrophysics Data System (ADS)

    Zhang, Feifei; Krishnaswamy, Sridhar; Lilley, Carmen M.

    2006-03-01

    In this paper, we compare two photoacoustic techniques to characterize the mechanical parameters of edge-supported aluminum and silicon nitride double-layer thin films. In a first set of experiments, a femtosecond transient pump-probe technique is used to investigate the Young's moduli of the aluminum and silicon nitride layers by launching ultra-high frequency bulk acoustic waves in the films. In a second set of experiments, dispersion curves of the A0 mode of the Lamb waves that propagate along the unsupported films are measured using a broadband photoacoustic guided-wave method. The residual stresses and flexural rigidities for the same set of double-layer membranes are determined from these dispersion curves. Comparisons of the results obtained by the two photoacoustic techniques are made.

  20. Approaching intrinsic performance in ultra-thin silicon nitride drum resonators

    NASA Astrophysics Data System (ADS)

    Adiga, V. P.; Ilic, B.; Barton, R. A.; Wilson-Rae, I.; Craighead, H. G.; Parpia, J. M.

    2012-09-01

    We have fabricated circular silicon nitride drums of varying diameter (20 μm to 1 mm) and thickness (15 nm-75 nm) using electron beam lithography and measured the dissipation (Q-1) of these amorphous silicon nitride resonators using optical interferometric detection. We observe that the dissipation is strongly dependent on mode type for relatively large, thick membranes as predicted by the current models of dissipation due to clamping loss. However, this dependence is drastically reduced for smaller or thinner resonators, with thinner resonators showing higher quality factors, for low order modes. Highest quality factors that can be reached for these thin resonators seems be limited by an intrinsic mechanism and scales linearly with the diameter of the membrane. Our results are promising for mass sensing and optomechanical applications where low mass and high Qs are desirable.

  1. 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.

  2. Role of fluorine in plasma nitridated ZrO{sub 2} thin films under irradiation

    SciTech Connect

    Huang, A. P.; Xiao, Z. S.; Liu, X. Y.; Wang, L.; Chu, Paul K.

    2008-09-22

    The role of fluorine in plasma-nitridated ZrO{sub 2} thin films under electron irradiation is investigated in situ by real-time high-resolution transmission electron microscopy. Fluorine and nitrogen codoping can suppress the microstructure evolution during electron beam bombardment and the corresponding origin is probed and verified. The results obtained by irradiation with an ultraviolet laser show that plasma fluorination can effectively remove the dissociative N or O particles in the ZrO{sub 2} thin films which can escape from the interstitial sites under electron irradiation. The mechanism of the irradiation stability of the F and N codoped ZrO{sub 2} thin film is also discussed.

  3. 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.

  4. Influence of the magnetron on the growth of aluminum nitride thin films deposited by reactive sputtering

    SciTech Connect

    Iriarte, G. F.

    2010-03-15

    Aluminum nitride (AlN) thin films deposited on high-vacuum systems without substrate heating generally exhibit a poor degree of c-axis orientation. This is due to the nonequilibrium conditions existing between the energy of the sputtered particles and the energy at the substrate surface. The application of substrate bias or substrate temperature is known to improve the adatom mobility by delivering energy to the substrate; both are hence well-established crystal growth promoting factors. It is well known that low sputtering pressures can be used as a parameter improving the growth of highly c-axis oriented aluminum nitride films at room temperature even without applying bias voltage to the substrate. Generally, the use of high pressures implies thermalization of particles within the gas phase and is considered to increase the energy gap between these and the substrate surface. However, in later experiments we have learned that the use of high processing pressures does not necessarily implies a detriment of crystallographic orientation in the films. By measuring (for the first time to the author's knowledge) the full width at half maximum value of the rocking curve of the 0002-AlN peak at several positions along the 100 mm diameter (100)-silicon wafers on which aluminum nitride thin films were deposited by reactive sputtering, a new effect was observed. Under certain processing conditions, the growth of the AlN thin films is influenced by the target magnetron. More precisely, their degree of c-axis orientation varies at wafer areas locally coincident under the target magnetron. This effect should be considered, especially where large area substrates are employed such as in silicon wafer foundry manufacturing processes.

  5. Iron-Nitride Thin Films Prepared by Arc-Discharge-Type Ion-Plating

    NASA Astrophysics Data System (ADS)

    Umeda, Kazuo; Kawashimo, Yasushi; Nakasone, Masami; Harada, Shigehisa; Tasaki, Akira

    1984-12-01

    Ferromagnetic iron-nitride thin films were studied as part of a programme of research into recording media. Samples were prepared by using a new type of ion-plating called “arc-discharge-type ion-plating”. In order to ionize metal vapor and nitrogen gas effectively, a new ionization electrode was introduced between 2× 10-4 and 2× 10-3 Torr. Nitrized films were obtained when the films were prepared above 2× 10-4 Torr. The composition of the films was analyzed using Mössbauer spectroscopy, and it was confirmed that the films were highly corrosion-resistant.

  6. Single Nanoparticle-Based Heteronanojunction as a Plasmon Ruler for Measuring Dielectric Thin Films.

    PubMed

    Li, Li; Hutter, Tanya; Li, Wenwu; Mahajan, Sumeet

    2015-06-18

    Nondestructive, noninvasive and accurate measurement of thin film thicknesses on dielectric substrates is challenging. In this work a ruler for measuring thin film thicknesses utilizes the heteronanojunction construct formed between a plasmonic nanoparticle and a high refractive index nonplasmonic substrate. The high near-field sensitivity in the nanojunction renders it suitable for measuring the thickness of intervening dielectric thin films. We demonstrate this by controlling the thickness of dielectric spacer layers created by overgrowing SiO2 thin films on commercially available silicon substrates. While Rayleigh (using dark-field) scattering measurements show that the spectral response is well correlated to the thickness of SiO2 spacer layers the distance-dependence is much steeper with surface-enhanced Raman scattering (SERS). Good agreement between 3D simulations and experimental results confirm the plasmon ruler construct's sensitivity to the dielectric thin film spacing. Thus, we postulate that this single nanoparticle based heteronanojunction configuration can serve as a convenient and simple ruler in metrology of thin films as well as a platform for SERS-based detection even in cases where plasmonically active films are not a suitable substrate. PMID:26266605

  7. Piezoelectric Behaviour of Sputtered Aluminium Nitride Thin Film for High Frequency Ultrasonic Sensors

    NASA Astrophysics Data System (ADS)

    Herzog, T.; Walter, S.; Bartzsch, H.; Gittner, M.; Gloess, D.; Heuer, H.

    2011-06-01

    Many new materials and processes require non destructive evaluation in higher resolutions by phased array ultrasonic techniques in a frequency range up to 250 MHz. This paper presents aluminium nitride, a promising material for the use as a piezoelectric sensor material in the considered frequency range, which contains the potential for high frequency phased array application in the future. This work represents the fundamental development of piezoelectric aluminium nitride films with a thickness of up to 10 μm. We have investigated and optimized the deposition process of the aluminium nitride thin film layers regarding their piezoelectric behavior. Therefore a specific test setup and a measuring station were created to determine the piezoelectric charge constant (d33) and the electro acoustic behavior of the sensor. Single element transducers were deposited on silicon substrates with aluminium electrodes for top and bottom, using different parameters for the magnetron sputter process, like pressure and bias voltage. Afterwards acoustical measurements up to 500 MHz in pulse echo mode have been carried out and the electrical and electromechanical properties were qualified. In two different parameter sets for the sputtering process excellent piezoelectric charge constant of about 8.0 pC/N maximum were obtained.

  8. Nanoindentation of plasma-deposited nitrogen-rich silicon nitride thin films

    NASA Astrophysics Data System (ADS)

    Soh, Martin T. K.; Fischer-Cripps, A. C.; Savvides, N.; Musca, C. A.; Faraone, L.

    2006-07-01

    Nanoindentation was performed on plasma-deposited nitrogen-rich silicon nitride thin films deposited on various substrates between 150 and 300°C. A very simple and effective depth-profiling method is introduced, which involves indentation of thin films deposited on substrates with different mechanical properties. The primary advantage of this method is that it avoids the complications associated with many of the complex mathematical models available to deconvolve thin film mechanical properties, while nevertheless allowing the user to visually identify thin film properties. This method is demonstrated on our thin films, which have a hardness between 14 and 21GPa, and reduced modulus between 120 and 160GPa. The initial rise in hardness at low contact depths, commonly attributed to an indentation-size effect, is shown to be due to elastic contact between the indenter and thin film surface. This demonstrates the perils of blindly following the 10% rule for hardness calculation. The contribution of elastic and plastic deformations from nanoindentation is used to clarify the physical meaning of hardness and reduced modulus.

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

    DOE PAGESBeta

    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; et al

    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

  10. 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.

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

    PubMed Central

    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

    2015-01-01

    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. PMID:26598075

  12. Low leakage current gate dielectrics prepared by ion beam assisted deposition for organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Chang Su; Jo, Sung Jin; Kim, Jong Bok; Ryu, Seung Yoon; Noh, Joo Hyon; Baik, Hong Koo; Lee, Se Jong; Kim, Youn Sang

    2007-12-01

    This communication reports on the fabrication of low operating voltage pentacene thin-film transistors with high-k gate dielectrics by ion beam assisted deposition (IBAD). These densely packed dielectric layers by IBAD show a much lower level of leakage current than those created by e-beam evaporation. These results, from the fact that those thin films deposited with low adatom mobility, have an open structure, consisting of spherical grains with pores in between, that acts as a significant path for leakage current. By contrast, our results demonstrate the potential to limit this leakage. The field effect mobility, on/off current ratio, and subthreshold slope obtained from pentacene thin-film transistors (TFTs) were 1.14 cm2/V s, 105, and 0.41 V/dec, respectively. Thus, the high-k gate dielectrics obtained by IBAD show promise in realizing low leakage current, low voltage, and high mobility pentacene TFTs.

  13. Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

    NASA Astrophysics Data System (ADS)

    Liang, Wei-Zheng; Ji, Yan-Da; Nan, Tian-Xiang; Huang, Jiang; Zeng, Hui-Zhong; Du, Hui; Chen, Chong-Lin; Lin, Yuan

    2012-06-01

    Barium titanate (BTO) thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition (PAD) technique. The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion. Crystal structures, surface morphologies, and dielectric performance were examined and compared for BTO thin films annealed under different temperatures. Correlations between the fabrication conditions, microstructures, and dielectric properties were discussed. BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with inr ~ 400 and tan δ < 0.025 at 100 kHz. The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.

  14. Effect of biphase on dielectric properties of Bi-doped lead strontium titanate thin films

    NASA Astrophysics Data System (ADS)

    Li, X. T.; Du, P. Y.; Zhao, Y. L.; Tu, Y.; Dai, J. L.; Weng, W. J.; Han, G. R.; Song, C. L.

    2010-11-01

    Pb 0.4Sr 0.6TiO 3 (PST) thin films doped with various concentration of Bi were prepared by a sol-gel method. The phase status, surface morphology and dielectric properties of these thin films were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance analyzer, respectively. Results showed that the thin films with the maximum dielectric constant and minimum dielectric loss were obtained for x=0.15. For x<0.15, only pure PST perovskite phase were in the thin films. For 0.2< x<0.4, the PST/Bi 2Ti 2O 7 biphase were obtained. The thin films with pure Bi 2Ti 2O 7 pyrochlore phase were obtained for x=0.67. The biphase thin films had high tunability and high figure of merit (FOM). The FOM of PST/Bi 2Ti 2O 7 biphase thin film was about 6 times higher than that thin films formed with pure perovskite phase or pure pyrochlore phase.

  15. 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.

  16. Thermal Contact Conductance Analysis of Nitride and Carbonitride Thin Film Coatings for Thermal Interface Material Application

    NASA Astrophysics Data System (ADS)

    Subramani, Shanmugan; Thing, Lee Yuan; Devarajan, Mutharasu

    2015-12-01

    In order to reduce and maintain the bond line thickness between substrate and LED package, solid thin film with good thermal conductivity is suggested as thermal interface material and the proposed film thickness is about less than 1 µ. The surface parameter such as roughness and hardness is a key factor which alters the contact conductance between the two matt surfaces. Consequently, filtered vacuum cathodic arc deposited nitride thin films (CrN, TiN, AlTiN, and TiCN) on copper substrate were tested for thermal interface material applications in electronic packaging. The thermal contact conductance of the prepared thin films was evaluated using surface properties such as microhardness and surface roughness. The results were verified with the theoretical model. The measured microhardness and surface roughness of CrN thin film are 17 GPa (low) and 0.768 µm (high), respectively. The measured thermal contact conductance of all thin films showed linear properties for applied pressure and very close to the values of theoretical model. High value in thermal contact conductance of about 256 W/m2 K was noticed with CrN thin film at 1100 kPa. The percentage of deviation for our measured contact conductance value from the theoretical model value was decreasing for the increased contact pressure and observed low value (7 pct) for CrN thin film at 1100 kPa. The thermal conductivity of all thin films was also calculated from the conductance model and observed high value (19.34 W/mK) with CrN thin film.

  17. 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.

  18. Sol processing of conjugated carbon nitride powders for thin-film fabrication.

    PubMed

    Zhang, Jinshui; Zhang, Mingwen; Lin, Lihua; Wang, Xinchen

    2015-05-18

    The chemical protonation of graphitic carbon nitride (CN) solids with strong oxidizing acids, for example HNO3, is demonstrated as an efficient pathway for the sol processing of a stable CN colloidal suspension, which can be translated into thin films by dip/disperse-coating techniques. The unique features of CN colloids, such as the polymeric matrix and the reversible hydrogen bonding, result in the thin-film electrodes derived from the sol solution exhibiting a high mechanical stability with improved conductivity for charge transport, and thus show a remarkably enhanced photo-electrochemical performance. The polymer system can in principle be broadly tuned by hybridization with desired functionalities, thus paving the way for the application of CN for specific tasks, as exemplified here by coupling with carbon nanotubes. PMID:25833791

  19. Influence of process parameters on properties of reactively sputtered tungsten nitride thin films

    SciTech Connect

    Addonizio, Maria L.; Castaldo, Anna; Antonaia, Alessandro; Gambale, Emilia; Iemmo, Laura

    2012-05-15

    Tungsten nitride (WN{sub x}) thin films were produced by reactive dc magnetron sputtering of tungsten in an Ar-N{sub 2} gas mixture. The influence of the deposition power on the properties of tungsten nitride has been analyzed and compared with that induced by nitrogen content variation in the sputtering gas. A combined analysis of structural, electrical and optical properties on thin WN{sub x} films obtained at different deposition conditions has been performed. It was found that at an N{sub 2} content of 14% a single phase structure of W{sub 2}N films was formed with the highest crystalline content. This sputtering gas composition was subsequently used for fabricating films at different deposition powers. Optical analysis showed that increasing the deposition power created tungsten nitride films with a more metallic character, which is confirmed with resistivity measurements. At low sputtering powers the resulting films were crystalline whereas, with an increase of power, an amorphous phase was also present. The incorporation of an excess of nitrogen atoms resulted in an expansion of the W{sub 2}N lattice and this effect was more pronounced at low deposition powers. Infrared analysis revealed that in WN{sub x} films deposited at low power, chemisorbed N{sub 2} molecules did not behave as ligands whereas at high deposition power they clearly appeared as ligands around metallic tungsten. In this study, the influence of the most meaningful deposition parameters on the phase transformation reaction path was established and deposition conditions suitable for producing thermally stable and highly crystalline W{sub 2}N films were found.

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

    SciTech Connect

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

    2005-08-15

    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.

  1. 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.

  2. Thickness dependence of Young's modulus and residual stress of sputtered aluminum nitride thin films

    NASA Astrophysics Data System (ADS)

    Schneider, M.; Bittner, A.; Schmid, U.

    2014-11-01

    Aluminum nitride thin films are commonly used as active layer in micro-/nanomachined devices due to their piezoelectric properties. In order to predict the performance of advanced device architectures, careful modelling and simulation using techniques such as finite element analysis are of the utmost importance. An accurate knowledge of the corresponding thin film material properties is therefore required. This work focuses on the mechanical properties residual stress and Young's modulus over a wide thickness range from 100 to 1200 nm. The load-deflection technique is used to measure the bending curve of a circumferentially clamped, circular aluminum nitride diaphragm under a uniformly distributed pressure load. The bending curves are analyzed using an advanced analytical approach rather than commonly used models for load-deflection methods, thus resulting in a higher accuracy. It is found that the Young's modulus is nearly independent of film thickness, whereas the tensile residual stress exhibits a maximum at a thickness of about 600 nm. A thorough discussion of possible error sources is presented and approaches to minimize their impact are discussed.

  3. 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.

  4. 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.

  5. Dielectric and Ferroelectric Performance of Pb(Zr(x)Ti(1-x))O3 Thin Films with Compositional Gradients.

    PubMed

    He, Gang; Zhou, Yongju; Peng, Chao; Zhang, Yao; Pan, Wei

    2015-09-01

    A series of PZT thin films with compositional gradients were fabricated at ease by a combinatorial chemical solution deposition process. Their dielectric and ferroelectric properties are significantly different from uniform composition PZT films, depending on the composition, the span, and the direction of the compositional gradient. Among samples with the same average Zr content, the down-gradient thin films exhibit better dielectric and ferroelectric properties. PZT thin films with a narrow compositional gradient span favour better dielectric and ferroelectric properties. The down-gradient thin film PZT654 with a Zr-rich layer closest to the Pt substrate, in which the average composition is close to the morphotropic phase boundary (MPB, x = 0.52), shows the best dielectric and ferroelectric performance. These distinct thin films with different dielectric and ferroelectric properties could be designed by adjusting factors such as content, span and direction of the compositional gradient. PMID:26716290

  6. 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.

  7. 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

  8. Comparison of equivalent oxide thickness and electrical properties of atomic layer deposited hafnium zirconate dielectrics with thermal or decoupled plasma nitridation process

    NASA Astrophysics Data System (ADS)

    Chiang, Chen-Kuo; Wu, Chien-Hung; Liu, Chin-Chien; Lin, Jin-Fu; Yang, Chien-Lun; Wu, Jiun-Yuan; Wang, Shui-Jinn

    2012-10-01

    The NH3 thermal annealing and decoupled plasma nitridation (DPN) processes are compared for the equivalent oxide thickness (EOT) scaling of atomic-layer-deposited hafnium zirconate (HfZrO2) gate dielectric. Detailed physical, optical, and electrical characteristics of nitrided HfZrO2 (HfZrON) film are reported. It is found that DPN can yield a thinner SiOx interfacial layer (IL) (about 0.12 nm more in terms of EOT scaling) and a more densified HfZrO2 layer compared to those obtained using NH3 thermal annealing at a 16% nitrogen dose. NH3 thermal nitridation causes a large nitrogen distribution tail at the SiOx IL/Si substrate interface and increases leakage current, which suppresses EOT scalability.

  9. Partially hollowed ultra-thin dielectric meta-surface for transmission manipulation.

    PubMed

    Liu, Guiqiang; Fu, Guolan; Liu, Zhengqi; Huang, Zhenping; Chen, Jian

    2016-09-01

    Impressive optical properties are numerically demonstrated in the partially hollowed dielectric meta-surface (p-HDMS), which consists of an air cavity array intercalated in an ultra-thin (~λ/6) high-index dielectric film. Multispectral transmission band-stop response with near-perfect spectral modulation depth is achieved. The spectral slop is up to 80%/nm, indicating the sharp and narrowband transmission behavior. Classical Malus law is confirmed by this sub-wavelength platform. Moreover, the multispectral light propagation manipulation can be perfectly reproduced by using the actual dielectric with absorption loss. In this all-dielectric meta-surface, conduction loss is avoided compared to its metallic plasmonic counterpart. Such configurations can therefore serve as excellent alternatives for plasmonic meta-surfaces and constitute an important step in nanophotonics. PMID:27607661

  10. Light absorption enhancement in thin-film solar cells using whispering gallery modes in dielectric nanospheres

    SciTech Connect

    Grandidier, Jonathan; Callahan, Dennis M; Munday, Jeremy N; Atwater, Harry A.

    2011-03-07

    A novel approach to increasing light absorption in thin-film solar cells is demonstrated. This new method involves redirecting the incident sunlight into the cell via coupling to the whispering gallery modes of dielectric spheres, which lie atop the cell. Such a scheme leads to a predicted current enhancement of >12% for a-Si.

  11. Dielectric properties of fluorocarbon thin films deposited by radio frequency sputtering of polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Gonon, P.; Sylvestre, A.

    2002-10-01

    We investigate the dielectric properties of fluorocarbon thin films deposited by radio-frequency magnetron sputtering of polytetrafluroethylene. The dielectric constant and the loss factor are studied as a function of frequency (0.1 Hz-1 MHz, infrared frequencies) and temperature (room temperature to 100 °C). The value of the dielectric constant is 1.8 at optical frequencies, and around 2.3 in the 0.1 Hz-1 MHz range. The background loss factor is around 0.8% in these samples. Two different polarization mechanisms are identified (β and γ relaxations). The γ process dominates the dielectric constant from 0.1 to 1 MHz. In this frequency range the dielectric constant decreases with temperature (about -4% from room temperature to 100 °C). Temperature dependence of the dielectric constant is well described by a simple Debye model (linear variation of the dielectric constant with 1/T). The γ relaxation is tentatively ascribed to C-F bonds (Nμ2=4×10-32 C2 m-1). The β relaxation has a loss peak located at very low frequencies (<0.1 Hz). It leads to an increase of loss below 10 Hz when temperature is increased above 75 °C. The high-frequency part of the β loss peak decreases as ω-0.35. Study of its temperature dependence leads to an activation energy of 0.66 eV.

  12. Methods for investigating thin dielectric films in the millimeter range

    NASA Astrophysics Data System (ADS)

    Vlasov, S. N.; Parshin, V. V.; Serov, E. A.

    2010-12-01

    An original method based on determining the characteristics of open Fabry-Perot resonator modes with different polarizations is proposed for measuring parameters of dielectric plates and films with a thickness smaller than λ/2 in the millimeter and submillimeter wavelength ranges. This method is used for determining the refractive index and tanδ, as well as the thickness of films made of isotropic materials. For anisotropic films of known thickness, the method makes it possible to measure the permittivity tensor components. Popular film materials such as Teflon (polytetrafluoroethylene, PTFE), lavsan (Mylar, polyethyleneterephthalate, PETP), and polyamide with a minimal thickness of ˜5 μm are investigated. Appreciable anisotropy of roll film materials and the dependence of the dielectric properties on the thickness, which is associated with manufacturing technology, are revealed. The dependence of the refractive index and tanδ on the air humidity is investigated

  13. 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. PMID:23220817

  14. Plasmonic arrays of titanium nitride nanoparticles fabricated from epitaxial thin films.

    PubMed

    Murai, Shunsuke; Fujita, Koji; Daido, Yohei; Yasuhara, Ryuichiro; Kamakura, Ryosuke; Tanaka, Katsuhisa

    2016-01-25

    We have fabricated two-dimensional periodic arrays of titanium nitride (TiN) nanoparticles from epitaxial thin films. The thin films of TiN, deposited on sapphire and single crystalline magnesium oxide substrates by a pulsed laser deposition, are metallic and show reasonably small optical loss in the visible and near infrared regions. The thin films prepared were structured to the arrays of nanoparticles with the pitch of 400 nm by the combination of nanoimprint lithography and reactive ion etching. Optical transmission indicates that the arrays support the collective plasmonic modes, where the localized surface plasmon polaritons in TiN nanoparticles are radiatively coupled through diffraction. Numerical simulation visualizes the intense fields accumulated both in the nanoparticles and in between the particles, confirming that the collective mode originates from the simultaneous excitation of localized surface plasmon polaritons and diffraction. This study experimentally verified that the processing of TiN thin films with the nanoimprint lithography and reactive ion etching is a powerful and versatile way of preparing plasmonic nanostructures. PMID:26832498

  15. Resonant x-ray reflectivity study of partial decomposed boron nitride thin films using Indus-1 synchrotron

    SciTech Connect

    Nayak, Maheswar Lodha, Gyanendra S.

    2014-04-24

    We determined the microstructural parameters and chemical composition profile of partial decomposed boron nitride thin films using x-ray reflectivity near the respective absorption edges. The elemental specificity and optical contrast variation properties of the resonant effect are utilized to combine chemical analysis with physical microstructure of thin films from x-ray scattered intensities. We demonstrated these aspects through calculations and experiments in the soft x-ray region near the boron K-absorption edge.

  16. Correlation between the dielectric constant and porosity of nanoporous silica thin films deposited by the gas evaporation technique

    NASA Astrophysics Data System (ADS)

    Si, J. J.; Ono, H.; Uchida, K.; Nozaki, S.; Morisaki, H.; Itoh, N.

    2001-11-01

    Nanoporous silica thin films with low dielectric constants were deposited by gas evaporation of SiO2 nanoparticles in an argon atmosphere. With increasing gas pressure during the evaporation, the dielectric constant decreases, while the porosity increases. The correlation between the dielectric constant and porosity is well modeled by a serial connection of two capacitors, one with air and the other with SiO2 as the dielectric medium. This suggests that the dielectric constant of the nanoporous silica thin film using the gas evaporation technique is more effectively lowered by forming "uniformly" distributed voids of closed gaps than those of the nanoporous silica films with pores extending from the back to front surface. Therefore, the former nanoporous silica thin film requires less porosity to obtain a low dielectric constant and is regarded as an ideal low-k material.

  17. Electron transport of WS2 transistors in a hexagonal boron nitride dielectric environment

    PubMed Central

    Withers, Freddie; Bointon, Thomas Hardisty; Hudson, David Christopher; Craciun, Monica Felicia; Russo, Saverio

    2014-01-01

    We present the first study of the intrinsic electrical properties of WS2 transistors fabricated with two different dielectric environments WS2 on SiO2 and WS2 on h-BN/SiO2, respectively. A comparative analysis of the electrical characteristics of multiple transistors fabricated from natural and synthetic WS2 with various thicknesses from single- up to four-layers and over a wide temperature range from 300 K down to 4.2 K shows that disorder intrinsic to WS2 is currently the limiting factor of the electrical properties of this material. These results shed light on the role played by extrinsic factors such as charge traps in the oxide dielectric thought to be the cause for the commonly observed small values of charge carrier mobility in transition metal dichalcogenides.

  18. 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

  19. Substrate temperature influence on the trombogenicity in amorphous carbon nitride thin coatings

    NASA Astrophysics Data System (ADS)

    Galeano-Osorio, D. S.; Vargas, S.; López-Córdoba, L. M.; Ospina, R.; Restrepo-Parra, E.; Arango, P. J.

    2010-10-01

    Carbon nitride thin films were obtained through plasma assisted physical vapor deposition technique by pulsed arc, varying the substrate temperature and investigating the influence of this parameter on the films hemocompatibility. For obtaining approaches of blood compatibility, environmental scanning electron microscopy (ESEM) was used in order to study the platelets adherence and their morphology. Moreover, the elemental chemical composition was determined by using energy dispersive spectroscopy (EDS), finding C, N and O. The coatings hemocompatibility was evaluated by in vitro thrombogenicity test, whose results were correlated with the microstructure and roughness of the films obtained. During the films growth process, the substrate temperature was varied, obtaining coatings under different temperatures, room temperature ( Troom), 100 °C, 150 °C and 200 °C. Parameters as interelectrodic distance, voltage, work pressure and number of discharges, were remained constant. By EDS, carbon and nitrogen were found in the films. Visible Raman spectroscopy was used, and it revealed an amorphous lattice, with graphitic process as the substrate temperature was increased. However, at a critical temperature of 150 °C, this tendency was broken, and the film became more amorphous. This film showed the lowest roughness, 2 ± 1 nm. This last characteristic favored the films hemocompatibility. Also, it was demonstrated that the blood compatibility of carbon nitride films obtained were affected by the ID/ IG or sp 3/sp 2 ratio and not by the absolute sp 3 or sp 2 concentration.

  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. Fabrication of an interdigitated sample holder for dielectric spectroscopy of thin films

    NASA Astrophysics Data System (ADS)

    Shenouda, Mina; Oliver, Derek R.

    2015-06-01

    A planar interdigitated sample substrate has been designed to support a thin-film sample of a polymer while the frequency-dependent dielectric properties of the thin film are measured. Trenches for the electrodes were etched into a SiO2/Si wafer surface. Chromium was used as an adhesion layer prior to thermal evaporation of copper for the body of the electrode. The device was placed in a standard probe station and the dielectric character was recorded as a function of frequency with an impedance analyser. Devices with 20 to 70 fingers were measured and the results compared to analytical and finite element simulations. At 1 kHz, the total capacitance of a typical 20-finger device was 8 pF. The capacitive contribution of the thin film due to the fringing field in the polymer was about 2% of the total capacitance of the fabricated structures.

  2. 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.

  3. FDTD simulations and analysis of thin sample dielectric properties measurements using coaxial probes

    SciTech Connect

    Bringhurst, S.; Iskander, M.F.; White, M.J.

    1996-12-31

    A metallized ceramic probe has been designed for high temperature broadband dielectric properties measurements. The probe was fabricated out of an alumina tube and rod as the outer and inner conductors respectively. The alumina was metallized with a 3 mil layer of moly-manganese and then covered with a 0.5 mil protective layer of nickel plating. The probe has been used to make complex dielectric properties measurements over the complete frequency band from 500 MHz to 3 GHz, and for temperatures as high as 1,000 C. A 3D Finite-Difference Time-Domain (FDTD) code was used to help investigate the feasibility of this probe to measure the complex permittivity of thin samples. It is shown that by backing the material under test with a standard material of known dielectric constant, the complex permittivity of thin samples can be measured accurately using the developed FDTD algorithm. This FDTD procedure for making thin sample dielectric properties measurements will be described.

  4. Electrical Properties of PVP-SiO2-TMSPM Hybrid Thin Films as OFET Gate Dielectric

    NASA Astrophysics Data System (ADS)

    Bahari, A.; Shahbazi, M.

    2016-02-01

    Organic-inorganic polyvinylpyrrolidone-silicon dioxide-3-(trimethoxysilyl)propyl methacrylate (PVP-SiO2-TMSPM) hybrid solutions have been synthesized using the sol-gel process with different amounts of TMSPM as coupling agent and equivalent amounts of PVP and SiO2. Hybrid solutions were deposited on p-type Si(111) substrates using the spin coating technique, as a gate dielectric material for use in thin-film transistors. The structural properties of the samples were investigated using Fourier-transform infrared spectroscopy and x-ray diffraction analysis. Atomic force microscopy and scanning electron microscopy techniques were applied to study the topography and morphology of the hybrid thin-film samples. Current-voltage ( I- V) curves, capacitance-voltage ( C- V) measurements, and the electrical properties of the organic hybrid thin-film gate dielectrics were also studied in a metal-insulator/polymer-semiconductor structure. According to the results, the J GS curves in terms of V GS showed gate leakage current densities small enough for use as gate dielectric material at interface layers. At V DS = 30 V, in the saturation region, I DS curves in terms of V GS presented higher charge carrier mobility ( μ FET,S = 0.0584 cm2 s-1 V-1) due to lower dielectric constant ( k = 11.43) in the sample with 0.05 weight ratio of TMSPM compared with other samples with different weight ratios of TMSPM.

  5. Effect of the growth process on boron nitride thin films electrical properties

    SciTech Connect

    Badi, N.; Bousetta, A.; Lu, M.

    1995-12-31

    Boron nitride thin films were grown on Si substrates using electron cyclotron resonance (ECR) plasma-ion beam (IBD), and neutral beam (NBD) assisted vapor depositions. The electrical properties of the BN films were investigated using Hall measurements. It was found that the films grown by NBD technique where p-type, those grown by ECR technique where n-type, whereas those grown by IBD where either n- to p-type depending on the ion energy. The composition of the films was investigated using EPMA, and it was found that most films were off-Stoichiometric (B/N <1 for ECR and B/N> 1 for NBD and IBD). The B/N ratio was higher for IBD BN films (up to 22 %). A model based on native defects centers (nitrogen vacancy and boron anti-site) is presented to account for the conductivity of the BN films.

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

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Yang, Yingchao; Lou, Jun

    2016-09-01

    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. Properties of carbon nitride thin films prepared by ion and vapor deposition

    NASA Astrophysics Data System (ADS)

    Chubaci, J. F. D.; Sakai, T.; Yamamoto, T.; Ogata, K.; Ebe, A.; Fujimoto, F.

    1993-06-01

    This paper reports on mechanica, and optical properties of carbon nitride films coatings formed by the ion and vapor deposition (IVD) method. The thin films were formed by nitrogen ion bombardment and simultaneous carbon vapor deposition on substrates of fused silica and silicon (100) wafers. The energy of nitrogen ion was varied from 0.2 to 10.0 keV and the composition ratio (C/N) was varied from 5.0 to 14.0. The X-ray diffraction study indicated that the films were amorphous. The FT-IR spectra showed a small peak between 2100 and 2200 cm -1 indicating the presence of a triple bonded C-N stretching mode and the XPS ones showed a broad peak of i-carbon with a peak-shoulder at a bonding energy for diamondlike covalent bond. All formed films have a high hardness.

  8. Influence of polar distribution on piezoelectric response of aluminum nitride thin films

    SciTech Connect

    Kamohara, Toshihiro; Akiyama, Morito; Kuwano, Noriyuki

    2008-03-03

    The authors have investigated the influence of the crystal orientation and the polar distribution on the piezoelectric response of aluminum nitride (AlN) thin films prepared on Si, Mo/Si, and Mo/AlN-interlayer (IL)/Si substrates with increasing sputtering power. The crystal orientation of films prepared on Si improves with increasing sputtering power. On the other hand, the crystal orientation of films prepared on Mo/Si and Mo/AlN-IL/Si hardly changes. However, the piezoelectric response of all the films drastically changes from negative to positive values and the predominant polarity changes from N polarity to Al polarity. We found the proportional relationship between the polar distribution and piezoelectric response.

  9. Influence of oxygen concentration in sputtering gas on piezoelectric response of aluminum nitride thin films

    SciTech Connect

    Akiyama, Morito; Kamohara, Toshihiro; Kano, Kazuhiko; Teshigahara, Akihiko; Kawahara, Nobuaki

    2008-07-14

    The authors have investigated the influence of oxygen concentration in sputtering gas on the piezoelectric response of aluminum nitride (AlN) thin films prepared on silicon substrates. The piezoelectric response strongly depends on the oxygen concentration, and changes from +6.8 to -7.0 pC/N with increasing oxygen concentration from 0% to 1.2%. The polar direction drastically inverts from the Al polarity to N polarity. When the oxygen concentration in sputtering gas was 1.2%, the oxygen concentration in the AlN films was 7 at. %. Furthermore, the growth rate of the AlN films gradually decreases with increasing oxygen concentration in sputtering gas.

  10. Hardness and deformation mechanisms of highly elastic carbon nitride thin films as studied by nanoindentation

    SciTech Connect

    Hainsworth, S.V.; Page, T.F.; Sjoestroem, H.; Sundgren, J.E.

    1997-05-01

    Carbon nitride (CN{sub x}) thin films (0.18 < x < 0.43), deposited by magnetron sputtering of C in a N{sub 2} discharge, have been observed to be extremely resistant to plastic deformation during surface contact (i.e., exhibit a purely elastic response over large strains). Elastic recoveries as high as 90% have been measured by nanoindentation. This paper addresses the problems of estimating Young`s modulus (E) and hardness (H) in such cases and shows how different strategies involving analysis of both loading and unloading curves and measuring the work of indentation each present their own problems. The results of some cyclic contact experiments are also presented and possible deformation mechanisms in the fullerene-like CN{sub x} structures discussed.

  11. Hard and elastic amorphous carbon nitride thin films studied by 13C nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Gammon, W. J.; Malyarenko, D. I.; Kraft, O.; Hoatson, G. L.; Reilly, A. C.; Holloway, B. C.

    2002-10-01

    The chemical bonding of hard and elastic amorphous carbon nitride (a-CNx) thin films was examined using solid-state 13C NMR spectroscopy. The films were deposited by DC magnetron sputtering in a pure nitrogen discharge on Si(001) substrates at 300 °C. Nanoindentation tests reveal a recovery of 80%, a hardness of 5 GPa, and an elastic modulus of 47 GPa. This combination of low modulus and high strength means the material can be regarded as hard and elastic; the material gives when pressed on and recovers its shape when the load is released. The 13C NMR results conclusively demonstrate that hard and elastic a-CNx has an sp2 carbon bonded structure and that sp3 hybridized carbons are absent. Our results stand in contrast with earlier work that proposed that the interesting mechanical properties of hard and elastic a-CNx were due, in part, to sp3 bonded carbon.

  12. 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.

  13. The influence of atomic nitrogen flux on the composition of carbon nitride thin films

    SciTech Connect

    Merel, P.; Chaker, M.; Tabbal, M.; Moisan, M.

    1997-12-01

    Carbon nitride (CN{sub x}) thin films have been deposited using a hybrid system combining pulsed laser deposition of graphite with the surface-wave discharge atomic nitrogen source (3{percent} N{sub 2} in Ar). Using this system, an experiment is designed to study the influence of the atomic nitrogen flux on the composition of the CN{sub x} thin films at various laser intensities. The nitrogen percentage in the thin films is positively correlated with the N atom flux impinging on the substrate surface but it is counter-productive to use excessively high values of laser intensities on the graphite target. For a laser intensity of 6{times}10{sup 8}W/cm{sup 2}, the nitrogen percentage increases with the N atom flux and saturates at only about 16 at.{percent}. On the other hand, a maximum nitrogen percentage of 30 at.{percent} is obtained at the much lower laser intensity of 5{times}10{sup 7}W/cm{sup 2}. {copyright} {ital 1997 American Institute of Physics.}

  14. Early stages of growth and crystal structure evolution of boron nitride thin films

    NASA Astrophysics Data System (ADS)

    Henry, Anne; Chubarov, Mikhail; Czigány, Zsolt; Garbrecht, Magnus; Högberg, Hans

    2016-05-01

    A study of the nucleation and crystal structure evolution at the early stages of the growth of sp2-BN thin films on 6H-SiC and α-Al2O3 substrates is presented. The growth is performed at low pressure and high temperature in a hot wall CVD reactor, using ammonia and triethylboron as precursors, and H2 as carrier gas. From high-resolution transmission electron microscopy and X-ray thin film diffraction measurements we observe that polytype pure rhombohedral BN (r-BN) is obtained on 6H-SiC substrates. On α-Al2O3 an AlN buffer obtained by nitridation is needed to promote the growth of hexagonal BN (h-BN) to a thickness of around 4 nm followed by a transition to r-BN growth. In addition, when r-BN is obtained, triangular features show up in plan-view scanning electron microscopy which are not seen on thin h-BN layers. The formation of BN after already one minute of growth is confirmed by X-ray photoelectron spectroscopy.

  15. Flexible piezoelectric pressure sensors using oriented aluminum nitride thin films prepared on polyethylene terephthalate films

    NASA Astrophysics Data System (ADS)

    Akiyama, Morito; Morofuji, Yukari; Kamohara, Toshihiro; Nishikubo, Keiko; Tsubai, Masayoshi; Fukuda, Osamu; Ueno, Naohiro

    2006-12-01

    We have investigated the high sensitive piezoelectric response of c-axis oriented aluminum nitride (AlN) thin films prepared on polyethylene terephthalate (PET) films. The AlN films were deposited using a radio frequency magnetron sputtering method at temperatures close to room temperature. The c axes of the AlN films were perpendicularly oriented to the PET film surfaces. The sensor consisting of the AlN and PET films is flexible like PET films and the electrical charge is linearly proportional to the stress within a wide range from 0to8.5MPa. The sensor can respond to the frequencies from 0.3 to over 100Hz and measures a clear human pulse wave form by holding the sensor between thumb and middle finger. The resolution of the pulse wave form is comparable to a sphygmomanometer at stress levels of 10kPa. We think that the origin of the high performance of the sensor is the deflection effect, the thin thickness and high elastic modulus of the AlN layer, and the thin thickness and low elastic modulus of the PET film.

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    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.

  18. 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

  19. 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.

  20. Strongly enhanced mode selection in a thin dielectric-coated layered microcavity laser

    NASA Astrophysics Data System (ADS)

    Moon, Hee-Jong; Kang, Dong-Yun

    2007-06-01

    Strong mode selection through an enhanced interferential coupling effect was observed in a thin dielectric-coated layered cylindrical microcavity laser. The strong coupling effect was induced owing to an enhanced reflectivity of around 50% at the dielectric-coated inner boundary of a fused silica capillary filled with a dye-doped liquid. At an optimized coating thickness of about 0.4 μm, the lasing peaks appeared only at the wavelengths corresponding to the constructive interference condition, whereas those from a bare capillary were weakly modulated.

  1. Dynamic electrical response of thin dielectric films measured by Electrostatic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Williams, Clayton; Klein, Levente

    2002-03-01

    Electrostatic Force Microscopy measurements have been performed on thin dielectric films on conducting substrates. Cantilever oscillation amplitude versus distance curves are measured as a function of the frequency of the voltage applied between tip and sample. When a DC voltage is applied, the oscillation amplitude versus distance curve is significantly different from that when a low frequency (500 Hz) AC voltage is applied (cantilever resonance at 125 kHz). The frequency dependence of the AC force response for different dielectric films (SiO2 and Al_2O_3) are studied. The frequency dependence is accounted for by the movement of charge near the sample surface with a finite response time.

  2. The influence of the ion beam on the structure and optical properties of titanium nitride nano-scale thin films

    NASA Astrophysics Data System (ADS)

    Odeh, Ibrahim; Elian, Rajaa

    2015-12-01

    Titanium nitride nano-scale thin films have been prepared by ion beam assisted reactive DC magnetron sputtering. The films are characterized by XRD, SEM and TEM. The films are found to be amorphous. The effect of the ion beam during deposition was evident from smoothness of film surface (SEM and TEM images) and modifications in optical properties. Investigation of the optical constants shows stable refractive index dominating most of the visible range. The films are not highly absorptive in the visible range. An energy gap of 2.9 ± 0.1 eV is estimated for the IBAD amorphous titanium nitride nano-thin films. The stability of the films at normal room environment in addition to the golden color makes the nano-thin films suitable for hard and decorative coatings.

  3. 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.

  4. Synthesis and characterization of boron carbon nitride thin films as protective overcoat for hard disk drives

    NASA Astrophysics Data System (ADS)

    Chen, Yanfeng

    The current goal in the magnetic storage industry is to reach the areal density of 1Tbit/in2 in a few years. This requires the head-media spacing (HMS), which includes media overcoat, lubricant layer, air bearing, and head overcoat, not to exceed 5.0 nm. Trade-off between these layers results in requiring the protective overcoat to be 1.0 nm or less. The protective overcoat must be hard, wear-resistant, continuous, thermally stable, and compatible with the magnetic layer and lubricant. This thesis work is mainly to develop protective overcoat for ultra high density hard disk drives (HDD). Amorphous carbon nitride (a-CNx) thin films were synthesized using pulseDC magnetron sputtering. The influence of substrate bias, substrate tilt, and substrate rotation on film growth and properties was studied. X-ray reflectivity (XRR) was used to measure film density, roughness and thickness. Surface roughness and thickness measurements from XRR are comparable to AFM and surface profiler measurements respectively. a-CNx films have good mechanical properties. Auger electron spectroscopy (AES) and high resolution transmission microscope (HRTEM) were used to obtain the film composition and microstructure. HRTEM cross sectioned experiments showed that CN x film is amorphous. Chemical corrosion experiments display drastic decrease of corrosion spots for thin films synthesized under optimum conditions. In pursuit of new materials for hard disk drive protective overcoat, boron carbide (B4C) and boron carbon nitride (BxC yNz) thin films were synthesized by pulse-DC magnetron sputtering. Effects of target power, target pulse frequency, substrate bias and pulse frequency on surface roughness were studied by AFM. Nitrogen incorporation into B4C films, which gives BxCyNz thin films, has a beneficial effect to decrease the film roughness. Auger electron spectroscopy was used to characterize the film composition. High-resolution cross-sectioned TEM studies showed that both films are amorphous

  5. 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. PMID:26107806

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. A high-k ferroelectric relaxor terpolymer as a gate dielectric for orgnaic thin film transistors

    SciTech Connect

    Wu, Shan; Shao, Ming; Burlingame, Quinn; Chen, Xiangzhong; Lin, Minren; Xiao, Kai; Zhang, Qiming

    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

  11. Mechanism of Schottky barrier height modulation by thin dielectric insertion on n-type germanium

    NASA Astrophysics Data System (ADS)

    Tsui, Bing-Yue; Kao, Ming-Hong

    2013-07-01

    Although high channel electron mobility has been reported after some passivation techniques, the performance of n-channel Ge metal-oxide-semiconductor field-effect transistor is still limited by the high Schottky barrier height at the metal/n-Ge contact interface, which comes from the Fermi level pinning effect. Recent experiments demonstrated that the Schottky barrier height can be reduced by inserting a thin dielectric layer between metal and Ge. However, the mechanism has not been well clarified. In this paper, the metal induced gap state model, the dipole layer model, and the fixed charge model are verified by varying contact metals, dielectric thicknesses, as well as the annealing temperatures. The pinning factor is improved slightly by dielectric insertion but its value is independent of the dielectric thickness and is still much lower than the ideal value of the non-pinning case. This pinning effect is consistent with the Fermi level pinning at the metal/TiO2 interface. After thermal process, no interfacial layer forms at the TiO2/Ge interface and the TiO2 crystallizes gradually after annealing but the Schottky barrier height increases. Since the amount of fixed charges in the thin dielectric layer estimated from a metal-insulator-semiconductor structure is about 2 × 1011 cm-2 and is insufficient to produce the observed 0.5 eV Schottky barrier height reduction, it is thus recommended that the main mechanism comes from the change of interface dipoles and the annealing effect is attributed to the short-range ordering of the TiO2 layer. Furthermore, dielectric with low conduction band offset which has good thermal stability should be explored.

  12. Molecular Layer-seeded Ultra-thin Top-gate Dielectrics for High Transconductance Graphene Transistors

    NASA Astrophysics Data System (ADS)

    Sangwan, Vinod; Jariwala, Deep; Karmel, Hunter; Alaboson, Justice; Lauhon, Lincoln; Marks, Tobin; Hersam, Mark

    2012-02-01

    The potential of graphene in integrated analog and digital circuits can only be fully realized through incorporation of ultra-thin gate dielectrics to enable large-scale small-channel graphene field-effect transistors (GFETs). Atomic-layer deposition (ALD) is a viable technique to fabricate gate-dielectrics, however, it requires a seeding layer on otherwise inert graphene. Here, we demonstrate a single molecule thick perylene-3,4,9,10-tetracarboxylic dianhydride overlayer as an effective seeding layer to grow high-κ Al2O3 on mechanically exfoliated graphene for high-performance GFETs. Using an ultra-thin (< 1nm) seeding layer, in contrast to polymer films (5-10 nm), we demonstrate fabrication of the thinnest ALD-grown gate-dielectric (4 nm) reported to date in top-gated GFETs. This yields high performance GFETs with the intrinsic transconductance parameter approaching 2.4 mS and the field-effect mobility ˜3000 cm^2/Vs. We also demonstrate generalization of this molecular layer seeded-ALD growth method to higher- κ gate dielectrics, yielding further enhanced GFET transconductance for possible application to radio-frequency circuits.

  13. Growth, structural, dielectric and magnetic properties of epitaxial multiferroic NaMnF3 thin films

    NASA Astrophysics Data System (ADS)

    Kc, Amit; Borisov, Pavel; Lederman, David

    Epitaxial NaMnF3 thin films were grown on SrTiO3 (100) single crystal substrates via molecular beam epitaxy (MBE). The orthorhombically distorted perovskite fluoride NaMnF3 (Pnma space group) has been predicted to have a polar instability at low temperatures due to MnF6 octahedral tilts. Structural, magnetic and dielectric properties were studied. Thin film structural quality as a function of the substrate temperature and film thickness was investigated using X-ray diffraction (XRD), in-situ reflection high-energy electron diffraction (RHEED), and atomic force microscopy (AFM). The best films were smooth and single phase grown with four different twin domains. Magnetic characterization was performed using superconducting quantum interference device (SQUID) magnetometry. In-plane magnetization measurements revealed antiferromagnetic ordering with a Neel temperature TN = 66 K. For the dielectric studies, NaMnF3 films were grown on top of SrRuO3 (100) buffer layers grown via pulsed laser deposition that were used as bottom electrodes. Dielectric spectroscopy was performed at different temperatures between 11K and room temperature in a frequency range 100 Hz to 100 kHz. Significant temperature dependent dielectric properties were observed. This work was supported by the National Science Foundation.

  14. Electric-field noise above a thin dielectric layer on metal electrodes

    NASA Astrophysics Data System (ADS)

    Kumph, Muir; Henkel, Carsten; Rabl, Peter; Brownnutt, Michael; Blatt, Rainer

    2016-02-01

    The electric-field noise above a layered structure composed of a planar metal electrode covered by a thin dielectric is evaluated and it is found that the dielectric film considerably increases the noise level, in proportion to its thickness. Importantly, even a thin (mono) layer of a low-loss dielectric can enhance the noise level by several orders of magnitude compared to the noise above a bare metal. Close to this layered surface, the power spectral density of the electric field varies with the inverse fourth power of the distance to the surface, rather than with the inverse square, as it would above a bare metal surface. Furthermore, compared to a clean metal, where the noise spectrum does not vary with frequency (in the radio-wave and microwave bands), the dielectric layer can generate electric-field noise which scales in inverse proportion to the frequency. For various realistic scenarios, the noise levels predicted from this model are comparable to those observed in trapped-ion experiments. Thus, these findings are of particular importance for the understanding and mitigation of unwanted heating and decoherence in miniaturized ion traps.

  15. Non-contact C-V measurements of ultra thin dielectrics

    NASA Astrophysics Data System (ADS)

    Edelman, P.; Savtchouk, A.; Wilson, M.; D'Amico, J.; Kochey, J. N.; Marinskiy, D.; Lagowski, J.

    2004-07-01

    In this paper, we present a non-contact C-V technique for ultra-thin dielectrics on silicon. The technique uses incremental corona charging of dielectric and a measurement of the surface potential with a vibrating capacitive electrode. A differential quasistatic C-V curve is generated using time-resolved measurements. The technique incorporates transconductance corrections that enable corresponding ultra-low electrical oxide thickness (EOT) determination down to the sub-nanometer range. It also provides a means for monitoring the flat band voltage, V{FB}, the interface trap spectrum, D{IT}, and the total dielectric charge, Q{TOT}. This technique is seen as a replacement for not only MOS C-V measurements but also for mercury-probe C-V. In addition, EOT measurement by the corona C-V has a major advantage over optical thickness methods because it is not affected by water adsorption and molecular airborne contamination, MAC. These effects have been a problem for optical metrology of ultra-thin dielectrics.

  16. Investigation of optical pump on dielectric tunability in PZT/PT thin film by THz spectroscopy.

    PubMed

    Ji, Jie; Luo, Chunya; Rao, Yunkun; Ling, Furi; Yao, Jianquan

    2016-07-11

    The dielectric spectra of single-layer PbTiO3 (PT), single-layer PbZrxTi1-xO3 (PZT) and multilayer PZT/PT thin films under an external optical field were investigated at room temperature by time-domain terahertz (THz) spectroscopy. Results showed that the real part of permittivity increased upon application of an external optical field, which could be interpreted as hardening of the soft mode and increasing of the damping coefficient and oscillator strength. Furthermore, the central mode was observed in the three films. Among the dielectric property of the three thin films studied, the tunability of the PZT/PT superlattice was the largest. PMID:27410799

  17. Dielectric anomaly in Li-doped zinc oxide thin films grown by sol gel route

    NASA Astrophysics Data System (ADS)

    Dhananjay; Singh, Satyendra; Nagaraju, J.; Krupanidhi, S. B.

    2007-08-01

    Sol gel route was employed to grow polycrystalline thin films of Li-doped ZnO thin films (Zn1-xLixO, x=0.15). Polycrystalline films were obtained at a growth temperature of 400 500 °C. Ferroelectricity in Zn0.85Li0.15O was verified by examining the temperature variation of the real and imaginary parts of dielectric constant, and from the C V measurements. The phase transition temperature was found to be 330 K. The room-temperature dielectric constant and dissipation factor were 15.5 and 0.09 respectively, at a frequency of 100 kHz. The films exhibited well-defined hysteresis loop, and the values of spontaneous polarization (Ps) and coercive field were 0.15 μC/cm2 and 20 kV/cm, respectively, confirming the presence of ferroelectricity.

  18. 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.

  19. 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.

  20. 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.

  1. The effects of rare earth doping on gallium nitride thin films

    NASA Astrophysics Data System (ADS)

    McHale, Stephen R.

    The thermal neutron capture cross section of the rare earth (RE) metal isotope Gd-157 is the largest of all known natural elements, which distinguishes the material as a logical candidate for neutron detection. To address an incomplete understanding of rare earth doped Gallium Nitride (GaN) materials, investigations of the surface electronic structure and interface properties of GaN thin films doped with rare earths (Yb, Er, Gd) were undertaken. Lattice ion occupation, bonding, rare earth 4f occupation, and gold Schottky barrier formation were examined using synchrotron photoemission spectroscopy. Measured Debye temperatures indicate substitutional occupation of Ga sites by RE ions. The occupied RE 4f levels, deep within the valence band, suggest that intra-atomic f-f transitions may be more 'blue' than predicted by theoretical models. Thin layers of gold did not wet and uniformly cover the GaN surface, even with rare earth doping of the GaN. The resultant Schottky barrier heights for GaN:Yb, GaN:Er, and GaN:Gd, are 25--55% larger than those reported at the gold to undoped GaN interface. The utility of gadolinium as a neutron detection material was examined via fundamental nuclear and semiconductor physics. Low charge production and the large range of internal conversion electrons limits charge collection efficiency.

  2. 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.

  3. 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.

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

    PubMed

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

    2009-02-25

    Boron nitride (BN) microtubes were synthesized in a vertical induction furnace using Li(2)CO(3) 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 microm, lengths of up to hundreds of micrometers, and well-structured ultrathin walls only approximately 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 Li(2)O-B(2)O(3) 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 approximately 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. PMID:19417466

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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 SiO2 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 SiO2 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 SiO2 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-1. From X-ray diffraction analysis, the material crystallized on SiO2 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.

  7. The structure and dielectric properties of thin barium zirconate titanate films obtained by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Tumarkin, A. V.; Razumov, S. V.; Gagarin, A. G.; Altynnikov, A. G.; Stozharov, V. M.; Kaptelov, E. Yu.; Senkevich, S. V.; Pronin, I. P.

    2016-02-01

    Submicron thin layers of BaZr x Ti1- x O3 are grown in-situ by RF magnetron sputtering of a ceramic target ( x = 0.50) on a substrate of Pt/ r-cut leucosapphire Al2O3. It is shown that the composition of the ferroelectric layer is not identical to the composition of the sputtered target and is shifted toward barium zirconate. The reasons for such behavior are discussed. The obtained samples are characterized by high breakdown voltages (1 MV/cm and higher). The structural and high-frequency dielectric properties are studied, and high tunability of the capacitance of thin layers is revealed.

  8. 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.

  9. 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.

  10. Development of CrN precipitates during the initial stages of PIII nitriding of stainless steel thin films

    NASA Astrophysics Data System (ADS)

    Manova, D.; Höche, T.; Mändl, S.; Neumann, H.

    2009-05-01

    Stainless steel thin films produced by ion beam sputtering (IBS) were used as a model system to investigate the nitrogen diffusion and CrN formation after 10 min of nitrogen plasma immersion ion implantation (PIII) at 350 °C and 450 °C. At 350 °C, a thin nitrided layer of 70 nm is formed, with additional diffusion of nitrogen along grain boundaries and the growth of CrN precipitates along these grain boundaries. For 450 °C, a complete nitriding of the whole 400 nm thick layer was observed, with the lower 75 nm consisting of an expanded phase and the upper 330 nm of a decomposed phase with CrN precipitates formed inside the original grains. Such a layered structure capturing the transformation process has not been observed before. A determination of time-temperature dependencies of this process and the transfer of these results for bulk material should be possible.

  11. 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.

  12. 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.

  13. 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.

  14. The jump-into-contact effect in biased AFM probes on dielectric films and its application to quantify the dielectric permittivity of thin layers.

    PubMed

    Revilla, Reynier I

    2016-07-01

    The jump-into-contact (JIC) phenomenon in biased atomic force microscopy (AFM) probes on dielectric films is studied. The influence of the film thickness on the position at which the AFM tip collapses irreversibly into the sample surface was theoretically analyzed using a widely accepted analytical expression of the probe-sample electrostatic interaction force. It was demonstrated that for relatively high values of voltage (V > 10-20 V) applied between the probe and the substrate the cantilever deflection at the JIC is independent of the dielectric film thickness for thin-ultrathin layers (h < 10-50 nm). Under the same conditions the z-piezo distance at the JIC follows approximately a linear behavior with the film thickness. Based on this effect an empirical model was formulated to estimate the dielectric permittivity of thin/ultrathin dielectric films using the jump-into-contact distance. The procedure was successfully applied on thin PVD-SiO2 films, obtaining good agreement with a dielectric constant value previously reported for the same material. PMID:27199351

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  16. Local epitaxial growth of aluminum nitride and molybdenum thin films in fiber texture using aluminum nitride interlayer

    SciTech Connect

    Kamohara, Toshihiro; Akiyama, Morito; Ueno, Naohiro; Nonaka, Kazuhiro; Kuwano, Noriyuki

    2006-08-14

    The authors have found the local epitaxial growth of aluminum nitride (AlN) and molybdenum (Mo) films in fiber texture, although the interface between the AlN and Mo films has different crystal symmetries. The local heteroepitaxial relationship is (0001)AlN[2110](parallel sign)(110)Mo[111](parallel sign)(0001)AlN[2110]. The AlN films changes from nonequiaxed microstructures to equiaxed columnar structures. The authors think that the AlN interlayer is effective in decreasing the crystallization energy of the Mo electrode due to the coherent heteroepitaxial nucleation. It is interesting that the local heteroepitaxial relationship does not satisfy the criteria for heteroepitaxial growth.

  17. 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.

  18. Enhancement of near-field radiative heat transfer using polar dielectric thin films.

    PubMed

    Song, Bai; Ganjeh, Yashar; Sadat, Seid; Thompson, Dakotah; Fiorino, Anthony; Fernández-Hurtado, Víctor; Feist, Johannes; Garcia-Vidal, Francisco J; Cuevas, Juan Carlos; Reddy, Pramod; Meyhofer, Edgar

    2015-03-01

    Thermal radiative emission from a hot surface to a cold surface plays an important role in many applications, including energy conversion, thermal management, lithography, data storage and thermal microscopy. Recent studies on bulk materials have confirmed long-standing theoretical predictions indicating that when the gap between the surfaces is reduced to tens of nanometres, well below the peak wavelength of the blackbody emission spectrum, the radiative heat flux increases by orders of magnitude. However, despite recent attempts, whether such enhancements can be obtained in nanoscale dielectric films thinner than the penetration depth of thermal radiation, as suggested by theory, remains experimentally unknown. Here, using an experimental platform that comprises a heat-flow calorimeter with a resolution of about 100 pW (ref. 7), we experimentally demonstrate a dramatic increase in near-field radiative heat transfer, comparable to that obtained between bulk materials, even for very thin dielectric films (50-100 nm) when the spatial separation between the hot and cold surfaces is comparable to the film thickness. We explain these results by analysing the spectral characteristics and mode shapes of surface phonon polaritons, which dominate near-field radiative heat transport in polar dielectric thin films. PMID:25705866

  19. 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.

  20. Femtosecond-laser ablation dynamics of dielectrics: basics and applications for thin films.

    PubMed

    Balling, P; Schou, J

    2013-03-01

    Laser ablation of dielectrics by ultrashort laser pulses is reviewed. The basic interaction between ultrashort light pulses and the dielectric material is described, and different approaches to the modeling of the femtosecond ablation dynamics are reviewed. Material excitation by ultrashort laser pulses is induced by a combination of strong-field excitation (multi-photon and tunnel excitation), collisional excitation (potentially leading to an avalanche process), and absorption in the plasma consisting of the electrons excited to the conduction band. It is discussed how these excitation processes can be described by various rate-equation models in combination with different descriptions of the excited electrons. The optical properties of the highly excited dielectric undergo a rapid change during the laser pulse, which must be included in a detailed modeling of the excitations. The material ejected from the dielectric following the femtosecond-laser excitation can potentially be used for thin-film deposition. The deposition rate is typically much smaller than that for nanosecond lasers, but film production by femtosecond lasers does possess several attractive features. First, the strong-field excitation makes it possible to produce films of materials that are transparent to the laser light. Second, the highly localized excitation reduces the emission of larger material particulates. Third, lasers with ultrashort pulses are shown to be particularly useful tools for the production of nanocluster films. The important question of the film stoichiometry relative to that of the target will be thoroughly discussed in relation to the films reported in the literature. PMID:23439493

  1. 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.

  2. 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}.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (LaxAl1-xOy) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the LaxAl1-xOy 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 LaAlOy 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/cm2). TFTs employing solution processed LaAlOy 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 >106, subthreshold swing of ˜650 mV dec-1, and electron mobility of ˜12 cm2 V-1 s-1.

  4. Structure dependent resistivity and dielectric characteristics of tantalum oxynitride thin films produced by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Cristea, D.; Crisan, A.; Cretu, N.; Borges, J.; Lopes, C.; Cunha, L.; Ion, V.; Dinescu, M.; Barradas, N. P.; Alves, E.; Apreutesei, M.; Munteanu, D.

    2015-11-01

    The main purpose of this work is to present and to interpret the change of electrical properties of TaxNyOz thin films, produced by DC reactive magnetron sputtering. Some parameters were varied during deposition: the flow of the reactive gases mixture (N2 and O2, with a constant concentration ratio of 17:3); the substrate voltage bias (grounded, -50 V or -100 V) and the substrate (glass, (1 0 0) Si or high speed steel). The obtained films exhibit significant differences. The variation of the deposition parameters induces variations of the composition, microstructure and morphology. These differences cause variation of the electrical resistivity essentially correlated with the composition and structural changes. The gradual decrease of the Ta concentration in the films induces amorphization and causes a raise of the resistivity. The dielectric characteristics of some of the high resistance TaxNyOz films were obtained in the samples with a capacitor-like design (deposited onto high speed steel, with gold pads deposited on the dielectric TaxNyOz films). Some of these films exhibited dielectric constant values higher than those reported for other tantalum based dielectric films.

  5. Preparation of nitrogen doped zinc oxide nanoparticles and thin films by colloidal route and low temperature nitridation process

    NASA Astrophysics Data System (ADS)

    Valour, Arnaud; Cheviré, François; Tessier, Franck; Grasset, Fabien; Dierre, Benjamin; Jiang, Tengfei; Faulques, Eric; Cario, Laurent; Jobic, Stéphane

    2016-04-01

    Nitrogen doped zinc oxide (ZnO) nanoparticles have been synthesized using a colloidal route and low temperature nitridation process. Based on these results, 200 nm thick transparent ZnO thin films have been prepared by dip-coating on SiO2 substrate from a ZnO colloidal solution. Zinc peroxide (ZnO2) thin film was then obtained after the chemical conversion of a ZnO colloidal thin film by H2O2 solution. Finally, a nitrogen doped ZnO nanocrystalline thin film (ZnO:N) was obtained by ammonolysis at 250 °C. All the films have been characterized by scanning electron microscopy, X-ray diffraction, X-Ray photoelectron spectroscopy and UV-Visible transmittance spectroscopy.

  6. 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.

  7. Semiconducting properties of zinc-doped cubic boron nitride thin films

    SciTech Connect

    Nose, K.; Yoshida, T.

    2007-09-15

    We have examined the electronic properties of zinc-doped cubic boron nitride (cBN) thin films prepared by sputter deposition. The electric conductivity of films deposited in pure Ar increased as the concentration of zinc dopant increased, and hole conduction was identified by the measurement of thermoelectric currents. It was also found that the conductivity increment in such films was accompanied by a linear increase in the B/(B+N) ratio. At the same time, no modification of the composition and the conductivity by incorporated zinc was observed when film growth took place in presence of nitrogen gas. The effect of the excess boron on the conductivity emerged only when films show semi-insulating behavior. These results suggest that Zn substitution for nitrogen causes high electric conductivity of cBN. The electric contact between Ti electrode and semiconducting cBN was examined by the transfer length method, and Ohmic conduction was observed in the Ti/cBN contact. The specific contact resistance was affected by the specific resistance of cBN films, and it was reduced from 10{sup 5} to 100 {omega} cm{sup 2} by increasing the concentration of incorporated Zn.

  8. Influence of scandium concentration on power generation figure of merit of scandium aluminum nitride thin films

    SciTech Connect

    Akiyama, Morito; Nagase, Toshimi; Umeda, Keiichi; Honda, Atsushi

    2013-01-14

    The authors have investigated the influence of scandium concentration on the power generation figure of merit (FOM) of scandium aluminum nitride (Sc{sub x}Al{sub 1-x}N) films prepared by cosputtering. The power generation FOM strongly depends on the scandium concentration. The FOM of Sc{sub 0.41}Al{sub 0.59}N film was 67 GPa, indicating that the FOM is five times larger than that of AlN. The FOM of Sc{sub 0.41}Al{sub 0.59}N film is higher than those of lead zirconate titanate and Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-PbTiO{sub 3} films, which is the highest reported for any piezoelectric thin films. The high FOM of Sc{sub 0.41}Al{sub 0.59}N film is due to the high d{sub 31} and the low relative permittivity.

  9. 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).

  10. Process condition dependence of mechanical and physical properties of silicon nitride thin films

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

    This study uses a resonance method to determine Young's modulus (E), shear modulus (G), and Poisson's ratio (ν) of plasma-enhanced chemical vapor deposited silicon nitride (SiNxHy) thin films deposited under varying process conditions. The resonance method involves exciting the bending and torsional vibration modes of a microcantilever beam fabricated from a film. The E and G values can be extracted directly from the bending and torsional vibration modes, and the ν value can be determined from the calculated E and G values. The density (ρ) of the films was determined using a quartz crystal microbalance method. In order to determine the validity of the resonance method, finite element modeling was used to determine its dependence on microcantilever beam dimensions. Over a deposition temperature range of 100-300°C, measured E, G, and ν values varied within 54-193GPa, 22-77GPa, and 0.20-0.26 with changes in process conditions, respectively. Over the same deposition range, measured ρ values varied within 1.55-2.80g/cm3 with changes in process conditions.

  11. 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.

  12. 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.

  13. 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.

    1989-01-01

    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.

  14. 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

    2016-07-01

    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.

  15. Fiber textures of titanium nitride and hafnium nitride thin films deposited by off-normal incidence magnetron sputtering

    SciTech Connect

    Deniz, D.; Harper, J. M. E.

    2008-09-15

    We studied the development of crystallographic texture in titanium nitride (TiN) and hafnium nitride (HfN) films deposited by off-normal incidence reactive magnetron sputtering at room temperature. Texture measurements were performed by x-ray pole figure analysis of the (111) and (200) diffraction peaks. For a deposition angle of 40 deg. from substrate normal, we obtained TiN biaxial textures for a range of deposition conditions using radio frequency (rf) sputtering. Typically, we find that the <111> orientation is close to the substrate normal and the <100> orientation is close to the direction of the deposition source, showing substantial in-plane alignment. We also introduced a 150 eV ion beam at 55 deg. with respect to substrate normal during rf sputtering of TiN. Ion beam enhancement caused TiN to align its out-of-plane texture along <100> orientation. In this case, (200) planes are slightly tilted with respect to the substrate normal away from the ion beam source, and (111) planes are tilted 50 deg. toward the ion beam source. For comparison, we found that HfN deposited at 40 deg. without ion bombardment has a strong <100> orientation parallel to the substrate normal. These results are consistent with momentum transfer among adatoms and ions followed by an increase in surface diffusion of the adatoms on (200) surfaces. The type of fiber texture results from a competition among texture mechanisms related to surface mobilities of adatoms, geometrical, and directional effects.

  16. Black metal thin films by deposition on dielectric antireflective moth-eye nanostructures

    PubMed Central

    Christiansen, Alexander B.; Caringal, Gideon P.; Clausen, Jeppe S.; Grajower, Meir; Taha, Hesham; Levy, Uriel; Asger Mortensen, N.; Kristensen, Anders

    2015-01-01

    Although metals are commonly shiny and highly reflective, we here show that thin metal films appear black when deposited on a dielectric with antireflective moth-eye nanostructures. The nanostructures were tapered and close-packed, with heights in the range 300-600 nm, and a lateral, spatial frequency in the range 5–7 μm−1. A reflectance in the visible spectrum as low as 6%, and an absorbance of 90% was observed for an Al film of 100 nm thickness. Corresponding experiments on a planar film yielded 80% reflectance and 20% absorbance. The observed absorbance enhancement is attributed to a gradient effect causing the metal film to be antireflective, analogous to the mechanism in dielectrics and semiconductors. We find that the investigated nanostructures have too large spatial frequency to facilitate efficient coupling to the otherwise non-radiating surface plasmons. Applications for decoration and displays are discussed. PMID:26035526

  17. A non-resonant dielectric metamaterial for the enhancement of thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Omelyanovich, M.; Ovchinnikov, V.; Simovski, C.

    2015-02-01

    Recently, we have suggested a dielectric metamaterial composed of an array of submicron dielectric spheres located on top of an amorphous thin-film solar cell. We have theoretically shown that this metamaterial can decrease the reflection and simultaneously suppress the transmission through the photovoltaic layer because it transforms the incident plane wave into a set of focused light beams. This theoretical concept has been strongly developed and experimentally confirmed in the present paper. Here we consider the metamaterial for oblique angle illumination, redesign the solar cell and present a detailed experimental study of the whole structure. In contrast to our previous theoretical study we show that our omnidirectional light-trapping structure may operate better than the optimized flat coating obtained by plasma-enhanced chemical vapor deposition.

  18. 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.

  19. 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. PMID:17672789

  20. Synthesis and characterization of wear-resistant boron-carbon-nitride thin films

    NASA Astrophysics Data System (ADS)

    Guruz, Murat Unal

    2001-12-01

    In this thesis research, synthesis and characterization of a number of technologically and scientifically interesting B-C-N thin films was investigated. These solids, owing to their short and strong covalent bonds, have the potential to be very hard. Magnetron sputtering was utilized for film deposition and the films were characterization by a wide variety of techniques to obtain information on hardness, microstructure, composition, surface morphology, corrosion performance, and wear rate. Ultrathin carbon nitride coatings were grown for use as protective overcoats in computer hard drives. In order to obtain an areal storage density of 100 Gbits/in2, the overcoat thickness is required to be within 2 nm, and the coating needs to be wear-resistant, smooth and defect-free. These requirements were satisfied for films grown under an optimum substrate bias where the energy distribution of the incoming ions was minimized and the substrate and target power supplies were pulsed at high frequency. Synthesis of cubic boron nitride coatings was possible in films grown under intense ion bombardment, where the ion flux was controlled by an externally applied magnetic field. These films were prone to rapid delamination, especially in humid environments. Films grown under mild bombardment had the hexagonal structure, did not exhibit any tendency for delamination, and were relatively hard, with smooth surface morphology and were highly resistive. In order to obtain thick and adherent c-BN films, deposition of multilayer BN coatings was proposed. This was accomplished by varying the substrate bias as well as the incoming ion flux, however, no significant improvement in film adhesion was observed. As an alternative to c-BN growth, deposition of boron carbide films was investigated. Such films exhibited high hardness, low surface roughness, along with high elasticity, and high wear resistance and did not show any signs of delamination under optimum growth conditions. The required

  1. 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.

  2. Suppression of thermally activated carrier transport in atomically thin MoS2 on crystalline hexagonal boron nitride substrates

    NASA Astrophysics Data System (ADS)

    Chan, Mei Yin; Komatsu, Katsuyoshi; Li, Song-Lin; Xu, Yong; Darmawan, Peter; Kuramochi, Hiromi; Nakaharai, Shu; Aparecido-Ferreira, Alex; Watanabe, Kenji; Taniguchi, Takashi; Tsukagoshi, Kazuhito

    2013-09-01

    We present the temperature-dependent carrier mobility of atomically thin MoS2 field-effect transistors on crystalline hexagonal boron nitride (h-BN) and SiO2 substrates. Our results reveal distinct weak temperature dependence of the MoS2 devices on h-BN substrates. The room temperature mobility enhancement and reduced interface trap density of the single and bilayer MoS2 devices on h-BN substrates further indicate that reducing substrate traps is crucial for enhancing the mobility in atomically thin MoS2 devices.We present the temperature-dependent carrier mobility of atomically thin MoS2 field-effect transistors on crystalline hexagonal boron nitride (h-BN) and SiO2 substrates. Our results reveal distinct weak temperature dependence of the MoS2 devices on h-BN substrates. The room temperature mobility enhancement and reduced interface trap density of the single and bilayer MoS2 devices on h-BN substrates further indicate that reducing substrate traps is crucial for enhancing the mobility in atomically thin MoS2 devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03220e

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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/SiNx 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 SiNx part of the films. Scanning electron microscopy revealed a porous-like reaction layer on top of SiNx. 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.

  4. 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.

  5. 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. PMID:27136888

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

    DOEpatents

    Raffetto, Mark; Bharathan, Jayesh; Haberern, Kevin; Bergmann, Michael; Emerson, David; Ibbetson, James; Li, Ting

    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.

  7. An electrode-free method of characterizing the microwave dielectric properties of high-permittivity thin films

    NASA Astrophysics Data System (ADS)

    Bovtun, V.; Pashkov, V.; Kempa, M.; Kamba, S.; Eremenko, A.; Molchanov, V.; Poplavko, Y.; Yakymenko, Y.; Lee, J. H.; Schlom, D. G.

    2011-01-01

    A thin dielectric resonator consisting of a dielectric substrate and the thin film deposited upon it is shown to suffice for microwave characterization and dielectric parameter measurement of high-permittivity thin films without electrodes. The TE01δ resonance mode was excited and measured in thin (down to 0.1 mm) rectangular- or disk-shaped low-loss dielectric substrates (D ˜10 mm) with permittivity ɛ'≥10 inserted into a cylindrical shielding cavity or rectangular waveguide. The in-plane dielectric permittivity and losses of alumina, DyScO3, SmScO3, and (LaAlO3)0.29(SrAl1/2Ta1/2O3)0.71 (LSAT) substrates were measured from 10 to 18 GHz. The substrate thickness optimal for characterization of the overlying thin film was determined as a function of the substrate permittivity. The high sensitivity and efficiency of the method, i.e., of a thin dielectric resonator to the dielectric parameters of an overlying film, was demonstrated by characterizing ultrathin strained EuTiO3 films. A 22 nm thick EuTiO3 film grown on a (100) LSAT substrate and strained in biaxial compression by 0.9% exhibited an increase in microwave permittivity at low temperatures consistent with it being an incipient ferroelectric; no strain-induced ferroelectric phase transition was seen. In contrast, a 100 nm thick EuTiO3 film grown on a (110) DyScO3 substrate and strained in biaxial tension by 1% showed two peaks as a function of temperature in microwave permittivity and loss. These peaks correspond to a strain-induced ferroelectric phase transition near 250 K and to domain wall motion.

  8. The jump-into-contact effect in biased AFM probes on dielectric films and its application to quantify the dielectric permittivity of thin layers

    NASA Astrophysics Data System (ADS)

    Revilla, Reynier I.

    2016-07-01

    The jump-into-contact (JIC) phenomenon in biased atomic force microscopy (AFM) probes on dielectric films is studied. The influence of the film thickness on the position at which the AFM tip collapses irreversibly into the sample surface was theoretically analyzed using a widely accepted analytical expression of the probe–sample electrostatic interaction force. It was demonstrated that for relatively high values of voltage (V > 10–20 V) applied between the probe and the substrate the cantilever deflection at the JIC is independent of the dielectric film thickness for thin–ultrathin layers (h < 10–50 nm). Under the same conditions the z–piezo distance at the JIC follows approximately a linear behavior with the film thickness. Based on this effect an empirical model was formulated to estimate the dielectric permittivity of thin/ultrathin dielectric films using the jump-into-contact distance. The procedure was successfully applied on thin PVD–SiO2 films, obtaining good agreement with a dielectric constant value previously reported for the same material.

  9. 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.

  10. Dielectric loss peak due to platinum electrode porosity in lead zirconate titanate thin-film capacitors

    NASA Astrophysics Data System (ADS)

    Jung, D. J.; Dawber, M.; Ruediger, A.; Scott, J. F.; Kim, H. H.; Kim, Kinam

    2002-09-01

    Impedance spectroscopy measurements were carried out in situ on lead zirconate titanate capacitors 1.2×1.2 μm2 in size on a Samsung 4 Mbit 6 in, wafer. We show here that large dielectric loss appears at low frequencies, which is a constriction effect due to the porosity of the platinum electrode. Porous platinum electrodes facilitate an oxygen electrode reaction. The effect may be removed by annealing the platinum electrode at moderate temperature (300 °C). Such an anneal should thus be considered an essential step in the fabrication of a ferroelectric thin-film capacitor on Pt.