Sample records for ultrathin hfo2 dielectric

  1. Features of formation of high-k dielectric layer in w/ultrathin HfO2/Si (100) structures under annealing

    NASA Astrophysics Data System (ADS)

    Rudakov, Valery I.; Bogoyavlenskaya, Elena A.; Denisenko, Yury I.; Naumov, V. V.

    2013-01-01

    The initial structures of two types - HfO2(50 nm)/Si (100) and W(150 nm)/HfO2(5 nm)/Si (100) - were prepared by radio frequency magnetron sputtering (RF-MS) in Ar+-plasma and further were subjected to the annealing at 500-950 °C followed by forming an ohmic contact to Si-substrate. Investigation of the first type structures show that differences in various crystalline modifications and kind of I-V curves strongly depend on conditions of growth of the HfO2 films during RF-MS process where RF bias Ubias, applying to the substrate, is an effective parameter for quality and growth process control of the HfO2 films. For the second type structures, the ultrathin HfO2 films were grown at Ubias= -7 V, then an effect of RTA at 950 °C in a neutral atmosphere on both electrical characteristics and chemical state at interfaces was studied. In comparison with as-deposited structures, RTA leads to decrease in the both the maximum specific capacitance in accumulation of C-V characteristics (by 30 %) and the dielectric constant (from 27 to 23). The thermally activated processes of formation of WOx phase at the W/HfO2 interface and Hf-silicate phase (HfSixOy) at the HfO2/Si (100) interface were observed. The total thickness of formed oxide layer exceeded the thickness of as-deposited HfO2 film by 30 %.

  2. Metal gate MOSFETs with HfO2 gate dielectric

    Microsoft Academic Search

    S. B. Samavedam; H. H. Tseng; P. J. Tobin; J. Mogab; S. Dakshina-Murthy; L. B. La; J. Smith; J. Schaeffer; M. Zavala; R. Martin; B.-Y. Nguyen; L. Hebert; O. Adetutu; V. Dhandapani; T.-Y. Luo; R. Garcia; P. Abramowitz; M. Moosa; D. C. Gilmer; C. Hobbs; W. J. Taylor; J. M. Grant; R. Hegde; S. Bagchi; E. Luckowski; V. Arunachalam; M. Azrak

    2002-01-01

    We report for the first time electrical characterization of HfO2 p- and n-MOSFETs with CVD TiN and PVD TaSiN gates respectively fabricated using conventional CMOS integration. Their performance is compared to PVD TiN-gated HfO2 and SiO2 n- and p-MOSFETs. To understand the issues with metal gates on high K gate dielectrics, PVD TiN MOSFETs were extensively characterized. At 10 nA\\/?m

  3. Electrical characteristics of highly reliable ultrathin hafnium oxide gate dielectric

    Microsoft Academic Search

    Laegu Kang; Byoung Hun Lee; Wen-Jie Qi; Yongjoo Jeon; Renee Nieh; Sundar Gopalan; Katsunori Onishi; Jack C. Lee

    2000-01-01

    Electrical and reliability properties of ultrathin HfO2 have been investigated. Pt electroded MOS capacitors with HfO2 gate dielectric (physical thickness ~45-135 Å and equivalent oxide thickness ~13.5-25 Å) were fabricated. HfO2 was deposited using reactive sputtering of a Hf target with O2 modulation technique. The leakage current of the 45 Å HfO2 sample was about 1×10-4 A\\/cm 2 at +1.0

  4. Atomic layer etching of ultra-thin HfO2 film for gate oxide in MOSFET devices

    Microsoft Academic Search

    Jae Beom Park; Woong Sun Lim; Byoung Jae Park; Ih Ho Park; Young Woon Kim; Geun Young Yeom

    2009-01-01

    Precise etch depth control of ultra-thin HfO2 (3.5 nm) films applied as a gate oxide material was investigated by using atomic layer etching (ALET) with an energetic Ar beam and BCl3 gas. A monolayer etching condition of 1.2 Å\\/cycle with a low surface roughness and an unchanged surface composition was observed for ultra-thin, ALET-etched HfO2 by supplying BCl3 gas and

  5. Atomic layer etching of ultra-thin HfO 2 film for gate oxide in MOSFET devices

    Microsoft Academic Search

    Jae Beom Park; Woong Sun Lim; Byoung Jae Park; Young Woon Kim; Geun Young Yeom

    2009-01-01

    Precise etch depth control of ultra-thin HfO2 (3.5nm) films applied as a gate oxide material was investigated by using atomic layer etching (ALET) with an energetic Ar beam and BCl3 gas. A monolayer etching condition of 1.2Å\\/cycle with a low surface roughness and an unchanged surface composition was observed for ultra-thin, ALET-etched HfO2 by supplying BCl3 gas and an Ar

  6. Dual-metal gate CMOS with HfO2 gate dielectric

    Microsoft Academic Search

    S. B. Samavedam; L. B. La; J. Smith; S. Dakshina-Murthy; E. Luckowski; J. Schaeffer; M. Zavala; R. Martin; V. Dhandapani; D. Triyoso; H. H. Tseng; P. J. Tobin; D. C. Gilmer; C. Hobbs; W. J. Taylor; J. M. Grant; R. I. Hegde; J. Mogab; C. Thomas; P. Abramowitz; M. Moosa; J. Conner; J. Jiang; V. Arunachalarn; M. Sadd; B.-Y. Nguyen; B. White

    2002-01-01

    We report for the first time on a novel dual-metal gate CMOS integration on HfO2 gate dielectric using TiN (PMOS) and TaSiN (NMOS) gate electrodes. Compared to a single metal integration, the dual-metal integration does not degrade gate leakage, mobility and charge trapping behavior. Promising preliminary TDDB data were obtained from dual-metal gate MOSFETs, while still delivering much improved gate

  7. Threshold energy for plasma etching of high-k dielectric HfO2 films in BCl3-containing plasmas

    Microsoft Academic Search

    Yoshinori Ueda; Keisuke Nakamura; Hiroaki Kiyokami; Hiroaki Ohta; Koji Eriguchi; Kouichi Ono

    2008-01-01

    Plasma etching of high dielectric constant (k) materials is indispensable for fabricating of future high performance ULSIs. This paper presents the dependence of HfO2 etch rate on incident ion energy onto a wafer stage, with emphasis being placed on the threshold energy for HfO2 etching in BCl3-containing plasmas. Experiments were performed in both an electron cyclotron resonance (ECR) and an

  8. Cubic HfO2 Doped with Y2O3 for Advanced Gate Dielectrics by MBE.

    NASA Astrophysics Data System (ADS)

    Yang, Zhikai; Lee, W. C.; Chang, Pen; Huang, Molin; Huang, Yi Lin; Hong, Minghwei; Huang, C. M.; Hsu, C. H.; Kwo, Raynien

    2006-03-01

    High ? HfO2 (? =20) is currently employed as an alternative gate dielectric replacing SiO2 in CMOS scaling. There are three known crystal structures of HfO2, monoclinic, cubic, and tetragonal with varying dielectric constants [1]. Recently we showed HfO2 films epitaxially grown on GaAs(100) formed the stable monoclinic phase (?=? = 90° and ? ˜ 99°) with the a and b axes aligned with the in-plane GaAs100axes resulting in four equivalent domains. This work demonstrates the successful alteration of the crystal structure of HfO2 from the lower ? monoclinic phase to the higher ? (? =30) cubic phase stabilized through epitaxy on GaAs(100) and Si(100) with the aid of Y2O3 doping (˜ 20% based on XPS). X-ray diffraction scans on these films clearly indicated the cubic symmetry. Doping Y2O3 is also to enhance the thermal stability of amorphous HfO2. Y2O3 doping was shown to help raise the re-crystallization temperature of HfO2 to becompatible with high temperature processing. [1] X. Zhao et al, PRB 65, 233106, (2002).

  9. Grain boundary-driven leakage path formation in HfO 2 dielectrics

    NASA Astrophysics Data System (ADS)

    Bersuker, G.; Yum, J.; Vandelli, L.; Padovani, A.; Larcher, L.; Iglesias, V.; Porti, M.; Nafría, M.; McKenna, K.; Shluger, A.; Kirsch, P.; Jammy, R.

    2011-11-01

    The evolution over time of the leakage current in HfO2-based MIM capacitors under continuous or periodic constant voltage stress (CVS) was studied for a range of stress voltages and temperatures. The data were analyzed based on the results of conductive atomic force microscopy (AFM) measurements demonstrating preferential current flow along grain boundaries (GBs) in the HfO2 dielectric and ab initio calculations, which show the formation of a conductive sub-band due to the precipitation of oxygen vacancies at the GBs. The simulations using the statistical multi-phonon trap-assisted tunneling (TAT) current description successfully reproduced the experimental leakage current stress time dependency by using the calculated energy characteristics of the O-vacancies. The proposed model suggests that the observed reversible increase in the stress current is caused by segregation of the oxygen vacancies at the GBs and their conversion to the TAT-active charge state caused by reversible electron trapping during CVS.

  10. HfO2 gate dielectric with 0.5 nm equivalent oxide thickness

    NASA Astrophysics Data System (ADS)

    Harris, H.; Choi, K.; Mehta, N.; Chandolu, A.; Biswas, N.; Kipshidze, G.; Nikishin, S.; Gangopadhyay, S.; Temkin, H.

    2002-08-01

    Hafnium dioxide films have been deposited using reactive electron beam evaporation in oxygen on hydrogenated Si(100) surfaces. The capacitance-voltage curves of as-deposited metal(Ti)-insulator-semiconductor structures exhibited large hysteresis and frequency dispersion. With post-deposition annealing in hydrogen at 300 degC, the frequency dispersion decreased to less than 1%/decade, while the hysteresis was reduced to 20 mV at flatband. An equivalent oxide thickness of 0.5 nm was achieved for HfO2 thickness of 3.0 nm. We attribute this result to a combination of pristine hydrogen saturated silicon surfaces, room temperature dielectric deposition, and low temperature hydrogen annealing.

  11. Rotating compensator spectroscopic ellipsometry (RCSE) and its application to high-k dielectric film HfO2

    NASA Astrophysics Data System (ADS)

    Leng, JingMin; Li, Shifang; Opsal, Jon L.; Aspnes, David E.; Lee, Byoung H.; Lee, Jack C.

    2000-11-01

    High-k gate dielectric films with equivalent oxide thickness (EOT) of 3 nm or less are becoming the main theme of research and development in ultra-large-scale integrated circuits industry with device dimensions scaled down to less than 130 nm. Among the high-k gate dielectric materials hafnium dioxide (HfO2) is very promising with its high dielectric constant (approximately 30) and stability in contact with Si. The samples were prepared with a DC magnetron-reactive sputtering method and subsequently annealed in the furnace with a temperature range of 500- 850 degree(s)C. The thickness of the HfO2 varied from 3.5- 18nm with a hafnium silicate interface layer of approximately 1 nm. The electrical measurement showed that the breakdown voltage is inversely proportional to the physical thickness, suggesting the breakdown process occur at the HfO2 thin film rather than in the interface layer. To measure the physical thickness of hafnium dioxide and hafnium silicate interface simultaneously, a research grade bench top rotating compensator spectroscopic ellipsometry (RCSE) in the wavelength range of 195-915 nm was used. The dispersion of HfO2 film was characterized with a two-peak critical point (CP) model and the dispersion of the interface layer of hafnium silicate was characterized with a five-peak CP model. An interface layer thickness of 0.7-2 nm was found for all hafnium dioxide films on Si, depending on the process conditions such as annealing temperature and oxygen flow rate. The same wafers measured by RCSE were later studied by transmission electron microscopy (TEM). The thickness of hafnium dioxide and hafnium silicate determined by TEM is in good agreement with the noninvasive RCSE method.

  12. Effects of adding HfO2 on the microstructure and dielectric properties of giant dielectric constant ceramic CaCu3Ti4O12

    NASA Astrophysics Data System (ADS)

    Yuan, W. X.; Hark, S. K.

    2010-03-01

    CaCu3Ti4O12 (CCTO), an unusual perovskite-like ceramic, is known for its extraordinarily high (˜10^4) and relatively frequency independent dielectric constant. It has drawn a lot of attention recently because of its potential applications in microelectronics and microwave devices. In this investigation, HfO2 powder was added to a pre-reacted CCTO powder, which was synthesized by a conventional solid-state reaction, at different concentrations from 1 to 70 wt% and the mixture was sintered into disc-shaped ceramic samples. The effects of adding HfO2 on the microstructure and dielectric properties of CCTO ceramics were investigated. In general, we found that the dielectric constant tends to increase with HfO2 addition up to 8 wt% and then decrease with further addition. Moreover, the dielectric loss was also influenced by the addition of HfO2, and a low loss tangent of ˜0.035 was obtained. The ac conductivity, impedance, complex dielectric permittivity and electric modulus graphs were used to analyze the data. These observations were explained on the basis of the internal-barrier-layer capacitor model with Maxwell-Wagner relaxations.

  13. PostDeposition Annealing Analysis for HfO2 Thin Films Using GIXRR\\/GIXRD

    Microsoft Academic Search

    Wei-En Fu; Yong-Qing Chang; Yi-Ching Chen

    2009-01-01

    High-k materials, such as HfO2, Al2O3, and many others, have been employed to replace the SiO2 insulator in the gate dielectric device in order to offer significant gate leakage reduction. In this study, the physical properties of hafnium dioxide (HfO2) thin films were analyzed and characterized in the cases of `as-deposited' and `post-deposition annealing' (PDA). Ultra-thin hafnium dioxide films of

  14. Ge diffusion in Ge metal oxide semiconductor with chemical vapor deposition HfO2 dielectric

    Microsoft Academic Search

    N. Lu; W. Bai; A. Ramirez; C. Mouli; A. Ritenour; M. L. Lee; D. Antoniadis; D. L. Kwong

    2005-01-01

    We report a study on Ge diffusion and its impact on the electrical properties of TaN\\/HfO2\\/Ge metal-oxide-semiconductor (MOS) device. It is found that Ge diffusion depends on the amount of GeO2 formed at the HfO2\\/Ge interface and can be retarded by surface nitridation. It is speculated that Ge diffusion is in the form of GeO or Ge-riched HfGeO. Effective suppression

  15. Negative photoconductivity and memory effects of germanium nanocrystals embedded in HfO2 dielectric.

    PubMed

    Wang, Shiye; Liu, Weili; Zhang, Miao; Song, Zhitang; Lin, Chenglu; Dai, J Y; Lee, P F; Chan, H L W; Choy, C L

    2006-01-01

    A metal-insulator-semiconductor (MIS) structure containing an HfO2/SiO2 stack tunnel layer, isolated Germanium (Ge) nanocrystals, and an HfO2 capping layer, was obtained by an electron-beam evaporation method. A high-resolution transmission electron microscopy (HRTEM) study revealed that uniform and pronounced Ge nanocrystals had formed after annealing. Raman spectroscopy provided evidence for the formation of Ge-Ge bonds and the optimal annealing temperature for the crystallization ratio of the Ge. The electric properties of the MIS structure were characterized by capacitance-voltage (C-V) and current-voltage (I-V) measurements at room temperature. Negative photoconductivity was observed when the structure was under a forward bias, which screened the bias voltage, resulting in a decrease in the current at a given voltage and a negative shift in flat band voltage. A relatively high stored charge density of 3.27 x 10(12) cm 2 was also achieved. PMID:16578903

  16. HfO2 and Al2O3 gate dielectrics on GaAs grown by atomic layer deposition Martin M. Franka

    E-print Network

    Garfunkel, Eric

    HfO2 and Al2O3 gate dielectrics on GaAs grown by atomic layer deposition Martin M. Franka IBM Semiconductor Research and Development Center (SRDC), Thomas J. Watson Research Center, Yorktown Heights, New; published online 4 April 2005 High-performance metal-oxide-semiconductor field effect transistors MOSFETs

  17. Optical and electrical diagnostics of fluorine- and chlorine-containing plasmas during etching of high dielectric constant HfO2 films

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazuo; Ono, Kouichi; Setsuhara, Yuichi

    2004-09-01

    Plasma etching of high dielectric constant (k) materials is required for integration of these materials as gate dielectrics in device fabrication. The etch selectivity of high-k materials over Si substrate is a key issue in the fabrication, being dependent largely on composition of reactive species and on energy of incident ions. This paper presents optical and electrical diagnostics of high-density plasmas with fluorine- and chlorine-containing gases during etching of HfO2 thin films on Si substrate, as a function of gas composition and rf bias power. Experiments were performed by employing inductively coupled plasma (ICP) and electron cyclotron resonance (ECR) plasma sources with Ar/C_4F_8/H2 and Ar/Cl_2/BCl3 chemistries at a gas pressure of 10-20 mTorr. Several diagnostics were employed to characterize the plasma around the wafer position, including optical emission spectroscopy, microwave interferomery, Langmuir probe, and quadrupole mass spectrometry. The measurements, compared with etching characteristics, indicated that the higher concentration of halogen atoms and the higher ion energy increase the HfO2 etch rate; moreover, the higher concentration of species for passivation layer formation on Si decreases the etch rate of Si, which results in an increase in the etch selectivity. We discuss the etch mechanisms for HfO2 on Si in high-density fluorine- and chlorine-containing plasmas, with emphasis of the effects of small additives on plasma and surface chemistries.

  18. Atomic layer deposition of Y2O3 and yttrium-doped HfO2 using a newly synthesized Y(iPrCp)2(N-iPr-amd) precursor for a high permittivity gate dielectric

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Seung; Kim, Woo-Hee; Oh, Il-Kwon; Kim, Min-Kyu; Lee, Gyeongho; Lee, Chang-Wan; Park, Jusang; Lansalot-Matras, Clement; Noh, Wontae; Kim, Hyungjun

    2014-04-01

    We systematically investigated the effects of Y doping in HfO2 dielectric layer, focusing on structural phase transformation and the dielectric properties of the resultant films. Y doping was carried out using atomic layer deposition (ALD) with a novel Y(iPrCp)2(N-iPr-amd) precursor, which exhibits good thermal stability without any decomposition and clean evaporation. As a result, the ALD process of the Y2O3 films showed well-saturated and linear growth characteristics of ˜0.45 Å/cycle without significant incubation delays and produced pure Y2O3 films. Then, yttrium-doped HfO2 films with various Y/(Y + Hf) compositions (yttrium content: 0.6- 4.8 mol%) were prepared by alternating Y2O3 and HfO2 growth cycles. Structural and electrical characterization revealed that the addition of yttrium to HfO2 induced phase transformations from the monoclinic to the cubic or tetragonal phases, even at low post-annealing temperatures of 600 °C, and improved leakage current densities by inducing oxygen vacancy-related complex defects. A maximum relative dielectric constant of ˜33.4 was obtained for films with a yttrium content of ˜1.2 mol%. Excellent EOT scalability was observed down to ˜1 nm without dielectric constant degradation.

  19. Top-Gated Graphene Nanoribbon Transistors with Ultra-Thin High-k Dielectrics

    PubMed Central

    Liao, Lei; Bai, Jingwei; Cheng, Rui; Lin, Yungchen; Jiang, Shan; Huang, Yu; Duan, Xiangfeng

    2010-01-01

    The integration ultra-thin high dielectric constant (high-k) materials with graphene nanoribbons (GNRs) for top-gated transistors can push their performance limit for nanoscale electronics. Here we report the assembly of Si/HfO2 core/shell nanowires on top of individual GNRs as the top-gates for GNR field-effect transistors with ultra-thin high-k dielectrics. The Si/HfO2 core/shell nanowires are synthesized by atomic layer deposition of HfO2 shell on highly-doped silicon nanowires with a precise control of the dielectric thickness down to 1–2 nm. Using the core/shell nanowires as the top-gates, high performance GNR transistors have been achieved with transconductance reaching 3.2 mS ?m?1, the highest value for GNR transistors reported to date. This method, for the first time, demonstrates the effective integration of ultra-thin high-k dielectrics with graphene with precisely controlled thickness and quality, representing an important step towards high performance graphene electronics. PMID:20380441

  20. Thermal Properties of Ultrathin Hafnium Oxide Gate Dielectric Films

    Microsoft Academic Search

    Matthew A. Panzer; Michael Shandalov; Jeremy A. Rowlette; Yasuhiro Oshima; Yi Wei Chen; Paul C. McIntyre; Kenneth E. Goodson

    2009-01-01

    Thin-film HfO2 is a promising gate dielectric material that will influence thermal conduction in modern transistors. This letter reports the temperature dependence of the intrinsic thermal conductivity and interface resistances of 56-200-Aring-thick HfO2 films. A picosecond pump-probe thermoreflectance technique yields room-temperature intrinsic thermal conductivity values between 0.49 and 0.95 W\\/(mmiddotK). The intrinsic thermal conductivity and interface resistance depend strongly on

  1. Critical metrology for ultrathin high k dielectrics

    NASA Astrophysics Data System (ADS)

    Vandervorst, W.; Brijs, B.; Bender, H.; Conard, T.; Petry, J.; Richard, O.; Blasco, X.; Nafría, M.

    2003-09-01

    Targeting very thin equivalent oxides (<1 nm) requires the deposition of (very) thin dielectrics onto silicon surfaces with minimal interfacial oxide. Typically, high-k dielectric layers are deposited using ALD or MOCVD with, at present, a prime emphasis on Hf-based high-k dielectrics, either as pure HfO2, as silicate, or mixed with Al2O3. Depending on the deposition conditions, serious deficiencies in terms of film closure and material density occur for the ultra thin (<3 nm) films which are required for very small EOT's. As such, critical metrology needs arise enabling one to study details of the film growth and its evolution upon thermal anneal. As discussed in this paper, many tools are required such as Rutherford Backscattering Spectrometry and high-resolution elastic recoil detection (ERDA), Low Energy Ion Scattering, Time-of-flight SIMS, (spectroscopic) ellipsometry and X-ray photoelectron spectroscopy. When trying to correlate these different methods one must be aware of potential discrepancies due to non-homogeneous growth and reduced material density. Local electrical measurements based on tunneling atomic force microscopy reveal very fine scale inhomogeneities, which can be correlated to local structural defects.

  2. Low-frequency noise in submicrometer MOSFETs with HfO2, HfO2\\/Al2O3 and HfAlOx gate stacks

    Microsoft Academic Search

    Bigang Min; Siva Prasad Devireddy; Zeynep Çelik-Butler; Fang Wang; Ania Zlotnicka; Hsing-Huang Tseng; Philip J. Tobin

    2004-01-01

    Low-frequency noise measurements were performed on p- and n-channel MOSFETs with HfO2, HfAlOx and HfO2\\/Al2O3 as the gate dielectric materials. The gate length varied from 0.135 to 0.36 ?m with 10.02 ?m gate width. The equivalent oxide thicknesses were: HfO2 23 Å, HfAlOx 28.5 Å and HfO2\\/Al2O3 33 Å. In addition to the core structures with only about 10 Å

  3. Interface studies of GaAs metal-oxide-semiconductor structures using atomic-layer-deposited HfO2/Al2O3 nanolaminate gate dielectric

    E-print Network

    Ye, Peide "Peter"

    concentrations of 4­6 1017 /cm3 . After NH4OH based surface pretreatment,10 8 nm ALD Al2O3/HfO2 nanolaminate. Negligible difference was found on C-V results, compared to those from NH4OH passivation.10 The NH4OH contamination for CMOS manufacture lines. The C-V results presented in this letter are all obtained from NH4OH

  4. Ultrathin high-K metal oxides on silicon: processing, characterization and integration issues

    Microsoft Academic Search

    E. P Gusev; E Cartier; D. A Buchanan; M Gribelyuk; M Copel; H Okorn-Schmidt; C D’Emic

    2001-01-01

    An overview of our recent work on ultrathin (<100 Å) films of metal oxides deposited on silicon for advanced gate dielectrics applications will be presented. Data on ultrathin Al2O3, ZrO2, HfO2, and Y2O3 will be shown to illustrate the complex processing, integration and device-related issues for high dielectric constant (‘high-K’) materials. Both physical and electrical properties, as well as the

  5. Thermal stability of HfO2 nanotube arrays

    SciTech Connect

    Qiu, Xiaofeng [ORNL; Howe, Jane Y [ORNL; Meyer III, Harry M [ORNL; Tuncer, Enis [ORNL; Paranthaman, Mariappan Parans [ORNL

    2010-01-01

    Thermal stability of highly ordered hafnium oxide (HfO2) nanotube arrays prepared through an electrochemical anodization method in the presence of ammonium fluoride is investigated in a temperature range of room temperature to 900 C in flowing argon atmosphere. The formation of the HfO2 nanotube arrays was monitored by current density transient characteristics during anodization of hafnium metal foil. Morphologies of the as-grown and post-annealed HfO2 nanotube arrays were analyzed by powder Xray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Although monoclinic HfO2 is thermally stable up to 2000K in bulk, the morphology of HfO2 nanotube arrays degraded at 900 C. A detailed X-ray photoelectron spectroscopy (XPS) study revealed that the thermal treatment significantly impacted the composition and the chemical environment of the core elements (Hf and O), as well as F content coming from the electrolyte. Possible reasons for the degradation of the nanotube at high temperature were discussed based on XPS study and possible future improvements have also been suggested. Moreover, dielectric measurements were carried out on both the as-grown amorphous film and 500 C post-annealed crystalline film. This study will help us to understand the temperature impact on the morphology of nanotube arrays, which is important to its further applications at elevated temperatures.

  6. 1\\/F Noise in Mosfets with Ultrathin Gate Dielectrics

    Microsoft Academic Search

    Blaine Jeffrey Gross

    1992-01-01

    This thesis is concerned with the mechanisms involved in 1\\/f noise in MOSFETs with ultrathin gate dielectrics. A portion of this thesis is concerned with the development of an optimized 850^circC thin (10 nm) low-pressure-furnace reoxidized nitrided oxide (ROXNOX) process. Electrical characterization of capacitors and transistors with the 850^circ C ROXNOX dielectric is presented. Deep-submicron self-aligned NMOS transistors with both

  7. Ultrathin hafnium oxide with low leakage and excellent reliability for alternative gate dielectric application

    Microsoft Academic Search

    Byoung Hun Lee; Laegu Kang; Wen-Jie Qi; Renee Nieh; Yongjoo Jeon; Katsunori Onishi; J. C. Lee

    1999-01-01

    Physical, electrical and reliability characteristics of ultra thin HfO2 as an alternative gate dielectric were studied for the first time. Crucial process parameters of oxygen modulated dc magnetron sputtering were optimized to achieve an equivalent oxide thickness (EOT) of 11.5 Å without deducting the quantum mechanical effect. Leakage current was 3×10-2 A\\/cm2 at +1 V. Excellent dielectric properties such as

  8. Chemical vapor deposition of HfO2 films on Si(100)

    Microsoft Academic Search

    S. Sayan; S. Aravamudhan; B. W. Busch; W. H. Schulte; F. Cosandey; G. D. Wilk; T. Gustafsson; E. Garfunkel

    2002-01-01

    HfO2 films were grown on Si(100) by chemical vapor deposition as an attempt to develop an industrially straightforward gate dielectric deposition process. During deposition at ~400 °C the decomposition of the hafnium-tetra-tert-butoxide Hf(C4H9O)4 precursor provides sufficient oxygen to produce a stoichiometric HfO2 film. Medium energy ion scattering, high resolution transmission electron microscopy, atomic force microscopy, and ellipsometry were used to

  9. A multi-probe correlated bulk defect characterization scheme for ultra-thin high-dielectric

    E-print Network

    Alam, Muhammad A.

    . Masuduzzaman, A.E. Islam, and M.A. Alam Dept. of ECE, Purdue University West Lafayette, IN-47907, USA *PhoneA multi-probe correlated bulk defect characterization scheme for ultra-thin high- dielectric *M

  10. Author's personal copy Properties of atomic layer deposited HfO2 thin films

    E-print Network

    Gougousi, Theodosia

    and as insulating dielectrics in memory devices. The electrical and interface properties of Hf-based thin films from Sigma-Aldrich in a sealed glass ampoule and transferred to a stainless steel vessel in a nitrogenAuthor's personal copy Properties of atomic layer deposited HfO2 thin films Justin C. Hackley 1

  11. 1/F Noise in Mosfets with Ultrathin Gate Dielectrics

    NASA Astrophysics Data System (ADS)

    Gross, Blaine Jeffrey

    1992-01-01

    This thesis is concerned with the mechanisms involved in 1/f noise in MOSFETs with ultrathin gate dielectrics. A portion of this thesis is concerned with the development of an optimized 850^circC thin (10 nm) low-pressure-furnace reoxidized nitrided oxide (ROXNOX) process. Electrical characterization of capacitors and transistors with the 850^circ C ROXNOX dielectric is presented. Deep-submicron self-aligned NMOS transistors with both conventional oxide and with reoxidized nitrided oxide gate dielectrics were fabricated. These devices are small enough that the removal of a single electron from the channel due to trapping causes an appreciable change in device current. Furthermore, the small channel area increases the probability that only one electron trap will be active at a given bias and temperature. These two effects make characterization of single trapping events possible. Single-electron traps were characterized through measurements over a range of gate bias and temperatures (from 80 K to 350 K). The time constant of the traps was found to be a strong function of temperature, displaying in general activation energies of hundreds of milli-electron volts. The time constant of individual traps was also found to be a relatively strong function of gate bias. Both of these results conflict with past assumptions of the behavior of single traps, an ensemble of which make up the 1/f noise spectrum observed in MOSFETs. 1/f noise measurements are performed on N- and P-MOSFET transistors with both conventional oxide and ROXNOX dielectrics in the linear region over a range of bias and temperatures. The normalized drain current noise for both N- and P-MOSFET devices with thin (10 nm) dielectrics is found to be a strongly increasing function of gate bias, in contrast to the constant value observed for thicker oxides, and the constant value expected from the number fluctuation noise model. The behavior of PMOS transistor 1/f noise power is found to display a square law dependence on absolute temperature, in contrast to the linear temperature predicted by the Christensson et al. noise model (3). The behavior of NMOS transistor 1/f noise at low gate bias is found to be relatively temperature independent. A model of 1/f noise in MOSFETs which incorporates the measured single-electron trap characteristics is reported. The model demonstrates that the noise in the MOSFET is due to the fluctuation of the number of carriers in the channel, and these fluctuations inducing local correlated fluctuations in the channel mobility. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.) (Abstract shortened with permission of school.).

  12. Downscaling ferroelectric field effect transistors by using ferroelectric Si-doped HfO2

    NASA Astrophysics Data System (ADS)

    Martin, Dominik; Yurchuk, Ekaterina; Müller, Stefan; Müller, Johannes; Paul, Jan; Sundquist, Jonas; Slesazeck, Stefan; Schlösser, Till; van Bentum, Ralf; Trentzsch, Martin; Schröder, Uwe; Mikolajick, Thomas

    2013-10-01

    Throughout the 22 nm technology node HfO2 is established as a reliable gate dielectric in contemporary complementary metal oxide semiconductor (CMOS) technology. The working principle of ferroelectric field effect transistors FeFET has also been demonstrated for some time for dielectric materials like Pb[ZrxTi1-x]O3 and SrBi2Ta2O9. However, integrating these into contemporary downscaled CMOS technology nodes is not trivial due to the necessity of an extremely thick gate stack. Recent developments have shown HfO2 to have ferroelectric properties, given the proper doping. Moreover, these doped HfO2 thin films only require layer thicknesses similar to the ones already in use in CMOS technology. This work will show how the incorporation of Si induces ferroelectricity in HfO2 based capacitor structures and finally demonstrate non-volatile storage in nFeFETs down to a gate length of 100 nm. A memory window of 0.41 V can be retained after 20,000 switching cycles. Retention can be extrapolated to 10 years.

  13. Improved thermal stability and device performance of ultra-thin (EOT<10 Å) gate dielectric MOSFETs by using hafnium oxynitride (HfOxNy)

    Microsoft Academic Search

    Chang Seok Kang; H.-J. Cho; K. Onishi; R. Choi; R. Nieh; S. Goplan; S. Krishnan; J. C. Lee

    2002-01-01

    Hafnium oxynitride (HfOxNy) film was prepared and characterized for gate dielectrics application with EOT<10 Å for the first time. Thermal stability and crystallization during the subsequent thermal process were improved significantly by using HfOxNy over HfO2. Furthermore, excellent transistor characteristics were obtained for both p and nMOSFETs.

  14. Direct tunneling through high-? amorphous HfO2: Effects of chemical modification

    NASA Astrophysics Data System (ADS)

    Wang, Yin; Yu, Zhizhou; Zahid, Ferdows; Liu, Lei; Zhu, Yu; Wang, Jian; Guo, Hong

    2014-07-01

    We report first principles modeling of quantum tunneling through amorphous HfO2 dielectric layer of metal-oxide-semiconductor (MOS) nanostructures in the form of n-Si/HfO2/Al. In particular, we predict that chemically modifying the amorphous HfO2 barrier by doping N and Al atoms in the middle region—far from the two interfaces of the MOS structure—can reduce the gate-to-channel tunnel leakage by more than one order of magnitude. Several other types of modification are found to enhance tunneling or induce substantial band bending in the Si, both are not desired from leakage point of view. By analyzing transmission coefficients and projected density of states, the microscopic physics of electron traversing the tunnel barrier with or without impurity atoms in the high-? dielectric is revealed.

  15. PROOF COPY 006410JES Electrical Characteristics of Thermally Evaporated HfO2

    E-print Network

    Misra, Durgamadhab "Durga"

    current density of 10 7 A/cm2 at 1 V and reduced bulk oxide charges 1.61 1011 /cm2 were also observed. The interface state density and low-temperature charge trapping behavior of these films were also investigated the effectiveness of these materials when directly in contact with silicon.3 An HfO2 film has a high dielectric

  16. Resonance behavior of single ultrathin slot antennas on finite dielectric substrates in terahertz regime

    E-print Network

    Park, Namkyoo

    Resonance behavior of single ultrathin slot antennas on finite dielectric substrates in terahertz May 2010 We investigate resonance behaviors of optically thin metallic slot antennas on finite observe that slot antennas fabricated in a gold film with a thickness below the skin depth of gold show

  17. Ultra-thin polymer gate dielectrics for top-gate polymer field-effect transistors

    Microsoft Academic Search

    Yong-Young Noh; Henning Sirringhaus

    2009-01-01

    We have demonstrated top-gate polymer field-effect transistors (FETs) with ultra-thin (30–50nm), room-temperature crosslinkable polymer gate dielectrics based on blending an insulating base polymer such as poly(methyl methacrylate) with an organosilane crosslinking agent, 1,6-bis(trichlorosilyl)hexane. The top-gate polymer transistors with thin gate dielectrics were operated at gate voltages less than ?8V with a relatively high dielectric breakdown strength (>3MV\\/cm) and a low

  18. Crystal structure of Si-doped HfO2

    NASA Astrophysics Data System (ADS)

    Zhao, Lili; Nelson, Matthew; Aldridge, Henry; Iamsasri, Thanakorn; Fancher, Chris M.; Forrester, Jennifer S.; Nishida, Toshikazu; Moghaddam, Saeed; Jones, Jacob L.

    2014-01-01

    Si-doped HfO2 was prepared by solid state synthesis of the starting oxides. Using Rietveld refinement of high resolution X-ray diffraction patterns, a substitutional limit of Si in HfO2 was determined as less than 9 at. %. A second phase was identified as Cristobalite (SiO2) rather than HfSiO4, the latter of which would be expected from existing SiO2-HfO2 phase diagrams. Crystallographic refinement with increased Si-dopant concentration in monoclinic HfO2 shows that c/b increases, while ? decreases. The spontaneous strain, which characterizes the ferroelastic distortion of the unit cell, was calculated and shown to decrease with increasing Si substitution.

  19. Characterization, engineering, and reliability of nano-scale high-k dielectrics and semiconductors interfaces

    NASA Astrophysics Data System (ADS)

    Seo, Kang-Ill

    The continued scaling of silicon complementary metal-oxide-semiconductor devices has lead to a need to replace the SiO2 gate insulator with high-k dielectric oxides, such as ZrO2 and HfO 2-based materials, to maintain a smaller leakage current without losing electrostatic gate control of the channel region. The main objectives of this dissertation are to understand the physical and electronic structure of the high-k/semiconductor interfaces, and based on that understanding, to develop new techniques that can modify or passivate the high-k /semiconductor interfaces for improved performance and reliability. First, we investigated chemical bonding structures and valence band alignments at the high-k (HfO2) and semiconductor (Si, Ge) interfaces using Synchrotron radiation photoemission spectroscopy. We found that highly non-stoichiometric GeOx exists at the HfO2/Ge interface, while stoichiometric SiOx was analyzed at the HfO 2/Si interface. From the valence band spectra the valence band offsets between HfO2 and Si or Ge were determined. Second, we demonstrated that the Zr-silicate interfacial layer (IL) can be formed between ZrO2 and a Si substrate by controlling the solid state reaction between Zr and an underlying SiO2/Si substrate. Incorporation of the metal-silicate layer improved the electrical properties, and reduced the stack equivalent oxide thickness. We also determined changes in chemical bonding at the HfO2/Si interface and associated electrical properties after the SiO2 IL is gettered by a Ti metal overlayer. We found that the removal of a part of SiO2 IL by oxygen-gettering Ti electrodes may be a promising approach for engineering ultrathin EOT without provoking a significant increase in interface trap density. Finally, for the first time, we developed a new technique to incorporate fluorine in high-k stack (HfO2/SiO2), and discovered that the negative bias temperature instability problems, such as positive charge trapping, interface trap generation, and C-V hysteresis were significantly reduced (< 50%) in HfO2/SiO2 stacks with engineered fluorine profile. Fluorine is suggested to effectively passivate charge trapping sites located at the HfO2/SiO2 interface and interface traps at the SiO2/Si interface by forming strong Hf-F and Si-F bonds.

  20. Effects of Metal Gates and Back-End-of-Line Materials on X-Ray Dose in ${\\\\rm HfO}_{2}$ Gate Oxide

    Microsoft Academic Search

    Aritra Dasgupta; Daniel M. Fleetwood; Robert A. Reed; Robert A. Weller; Marcus H. Mendenhall

    2011-01-01

    The effects of 10-keV and 400-keV endpoint-energy bremsstrahlung x-rays have been studied using the Monte Carlo simulator, MRED, for MOS capacitors with ${\\\\rm HfO}_{2}$ gate dielectrics and TiN and TaN metal gates. We compute the reduction in dose that occurs for 10-keV x-ray irradiation of thin ${\\\\rm HfO}_{2}$ gate dielectrics sandwiched between the metal gate and the Si substrate. We

  1. Competitive Si and La effect in HfO2 phase stabilization in multi-layer (La2O3)0.08(HfO2) films

    NASA Astrophysics Data System (ADS)

    Cao, Duo; Cheng, Xinhong; Yu, Yuehui; Li, Xiaolong; Liu, Chunze; Shen, Dashen; Mändl, Stephan

    2013-08-01

    The effect of Si diffusion in HfO2 and the presence of La on phase transformation were investigated. Tetragonal HfO2 structures exhibited high permittivity, and the addition of exotic atoms to HfO2 facilitated tetragonal phase transformation. In multi-layer (La2O3)0.08(HfO2) films, the top HfO2 layer was transformed into a perfect tetragonal structure, and the bottom HfO2 layer near the interfacial layer was of a cubic structure, after annealing at 800 °C. The permittivity reached 50-60. Si diffusion into the HfO2 film stabilized the tetragonal structure, and La incorporation into HfO2 facilitated the transition of the cubic structure.

  2. Dielectric properties of cobalt ferrite nanoparticles in ultrathin nanocomposite films.

    PubMed

    Alcantara, Gustavo B; Paterno, Leonardo G; Fonseca, Fernando J; Pereira-da-Silva, Marcelo A; Morais, Paulo C; Soler, Maria A G

    2013-12-01

    Multilayered nanocomposite films (thickness 50-90 nm) of cobalt ferrite nanoparticles (np-CoFe2O4, 18 nm) were deposited on top of interdigitated microelectrodes by the layer-by-layer technique in order to study their dielectric properties. For that purpose, two different types of nanocomposite films were prepared by assembling np-CoFe2O4 either with poly(3,4-ethylenedioxy thiophene):poly(styrene sulfonic acid) or with polyaniline and sulfonated lignin. Despite the different film architectures, the morphology of both was dominated by densely-packed layers of nanoparticles surrounded by polyelectrolytes. The dominant effect of np-CoFe2O4 was also observed after impedance spectroscopy measurements, which revealed that dielectric behavior of the nanocomposites was largely influenced by the charge transport across nanoparticle-polyelectrolyte interfaces. For example, nanocomposites containing np-CoFe2O4 exhibited a single low-frequency relaxation process, with time constants exceeding 15 ms. At 1 kHz, the dielectric constant and the dissipation factor (tan ?) of these nanocomposites were 15 and 0.15, respectively. These values are substantially inferior to those reported for pressed pellets made exclusively of similar nanoparticles. Impedance data were further fitted with equivalent circuit models from which individual contributions of particle's bulk and interfaces to the charge transport within the nanocomposites could be evaluated. The present study evidences that such nanocomposites display a dielectric behavior dissimilar from that exhibited by their individual counterparts much likely due to enlarged nanoparticle-polyelectrolyte interfaces. PMID:24145704

  3. Improvement on low-temperature deposited HfO 2 film and interfacial layer by high-pressure oxygen treatment

    Microsoft Academic Search

    Po-Chun Yang; Ting-Chang Chang; Shih-Ching Chen; Hsuan-Hsiang Su; Jin Lu; Hui-Chun Huang; Der-Shin Gan; New-Jin Ho

    2011-01-01

    In this study, high-pressure oxygen (O2 and O2 + UV light) technologies were employed to effectively improve the properties of low-temperature-deposited metal oxide dielectric films and interfacial layer. In this work, 13nm HfO2 thin films were deposited by sputtering method at room temperature. Then, the oxygen treatments with a high-pressure of 1500psi at 150°C were performed to replace the conventional

  4. Cross linking molecular systems to form ultrathin dielectric layers

    NASA Astrophysics Data System (ADS)

    Feng, Danqin

    Dehydrogenation leads to cross linking of polymer or polymer like formation in very different systems: self-assembled monolayers and in closo -carboranes leading to the formation of semiconducting and dielectric boron carbide. We find evidence of intermolecular interactions for a self-assembled monolayer (SAM) formed from a large molecular adsorbate, [1,1';4',1"-terphenyl]-4,4"-dimethanethiol, from the dispersion of the molecular orbitals with changing the wave vector k and from the changes with temperature. With the formation self assembled molecular (SAM) layer, the molecular orbitals hybridize to electronic bands, with indications of significant band dispersion of the unoccupied molecular orbitals. Although organic adsorbates and thin films are generally regarded as "soft" materials, the effective Debye temperature, indicative of the dynamic motion of the lattice normal to the surface, can be very high, e.g. in the multilayer film formed from [1,1'-biphenyl]-4,4'-dimethanethiol (BPDMT). Depending on molecular orientation, the effective Debye temperature can be comparable to that of graphite due to the 'stiffness' of the benzene rings, but follows the expected Debye-Waller behavior for the core level photoemission intensities with temperature. This is not always the case. We find that a monomolecular film formed from [1,1';4',1"-terphenyl]-4,4"-dimethanethiol deviates from Debye-Waller temperature behavior and is likely caused by temperature dependent changes in molecular orientation. We also find evidence for the increase in dielectric character with polymerization (cross-linking) in spite of the decrease in the HOMO-LUMO gap upon irradiation of TPDMT. The changes in the HOMO-LUMO gap, with cross-linking, are roughly consistent with the band dispersion. The decomposition and cross-linking processes are also accompanied by changes in molecular orientation. The energetics of the three isomeric carborane cage compounds [ closo-1,2-orthocarborane, closo-1,7-metacarborane, closo-1,12-paracarborane (C2B10H12)] decomposition are investigated. Thermodynamic Born-Haber cycles are constructed for neutral and ionic species in an attempt to systemically characterize closo-carborane decomposition process. The decomposition processes are in favor of lower energy decomposition processes. Among the ionic species the photon induced decomposition is dominated by BH+ and BH 2+ fragment loss, and associated with core to bound excitations. It has been observed that dehydrogenation of the closo-carboranes leads to possible cross-linking and formation of a boron rich semiconductor with good dielectric properties.

  5. Work function changes induced by deposition of ultrathin dielectric films on metals: A theoretical analysis

    NASA Astrophysics Data System (ADS)

    Prada, Stefano; Martinez, Umberto; Pacchioni, Gianfranco

    2008-12-01

    Ultrathin dielectric films deposited on a metal surface induce variations in the work function that can be relevant for the final properties of the metal/oxide interface. In this work we analyze with the help of density-functional theory calculations the effect of depositing three-layer films of insulating materials such as LiF, NaCl, MgO, CaS, and BaO on various (001) metal surfaces. We found that the change in work function ?? is due to three main contributions: an electrostatic “compression” effect which dominates for highly ionic films such as LiF, a charge-transfer effect which is largest for less ionic films such as BaO, and the surface relaxation induced by the formation of the interface bond which largely depends on the lattice mismatch between the dielectric film and the metal. Finally, we propose a universal correlation between the work function change and the energy difference between the position of the Fermi level of the metal surface and the top of the valence band of the dielectric film.

  6. Materials characterization of ZrO2-SiO2 and HfO2-SiO2 binary oxides deposited by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Neumayer, D. A.; Cartier, E.

    2001-08-01

    The thermal stability, microstructure, and electrical properties of xZrO2?(100-x)SiO2 (ZSO) and xHfO2?(100-x)SiO2 (HSO) (x=15%, 25%, 50%, and 75%) binary oxides were evaluated to help assess their suitability as a replacement for silicon dioxide gate dielectrics in complementary metal-oxide-semiconductor transistors. The films were prepared by chemical solution deposition using a solution prepared from a mixture of zirconium, hafnium, and silicon butoxyethoxides dissolved in butoxyethanol. The films were spun onto SiOxNy coated Si wafers and furnace annealed at temperatures from 500 to 1200 °C in oxygen for 30-60 min. The microstructure and electrical properties of ZSO and HSO films were examined as a function of the Zr/Si and Hf/Si ratio and annealing temperature. The films were characterized by x-ray diffraction, mid- and far-Fourier transform infrared (FTIR), Rutherford backscattering spectroscopy, and Auger electron spectroscopy. At ZrO2 or HfO2 concentrations ?50%, phase separation and crystallization of tetragonal ZrO2 or HfO2 were observed at 800 °C. At ZrO2 or HfO2 concentrations ? 25%, phase separation and crystallization of tetragonal ZrO2 or HfO2 were observed at 1000 °C. As the annealing temperature increased, a progressive change in microstructure was observed in the FTIR spectra. Additionally, the FTIR spectra suggest that HfO2 is far more disruptive of the silica network than ZrO2 even at HfO2 concentrations ?25%. The dielectric constants of the 25%, 50%, and 75% ZSO films were measured and were observed to be less than the linear combination of ZrO2 and SiO2 dielectric constants. The dielectric constant was also observed to increase with increasing ZrO2 content. The dielectric constant was also observed to be annealing temperature dependent with larger dielectric constants observed in nonphase separated films. The Clausius-Mossoti equation and a simple capacitor model for a phase separated system were observed to fit the data with the prediction that to achieve a dielectric constant larger than 10 doping concentrations of ZrO2 would have to be greater than 70%.

  7. Atomic-layer-deposited silver and dielectric nanostructures for plasmonic enhancement of Raman scattering from nanoscale ultrathin films.

    PubMed

    Ko, Chung-Ting; Yang, Po-Shuan; Han, Yin-Yi; Wang, Wei-Cheng; Huang, Jhih-Jie; Lee, Yen-Hui; Tsai, Yi-Jen; Shieh, Jay; Chen, Miin-Jang

    2015-07-01

    Plasmonic silver nanostructures and a precise ZnO cover layer prepared by capacitively coupled plasma atomic layer deposition (ALD) were exploited to enhance the Raman scattering from nanoscale ultrathin films on a Si substrate. The plasmonic activity was supported by a nanostructured Ag (nano-Ag) layer, and a ZnO cover layer was introduced upon the nano-Ag layer to spectrally tailor the localized surface plasmon resonance to coincide with the laser excitation wavelength. Because of the optimized dielectric environment provided by the precise growth of ZnO cover layer using ALD, the intensity of Raman scattering from nanoscale ultrathin films was significantly enhanced by an additional order of magnitude, leading to the observation of the monoclinic and tetragonal phases in the nanoscale ZrO2 high-K gate dielectric as thin as ?6 nm on Si substrate. The excellent agreement between the finite-difference time-domain simulation and experimental measurement further confirms the so-called [Formula: see text] dependence of the surface-enhanced Raman scattering. This technique of plasmonic enhancement of Raman spectroscopy, assisted by the nano-Ag layer and optimized dielectric environment prepared by ALD, can be applied to characterize the structures of ultrathin films in a variety of nanoscale materials and devices, even on a Si substrate with overwhelming Raman background. PMID:26057412

  8. Atomic-layer-deposited silver and dielectric nanostructures for plasmonic enhancement of Raman scattering from nanoscale ultrathin films

    NASA Astrophysics Data System (ADS)

    Ko, Chung-Ting; Yang, Po-Shuan; Han, Yin-Yi; Wang, Wei-Cheng; Huang, Jhih-Jie; Lee, Yen-Hui; Tsai, Yi-Jen; Shieh, Jay; Chen, Miin-Jang

    2015-07-01

    Plasmonic silver nanostructures and a precise ZnO cover layer prepared by capacitively coupled plasma atomic layer deposition (ALD) were exploited to enhance the Raman scattering from nanoscale ultrathin films on a Si substrate. The plasmonic activity was supported by a nanostructured Ag (nano-Ag) layer, and a ZnO cover layer was introduced upon the nano-Ag layer to spectrally tailor the localized surface plasmon resonance to coincide with the laser excitation wavelength. Because of the optimized dielectric environment provided by the precise growth of ZnO cover layer using ALD, the intensity of Raman scattering from nanoscale ultrathin films was significantly enhanced by an additional order of magnitude, leading to the observation of the monoclinic and tetragonal phases in the nanoscale ZrO2 high-K gate dielectric as thin as ?6 nm on Si substrate. The excellent agreement between the finite-difference time-domain simulation and experimental measurement further confirms the so-called {{?ft| {\\overset{\\scriptscriptstyle\\rightharpoonup}{E}} \\right|}4} dependence of the surface-enhanced Raman scattering. This technique of plasmonic enhancement of Raman spectroscopy, assisted by the nano-Ag layer and optimized dielectric environment prepared by ALD, can be applied to characterize the structures of ultrathin films in a variety of nanoscale materials and devices, even on a Si substrate with overwhelming Raman background.

  9. Electron beam induced local crystallization of HfO2 nanopores for biosensing applications

    PubMed Central

    Shim, Jiwook; Rivera, Jose; Bashir, Rashid

    2013-01-01

    We report the development of single, locally crystallized nanopores in HfO2 membranes for biosensing applications. HfO2 is chosen for its isoelectric point of 7.0, mechanical and chemical stability in solution, and for its potential as a high-k material for nanopore ionic field effect transistor applications. The HfO2 membrane is deposited on a graphene layer suspended over a 300 nm FIB hole, where graphene is used as the mechanical support. Exposure of the membrane to a focused electron beam causes crystallization in the vicinity of the nanopore during pore formation. We investigate the effects of crystallization on the electrical and surface properties of HfO2 films. Our surface analysis of HfO2 reveals improved hydrophilicity of crystallized HfO2, a notable advantage over the hydrophobicity of as-deposited HfO2. We also demonstrate detection of dsDNA translocation through HfO2 nanopores under various applied bias levels. In addition, our device architecture also presents a promising first step toward the realization of high-k HfO2 nanopore transistors. PMID:23945603

  10. Electron beam induced local crystallization of HfO2 nanopores for biosensing applications.

    PubMed

    Shim, Jiwook; Rivera, Jose A; Bashir, Rashid

    2013-11-21

    We report the development of single, locally crystallized nanopores in HfO2 membranes for biosensing applications. HfO2 is chosen for its isoelectric point of 7.0, mechanical and chemical stability in solution, and for its potential as a high-k material for nanopore ionic field effect transistor applications. The HfO2 membrane is deposited on a graphene layer suspended over a 300 nm FIB hole, where graphene is used as the mechanical support. Exposure of the membrane to a focused electron beam causes crystallization in the vicinity of the nanopore during pore formation. We investigate the effects of crystallization on the electrical and surface properties of HfO2 films. Our surface analysis of HfO2 reveals improved hydrophilicity of crystallized HfO2, a notable advantage over the hydrophobicity of as-deposited HfO2. We also demonstrate detection of dsDNA translocation through HfO2 nanopores under various applied bias levels. In addition, our device architecture also presents a promising first step toward the realization of high-k HfO2 nanopore transistors. PMID:23945603

  11. TiO2 and HfO2 in electrolyte-oxide-silicon configuration for applications in bioelectronics

    NASA Astrophysics Data System (ADS)

    Wallrapp, Frank; Fromherz, Peter

    2006-06-01

    We study the electrical properties of thin TiO2 films made by atomic layer deposition (ALD) on p-doped silicon in an electrolyte-oxide-silicon (EOS) configuration. The electrolyte contact of the TiO2/Si heterostructure allows measurements of the differential capacitance for a wide range of bias voltages as they cannot be performed in a metal-oxide-silicon structure because of extensive leakage currents. In the accumulation region of p-silicon, we find a saturation of capacitance that decreases with oxide thickness, indicating an insulator with a dielectric constant of 34. In the inversion region of p-silicon, the capacitance increases in two steps far beyond the saturation capacitance. We assign this effect to the presence of electrons in TiO2 which is controlled by the bias voltage and by immobile positive charges at the TiO2/Si interface: When the Fermi energy in p-silicon is raised to the level of the low lying conduction band of TiO2, electrons accumulate in two layers near the TiO2/Si interface and at the electrolyte/TiO2 interface with a concomitantly enhanced differential capacitance. As a control, we study HfO2 films also made by ALD. We obtain a dielectric constant of 15 from the capacitance in the accumulation region of p-silicon. For HfO2 with a high lying conduction band, the capacitance decreases as expected in the inversion region for the high-frequency limit of silicon. The electrical characterization of TiO2 and HfO2 in EOS junctions opens future applications of high-? materials in bioelectronics for efficient capacitive interaction of silicon chips and living cells.

  12. Dielectric polarization and refractive indices of ultrathin barium titanate films on strontium titanate single crystals.

    PubMed

    Chaib, H; Eng, L M; Otto, T

    2005-01-12

    The electrical and optical properties of ultrathin films of tetragonal barium titanate (BaTiO(3)) on strontium titanate (SrTiO(3)) single-crystal substrates are theoretically investigated using a microscopic quantum mechanical model based on the orbital approximation in correlation with the dipole-dipole interaction. First-, second-, and third-order electronic polarizabilities had to be considered in this calculation in order to obtain accurate results for both the dielectric spontaneous polarization and the refractive indices of the BaTiO(3) overlayer. The spontaneous polarization is drastically reduced in the film as its thickness decreases. However, an electronic polarization appears within the SrTiO(3) substrate in the neighbourhood of the interface. This polarization, which vanishes far away from the interface into the SrTiO(3) bulk, is induced by the polarization of the BaTiO(3) film. Furthermore, we find the refractive index for both the BaTiO(3) film and the SrTiO(3) substrate to be deeply reduced for light polarized perpendicular to the surface. PMID:21690676

  13. Vacuum ultraviolet thin films. I - Optical constants of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 thin films. II - Vacuum ultraviolet all-dielectric narrowband filters

    NASA Technical Reports Server (NTRS)

    Zukic, Muamer; Torr, Douglas G.; Spann, James F.; Torr, Marsha R.

    1990-01-01

    An iteration process matching calculated and measured reflectance and transmittance values in the 120-230 nm VUV region is presently used to ascertain the optical constants of bulk MgF2, as well as films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on MgF2 substrates. In the second part of this work, a design concept is demonstrated for two filters, employing rapidly changing extinction coefficients, centered at 135 nm for BaF2 and 141 nm for SiO2. These filters are shown to yield excellent narrowband spectral performance in combination with narrowband reflection filters.

  14. Solid-State Densification of Spun-Cast Self-Assembled Monolayers for Use in Ultra-Thin Hybrid Dielectrics.

    PubMed

    Hutchins, Daniel O; Acton, Orb; Weidner, Tobias; Cernetic, Nathan; Baio, Joe E; Castner, David G; Ma, Hong; Jen, Alex K-Y

    2012-11-15

    Ultra-thin self-assembled monolayer (SAM)-oxide hybrid dielectrics have gained significant interest for their application in low-voltage organic thin film transistors (OTFTs). A [8-(11-phenoxy-undecyloxy)-octyl]phosphonic acid (PhO-19-PA) SAM on ultrathin AlOx (2.5 nm) has been developed to significantly enhance the dielectric performance of inorganic oxides through reduction of leakage current while maintaining similar capacitance to the underlying oxide structure. Rapid processing of this SAM in ambient conditions is achieved by spin coating, however, as-cast monolayer density is not sufficient for dielectric applications. Thermal annealing of a bulk spun-cast PhO-19-PA molecular film is explored as a mechanism for SAM densification. SAM density, or surface coverage, and order are examined as a function of annealing temperature. These SAM characteristics are probed through atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). It is found that at temperatures sufficient to melt the as-cast bulk molecular film, SAM densification is achieved; leading to a rapid processing technique for high performance SAM-oxide hybrid dielectric systems utilizing a single wet processing step. To demonstrate low-voltage devices based on this hybrid dielectric (with leakage current density of 7.7×10(-8) A cm(-2) and capacitance density of 0.62 µF cm(-2) at 3 V), pentacene thin-film transistors (OTFTs) are fabricated and yield sub 2 V operation and charge carrier mobilites of up to 1.1 cm(2) V(-1) s(-1). PMID:24288423

  15. Solid-State Densification of Spun-Cast Self-Assembled Monolayers for Use in Ultra-Thin Hybrid Dielectrics

    PubMed Central

    Hutchins, Daniel O.; Acton, Orb; Weidner, Tobias; Cernetic, Nathan; Baio, Joe E.; Castner, David G.; Ma, Hong; Jen, Alex K.-Y.

    2013-01-01

    Ultra-thin self-assembled monolayer (SAM)-oxide hybrid dielectrics have gained significant interest for their application in low-voltage organic thin film transistors (OTFTs). A [8-(11-phenoxy-undecyloxy)-octyl]phosphonic acid (PhO-19-PA) SAM on ultrathin AlOx (2.5 nm) has been developed to significantly enhance the dielectric performance of inorganic oxides through reduction of leakage current while maintaining similar capacitance to the underlying oxide structure. Rapid processing of this SAM in ambient conditions is achieved by spin coating, however, as-cast monolayer density is not sufficient for dielectric applications. Thermal annealing of a bulk spun-cast PhO-19-PA molecular film is explored as a mechanism for SAM densification. SAM density, or surface coverage, and order are examined as a function of annealing temperature. These SAM characteristics are probed through atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). It is found that at temperatures sufficient to melt the as-cast bulk molecular film, SAM densification is achieved; leading to a rapid processing technique for high performance SAM-oxide hybrid dielectric systems utilizing a single wet processing step. To demonstrate low-voltage devices based on this hybrid dielectric (with leakage current density of 7.7×10?8 A cm?2 and capacitance density of 0.62 µF cm?2 at 3 V), pentacene thin-film transistors (OTFTs) are fabricated and yield sub 2 V operation and charge carrier mobilites of up to 1.1 cm2 V?1 s?1. PMID:24288423

  16. Effects of Y doping on the structural stability and defect properties of cubic HfO2

    E-print Network

    Gong, Xingao

    Effects of Y doping on the structural stability and defect properties of cubic HfO2 G. H. Chen,1 Z the structural and electronic properties of pure and Y-doped cubic HfO2. It is found that Y doping in HfO2 would of the cubic phase of HfO2 by the addition of Y. The calculated formation energy of the VO­YHf complex defect

  17. Seeding atomic layer deposition of high-k dielectric on graphene with ultrathin poly(4-vinylphenol) layer for enhanced device performance and reliability

    NASA Astrophysics Data System (ADS)

    Cheol Shin, Woo; Yong Kim, Taek; Sul, Onejae; Jin Cho, Byung

    2012-07-01

    We demonstrate that ultrathin poly(4-vinylphenol) (PVP) acts as an effective organic seeding layer for atomic layer deposition (ALD) of high-k dielectric on large-scale graphene fabricated by chemical vapor deposition (CVD). While identical ALD conditions result in incomplete and rough dielectric deposition on CVD graphene, the reactive groups provided by the PVP seeding layer yield conformal and pinhole-free dielectric films throughout the large-scale graphene. Top-gate graphene field effect transistors fabricated with the high quality, PVP-seeded Al2O3 gate dielectric show superior carrier mobility and enhanced reliability performance, which are desirable for graphene nanoelectronics.

  18. Vox\\/Eox-Driven Breakdown of Ultrathin SiON Gate Dielectrics in p-Type Metal Oxide Semiconductor Field Effect Transistors under Low-Voltage Inversion Stress

    Microsoft Academic Search

    Shimpei Tsujikawa; Katsuya Shiga; Hiroshi Umeda; Jiro Yugami

    2007-01-01

    The breakdown mechanism of ultrathin SiON gate dielectrics in p-type metal oxide semiconductor field effect transistors having p+gates (p+gate-pMOSFETs) has been studied. Systematic study with varying gate doping concentrations has revealed that, in the case of p+gate-pMOSFET in inversion mode, gate dielectric breakdown under stress voltage lower than -4 V is driven by oxide voltage (Vox) or oxide field (Eox),

  19. VoxEox-driven breakdown of ultra-thin SiON gate dielectric in p+gate-pMOSFET under low stress voltage of inversion mode

    Microsoft Academic Search

    Shimpei Tsujikawa; Katsuya Shiga; Hiroshi Umeda; Yasuhiko Akamatsu; Jiro Yugami; Yoshikazu Ohno; Masahiro Yoneda

    2005-01-01

    We have studied the breakdown mechanism of ultra-thin SiON gate dielectrics in p+gate-pMOSFET. Systematic study with varying gate doping concentrations has revealed that, in the case of p+gate-pMOSFET in inversion mode, gate dielectric breakdown under low stress voltage is driven by oxide voltage (Vox) or oxide field (Eox), while the breakdown under higher stress voltage is driven by gate voltage

  20. Optical characteristics of H2O-based and O3-based HfO2 films deposited by ALD using spectroscopy ellipsometry

    NASA Astrophysics Data System (ADS)

    Fan, Xiaojiao; Liu, Hongxia; Zhong, Bo; Fei, Chenxi; Wang, Xing; Wang, Qianqiong

    2015-06-01

    Optical properties of thin atomic layer-deposited HfO2 films grown by H2O and O3 are analyzed by variable angle spectroscopic ellipsometry. By investigating the dielectric constant, it is found that a higher real part of the dielectric constant ( ? 1) value is observed for H2O-based film due to less silicate component in the film. Careful examination of the log scale of imaginary part of the dielectric constant ( ? 2) leads to the conclusion that the absorption features in the energy range of 3.2-5.35 eV originate from the interface layer between the silicon substrate and the native oxide. In particular, O3-based gate stacks have less sub-band gap defect states besides the silicon's critical features. Moreover, a larger high-frequency dielectric constant, direct and indirect band gap values are obtained for O3-based film. Meanwhile, suitable valence band offsets (3.38 and 3.55 eV) and conduction band offsets (1.58 and 1.47 eV) are obtained for H2O- and O3-based HfO2 gate stacks, respectively, indicating both type of dielectric films can provide sufficient tunneling barriers for both electrons and holes.

  1. Temperature dependent structural, optical and hydrophobic properties of sputtered deposited HfO2 films

    NASA Astrophysics Data System (ADS)

    Dave, V.; Dubey, P.; Gupta, H. O.; Chandra, R.

    2014-01-01

    Hafnium oxide being high-k dielectric has been successfully utilized in electronic and optical applications. Being thermodynamically stable and having good mechanical strength, it can be used as a protective coating for outdoor HV insulators which are suffering from surface flashover problem due to contamination. In this paper, we are investigating the effect of substrate temperature on structural, optical and hydrophobic properties of hafnium oxide coating deposited over glass insulators by DC magnetron sputtering. X-ray diffraction is applied to determine the crystalline phase and crystallite size of the film. The morphology of the samples is examined using atomic force microscopy. The optical properties are studied using UV-vis-NIR spectrophotometer. The wettability of the film is investigated using contact angle meter. The thickness is measured using surface profilometer and verified through optical data. The relationship between substrate temperature with grain size, roughness, refractive index, and hydrophobicity is manifested. The maximum contact angle for HfO2 film was found to be 106° at 400°C.

  2. Chemical structures and electrical properties of atomic layer deposited HfO2 thin films grown at an extremely low temperature (?100 °C) using O3 as an oxygen source

    NASA Astrophysics Data System (ADS)

    Kim, Jeong Hwan; Park, Tae Joo; Kim, Seong Keun; Cho, Deok-Yong; Jung, Hyung-Suk; Lee, Sang Young; Hwang, Cheol Seong

    2014-02-01

    The properties of atomic layer deposited (ALD) HfO2 films grown at low temperatures (?100 °C) were examined for potential applications in flexible display and bioelectronics. A saturated ALD growth behavior was observed even at an extremely low temperature (30 °C) due to the strong oxidizing potential of O3. However, HfO2 films grown at low temperatures showed a low film density and high impurity concentration, because the thermal energy during film growth was insufficient to remove ligands completely from Hf ions in precursor molecule. This resulted in low dielectric constant and high leakage current density of the films. Nevertheless, HfO2 film grown at 100 °C using O3 gas with a high concentration (390 g/Nm3) showed a tolerable impurity concentration with the dielectric constant of ?16 and breakdown field of ?4 MV/cm, which are approximately two-thirds of those of HfO2 film grown at 250 °C.

  3. III-Nitride grating grown on freestanding HfO2 gratings.

    PubMed

    Wang, Yongjin; Wu, Tong; Hu, Fangren; Kanamori, Yoshiaki; Zhu, Hongbo; Hane, Kazuhiro

    2011-01-01

    We report here the epitaxial growth of III-nitride material on freestanding HfO2 gratings by molecular beam epitaxy. Freestanding HfO2 gratings are fabricated by combining film evaporation, electron beam lithography, and fast atom beam etching of an HfO2 film by a front-side silicon process. The 60-?m long HfO2 grating beam can sustain the stress change during the epitaxial growth of a III-nitride material. Grating structures locally change the growth condition and vary indium composition in the InGaN/GaN quantum wells and thus, the photoluminescence spectra of epitaxial III-nitride grating are tuned. Guided mode resonances are experimentally demonstrated in fabricated III-nitride gratings, opening the possibility to achieve the interaction between the excited light and the grating structure through guided mode resonance.PACS: 78.55.Cr; 81.65.Cf; 81.15.Hi. PMID:21849084

  4. Room temperature ferromagnetism in un-doped amorphous HfO2 nano-helix arrays

    NASA Astrophysics Data System (ADS)

    Xie, Qian; Wang, Wei-Peng; Xie, Zheng; Zhan, Peng; Li, Zheng-Cao; Zhang, Zheng-Jun

    2015-05-01

    Amorphous HfO2 nano-helix arrays with different screw pitches were fabricated by the glancing angle deposition technique. Room temperature ferromagnetism was achieved in this undoped amorphous HfO2 nanostructure, which is attributed to singly charged oxygen vacancies. The different magnetic behavior and photoluminescence in flat film and nano-helix arrays originate from the distinction of defect components. This study could facilitate the understanding of ferromagnetism origin in undoped HfO2, it also suggests a possible way to alter the intrinsic defects in amorphous HfO2. Project supported by the National Natural Science Foundation of China (Grant Nos. 51372135 and 61176003) and the Tsinghua University Initiative Scientific Research Program, China.

  5. High-reflectivity HfO2/SiO2 ultraviolet mirrors

    NASA Astrophysics Data System (ADS)

    Torchio, Philippe; Gatto, Alexandre; Alvisi, Marco; Albrand, Gerard; Kaiser, Norbert; Amra, Claude

    2002-06-01

    High-reflectivity dense multilayer coatings were produced for the ultraviolet spectral region. Thin-film single layers and UV mirrors were deposited by ion plating and plasma ion-assisted deposition high-energetic technologies. Optical characterizations of HfO2 and SiO2 single layers are made. The optical constants obtained for these two materials are presented. HfO2 and SiO2 mirrors with a reflectance of approx99% near 250 nm are reported.

  6. MoS2 on an amorphous HfO2 surface: An ab initio investigation

    NASA Astrophysics Data System (ADS)

    Scopel, W. L.; Miwa, R. H.; Schmidt, T. M.; Venezuela, P.

    2015-05-01

    The energetic stability, electronic and structural properties of MoS2 adsorbed on an amorphous a-HfO2 surface (MoS2/HfO2) are examined through ab initio theoretical investigations. Our total energy results indicate that the formation of MoS2/HfO2 is an exothermic process with an adsorption energy of 34 meV/Å2, which means that it is more stable than similar systems like graphene/HfO2 and MoS2/SiO2. There are no chemical bonds at the MoS2-HfO2 interface. Upon formation of MoS2/HfO2, the electronic charge distribution is mostly localized at the interface region with no net charge transfer between the adsorbed MoS2 sheet and -HfO2 surface. However, the MoS2 sheet becomes n-type doped when there are oxygen vacancies in the HfO2 surface. Further investigation of the electronic distribution reveals that there are no electron- and hole-rich regions (electron-hole puddles) on the MoS2 sheet, which makes this system promising for use in high-speed nanoelectronic devices.

  7. Adsorption kinetics of ultrathin polymer films in the melt probed by dielectric spectroscopy and second-harmonic generation.

    PubMed

    Rotella, Cinzia; Napolitano, Simone; Vandendriessche, Stefaan; Valev, Ventsislav K; Verbiest, Thierry; Larkowska, Maria; Kucharski, Stanislaw; Wübbenhorst, Michael

    2011-11-15

    We studied the adsorption kinetics of supported ultrathin films of dye-labeled polystyrene (l-PS) by combining dielectric spectroscopy (DS) and the interface-specific nonlinear optical second harmonic generation (SHG) technique. While DS is sensitive to the fraction of mobile dye moieties (chromophores), the SHG signal probes their anisotropic orientation. Time-resolved measurements were performed above the glass transition temperature on two different sample geometries. In one configuration, the l-PS layer is placed in contact with the aluminum surface, while in the other one, the deposition is done on a strongly adsorbed layer of neat PS. From the time dependence of the dielectric strength and SHG signal of the l-PS layer in contact with the metal, we detected two different kinetics regimes. We interpret these regimes in terms of the interplay between adsorption and orientation of the adsorbing labeling moieties. At early times, dye moieties get adsorbed adopting an orientation parallel to the surface. When adsorption proceeds to completeness, the kinetics slows down and the dye moieties progressively orient normal to the surface. Conversely, when the layer of l-PS layer is deposited on the strongly adsorbed layer of neat PS, both the dielectric strength and the SHG signal do not show any variation with time. This means that no adsorption takes place. PMID:21950967

  8. Charge trapping in ultrathin hafnium oxide

    Microsoft Academic Search

    W. J. Zhu; T. P. Ma; S. Zafar; T. Tamagawa

    2002-01-01

    The charge trapping properties of ultrathin HfO2 in MOS capacitors during constant voltage stress have been investigated. The effects of stress voltage, substrate type, annealing temperature, and gate electrode are presented in this letter. It is shown that the generation of interface-trap density under constant-voltage stress is much more significant for samples with Pt gate electrodes than that with Al

  9. Schottky barrier height reduction for metal/n-InP by inserting ultra-thin atomic layer deposited high-k dielectrics

    SciTech Connect

    Zheng, Shan; Yang, Wen; Sun, Qing-Qing, E-mail: qqsun@fudan.edu.cn, E-mail: linchen@fudan.edu.cn; Zhou, Peng; Wang, Peng-Fei; Wei Zhang, David [State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433 (China)] [State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433 (China); Chen, Lin; Xiao, Fei [Department of Materials Science, Fudan University, Shanghai 200433 (China)] [Department of Materials Science, Fudan University, Shanghai 200433 (China)

    2013-12-23

    Fermi level pinning at metal/n-InP interface and effective Schottky barrier height (?{sub B,eff}) were optimized by inserting ultrathin dielectrics in this work. Comparing the inserted monolayer and bilayer high-k dielectrics, we demonstrated that the introduction of bilayer dielectrics can further reduce ?{sub B,eff} (from 0.49?eV to 0.22?eV) than the monolayer dielectric (from 0.49?eV to 0.32?eV) even though the overall dielectric thickness was thicker. The additional dipole formed at high-k/high-k interfaces could be used to expound the mechanism. This work proposed an effective solution to reduce resistance contacts for InP based transistors and Schottky barrier transistors.

  10. High performance p-type organic thin film transistors with an intrinsically photopatternable, ultrathin polymer dielectric layer?

    PubMed Central

    Petritz, Andreas; Wolfberger, Archim; Fian, Alexander; Krenn, Joachim R.; Griesser, Thomas; Stadlober, Barbara

    2013-01-01

    A high-performing bottom-gate top-contact pentacene-based oTFT technology with an ultrathin (25–48 nm) and electrically dense photopatternable polymeric gate dielectric layer is reported. The photosensitive polymer poly((±)endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, diphenylester) (PNDPE) is patterned directly by UV-exposure (? = 254 nm) at a dose typical for conventionally used negative photoresists without the need for any additional photoinitiator. The polymer itself undergoes a photo-Fries rearrangement reaction under UV illumination, which is accompanied by a selective cross-linking of the macromolecules, leading to a change in solubility in organic solvents. This crosslinking reaction and the negative photoresist behavior are investigated by means of sol–gel analysis. The resulting transistors show a field-effect mobility up to 0.8 cm2 V?1 s?1 at an operation voltage as low as ?4.5 V. The ultra-low subthreshold swing in the order of 0.1 V dec?1 as well as the completely hysteresis-free transistor characteristics are indicating a very low interface trap density. It can be shown that the device performance is completely stable upon UV-irradiation and development according to a very robust chemical rearrangement. The excellent interface properties, the high stability and the small thickness make the PNDPE gate dielectric a promising candidate for fast organic electronic circuits. PMID:24748853

  11. Electron spin resonance spectroscopy investigation of ion beam sputtered HfO2 and SiO2 thin films

    NASA Astrophysics Data System (ADS)

    Langdon, B.; Patel, D.; Krous, E.; Langston, P.; Menoni, C. S.; Shinn, Michelle

    2008-10-01

    In this work we use electron spin resonance (ESR) spectroscopy to investigate defects in dual ion beam sputtered HfO2 and SiO2 films. "As-grown" SiO2 films exhibit an ESR feature consistent with an E' center associated with an oxygen vacancy previously reported. A similar feature with axial symmetry is seen in HfO2 films. The defect giving rise to the HfO2 ESR feature is distributed throughout the film. In addition, post process annealing of HfO2 and SiO2 films greatly reduces these defects.

  12. Double Gate Tunnel FET with ultrathin silicon body and high-k gate dielectric

    Microsoft Academic Search

    Kathy Boucart; Adrian Mihai Ionescu

    2006-01-01

    In this paper we propose a novel design for a double gate tunnel field effect transistor (DG TFET), for which the simulations show significant improvements compared with single gate devices with a SiO 2 gate dielectric. For the first time, double gate devices using a high-K gate dielectric are explored, showing on-current as high as 1 mA for a gate

  13. In-Line Compositional and Thickness Metrology Using XPS for Ultra-Thin Dielectric Films

    SciTech Connect

    Truman, J. Kelly; Gurer, Emir; Larson, C. Thomas; Reed, David [ReVera, Inc., 810 Kifer Road, Sunnyvale, CA 94086 (United States)

    2005-09-09

    65 nm and 45 nm silicon devices will utilize compositionally critical processes for gate dielectrics, capacitor dielectrics, gate and capacitor electrodes, and ultra shallow junction layers. For example, small changes in nitrogen composition have been correlated with unacceptable shifts in electrical properties of devices with SiOxNy gate dielectrics. Present optically-based metrology technologies for such applications are reaching limits for precise thickness measurements and do not provide direct and adequately precise compositional information. As a result, mature analytical techniques, such as x-ray photoelectron spectroscopy (XPS), are now being transitioned to in-line production metrology usage.We discuss the application of XPS optimized for 200/300 mm production to compositional and thickness metrology of SiOxNy and high k gate dielectrics, high k capacitor dielectrics, and new electrode materials. The development of optimized hardware, robust data analysis algorithms and high throughput, fully automated operation has led to production implementation of XPS in advanced logic applications. The precise correlation of plasma nitridation metrology data with electrical device parameters has proven valuable in detecting process drifts early in the process flow, without the need to prepare devices through the first metal layer for testing. High density maps of film thickness and composition have enabled optimization of oxidation, nitridation and post-nitridation anneal processes for SiOxNy film production for 90 nm, 65 nm and below. High precision compositional and thickness metrology data for high-k gate and capacitor dielectrics is also presented.

  14. In-Line Compositional and Thickness Metrology Using XPS for Ultra-Thin Dielectric Films

    NASA Astrophysics Data System (ADS)

    Truman, J. Kelly; Gurer, Emir; Larson, C. Thomas; Reed, David

    2005-09-01

    65 nm and 45 nm silicon devices will utilize compositionally critical processes for gate dielectrics, capacitor dielectrics, gate and capacitor electrodes, and ultra shallow junction layers. For example, small changes in nitrogen composition have been correlated with unacceptable shifts in electrical properties of devices with SiOxNy gate dielectrics. Present optically-based metrology technologies for such applications are reaching limits for precise thickness measurements and do not provide direct and adequately precise compositional information. As a result, mature analytical techniques, such as x-ray photoelectron spectroscopy (XPS), are now being transitioned to in-line production metrology usage. We discuss the application of XPS optimized for 200/300 mm production to compositional and thickness metrology of SiOxNy and high k gate dielectrics, high k capacitor dielectrics, and new electrode materials. The development of optimized hardware, robust data analysis algorithms and high throughput, fully automated operation has led to production implementation of XPS in advanced logic applications. The precise correlation of plasma nitridation metrology data with electrical device parameters has proven valuable in detecting process drifts early in the process flow, without the need to prepare devices through the first metal layer for testing. High density maps of film thickness and composition have enabled optimization of oxidation, nitridation and post-nitridation anneal processes for SiOxNy film production for 90 nm, 65 nm and below. High precision compositional and thickness metrology data for high-k gate and capacitor dielectrics is also presented.

  15. Enhanced non-volatile memory characteristics with quattro-layer graphene nanoplatelets vs . 2.85-nm Si nanoparticles with asymmetric Al2O3/HfO2 tunnel oxide

    NASA Astrophysics Data System (ADS)

    El-Atab, Nazek; Turgut, Berk Berkan; Okyay, Ali K.; Nayfeh, Munir; Nayfeh, Ammar

    2015-06-01

    In this work, we demonstrate a non-volatile metal-oxide semiconductor (MOS) memory with Quattro-layer graphene nanoplatelets as charge storage layer with asymmetric Al2O3/HfO2 tunnel oxide and we compare it to the same memory structure with 2.85-nm Si nanoparticles charge trapping layer. The results show that graphene nanoplatelets with Al2O3/HfO2 tunnel oxide allow for larger memory windows at the same operating voltages, enhanced retention, and endurance characteristics. The measurements are further confirmed by plotting the energy band diagram of the structures, calculating the quantum tunneling probabilities, and analyzing the charge transport mechanism. Also, the required program time of the memory with ultra-thin asymmetric Al2O3/HfO2 tunnel oxide with graphene nanoplatelets storage layer is calculated under Fowler-Nordheim tunneling regime and found to be 4.1 ns making it the fastest fully programmed MOS memory due to the observed pure electrons storage in the graphene nanoplatelets. With Si nanoparticles, however, the program time is larger due to the mixed charge storage. The results confirm that band-engineering of both tunnel oxide and charge trapping layer is required to enhance the current non-volatile memory characteristics.

  16. Enhanced non-volatile memory characteristics with quattro-layer graphene nanoplatelets vs. 2.85-nm Si nanoparticles with asymmetric Al2O 3/HfO 2 tunnel oxide.

    PubMed

    El-Atab, Nazek; Turgut, Berk Berkan; Okyay, Ali K; Nayfeh, Munir; Nayfeh, Ammar

    2015-12-01

    In this work, we demonstrate a non-volatile metal-oxide semiconductor (MOS) memory with Quattro-layer graphene nanoplatelets as charge storage layer with asymmetric Al2O3/HfO2 tunnel oxide and we compare it to the same memory structure with 2.85-nm Si nanoparticles charge trapping layer. The results show that graphene nanoplatelets with Al2O3/HfO2 tunnel oxide allow for larger memory windows at the same operating voltages, enhanced retention, and endurance characteristics. The measurements are further confirmed by plotting the energy band diagram of the structures, calculating the quantum tunneling probabilities, and analyzing the charge transport mechanism. Also, the required program time of the memory with ultra-thin asymmetric Al2O3/HfO2 tunnel oxide with graphene nanoplatelets storage layer is calculated under Fowler-Nordheim tunneling regime and found to be 4.1 ns making it the fastest fully programmed MOS memory due to the observed pure electrons storage in the graphene nanoplatelets. With Si nanoparticles, however, the program time is larger due to the mixed charge storage. The results confirm that band-engineering of both tunnel oxide and charge trapping layer is required to enhance the current non-volatile memory characteristics. PMID:26055483

  17. Microwave and power characteristics of AlGaN/GaN/Si high-electron mobility transistors with HfO2 and TiO2 passivation

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Shyan; Lin, Shin-Fu; Hsu, Wei-Chou

    2015-01-01

    This work presents AlGaN/GaN high-electron mobility transistors (HEMTs) that are grown on silicon. Various passivation layers are deposited on AlGaN/GaN HEMTs. AlGaN/GaN HEMTs were fabricated with TiO2 dielectrics, and their performance was compared with that of unpassivated and that of HfO2-passivated HEMTs. The TiO2-passivated HEMT with a gate length of 1 ?m exhibits a maximum extrinsic transconductance of 134.4 mS mm?1, a current-gain cutoff frequency of 10.62 GHz, and a maximum frequency of oscillation of 16.37 GHz. Capping with any of the dielectric materials used herein improves the device performance over that of the unpassivated HEMTs. Additionally, experimental data demonstrate that the use of TiO2 is a favorable alternative to HfO2 passivation. This work is the first to present the microwave power of TiO2-passivated AlGaN/GaN HEMTs.

  18. High-reflectivity HfO2/SiO2 ultraviolet mirrors.

    PubMed

    Torchio, Philippe; Gatto, Alexandre; Alvisi, Marco; Albrand, Gérard; Kaiser, Norbert; Amra, Claude

    2002-06-01

    High-reflectivity dense multilayer coatings were produced for the ultraviolet spectral region. Thin-film single layers and UV mirrors were deposited by ion plating and plasma ion-assisted deposition high-energetic technologies. Optical characterizations of HfO2 and SiO2 single layers are made. The optical constants obtained for these two materials are presented. HfO2 and SiO2 mirrors with a reflectance of approximately 99% near 250 nm are reported. PMID:12064410

  19. hal-00197196,version1-14Dec2007 Magnetic properties of HfO2 thin films.

    E-print Network

    Boyer, Edmond

    hal-00197196,version1-14Dec2007 Magnetic properties of HfO2 thin films. N Hadacek, A Nosov, L Ranno physical properties of these thin films appear to depend on the oxygen pressure during growth: the film #12;Magnetic properties of HfO2 thin films 2 1. Introduction The unexpected ferromagnetism at high

  20. Ultra-thin gate dielectrics: they break down, but do they fail?

    Microsoft Academic Search

    B. E. Weir; P. J. Silverman; D. Monroe; K. S. Krisch; M. A. Alam; G. B. Alers; T. W. Sorsch; G. L. Timp; F. Baumann; C. T. Liu; Y. Ma; D. Hwang

    1997-01-01

    We study breakdown in high-quality 2-7 nm gate dielectrics, and find that soft breakdown becomes more likely for thinner oxides and for oxides stressed at lower voltages. For 2 nm oxides, an increase in gate noise is the only precise indication of soft breakdown. For many applications, devices should remain functional with the level of gate noise we have observed,

  1. Optimal migration path of Ag in HfO2: A first-principles study

    NASA Astrophysics Data System (ADS)

    Dai, Yue-Hua; Chen, Zhen; Jin, Bo; Li, Ning; Li, Xiao-Feng

    2015-07-01

    First-principles calculations are used to investigate the migration path of Ag in the HfO2-based resistive random access memory (ReRAM). The formation energy calculation suggests that there are two different sites (site 1 and site 3) for the incorporation of Ag atoms into the HfO2 unit cell. Thermodynamic analysis shows that the motion of Ag atom in the HfO2 supercell appears to be anisotropic, which is due to the fact that the Ag atom at site 3 moves along the orientation, but the Ag atom at site 1 moves along the [001] orientation. The migration barriers of the Ag atoms hopping between neighboring unit cells are calculated along five different orientations. Difficulty in producing motion of the Ag atom varies with the migration barrier: this motion is minimized along orientation. Furthermore, The optimal circulation path for Ag migration within the HfO2 supercells is obtained, and is found to be approximately along the orientation. Therefore, it is proposed that the positive voltage should be applied along this orientation, the conduction filament may form more easily, which could improve the response time and reduce the power consumption in ReRAM applications. Project supported by the National Natural Science Foundation of China (Grant No. 61376106).

  2. Ferroelectricity in Si-doped HfO2 revealed: a binary lead-free ferroelectric.

    PubMed

    Martin, Dominik; Müller, Johannes; Schenk, Tony; Arruda, Thomas M; Kumar, Amit; Strelcov, Evgheni; Yurchuk, Ekaterina; Müller, Stefan; Pohl, Darius; Schröder, Uwe; Kalinin, Sergei V; Mikolajick, Thomas

    2014-12-23

    Static domain structures and polarization dynamics of silicon doped HfO2 are explored. The evolution of ferroelectricity as a function of Si-doping level driving the transition from paraelectricity via ferroelectricity to antiferroelectricity is investigated. Ferroelectric and antiferroelectric properties can be observed locally on the pristine, poled and electroded surfaces, providing conclusive evidence to intrinsic ferroic behavior. PMID:25352107

  3. Compatibility of silicon gates with hafnium-based gate dielectrics

    Microsoft Academic Search

    D. C. Gilmer; R. Hegde; R. Cotton; J. Smith; L. Dip; R. Garcia; V. Dhandapani; D. Triyoso; D. Roan; A. Franke; R. Rai; L. Prabhu; C. Hobbs; J. M. Grant; L. La; S. Samavedam; B. Taylor; H. Tseng; P. Tobin

    2003-01-01

    Silicon gate compatibility problems with hafnium-based gate dielectrics are reported. It generally can be stated that chemical vapor deposition (CVD) silicon gates using silane deposited directly onto polycrystalline HfO2 at conventional temperatures (near 620°C) results in (1) a low density of large inhomogeneous polycrystalline-silicon (poly-Si) grains, (2) electrical properties much worse compared to similar HfO2 films using metal gates or

  4. Suppression of endurance degradation by utilizing oxygen plasma treatment in HfO2 resistive switching memory

    NASA Astrophysics Data System (ADS)

    Chand, Umesh; Huang, Chun-Yang; Jieng, Jheng-Hong; Jang, Wen-Yueh; Lin, Chen-Hsi; Tseng, Tseung-Yuen

    2015-04-01

    Based on the phenomenon of endurance degradation problem caused by no sufficient oxygen ions for resistive switching, we use the oxygen plasma treatment in HfO2 layer to increase the extra available oxygen ions in resistive random access memory devices. To avoid the Ti top electrode directly absorbing the additional oxygen ions from HfO2 layer with oxygen plasma treatment, a thin HfO2 film is inserted to separate them. Therefore, the endurance degradation can be suppressed in the present structure. High speed (30 ns) and large endurance cycles (up to 1010 cycles) are achieved in this device structure for next generation nonvolatile memory application.

  5. Luminescence of RE-ions in HfO 2 thin films and some possible applications

    NASA Astrophysics Data System (ADS)

    Lange, S.; Kiisk, V.; Reedo, V.; Kirm, M.; Aarik, J.; Sildos, I.

    2006-08-01

    Photoluminescence (PL) of rare-earth (Sm, Eu, Tb) ions in HfO 2 thin films has been investigated at 10 and 300 K. Samples were prepared by using the sol-gel and the atomic layer deposition (ALD) methods. An intense PL emission characteristic of 4f-shell transitions of RE 3+ ions was observed under the excitation photon energies exceeding the band-gap energy of the host material. The measured PL excitation spectra that were similar to those of intrinsic emission confirmed the efficient energy transfer from the host material to dopants. The kinetics of RE 3+ emission revealed a non-exponential behaviour in all studied materials, strongly depending on the thermal treatment of the materials. The results obtained suggest the application potential of RE-doped HfO 2 in scintillators as well as in chemical sensors.

  6. Luminescence of RE-ions in HfO 2 thin films and some possible applications

    Microsoft Academic Search

    S. Lange; V. Kiisk; V. Reedo; M. Kirm; J. Aarik; I. Sildos

    2006-01-01

    Photoluminescence (PL) of rare-earth (Sm, Eu, Tb) ions in HfO2 thin films has been investigated at 10 and 300K. Samples were prepared by using the sol–gel and the atomic layer deposition (ALD) methods. An intense PL emission characteristic of 4f-shell transitions of RE3+ ions was observed under the excitation photon energies exceeding the band-gap energy of the host material. The

  7. Enhanced performance of supported HfO2 counter electrodes for redox couples used in dye-sensitized solar cells.

    PubMed

    Yun, Sining; Pu, Haihui; Chen, Junhong; Hagfeldt, Anders; Ma, Tingli

    2014-02-01

    Mesoporous-graphitic-carbon-supported HfO2 (HfO2 -MGC) nanohybrids were synthesized by using a soft-template route. Characterization and a systematic investigation of the catalytic properties, stability, and catalytic mechanism were performed for HfO2 -MGC counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). The new HfO2 -MGC as a CE in DSSCs showed a surprisingly high efficiency of 7.75 % for the triiodide/iodide redox couple and 3.69 % for the disulfide/thiolate redox couple, greater than the Pt electrode in the corresponding electrolyte system, which opens up a possibility for its practical application. PMID:24399514

  8. PHYSICAL REVIEW B 83, 115329 (2011) Diffusion and interface growth in hafnium oxide and silicate ultrathin films on Si(001)

    E-print Network

    Garfunkel, Eric

    2011-01-01

    PHYSICAL REVIEW B 83, 115329 (2011) Diffusion and interface growth in hafnium oxide and silicate ultrathin films on Si(001) L.V. Goncharova,1,* M. Dalponte,1 T. Feng,1 T. Gustafsson,1 E. Garfunkel,2 P elemental depth distributions and elucidate oxygen transport in 2­5 nm thick HfO2 and HfSiOx films grown

  9. The effect of thickness and loading force on wear behavior of HfO2

    NASA Astrophysics Data System (ADS)

    He, B.-C.; Fu, W.-E.; Chang, Y.-Q.; Liou, H.-C.

    2014-03-01

    The effect of annealing treatment on hafnium oxide (HfO2) thin films with two thicknesses (20 and 50 nm) has been observed. The surface morphology and tribological properties of HfO2 thin films were measured through atomic force microscopy (AFM). It is found that annealing treatment and increasing thickness of thin film would promote the formation and growth of island-like grains, which contributes a raise in surface roughness. During scratch test, plowing behavior dominated the deformation mechanism in the form of lumps along the edge of grooves by AFM-3D images. Besides, slower scratch speed led to larger deformation energy and caused a serious fracture. The annealing-induced crystallization resulted in reduced penetration depth and coefficient of friction (COF). The varied COF with respect to different normal forces reflected substrate effect. The thicker HfO2 films exhibited better wear resistance regardless of annealing conditions. It is because that increase in film thickness accompanied growth of polycrystalline structure.

  10. Ion irradiation temperature effect on HfO 2/MgO multi-layer structures

    NASA Astrophysics Data System (ADS)

    Usov, I. O.; Valdez, J. A.; Won, J.; Devlin, D. J.

    2012-01-01

    Properties of nuclear materials may be improved by employing composite materials. However, these properties usually degrade during the operation in a nuclear reactor environment due to radiation damage accumulation. For this study we fabricated a multi-layer structure composed of MgO and HfO 2 thin films on a sapphire substrate. This multi-layer structure was designed to mimic a CERCER (ceramic-ceramic) composite fuel form. The goal of this study was to investigate features of radiation damage evolution cause by ion beam irradiation in a wide temperature range. We observed phase transformation in HfO 2 from monoclinic to the tetragonal polymorph and no changes in MgO. Formation of thin amorphous regions adjacent to the MgO/HfO 2 and HfO 2/sapphire substrate interfaces was identified in both cases. Phase and microstructural changes demonstrated pronounced dependence on irradiation temperature, which we attributed to either enhanced annihilation of irradiation induced point defects or intermixing between the components of our multi-layered structure.

  11. Thermoluminescent characterization of HfO2:Tb3+ synthesized by hydrothermal route.

    PubMed

    Montes, E; Cerón, P; Rivera Montalvo, T; Guzmán, J; García-Hipólito, M; Soto-Guzmán, A B; García-Salcedo, R; Falcony, C

    2014-01-01

    Thermo and photoluminescent properties of nanoparticles (NPs) of hafnium oxide (HfO2), both intrinsic and doped with terbium (Tb(3+)) are reported. The NPs of HfO2 were synthesized by hydrothermal route, using hafnium tetrachloride (HfCl4) and terbium chloride hexahydrated (TbCl3?6H2O) as precursors and sodium hydroxide (NaOH) to adjust the pH. Deionized water was used as solvent in all cases. The synthesis was carried out at different dopant concentrations from 0 to 20 at% of terbium with respect to the amount of hafnium in the precursor solution. The temperature of hydrothermal treatment was 200 °C and 80 min of reaction time. X-ray diffraction results show that at terbium concentrations higher than 15 at% the HfO2 nanoparticles have a crystalline structure corresponding to the tetragonal phase. Thermoluminescent (TL) characterization was performed after 5 min irradiation of the samples with ultraviolet light of 200 nm wavelength. The highest TL emission was observed on samples with 7 at% of Tb, with the TL peak centered at 128 °C. Thermoluminescence analysis shows behavior associated with second-order kinetics with activation energy of 0.49 eV. Photoluminescent spectrum present the characteristics (5)D4?(7)FJ (J=3-6) terbium ion electronic transitions lines centered on 489 nm, 543 nm, 584 nm and 622 nm. PMID:23948482

  12. Preparation and high temperature oxidation of SiC compositionally graded graphite coated with HfO 2

    Microsoft Academic Search

    Shiro Shimada; Takeshi Sato

    2002-01-01

    SiC compositionally graded (SCG) graphite was coated with sol–gel-derived HfO2 films and oxidized at 1500°C in air. SCGed graphite was produced by reaction of graphite with molten Si at 1450°C for 10 h. The sol–gel HfO2 precursor solution was prepared by dissolving HfCl4 in ethanol and refluxing with diethanol-amine and HNO3, and was coated on SCGed graphite by dipping. The

  13. First-principles investigation of H2O on HfO2 (1 1 0) surface

    NASA Astrophysics Data System (ADS)

    Li, Lu; Huang, Xin; Zhang, Yong-Fan; Guo, Xin; Chen, Wen-Kai

    2013-01-01

    As the water to be an important precursor mater in atomic layer deposition (ALD) of preparation of HfO2 thin film, water-gas shift (WGS) reaction and heterogeneous catalysis, surface hydroxyl groups played a vital role as the reactive species that remain on the surface. First-principle calculation based on density functional (DFT) approach and generalized gradient approximation (GGA) have been utilized to investigate the molecular and dissociative adsorption of water molecule on the stoichiometric cubic HfO2 (1 1 0) surface with different sites at different coverages. The calculation employed slab geometry and periodic boundary condition with partial relaxation of atom position. Adsorption geometries, Mulliken population charges and density of states for HfO2sbnd H2O, HfO2sbnd OH, HfO2sbnd O and HfO2sbnd H at the coverage of 0.5 ML were also calculated. It was found that the adsorption energies varied a little as coverages increased, and the most favorable configuration of H2O on HfO2 surface was corresponding to the coordination of H2O via its oxygen with the surface (surface Hf atom). It was also confirmed that the coordination interaction and hydrogen bonding were the main contributions in dissociative adsorption process. For both molecular and dissociative adsorption, it has been elucidated that the surface hafnium played a key role as the active site. For dissociation reaction H2O (ads) ? H (ads) + OH (ads), the barrier energy calculated to be 17.3 kJ/mol, whereas, the second step dehydrogenation reaction OH (ads) + H (ads) ? O (ads) + 2H (ads), hardly occurred on this surface because of the high barrier energy 208.3 kJ/mol.

  14. First-principles study of structural, vibrational, and lattice dielectric properties of hafnium oxide

    Microsoft Academic Search

    Xinyuan Zhao; David Vanderbilt

    2002-01-01

    Crystalline structures, zone-center phonon modes, and the related dielectric response of the three low-pressure phases of HfO2 have been investigated in density-functional theory using ultrasoft pseudopotentials and a plane-wave basis. The structures of low-pressure HfO2 polymorphs are carefully studied with both the local-density approximation (LDA) and the generalized gradient approximation. The fully relaxed structures obtained with either exchange-correlation scheme agree

  15. Effects of different dopants on switching behavior of HfO2-based resistive random access memory

    NASA Astrophysics Data System (ADS)

    Deng, Ning; Pang, Hua; Wu, Wei

    2014-10-01

    In this study the effects of doping atoms (Al, Cu, and N) with different electro-negativities and ionic radii on resistive switching of HfO2-based resistive random access memory (RRAM) are systematically investigated. The results show that forming voltages and set voltages of Al/Cu-doped devices are reduced. Among all devices, Cu-doped device shows the narrowest device-to-device distributions of set voltage and low resistance. The effects of different dopants on switching behavior are explained with deferent types of CFs formed in HfO2 depending on dopants: oxygen vacancy (Vo) filaments for Al-doped HfO2 devices, hybrid filaments composed of oxygen vacancies and Cu atoms for Cu-doped HfO2 devices, and nitrogen/oxygen vacancy filaments for N-doped HfO2 devices. The results suggest that a metal dopant with a larger electro-negativity than host metal atom offers the best comprehensive performance.

  16. Resistive switching characteristics of HfO2-based memory devices on flexible plastics.

    PubMed

    Han, Yong; Cho, Kyoungah; Park, Sukhyung; Kim, Sangsig

    2014-11-01

    In this study, we examine the characteristics of HfO2-based resistive switching random access memory (ReRAM) devices on flexible plastics. The Pt/HfO2/Au ReRAM devices exhibit the unipolar resistive switching behaviors caused by the conducting filaments. From the Auger depth profiles of the HfO2 thin film, it is confirmed that the relatively lower oxygen content in the interface of the bottom electrode is responsible for the resistive switching by oxygen vacancies. And the unipolar resistive switching behaviors are analyzed from the C-V characteristics in which negative and positive capacitances are measured in the low-resistance state and the high-resistance state, respectively. The devices have a high on/off ratio of 10(4) and the excellent retention properties even after a continuous bending test of two thousand cycles. The correlation between the device size and the memory characteristics is investigated as well. A relatively smaller-sized device having a higher on/off ratio operates at a higher voltage than a relatively larger-sized device. PMID:25958498

  17. AFM applications to study the morphology of HfO2 multilayer thin films

    NASA Astrophysics Data System (ADS)

    Ramzan, M.; Ahmed, E.; Niaz, N. A.; Rana, A. M.; Bhatti, A. S.; Khalid, N. R.; Nadeem, M. Y.

    2015-06-01

    Atomic force microscopy (AFM) is a technique that has extensively been used to reveal details on surfaces using different scanning techniques. Multilayer hafnium oxide (HfO2) thin films deposited by electron beam evaporation at room temperature on three different glass substrates (including Corning, commercial and wind screen glasses) are discussed for their surface analysis using atomic force microscopy. AFM characterization involves structural morphology, grain size and grain distribution, etc. AFM micrographs show that the films are uniform and crack-free. The average roughness, maximum peak to valley height, root mean square (RMS) roughness, surface skewness and kurtosis parameters are investigated to analyze the surface morphology of HfO2 multilayer thin films. Results show that the RMS surface roughness decreases for commercial glass substrate to Corning to wind screen glass. On the other hand grain size demonstrates an opposite trend. Thus an increase in grain boundary area with decreasing grain size might be associated with the rise in RMS surface roughness. These films show an almost homogeneous and uniform distribution of grains according to AFM images.

  18. Copper Wiring Encapsulation with Ultra-thin Barriers to Enhance Wiring and Dielectric Reliabilities for 32-nm Nodes and Beyond

    Microsoft Academic Search

    H. Kudo; M. Haneda; H. Ochimizu; A. Tsukune; S. Okano; N. Ohtsuka; M. Sunayama; H. Sakai; T. Suzuki; H. Kitada; S. Amari; T. Tabira; H. Matsuyama; N. Shimizu; T. Futatsugi; T. Sugii

    2007-01-01

    We successfully encapsulated Cu wiring with an ultra-thin self-forming barrier consisting of MnO and a bi-layer of MnO\\/Ta. TDDB test showed that the ILDs lifetime increased by a factor of 100 over that of our control sample. The encapsulated Cu wiring increased EM lifetime by a factor of more than 47. For via chains that are vulnerable to thermal stress,

  19. Vox/Eox-Driven Breakdown of Ultrathin SiON Gate Dielectrics in p-Type Metal Oxide Semiconductor Field Effect Transistors under Low-Voltage Inversion Stress

    NASA Astrophysics Data System (ADS)

    Tsujikawa, Shimpei; Shiga, Katsuya; Umeda, Hiroshi; Yugami, Jiro

    2007-01-01

    The breakdown mechanism of ultrathin SiON gate dielectrics in p-type metal oxide semiconductor field effect transistors having p+gates (p+gate-pMOSFETs) has been studied. Systematic study with varying gate doping concentrations has revealed that, in the case of p+gate-pMOSFET in inversion mode, gate dielectric breakdown under stress voltage lower than -4 V is driven by oxide voltage (Vox) or oxide field (Eox), while the breakdown under stress voltage higher than -4 V is driven by gate voltage (Vg). The Vox/Eox-driven breakdown observed under low stress voltage is quite important to the reliability of low-voltage complementary metal oxide semiconductor (CMOS). By studying the mechanism of the breakdown, it has been clarified that the breakdown is not induced by electron current. The concept that the breakdown is due to same mechanism as the negative bias temperature instability (NBTI), namely the interfacial hydrogen release driven by Eox, has been shown to be possible. However, direct tunneling of holes driven by Vox has also been found to be a possible driving force of the breakdown. Although a decisive conclusion concerning the mechanism issue has not yet been obtained, the key factor that governs the breakdown has been shown to be Vox or Eox.

  20. High-magnetic field annealing effect on room-temperature ferromagnetism enhancement of un-doped HfO2 thin films

    NASA Astrophysics Data System (ADS)

    Xie, Qian; Wang, Weipeng; Xie, Zheng; Ning, Shuai; Li, Zhengcao; Zhang, Zhengjun

    2015-06-01

    Monoclinic HfO2 thin films with intrinsic defects were prepared by annealing in flowing argon. The behavior of the HfO2 films could be manipulated by applying an external magnetic field during annealing processing. Room-temperature ferromagnetism and visible photoluminescence were observed in these un-doped HfO2 films due to the involvement of oxygen vacancies. The results demonstrated that the density of oxygen vacancies in HfO2 films could be controlled by varying the intensity of the magnetic field. This study could facilitate understanding of ferromagnetism origin in un-doped oxides, also suggests an effective way to alter the intrinsic defects in HfO2 to improve its performance.

  1. Investigation of thermal stability and reliability of HfO2 based resistive random access memory devices with cross-bar structure

    NASA Astrophysics Data System (ADS)

    Chand, Umesh; Huang, Kuan-Chang; Huang, Chun-Yang; Ho, Chia-Hua; Lin, Chen-Hsi; Tseng, Tseung-Yuen

    2015-05-01

    The effect of the annealing treatment of a HfO2 resistive switching layer and the memory performance of a HfO2-based resistive random access memory (cross-bar structure) device were investigated. Oxygen is released from HfO2 resistive switching layers during vacuum annealing, leading to unstable resistive switching properties. This oxygen release problem can be suppressed by inserting an Al2O3 thin film, which has a lower Gibbs free energy, between the HfO2 layer and top electrode to form a Ti/Al2O3/HfO2/TiN structure. This device structure exhibited good reliability after high temperature vacuum annealing and post metal annealing (PMA) treatments. Moreover, the endurance and retention properties of the device were also improved after the PMA treatment.

  2. Pressure-induced structures of Si-doped HfO2

    NASA Astrophysics Data System (ADS)

    Fancher, Chris M.; Zhao, Lili; Nelson, Matthew; Bai, Ligang; Shen, Guoyin; Jones, Jacob L.

    2015-06-01

    The effect of hydrostatic pressure on the structure of Si-doped HfO2 (Si:HfO2) was studied by using a diamond anvil cell in combination with high-energy X-ray diffraction at a synchrotron source. Diffraction data were measured in situ during compression up to pressures of 31 GPa. Si:HfO2 with 3, 5, and 9 at. % Si were found to undergo a monoclinic to orthorhombic transition at pressures between 7 and 15 GPa. Whole pattern analysis was carried out using nonpolar (Pbca) and polar (Pca21) crystallographic models to investigate the symmetry of the observed high-pressure orthorhombic phase. Rietveld refinement results cannot discriminate a reliable difference between the Pbca and Pca21 structures as they nearly equally model the measured diffraction data. The pressure dependent lattice parameters, relative volume, and spontaneous strain are reported.

  3. Effects of water vapor in high vacuum chamber on the properties of HfO2 films

    Microsoft Academic Search

    Bo Ling; Hongbo He; Jianda Shao

    2007-01-01

    The influence of water vapor content in high vacuum chamber during the coating process on physical properties of HfO2 films was investigated. Coatings were deposited on BK7 substrates by electron beam evaporation and photoelectric maximum control method. An in situ residual gas analyzer (RGA) was used to monitor the residual gas composition in the vacuum chamber. The optical properties, microstructure,

  4. Charge trapping and interface characteristics of thermally evaporated HfO2 N. A. Chowdhury, R. Garg, and D. Misraa)

    E-print Network

    Misra, Durgamadhab "Durga"

    density distribution observed at low temperatures suggests that charge-trapping behavior of these films material systems, key issues like charge trapping, specifically bulk and interface charge trapping, poseCharge trapping and interface characteristics of thermally evaporated HfO2 N. A. Chowdhury, R. Garg

  5. SiC, , composite materials, HfO2, ZrO2 Pyrolytic graphite (PG/002)

    E-print Network

    #12;#12;SiC, , composite materials, HfO2, ZrO2 #12;#12;Ge Pyrolytic graphite (PG/002) Ge Pyrolytic µµ µ in situ Si (111) bent crystal SampleBent Si (111) analyser Position sensitive detector Be filter Sample Image plate detector Mirror #12

  6. Growth and properties of hafnicone and HfO(2)/hafnicone nanolaminate and alloy films using molecular layer deposition techniques.

    PubMed

    Lee, Byoung H; Anderson, Virginia R; George, Steven M

    2014-10-01

    Molecular layer deposition (MLD) of the hafnium alkoxide polymer known as "hafnicone" was grown using sequential exposures of tetrakis(dimethylamido) hafnium (TDMAH) and ethylene glycol (EG) as the reactants. In situ quartz crystal microbalance (QCM) experiments demonstrated self-limiting reactions and linear growth versus the number of TDMAH/EG reaction cycles. Ex situ X-ray reflectivity (XRR) analysis confirmed linear growth and measured the density of the hafnicone films. The hafnicone growth rates were temperature-dependent and decreased from 1.2 Å per cycle at 105 °C to 0.4 Å per cycle at 205 °C. The measured density was ?3.0 g/cm(3) for the hafnicone films at all temperatures. Transmission electron microscopy images revealed very uniform and conformal hafnicone films. The XRR studies also showed that the hafnicone films were very stable with time. Nanoindentation measurements determined that the elastic modulus and hardness of the hafnicone films were 47 ± 2 and 2.6 ± 0.2 GPa, respectively. HfO2/hafnicone nanolaminate films also were fabricated using HfO2 atomic layer deposition (ALD) and hafnicone MLD at 145 °C. The in situ QCM measurements revealed that HfO2 ALD nucleation on the hafnicone MLD surface required at least 18 TDMAH/H2O cycles. Hafnicone alloys were also fabricated by combining HfO2 ALD and hafnicone MLD at 145 °C. The composition of the hafnicone alloy was varied by adjusting the relative number of TDMAH/H2O ALD cycles and TDMAH/EG MLD cycles in the reaction sequence. The electron density changed continuously from 8.2 × 10(23) e(-)/cm(3) for pure hafnicone MLD films to 2.4 × 10(24) e(-)/cm(3) for pure HfO2 ALD films. These hafnicone films and the HfO2/hafnicone nanolaminates and alloys may be useful for flexible thin-film devices. PMID:25203487

  7. Achieving 1 nm capacitive effective thickness in atomic layer deposited HfO2 on In0.53Ga0.47As

    NASA Astrophysics Data System (ADS)

    Lee, K. Y.; Lee, Y. J.; Chang, P.; Huang, M. L.; Chang, Y. C.; Hong, M.; Kwo, J.

    2008-06-01

    A capacitive effective thickness (CET) value of 1.0nm has been achieved in atomic layer deposited (ALD) high ? dielectrics HfO2 on In0.53Ga0.47As /InP. The key is a short air exposure under 10min between removal of the freshly grown semiconductor epilayers and loading to the ALD reactor. This has led to minimal formation of the interfacial layer thickness, as confirmed using x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. The measured electrical characteristics of metal-oxide-semiconductor diodes of Au /Ti/HfO2(4.5nm)/In0.53Ga0.47As showed a low leakage current density of 3.8×10-4A/cm2 at VFB+1V, which is about eight orders of magnitudes lower than that of SiO2 with the same CET. The capacitance-voltage curves show an overall ? value of 17-18, a nearly zero flatband shift, and an interfacial density of states Dit of 2×1012cm-2eV-1.

  8. Microcontact-printed self-assembled monolayers as ultrathin gate dielectrics in organic thin-film transistors and complementary circuits.

    PubMed

    Zschieschang, Ute; Halik, Marcus; Klauk, Hagen

    2008-03-01

    We have developed a manufacturing process for organic thin-film transistors and organic complementary circuits in which a microcontact-printed phosphonic acid self-assembled monolayer is employed first as an etch resist to pattern aluminum gate electrodes by wet etching and then as the gate dielectric of the same device. To our knowledge, this is the first report of a printing process for electronic devices that combines the concepts of direct and indirect printing in the same printing step and for the same material by employing a transferred pattern both as an etch resist (indirect printing) and as a functional material as part of the final device (direct printing). Owing to the small thickness and the high quality of the monolayer gate dielectric, the transistors and circuits operate at a low voltage of 3 V. PMID:18198917

  9. Feature Modeling of HfO2 Atomic Layer Deposition Using HfCl4/H2O

    NASA Astrophysics Data System (ADS)

    Stout, Phillip J.; Adams, Vance; Ventzek, Peter L. G.

    2003-03-01

    A Monte Carlo based feature scale model (Papaya) has been applied to atomic layer deposition (ALD) of HfO2 using HfCl_4/H_20. The model includes physical effects of transport to surface, specular and diffusive reflection within feature, adsorption, surface diffusion, deposition and etching. Discussed will be the 3D feature modeling of HfO2 deposition in assorted features (vias and trenches). The effect of feature aspect ratios, pulse times, cycle number, and temperature on film thickness, feature coverage, and film Cl fraction (surface/bulk) will be discussed. Differences between HfO2 ALD on blanket wafers and in features will be highlighted. For instance, the minimum pulse times sufficient for surface reaction saturation on blanket wafers needs to be increased when depositing on features. Also, HCl products created during the HfCl4 and H_20 pulses are more likely to react within a feature than at the field, reducing OH coverage within the feature (vs blanket wafer) thus limiting the maximum coverage attainable for a pulse over a feature.

  10. Study of HfO 2 films prepared by ion-assisted deposition using a gridless end-hall ion source

    Microsoft Academic Search

    M. Gilo; N Croitoru

    1999-01-01

    HfO2 thin films were deposited using e-beam gun evaporation with ion assisted deposition (IAD) of low energy oxygen ions (40–100 eV) from an end-Hall ion source. A comparison was made using Hf and HfO2 starting materials. The index of refraction was measured as a function of the ion source voltage and compared to results without IAD. Application to high power

  11. Soft breakdown of ultra-thin gate oxide layers

    Microsoft Academic Search

    Michel Depas; Tanya Nigam; Marc M. Heyns

    1996-01-01

    The dielectric breakdown of ultra-thin 3 nm and 4 nm SiO2 layers used as a gate dielectric in poly-Si gate capacitors is investigated. The ultra-thin gate oxide reliability was determined using tunnel current injection stressing measurements. A soft breakdown mechanism is demonstrated for these ultra-thin gate oxide layers. The soft breakdown phenomenon corresponds with an anomalous increase of the stress

  12. Electronic properties of defects in polycrystalline dielectric materials

    Microsoft Academic Search

    K. P. McKenna; A. L. Shluger

    2009-01-01

    Grain boundaries have been implicated in current leakage and dielectric breakdown of CMOS devices. We calculate the electronic properties of oxygen vacancy defects near grain boundaries in the dielectric insulators MgO and HfO2 using first principles methods. In both materials we find that oxygen vacancies favourably segregate to grain boundaries, in various charge states. Their electronic properties are different from

  13. High on/off current ratio AlGaN/GaN MOS-HEMTs employing RF-sputtered HfO2 gate insulators

    NASA Astrophysics Data System (ADS)

    Seok, Ogyun; Ahn, Woojin; Han, Min-Koo; Ha, Min-Woo

    2013-02-01

    We fabricated AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) on Si substrates with RF-sputtered HfO2 as a gate insulator. We obtained a high breakdown voltage of 1524 V and a high on/off current ratio of 2.37 × 1010 in the MOS-HEMT with a 15 nm-thick RF-sputtered HfO2 while a conventional HEMT had 470 V and 7.61 × 103. The MOS-HEMT with the HfO2 showed a gate leakage current of -67 pA mm-1 at VGS = -10 V and VDS = 100 V and the drain leakage current was not considerably altered for 100 s. However, the conventional HEMT without a gate insulator had a large gate leakage current of -44.7 µA mm-1 and the drain leakage current was increased from 57.5 to 496 µA mm-1 for 100 s. We have also evaluated the blocking characteristics and passivation effects of HfO2 by measuring various electrical properties such as pulsed I-V and the surface leakage current at a mesa-isolated two-ohmic pad before and after HfO2 sputtering.

  14. Temperature dependent electron effective mass and barrier height in HfO2 based metal/oxide/metal devices

    NASA Astrophysics Data System (ADS)

    El Kamel, F.

    2015-07-01

    Electrical measurements are realized on Cu/HfO2/Pt capacitors to extract the electron effective mass in HfO2 and the barrier height at the Cu/HfO2 interface. The dominant conduction mechanisms are found to be the Schottky emission at medium voltages and the Fowler–Nordheim tunneling at high voltages. Previous research has usually been carried out by assuming a constant value for either the electron effective mass in oxide or the interfacial potential barrier height to determine the other parameter. However, in contrast to that general practice, an iterative method was proposed in the present study to determine, at the same time, the electron effective mass in HfO2 and the barrier height at the Cu/HfO2 interface without making any prior assumption about their values. The temperature dependence of these two parameters was also studied in the 298–423?K range. It is found that they strongly vary with temperature. The effective mass decreases quadratically with temperature, while the barrier height increases linearly with temperature.

  15. Characteristics of TaN gate MOSFET with ultrathin hafnium oxide (8 Å-12 Å)

    Microsoft Academic Search

    Byoung Hun Lee; R. Choi; L. Kang; S. Gopalan; R. Nieh; K. Onishi; Y. Jeon; Wen-Jie Qi; C. Kang; J. C. Lee

    2000-01-01

    MOSFET's with equivalent oxide thickness of 8-12 Å have been demonstrated by using high-K gate dielectric thin films (HfO2) and TaN gate electrode. Both self-aligned (higher thermal budget process) and non-self-aligned process (low thermal budget as in the replacement gate process) were used and compared. Excellent electrical characteristics (e.g. S~68 mV\\/dec) and reliability characteristics (e.g. high EBD, low charge trapping

  16. Formation of hafnium-aluminum-oxide gate dielectric using single cocktail liquid source in MOCVD process

    Microsoft Academic Search

    Moon Sig Joo; Byung Jin Cho; Chia Ching Yeo; Daniel Siu Hung Chan; Sung Jin Whoang; S. Mathew; L. Kanta Bera; N. Balasubramanian; Dim-Lee Kwong

    2003-01-01

    We demonstrate that a high quality metal organic chemical vapor deposition (MOCVD) HfAlxOy (hereafter HfAlO) dielectric film can successfully be deposited with a wide range of composition controllability between HfO2 and Al2O3 in HfAlO using a single cocktail liquid source HfAl(MMP)2(OiPr)5. A composition ratio between 45 to 90% of HfO2 in HfAlO is achieved by controlling deposition process parameters. The

  17. Growth, microstructure and electrical properties of sputter-deposited hafnium oxide (HfO2) thin films grown using HfO2 ceramic target

    SciTech Connect

    Aguirre, B.; Vemuri, R. S.; Zubia, David; Engelhard, Mark H.; Shutthanandan, V.; Kamala Bharathi, K.; Ramana, Chintalapalle V.

    2011-01-01

    Hafnium oxide (HfO?) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(100) substrates under varying growth temperature (Ts). HfO? ceramic target has been employed for sputtering while varying the Ts from room temperature to 500?C during deposition. The effect of Ts on the growth and microstructure of deposited HfO? films has been studied using grazing incidence x-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive x-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO? films. Structural characterization indicates that the HfO? films grown at Ts<200 ?C are amorphous while films grown at Ts>200 ?C are nanocrystalline. An amorphous-to-crystalline transition occurs at Ts=200 ?C. Nanocrystalline HfO? films crystallized in a monoclinic structure with a (-111) orientation. XPS measurements indicated the high surface-chemical quality and stoichiometric nature of the grown HfO? films. An interface layer (IL) formation occurs due to reaction at the HfO?-Si interface for HfO? films deposited at Ts>200 ?C. The thickness of IL increases with increasing Ts. XPS and EDS at the HfO?-Si cross-section indicate the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing Ts.

  18. The role of pulse length in target poisoning during reactive HiPIMS: application to amorphous HfO2

    NASA Astrophysics Data System (ADS)

    Ganesan, R.; Murdoch, B. J.; Treverrow, B.; Ross, A. E.; Falconer, I. S.; Kondyurin, A.; McCulloch, D. G.; Partridge, J. G.; McKenzie, D. R.; Bilek, M. M. M.

    2015-06-01

    In conventional reactive magnetron sputtering, target poisoning frequently leads to an instability that requires the reactive gas flow rate to be actively regulated to maintain a constant composition of the deposited layers. Here we demonstrate that the pulse length in high power impulse magnetron sputtering (HiPIMS) is important for determining the surface conditions on the target that lead to poisoning. By increasing the pulse length, a smooth transition can be achieved from a poisoned target condition (short pulses) to a quasi-metallic target condition (long pulses). Appropriate selection of pulse length eliminates the need for active regulation, enabling stable reactive magnetron sputter deposition of stoichiometric amorphous hafnium oxide (HfO2) from a Hf target. A model is presented for the reactive HiPIMS process in which the target operates in a partially poisoned mode with a distribution of oxide on its surface that depends on the pulse length.

  19. Giant magneto-optical Kerr effect in HfO2/Co/HfO2/Al/silicon structure

    NASA Astrophysics Data System (ADS)

    Zhang, S. Y.; Gao, J. L.; Xia, W. B.; Luo, X. J.; Tang, S. L.; Du, Y. W.

    2013-08-01

    An extraordinary enhancement of magneto-optical Kerr effect was demonstrated in HfO2/Co/HfO2/Al/substrate composite structure by experimental measurements as well as theoretical calculations. Giant polar Kerr rotation was observed within a broad spectral region, and especially a peak of -7.92° was found at wavelength of 496 nm, which is nearly forty times as large as that of a single Co film. In addition, a Kerr rotation reversal was also observed in short wavelength region in the longitudinal geometry. We proposed that the multiple reflections and optical interference in the optical cavities lead to the enormous enhancement and modulation of the Kerr rotation.

  20. Voltage and Power-Controlled Regimes in the Progressive Unipolar RESET Transition of HfO2-Based RRAM

    PubMed Central

    Long, Shibing; Perniola, Luca; Cagli, Carlo; Buckley, Julien; Lian, Xiaojuan; Miranda, Enrique; Pan, Feng; Liu, Ming; Suñé, Jordi

    2013-01-01

    Resistive switching (RS) based on the formation and rupture of conductive filament (CF) is promising in novel memory and logic device applications. Understanding the physics of RS and the nature of CF is of utmost importance to control the performance, variability and reliability of resistive switching memory (RRAM). Here, the RESET switching of HfO2-based RRAM was statistically investigated in terms of the CF conductance evolution. The RESET usually combines an abrupt conductance drop with a progressive phase ending with the complete CF rupture. RESET1 and RESET2 events, corresponding to the initial and final phase of RESET, are found to be controlled by the voltage and power in the CF, respectively. A Monte Carlo simulator based on the thermal dissolution model of unipolar RESET reproduces all of the experimental observations. The results contribute to an improved physics-based understanding on the switching mechanisms and provide additional support to the thermal dissolution model. PMID:24121547

  1. Thermal stability of ,,HfO2...x,,Al2O3...1x on Si H. Y. Yu, N. Wu, M. F. Li,a)

    E-print Network

    Fu, Li Ming

    ; accepted 13 September 2002 The kinetics of the interfacial layer IL growth between Hf aluminates and the Si the annealing ambient. Our results also show that Hf aluminates exhibit much stronger resistance to oxygen coefficient of Al2O3 than HfO2 , and ii higher crystallization temperature of the Hf aluminates. © 2002

  2. Resistance switching in HfO2 metal-insulator-metal devices P. Gonon, M. Mougenot, C. Valle, C. Jorel, V. Jousseaume et al.

    E-print Network

    Paris-Sud XI, Université de

    Laboratory for the Organization and Properties of Materials (LMOP), El Manar University, Tunis 1060, Tunisia is studied in Au/HfO2 10 nm / Pt, TiN devices, where HfO2 is deposited by atomic layer deposition. The study

  3. High Mobility and Excellent Electrical Stability of MOSFETs Using a Novel HfTaO Gate Dielectric

    E-print Network

    Fu, Li Ming

    -based gate dielectric for MOSFETs with TaN metal gate. By incorporating Ta into HfO2 films, significant) electron peak mobility is enhanced by more than two times; (4) charge trapping and threshold voltage shift. After gate patterning, phosphorus was implanted at 50 KeV with a dose of 5x1015 cm-2 . Dopant activation

  4. The electrical and material characterization of hafnium oxynitride gate dielectrics with TaN-gate electrode

    Microsoft Academic Search

    Chang Seok Kang; Hag-Ju Cho; Rino Choi; Young-Hee Kim; Chang Yong Kang; Se Jong Rhee; Changhwan Choi; M. S. Akbar; J. C. Lee

    2004-01-01

    Electrical and material characteristics of hafnium oxynitride (HfON) gate dielectrics have been studied in comparison with HfO2. HfON was prepared by a deposition of HfN followed by post-deposition-anneal (PDA). By secondary ion mass spectroscopy (SIMS), incorporated nitrogen in the HfON was found to pile up at the dielectric\\/Si interface layer. Based on the SIMS profile, the interfacial layer (IL) composition

  5. The Impact of Dielectric Material and Temperature on Dielectric Charging in RF MEMS Capacitive Switches

    Microsoft Academic Search

    George Papaioannou

    2010-01-01

    \\u000a The present work attempts to provide a better insight on the dielectric charging in RF-MEMS capacitive switches that constitutes\\u000a a key issue limiting parameter of their commercialization. The dependence of the charging process on the nature of dielectric\\u000a materials widely used in these devices, such as SiO2, Si3N4, AlN, Al2O3, Ta2O5, HfO2, which consist of covalent or ionic bonds and

  6. High-performance self-aligned inversion-channel In0.53Ga0.47As metal-oxide-semiconductor field-effect-transistors by in-situ atomic-layer-deposited HfO2

    NASA Astrophysics Data System (ADS)

    Lin, T. D.; Chang, W. H.; Chu, R. L.; Chang, Y. C.; Chang, Y. H.; Lee, M. Y.; Hong, P. F.; Chen, Min-Cheng; Kwo, J.; Hong, M.

    2013-12-01

    Self-aligned inversion-channel In0.53Ga0.47As metal-oxide-semiconductor field-effect-transistors (MOSFETs) have been fabricated using the gate dielectrics of in-situ directly atomic-layer-deposited (ALD) HfO2 followed by ALD-Al2O3. There were no surface pretreatments and no interfacial passivation/barrier layers prior to the ALD. TiN/Al2O3 (4 nm)/HfO2 (1 nm)/In0.53Ga0.47As/InP MOS capacitors exhibited well-behaved capacitance-voltage characteristics with true inversion behavior, low leakage current densities of ˜10-8 A/cm2 at ±1 MV/cm, and thermodynamic stability at high temperatures. Al2O3 (3 nm)/HfO2 (1 nm)/In0.53Ga0.47As MOSFETs of 1 ?m gate length, with 700 °C-800 °C rapid thermal annealing in source/drain activation, have exhibited high extrinsic drain current (ID) of 1.5 mA/?m, transconductance (Gm) of 0.84 mS/?m, ION/IOFF of ˜104, low sub-threshold swing of 103 mV/decade, and field-effect electron mobility of 1100 cm2/V . s. The devices have also achieved very high intrinsic ID and Gm of 2 mA/?m and 1.2 mS/?m, respectively.

  7. Chemical states and electronic structure of a HfO(-2) / Ge(001) interface

    SciTech Connect

    Seo, Kang-ill; McIntyre, Paul C.; /Stanford U., Materials Sci. Dept.; Sun, Shiyu; Lee, Dong-Ick; Pianetta, Piero; /SLAC, SSRL; Saraswat, Krishna C.; /Stanford U., Elect.

    2005-05-04

    We report the chemical bonding structure and valence band alignment at the HfO{sub 2}/Ge (001) interface by systematically probing various core level spectra as well as valence band spectra using soft x-rays at the Stanford Synchrotron Radiation Laboratory. We investigated the chemical bonding changes as a function of depth through the dielectric stack by taking a series of synchrotron photoemission spectra as we etched through the HfO{sub 2} film using a dilute HF-solution. We found that a very non-stoichiometric GeO{sub x} layer exists at the HfO{sub 2}/Ge interface. The valence band spectra near the Fermi level in each different film structure were carefully analyzed, and as a result, the valence band offset between Ge and GeO{sub x} was determined to be {Delta}E{sub v} (Ge-GeO{sub x}) = 2.2 {+-} 0.15 eV, and that between Ge and HfO{sub 2}, {Delta}E{sub v} (Ge-HfO{sub 2}) = 2.7 {+-} 0.15 eV.

  8. In situ study of the role of substrate temperature during atomic layer deposition of HfO2 on InP

    NASA Astrophysics Data System (ADS)

    Dong, H.; Santosh, K. C., Qin, X.; Brennan, B.; McDonnell, S.; Zhernokletov, D.; Hinkle, C. L.; Kim, J.; Cho, K.; Wallace, R. M.

    2013-10-01

    The dependence of the "self cleaning" effect of the substrate oxides on substrate temperature during atomic layer deposition (ALD) of HfO2 on various chemically treated and native oxide InP (100) substrates is investigated using in situ X-ray photoelectron spectroscopy. The removal of In-oxide is found to be more efficient at higher ALD temperatures. The P oxidation states on native oxide and acid etched samples are seen to change, with the total P-oxide concentration remaining constant, after 10 cycles of ALD HfO2 at different temperatures. An (NH4)2 S treatment is seen to effectively remove native oxides and passivate the InP surfaces independent of substrate temperature studied (200 °C, 250 °C and 300 °C) before and after the ALD process. Density functional theory modeling provides insight into the mechanism of the changes in the P-oxide chemical states.

  9. In situ infrared spectroscopy study of the interface self-cleaning during the atomic layer deposition of HfO2 on GaAs(100) surfaces

    NASA Astrophysics Data System (ADS)

    Ye, Liwang; Gougousi, Theodosia

    2014-09-01

    In situ attenuated total reflectance Fourier transform infrared spectroscopy was utilized to study the interface evolution during the atomic layer deposition (ALD) of HfO2 on GaAs surfaces using of tetrakis (dimethylamino) hafnium and H2O. The experiments were performed on chemical oxide and hydrogen fluoride etched GaAs(100) starting surfaces. For the deposition of HfO2 on chemical oxide GaAs surfaces at 275 °C, which corresponds to the optimal ALD process temperature, continuous arsenic oxide removal was observed for the first 20 ALD cycles. The oxide removal was more pronounced at the initial 1-2 cycles but nonetheless persisted, at a reduced rate, up to the 20th cycle. The substrate temperature was confirmed to affect the arsenic oxide removal; the rate was significant at temperatures above 250 °C while negligible below 200 °C.

  10. Wide band antireflective coatings Al2O3 / HfO2 / MgF2 for UV region

    NASA Astrophysics Data System (ADS)

    Winkowski, P.; Marsza?ek, Konstanty W.

    2013-07-01

    Deposition technology of the three layers antireflective coatings consists of hafnium compound are presented in this paper. Oxide films were deposited by means of e-gun evaporation in vacuum of 5x10-5 mbar in presence of oxygen and fluoride films by thermal evaporation. Substrate temperature was 250°C. Coatings were deposited onto optical lenses made from quartz glass (Corning HPFS). Thickness and deposition rate were controlled by thickness measuring system Inficon XTC/2. Simulations leading to optimization of thickness and experimental results of optical measurements carried during and after deposition process were presented. Physical thickness measurements were made during deposition process and were equal to 43 nm/74 nm/51 nm for Al2O3 / HfO2 / MgF2 respectively. Optimization was carried out for ultraviolet region from 230nm to the beginning of visible region 400 nm. In this region the average reflectance of the antireflective coating was less than 0.5% in the whole range of application.

  11. Low toxicity of HfO2, SiO2, Al2O3 and CeO2 nanoparticles to the yeast, Saccharomyces cerevisiae.

    PubMed

    García-Saucedo, Citlali; Field, James A; Otero-Gonzalez, Lila; Sierra-Álvarez, Reyes

    2011-09-15

    Increasing use of nanomaterials necessitates an improved understanding of their potential impact on environment health. This study evaluated the cytotoxicity of nanosized HfO(2), SiO(2), Al(2)O(3) and CeO(2) towards the eukaryotic model organism Saccharomyces cerevisiae, and characterized their state of dispersion in bioassay medium. Nanotoxicity was assessed by monitoring oxygen consumption in batch cultures and by analysis of cell membrane integrity. CeO(2), Al(2)O(3), and HfO(2) nanoparticles were highly unstable in yeast medium and formed micron-sized, settleable agglomerates. A non-toxic polyacrylate dispersant (Dispex A40) was used to improve nanoparticle stability and determine the impact of enhanced dispersion on toxicity. None of the NPs tested without dispersant inhibited O(2) uptake by yeast at concentrations as high as 1000 mg/L. Dispersant supplementation only enhanced the toxicity of CeO(2) (47% at 1000 mg/L). Dispersed SiO(2) and Al(2)O(3) (1000 mg/L) caused cell membrane damage, whereas dispersed HfO(2) and CeO(2) did not cause significant disruption of membrane integrity at the same concentration. These results suggest that the O(2) uptake inhibition observed with dispersed CeO(2) NPs was not due to reduced cell viability. This is the first study evaluating toxicity of nanoscale HfO(2), SiO(2), Al(2)O(3) and CeO(2) to S. cerevisiae. Overall the results obtained demonstrate that these nanomaterials display low or no toxicity to yeast. PMID:21782338

  12. Ultralow expansion ceramics in the HfO 2 -TiO 2 system synthesized by an hydrolysis and polycondensation technique

    Microsoft Academic Search

    G. Tilloca

    1992-01-01

    Ultra-refractory ceramics from the HfO2-TiO2 system in the range 30–40 mol% TiO2, with a near-zero thermal expansion, have been synthesized by hydrolysis and polycondensation of titanium alkoxide and hafnium dichloride alcoholic solutions and sintered at moderate temperature. Thermal stability, crystallization, density and microstructure of these materials have been examined. The as-prepared powder, amorphous at room temperature, crystallized quickly when heated

  13. Effect of current compliance and voltage sweep rate on the resistive switching of HfO2/ITO/Invar structure as measured by conductive atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Wu, You-Lin; Liao, Chun-Wei; Ling, Jing-Jenn

    2014-06-01

    The electrical characterization of HfO2/ITO/Invar resistive switching memory structure was studied using conductive atomic force microscopy (AFM) with a semiconductor parameter analyzer, Agilent 4156C. The metal alloy Invar was used as the metal substrate to ensure good ohmic contact with the substrate holder of the AFM. A conductive Pt/Ir AFM tip was placed in direct contact with the HfO2 surface, such that it acted as the top electrode. Nanoscale current-voltage (I-V) characteristics of the HfO2/ITO/Invar structure were measured by applying a ramp voltage through the conductive AFM tip at various current compliances and ramp voltage sweep rates. It was found that the resistance of the low resistance state (RLRS) decreased with increasing current compliance value, but resistance of high resistance state (RHRS) barely changed. However, both the RHRS and RLRS decreased as the voltage sweep rate increased. The reasons for this dependency on current compliance and voltage sweep rate are discussed.

  14. Fabrication of BaTiO3-Based Dielectrics for Ultrathin-Layer Multilayer Ceramic Capacitor Application by a Modified Coating Approach

    NASA Astrophysics Data System (ADS)

    Tian, Zhibin; Wang, Xiaohui; Zhang, Yichi; Song, Tae-Ho; Hur, Kang Heon; Li, Longtu

    2011-02-01

    The development of multilayer ceramic capacitor (MLCC) with base metal electrode (BME) requires precise controlling of the microstructure in a very thin dielectric layer (<1 µm). In this paper, a modified coating approach for high coverage of BaTiO3 powder for further MLCC application has been developed. The well dispersed and coated BaTiO3 powders are prepared and the relative mechanism has been discussed. Furthermore, the ultrafine grained X7R dielectric ceramics were produced by both conventional mixing and modified coating methods. Compared with the conventional mixing method, the ceramics prepared by the coating approach exhibited better TCC (the temperature coefficient of capacitance) performance, with dielectric constant over 2000 and grain size below 150 nm. In addition, it is found through the coating method the content of additives can be reduced to a relatively smaller amount than that required in conventional mixing method.

  15. Structural and dielectric properties of energetically deposited hafnium oxide films

    NASA Astrophysics Data System (ADS)

    Murdoch, B. J.; McCulloch, D. G.; Partridge, J. G.

    2014-12-01

    Amorphous hafnium oxide films, energetically deposited at room temperature from a filtered cathodic vacuum arc (FCVA) onto Si substrates, exhibit low current leakage (11 ?A cm?2 in an electric field of 100 kV cm?1), a dielectric constant (k) of 17 and a refractive index exceeding 2.1 over the visible spectrum. Cross-sectional transmission electron microscopy, energy-dispersive x-ray spectroscopy and electron energy loss spectroscopy revealed an amorphous microstructure and higher film density when compared with HfO2 deposited by reactive direct-current magnetron sputtering. The superior properties and higher density of the FCVA HfO2 are attributed to the elevated energy of the depositing flux.

  16. Interface trap and oxide charge generation under negative bias temperature instability of p-channel metal-oxide-semiconductor field-effect transistors with ultrathin plasma-nitrided SiON gate dielectrics

    SciTech Connect

    Zhu Shiyang; Nakajima, Anri; Ohashi, Takuo; Miyake, Hideharu [Research Center for Nanodevices and Systems, Hiroshima University, 1-4-2 Kagamiyama, Higashi-Hiroshima 739-8527 (Japan); Elpida Memory, Inc., 7-10 Yoshikawa-kogyo-danchi, Higashi-Hiroshima 739-0198 (Japan)

    2005-12-01

    The interface trap generation ({delta}N{sub it}) and fixed oxide charge buildup ({delta}N{sub ot}) under negative bias temperature instability (NBTI) of p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) with ultrathin (2 nm) plasma-nitrided SiON gate dielectrics were studied using a modified direct-current-current-voltage method and a conventional subthreshold characteristic measurement. Different stress time dependences were shown for {delta}N{sub it} and {delta}N{sub ot}. At the earlier stress times, {delta}N{sub it} dominates the threshold voltage shift ({delta}V{sub th}) and {delta}N{sub ot} is negligible. With increasing stress time, the rate of increase of {delta}N{sub it} decreases continuously, showing a saturating trend for longer stress times, while {delta}N{sub ot} still has a power-law dependence on stress time so that the relative contribution of {delta}N{sub ot} increases. The thermal activation energy of {delta}N{sub it} and the NBTI lifetime of pMOSFETs, compared at a given stress voltage, are independent of the peak nitrogen concentration of the SiON film. This indicates that plasma nitridation is a more reliable method for incorporating nitrogen in the gate oxide.

  17. CMUTs with high-K atomic layer deposition dielectric material insulation layer.

    PubMed

    Xu, Toby; Tekes, Coskun; Degertekin, F

    2014-12-01

    Use of high-? dielectric, atomic layer deposition (ALD) materials as an insulation layer material for capacitive micromachined ultrasonic transducers (CMUTs) is investigated. The effect of insulation layer material and thickness on CMUT performance is evaluated using a simple parallel plate model. The model shows that both high dielectric constant and the electrical breakdown strength are important for the dielectric material, and significant performance improvement can be achieved, especially as the vacuum gap thickness is reduced. In particular, ALD hafnium oxide (HfO2) is evaluated and used as an improvement over plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (Six)Ny)) for CMUTs fabricated by a low-temperature, complementary metal oxide semiconductor transistor-compatible, sacrificial release method. Relevant properties of ALD HfO2) such as dielectric constant and breakdown strength are characterized to further guide CMUT design. Experiments are performed on parallel fabricated test CMUTs with 50-nm gap and 16.5-MHz center frequency to measure and compare pressure output and receive sensitivity for 200-nm PECVD Six)Ny) and 100-nm HfO2) insulation layers. Results for this particular design show a 6-dB improvement in receiver output with the collapse voltage reduced by one-half; while in transmit mode, half the input voltage is needed to achieve the same maximum output pressure. PMID:25474786

  18. Nitrogen engineering of ultrathin oxynitrides by a thermal NO/O2/NO E. P. Gusev,a)

    E-print Network

    Gustafsson, Torgny

    Nitrogen engineering of ultrathin oxynitrides by a thermal NO/O2/NO process E. P. Gusev,a) H. C. Lu discusses nitrogen engineering of ultrathin ( 5 nm oxynitride gate dielectrics. The dielectric film that we have aimed for has two nitrogen enhanced layers: one at the SiO2/polysilicon interface to retard boron

  19. Pyroelectric and dielectric properties of ferroelectric films with interposed dielectric buffer layers

    NASA Astrophysics Data System (ADS)

    Espinal, Y.; Kesim, M. T.; Misirlioglu, I. B.; Trolier-McKinstry, S.; Mantese, J. V.; Alpay, S. P.

    2014-12-01

    The dielectric and pyroelectric properties of c-domain ferroelectric films with linear dielectric buffer layers were investigated theoretically. Computations were carried out for multilayers consisting of PbZr0.2Ti0.8O3 with Al2O3, SiO2, Si3N4, HfO2, and TiO2 buffers on metalized Si. It is shown that the dielectric and pyroelectric properties of such multilayers can be increased by the presence of the buffer compared to ferroelectric monolayers. Calculations for PbZr0.2Ti0.8O3 films with 1% Al2O3 interposed between electrodes on Si show that the dielectric and pyroelectric coefficients are 310 and 0.070 ?C cm-2 °C-1, respectively. Both values are higher than the intrinsic response of PbZr0.2Ti0.8O3 monolayer on Si.

  20. On the Physically Based Compact Gate C –V Model for Ultrathin Gate Dielectric MOS Devices Using the Modified Airy Function Approximation

    Microsoft Academic Search

    I. B. Shams; K. M. M. Habib; Q. D. M. Khosru; A. N. M. Zainuddin; A. Haque

    2007-01-01

    The exponent of the modified Airy function solution of the quantized energy levels in the MOS potential well, which is used in the physically based quantum-mechanical compact gate C-V model of Li et al., has been found to be dependent on the barrier height at the Si-dielectric interface and the substrate doping density. The physical origins of this dependence are

  1. Carbon Nanotube Field-Effect Transistors with Integrated Ohmic Contacts and High-kappa Gate Dielectrics

    Microsoft Academic Search

    Ali Javey; Jing Guo; Damon B. Farmer; Qian Wang; Dunwei Wang; Roy G. Gordon; Mark Lundstrom; Hongjie Dai

    2004-01-01

    High performance enhancement mode semiconducting carbon nanotube field-effect transistors (CNTFETs) are obtained by combining ohmic metal-tube contacts, high dielectric constant HfO2 films as gate insulators, and electrostatically doped nanotube segments as source\\/drain electrodes. The combination of these elements affords high ON currents, subthreshold swings of ~ 70-80 mV\\/decade, and allows for low OFF currents and suppressed ambipolar conduction. The doped

  2. Electrical properties of high- ? gate dielectrics: Challenges, current issues, and possible solutions

    Microsoft Academic Search

    M. Houssa; L. Pantisano; L.-Å. Ragnarsson; R. Degraeve; T. Schram; G. Pourtois; S. De Gendt; G. Groeseneken; M. M. Heyns

    2006-01-01

    High-? gate dielectrics like HfO2 and HfSiO(N) are considered for the replacement of SiO2 and SiON layers in advanced complementary metal–oxide–semiconductor (MOS) devices. Using these gate oxides allows indeed to drastically reduce the leakage current flowing through the device, as required by the specifications of the International Technology Roadmap for Semiconductors. However, major problems remain to be solved before the

  3. Optical properties of the Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings

    NASA Astrophysics Data System (ADS)

    Marsza?ek, Konstanty; Winkowski, Pawe?; Jaglarz, Janusz

    2014-01-01

    Investigations of bilayer and trilayer Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings are presented in this paper. The oxide films were deposited on a heated quartz glass by e-gun evaporation in a vacuum of 5 × 10-3 [Pa] in the presence of oxygen. Depositions were performed at three different temperatures of the substrates: 100 °C, 200 °C and 300 °C. The coatings were deposited onto optical quartz glass (Corning HPFS). The thickness and deposition rate were controlled with Inficon XTC/2 thickness measuring system. Deposition rate was equal to 0.6 nm/s for Al2O3, 0.6 nm - 0.8 nm/s for HfO2 and 0.6 nm/s for SiO2. Simulations leading to optimization of the thin film thickness and the experimental results of optical measurements, which were carried out during and after the deposition process, have been presented. The optical thickness values, obtained from the measurements performed during the deposition process were as follows: 78 nm/78 nm for Al2O3/SiO2 and 78 nm/156 nm/78 nm for Al2O3/HfO2/SiO2. The results were then checked by ellipsometric technique. Reflectance of the films depended on the substrate temperature during the deposition process. Starting from 240 nm to the beginning of visible region, the average reflectance of the trilayer system was below 1 % and for the bilayer, minima of the reflectance were equal to 1.6 %, 1.15 % and 0.8 % for deposition temperatures of 100 °C, 200 °C and 300 °C, respectively.

  4. Effects of vacuum ultraviolet and ultraviolet irradiation on ultrathin hafnium-oxide dielectric layers on (100)Si as measured with electron-spin resonance

    SciTech Connect

    Ren, H.; Shohet, J. L. [Department of Electrical and Computer Engineering, Plasma Processing and Technology Laboratory, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Cheng, S. L.; Nishi, Y. [Stanford University, Stanford, California 94305 (United States)

    2010-05-10

    The effects of vacuum ultraviolet (VUV) (7.2 eV) and UV (4.9 eV) irradiation on hafnium-oxide dielectric layers were studied with electron-spin resonance to detect defect states. Silicon dangling-bond defects (P{sub b} centers) and positively charged oxygen vacancies (E{sup '} centers) were detected with g-factor fitting. VUV irradiation increases the level of P{sub b} states, while UV decreases the level of P{sub b} states but increases the level of E{sup '} states significantly. Rapid thermal annealing appears to mitigate these effects. Absolute values of the defect-state concentrations are presented.

  5. Large, uni-directional actuation in dielectric elastomers achieved by fiber Jiangshui Huang, Tongqing Lu, Jian Zhu, David R. Clarke, and Zhigang Suo

    E-print Network

    Suo, Zhigang

    , 192902 (2012) Large actuation and high dielectric strength in metallized dielectric elastomer actuatorsLarge, uni-directional actuation in dielectric elastomers achieved by fiber stiffening Jiangshui, 104901 (2012) Intrinsic electrocaloric effect in ultrathin ferroelectric capacitors Appl. Phys. Lett. 100

  6. Plasmon Enhanced Ultrathin Film Broad-Band Nanoporous Absorber

    NASA Astrophysics Data System (ADS)

    Lu, Jin-You; Liu, Dong; Wilke, Kyle; Noorulla, Sumaya; Fang, Nicholas; Zhang, Tiejun

    2015-03-01

    Ultrathin absorbing films have attracted much attention due to their strong interference persisted inside the lossy dielectric film, which has much smaller thickness compared with conventional resonators. The absorber was realized by coating a lossy dielectric film with tens of nanometers in thickness on a metallic substrate. The ultrathin absorber was further developed to obtain perfect absorption at a given wavelength by inserting a spacer TiO2 between the dielectric and metallic substrate. However, this interference mode just contributes to the narrow band absorption. Here, we propose to combine the strong interference inside the ultrathin film absorber with localized surface plasmons (LSPs) to achieve broad-band absorption. This concept is realized by coating ultrathin absorbing Ge/Au films on nanoporous substrate, where the LSP mode is supported by pore-shape cavities. The near-field optical properties of ultrathin film on nanoporous substrate are analyzed by using the finite difference time domain method to study the spectroscopy and energy flow patterns. Simulation shows the absorption increases with the pore radius until the pore is too large to sustain LSP. Light is trapped in nanopores and penetrated into the lossy dielectric film around the pore entrance. Supported by cooperative agreement between Masdar Inst and MIT.

  7. High Dose Neutron Irradiation Performance of Dielectric Mirrors

    SciTech Connect

    Nimishakavi, Anantha Phani Kiran Kumar [ORNL; Leonard, Keith J [ORNL; Jellison Jr, Gerald Earle [ORNL; Snead, Lance Lewis [ORNL

    2015-01-01

    The study presents the high-dose behavior of dielectric mirrors specifically engineered for radiation-tolerance: alternating layers of Al2O3/SiO2 and HfO2/SiO2 were grown on sapphire substrates and exposed to neutron doses of 1 and 4 dpa at 458 10K in the High Flux Isotope Reactor (HFIR). In comparison to previously reported results, these higher doses of 1 and 4 dpa results in a drastic drop in optical reflectance, caused by a failure of the multilayer coating. HfO2/SiO2 mirrors failed completely when exposed to 1 dpa, whereas the reflectance of Al2O3/SiO2 mirrors reduced to 44%, eventually failing at 4 dpa. Transmission electron microscopy (TEM) observation of the Al2O3/SiO2 specimens showed SiO2 layer defects which increases size with irradiation dose. The typical size of each defect was 8 nm in 1 dpa and 42 nm in 4 dpa specimens. Buckling type delamination of the interface between the substrate and first layer was typically observed in both 1 and 4 dpa HfO2/SiO2 specimens. Composition changes across the layers were measured in high resolution scanning-TEM mode using energy dispersive spectroscopy. A significant interdiffusion between the film layers was observed in Al2O3/SiO2 mirror, though less evident in HfO2/SiO2 system. The ultimate goal of this work is the provide insight into the radiation-induced failure mechanisms of these mirrors.

  8. Integration of lead-free ferroelectric on HfO2/Si (100) for high performance non-volatile memory applications

    PubMed Central

    Kundu, Souvik; Maurya, Deepam; Clavel, Michael; Zhou, Yuan; Halder, Nripendra N.; Hudait, Mantu K.; Banerji, Pallab; Priya, Shashank

    2015-01-01

    We introduce a novel lead-free ferroelectric thin film (1-x)BaTiO3-xBa(Cu1/3Nb2/3)O3 (x = 0.025) (BT-BCN) integrated on to HfO2 buffered Si for non-volatile memory (NVM) applications. Piezoelectric force microscopy (PFM), x-ray diffraction, and high resolution transmission electron microscopy were employed to establish the ferroelectricity in BT-BCN thin films. PFM study reveals that the domains reversal occurs with 180° phase change by applying external voltage, demonstrating its effectiveness for NVM device applications. X-ray photoelectron microscopy was used to investigate the band alignments between atomic layer deposited HfO2 and pulsed laser deposited BT-BCN films. Programming and erasing operations were explained on the basis of band-alignments. The structure offers large memory window, low leakage current, and high and low capacitance values that were easily distinguishable even after ~106?s, indicating strong charge storage potential. This study explains a new approach towards the realization of ferroelectric based memory devices integrated on Si platform and also opens up a new possibility to embed the system within current complementary metal-oxide-semiconductor processing technology. PMID:25683062

  9. Nanosecond pulsed laser damage characteristics of HfO2/SiO2 high reflection coatings irradiated from crystal-film interface.

    PubMed

    Cheng, Xinbin; Jiao, Hongfei; Lu, Jiangtao; Ma, Bin; Wang, Zhanshan

    2013-06-17

    The nano-precursors in the subsurface of Nd:YLF crystal were limiting factor that decreased the laser-induced damage threshold (LIDT) of HfO(2)/SiO(2) high reflection (HR) coatings irradiated from crystal-film interface. To investigate the contribution of electric-field (E-field) to laser damage originating from nano-precursors and then to probe the distribution of vulnerable nano-precursors in the direction of subsurface depth, two 1064 nm HfO(2)/SiO(2) HR coatings having different standing-wave (SW) E-field distributions in subsurface of Nd:YLF c5424181043036123rystal were designed and prepared. Artificial gold nano-particles were implanted into the crystal-film interface prior to deposition of HR coatings to study the damage behaviors in a more reliable way. The damage test results revealed that the SW E-field rather than the travelling-wave (TW) E-field contributed to laser damage. By comparing the SW E-field distributions and LIDTs of two HR coating designs, the most vulnerable nano-precursors were determined to be concentrated in a thin redeposition layer that is within 100 nm from the crystal-film interface. PMID:23787674

  10. In situ atomic layer deposition study of HfO2 growth on NH4OH and atomic hydrogen treated Al0.25Ga0.75N

    NASA Astrophysics Data System (ADS)

    Qin, Xiaoye; Brennan, Barry; Dong, Hong; Kim, Jiyoung; Hinkle, Christopher L.; Wallace, Robert M.

    2013-06-01

    The atomic layer deposition (ALD) of HfO2 on the native oxide, NH4OH, and atomic hydrogen treated Al0.25Ga0.75N surface was studied using in situ X-ray photoelectron spectroscopy (XPS), after each individual "half cycle" of the ALD process. During the deposition process, minimal change in the chemical states of Ga and Al is detected, with no evidence of interfacial oxide generation. The initial HfO2 growth rate on the native oxide Al0.25Ga0.75N surface is very low, however, exposure of the Al0.25Ga0.75N surface to atomic hydrogen decreases the concentration of carbon and oxygen and enhances the HfO2 growth rate.

  11. Improved growth behavior of atomic-layer-deposited high-k dielectrics on multilayer MoS2 by oxygen plasma pretreatment.

    PubMed

    Yang, Jaehyun; Kim, Sunkook; Choi, Woong; Park, Sang Han; Jung, Youngkwon; Cho, Mann-Ho; Kim, Hyoungsub

    2013-06-12

    We report on the effect of oxygen plasma treatment of two-dimensional multilayer MoS2 crystals on the subsequent growth of Al2O3 and HfO2 films, which were formed by atomic layer deposition (ALD) using trimethylaluminum and tetrakis-(ethylmethylamino)hafnium metal precursors, respectively, with water oxidant. Due to the formation of an ultrathin Mo-oxide layer on the MoS2 surface, the surface coverage of Al2O3 and HfO2 films was significantly improved compared to those on pristine MoS2, even at a high ALD temperature. These results indicate that the surface modification of MoS2 by oxygen plasma treatment can have a major impact on the subsequent deposition of high-k thin films, with important implications on their integration in thin film transistors. PMID:23683268

  12. Atomic Layer Deposition of High k Dielectric and Metal Gate Stacks for MOS Devices

    SciTech Connect

    Senzaki, Yoshihide; Choi, Kisik; Kirsch, Paul D.; Majhi, Prashant; Lee, Byoung Hun [SEMATECH, 2706 Montopolis Drive, Austin, TX 78741 (United States)

    2005-09-09

    High-k gate stack fabrication via atomic layer deposition (ALD) of ultra thin HfO2 and HfxSi1-xO2 films is demonstrated utilizing metal-amide precursors and ozone as an oxidant. High resolution transmission electron microscopy (TEM) shows that films near 2.0 nm are reproducible. X-ray reflectivity (XRR) and Rutherford backscattering (RBS) indicate that this ALD chemistry proceeds similarly on multiple surface preparations including HF last without growth incubation. High field mobility of more than 85% of the universal SiO2 mobility has been achieved at EOT {approx}1nm with a reduction of more than two orders of magnitude in leakage current density as compared with a SiO2/poly Si gate. Various ALD metal nitrides such as TiN, HfN, HfSiN have been deposited on HfO2 and HfSiOx dielectrics which enabled a study of the interfacial reaction between high-k dielectrics and metal electrode materials. The thermal stability of PVD Ru deposited on ALD HfO2 has also been observed.

  13. A study on HfO2 RRAM in HRS based on I-V and RTN analysis

    NASA Astrophysics Data System (ADS)

    Puglisi, Francesco M.; Pavan, Paolo; Padovani, Andrea; Larcher, Luca

    2014-12-01

    This paper presents a statistical characterization of random telegraph noise (RTN) in hafnium-oxide-based resistive random access memories (RRAMs) in high resistive state (HRS). Complex RTN signals are analyzed exploiting a Factorial Hidden Markov Model (FHMM) approach, which allows to derive the statistical properties of the RTN signals, directly related to the physical properties of the traps responsible for the multi-level RTN measured in these devices. Noise characteristics in different reset conditions are explored through consecutive switching cycles. Noise spectral analysis is also performed to fully support the investigation. An RRAM compact model is also exploited to estimate the physical properties of the conductive filament and of the dielectric barrier from simple I-V data. These tools are combined together to prove the existence of a direct statistical relation between the reset conditions, the volume of the dielectric barrier created during the reset operation and the average number of active traps contributing to the RTN.

  14. The Impact of Dielectric Material and Temperature on Dielectric Charging in RF MEMS Capacitive Switches

    NASA Astrophysics Data System (ADS)

    Papaioannou, George

    The present work attempts to provide a better insight on the dielectric charging in RF-MEMS capacitive switches that constitutes a key issue limiting parameter of their commercialization. The dependence of the charging process on the nature of dielectric materials widely used in these devices, such as SiO2, Si3N4, AlN, Al2O3, Ta2O5, HfO2, which consist of covalent or ionic bonds and may exhibit piezoelectric properties is discussed taking into account the effect of deposition conditions and resulting material stoichiometry. Another key issue parameter that accelerates the charging and discharging processes by providing enough energy to trapped charges to be released and to dipoles to overcome potential barriers and randomize their orientation is the temperature will be investigated too. Finally, the effect of device structure will be also taken into account.

  15. The Development of the Non-contact Electrical Leakage Property Measurement System for the High-K Dielectric Materials on DRAM Capacitors

    Microsoft Academic Search

    Yusin Yang; Byung Sug Lee; Misung Lee; Chung Sam Jun; Tae Sung Kim

    2006-01-01

    We have used the non-contact electrical property measurement system to characterize the electrical leakage property of high-K materials such as Al2O3 and HfO2 on a patterned wafer. The basic technology is to measure the surface voltage with micro Kelvin probe after the corona charge deposition on a measurement area. Because of the charge decay through a dielectric material, voltage-time spectra

  16. ForPeerReview Copyright line will be provided by the publisher

    E-print Network

    Gougousi, Theodosia

    operational volt- age range owing to their high intrinsic breakdown field strength. The ultra-thin barrier Al of capacitance-voltage analysis which showed 10 MHz dielectric constants of 8.7 and 11.7 for the HfO2 and Ta2O5 of large tunnelling currents. Therefore, a gate insulator is necessary [4]. An assortment of dielectrics

  17. Investigation of etching properties of HfO based high-K dielectrics using inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Chen, Jinghao; Yoo, Won Jong; Tan, Zerlinda Yl; Wang, Yingqian; Chan, Daniel S. H.

    2004-07-01

    The etching properties of HfO based high dielectric constant (K) films, HfO2, HfON, HfSiO, and HfAlO, were investigated using inductively coupled plasma of Cl2/HBr/CHF3/CF4/O2. The etch rates varied depending on the chemical components in the films. Among HfO2, HfON, HfSiO, and HfAlO, the etch rates of HfSiO increased most significantly with increasing radio frequency bias power. This may be attributed to the ternary network of Hf-Si-O that is different from the binary network of other films of Hf-O, Hf-N, Si-O, and Al-O. The etch rates of HfON were higher than those of HfO2 due to the effect of the high Hf-N etch rates compared to the Hf-O etch rates, whereas the HfAlO etch rates were lower than those of HfO2 due to the effect of the low Al-O etch rates. Etch residues and chemical compositions of HfO based dielectrics were analyzed by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. A significant amount of fluorides existed on the surface after CF4/CHF3 etching whereas only a small amount of chloride and bromide existed after Cl2/HBr etching. The high temperature post-treatment step was effective in reducing the amount of residues. .

  18. An ultrathin directional carpet cloak based on generalized Snell's law

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Lei Mei, Zhong; Ru Zhang, Wan; Yang, Fan; Jun Cui, Tie

    2013-10-01

    Based on generalized Snell's law, we propose an ultrathin directional carpet cloak operating in the reflection geometry. The cloak is constructed by two identical ultrathin metal-backed dielectric slabs with metallic "H" patterns on the other sides to form a triangular region. When put on an infinite ground plane and illuminated by electromagnetic waves from overhead, it can manipulate the reflected wavefronts to mimic the infinite ground plane. We fabricate a microwave sample and perform near-field scanning experiments to verify the cloaking effect. The measurement results are in good agreement with full-wave simulations and theoretical analysis.

  19. Synthesis of sheet conductive layers on the surface of some insulator ceramics (TiO2, ZrO2, HfO2) by multipulse CO2-laser irradiation in an ammonia atmosphere

    Microsoft Academic Search

    I. Ursu; I. N. Mihailescu; Leona C. Nistor; V. S. Teodorescu; A. M. Prokhorov; V. I. Konov; P. I. Nikitin; S. A. Uglov

    1989-01-01

    It is shown that by multipulse TEA-CO2 laser irradiation of some insulator ceramic samples (TiO2, ZrO2, HfO2) in an ammonia atmosphere, surface layers are synthesized exhibiting a complicated morphology and having a complex structure containing, beside metallic nitrides, nonstoichiometric oxygen-depleted oxides, oxinitrides, etc. Such layers have a diminished sheet resistance, and display good conduction characteristics.

  20. Improved film growth and flatband voltage control of ALD HfO2 and Hf-Al-O with n+ poly-Si gates using chemical oxides and optimized post-annealing

    Microsoft Academic Search

    G. D. Wilk; M. L. Green; M.-Y. Ho; B. W. Busch; T. W. Sorsch; F. P. Klemens; B. Brijs; R. B. van Dover; A. Kornblit; T. Gustafsson; E. Garfunkel; S. Hillenius; D. Monroe; P. Kalavade; J. M. Hergenrother

    2002-01-01

    We demonstrate for the first time that chemical oxide underlayers ?5 Å thick provide improved growth and flatband voltage control of ALD HfO2 films compared to thermal oxides. Optimized annealing conditions are shown to greatly reduce both fixed charge and interfacial oxide growth in the high-? stacks. Extremely small flatband voltage shifts of <30 mV are achieved, corresponding to a

  1. Effect of SiO 2 protective layer on the femtosecond laser-induced damage of HfO 2\\/SiO 2 multilayer high-reflective coatings

    Microsoft Academic Search

    Lei Yuan; Yuanan Zhao; Congjuan Wang; Hongbo He; Zhengxiu Fan; Jianda Shao

    2007-01-01

    Two kinds of HfO2\\/SiO2 800nm high-reflective (HR) coatings, with and without SiO2 protective layer were deposited by electron beam evaporation. Laser-induced damage thresholds (LIDT) were measured for all samples with femtosecond laser pulses. The surface morphologies and the depth information of all samples were observed by Leica optical microscopy and WYKO surface profiler, respectively. It is found that SiO2 protective

  2. Comparative Scalability of PVD and CVD TiN on HfO2 as a Metal Gate Stack for FDSOI cMOSFETs down to 25nm Gate Length and Width

    Microsoft Academic Search

    F. Andrieu; O. Faynot; X. Garros; D. Lafond; C. Buj-Dufournet; L. Tosti; S. Minoret; V. Vidal; J. C. Barbe; F. Allain; E. Rouchouze; L. Vandroux; V. Cosnier; M. Casse; V. Delaye; C. Carabasse; M. Burdin; G. Rolland; B. Guillaumot; J. P. Colonna; P. Besson; L. Brevard; D. Mariolle; P. Holliger; A. Vandooren; C. Fenouillet-Beranger; F. Martin; S. Deleonibus

    2006-01-01

    This paper compares, for the first time, the scalability of physical- and chemical-vapor-deposited (PVD and CVD) TiN on HfO2 as a gate stack for FDSOI cMOSFETs down to 25nm gate length and width. It is shown that not only the intrinsic material properties but also the device architecture strongly influences the final gate stack properties. Reliability issues, stress and gate

  3. Thermal Conductivity and Stability of HfO2-Y2O3 and La2Zr2O7 Evaluated for 1650 Deg C Thermal/Environmental Barrier Coating Applications

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Bansal, Narottam P.; Miller, Robert A.

    2003-01-01

    HfO2-Y2O3 and La2Zr2O7 are candidate thermal and environmental barrier coating (T/EBC) materials for gas turbine ceramic matrix composite (CMC) combustor applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature stability of hot-pressed and plasma sprayed specimens with representative partially-stabilized and fully-cubic HfO2-Y2O3 compositions and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasmasprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC hexoloy or SiC/SiC CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermal/environmental barrier coating applications are also discussed.

  4. High dielectric constant oxides on III-V complementary metal-oxide-semiconductors

    NASA Astrophysics Data System (ADS)

    Chobpattana, Varistha

    Suitable gate dielectrics are needed for III-V channel metal-oxide-semiconductor field-effect transistors (MOSFETs). III-V semiconductor surfaces tend to have high interface trap state density (Dit). High quality gate dielectrics require a high dielectric constant, a stable interface, and low Dit. The major challenges are scaling down the dielectric to achieve high capacitance densities, understanding defects at the oxide/semiconductor interface, and developing techniques to passivate Dit at the interface. By using nitrogen plasma pre-treatment passivation technique, MOSCAPs with ALD HfO 2 directly on InGaAs as high-k gate stack, with accumulation capacitance density 2.4 mu F/cm2 (EOT=0.6 nm) and 2.5 x 10 12 cm2 eV-1 midgap Dit have been achieved.

  5. Interface studies of high dielectric constant gate stack material

    NASA Astrophysics Data System (ADS)

    Harris, Harlan Rusty

    To extend the minimum feature size beyond the 100 nm node in Ultra-Large Scale Integration, a suitable replacement must be found for silicon dioxide in the gate region of field effect transistors (FET). To reduce the power consumption, the silicon dioxide thickness is typically reduced to decrease the threshold voltage (VT) of the FET. The current thickness of silicon dioxide in production is about 2 nm, but any further reduction in thickness would increase the operating current exponentially due to quantum mechanical tunneling. The solution is to replace the silicon dioxide with a dielectric that has a significantly larger dielectric constant. This would allow a thicker gate dielectric to reduce current and threshold voltage at the same time, since VT is inversely proportional to dielectric constant. Several possible replacements have been identified that form a thermodynamically stable interface with silicon dioxide, the most promising of which are zirconium dioxide (ZrO2) and hafnium dioxide (HfO2). However, the dynamics of the interfacial layer formed with silicon are not very well understood. This dissertation describes the study of the interface using electron diffraction tools, including identification of ultra-clean silicon preparation, deposition of hafnium dioxide using reactive electron beam evaporation, and the subsequent electrical characterization. Also included are the design and implementation of an ultra-high vacuum deposition system with in situ observation of the surface using electron diffraction and the electrical characterization of HfO2 deposited in this chamber, as well as the characterization of subsequent films deposited in ultra-high vacuum.

  6. Enhancement of light absorption using high-k dielectric in localized surface plasmon resonance for silicon-based thin film solar cells

    Microsoft Academic Search

    Hua-Min Li; Gang Zhang; Cheng Yang; Dae-Yeong Lee; Yeong-Dae Lim; Tian-Zi Shen; Won Jong Yoo; Young Jun Park; Hyunjin Kim; Seung Nam Cha; Jong Min Kim

    2011-01-01

    The application of high-dielectric-constant (k) materials, e.g., Si3N4, ZrO2, and HfO2, to localized surface plasmon resonance (LSPR) excited by a Au nanoparticle structure has been investigated and simulated for the enhancement of light absorption in Si-based thin film solar cells by using Mie theory and three-dimensional finite-difference time-domain computational simulations. As compared to a conventional SiO2 dielectric spacing layer, the

  7. Effect of thin gate dielectrics and gate materials on simulated device characteristics of 3D double gate JNT

    NASA Astrophysics Data System (ADS)

    Baidya, A.; Krishnan, V.; Baishya, S.; Lenka, T. R.

    2015-01-01

    In this paper a novel Silicon based three dimensional (3D) double-gate Junctionless Nanowire Transistor (JNT) of 20 nm gate length is proposed. The device characteristics such as gate characteristics and drain characteristics are studied with the help of Sentaurus TCAD by using different gate materials such as Al, Ti, n+ Polysilicon, Au and using different ultra thin gate dielectrics such as SiO2, Si3N4 and HfO2. The effect of various work functions and dielectrics on the threshold voltage of the JNT is also analysed. From the TCAD simulation results it is observed that high-K material (HfO2) as gate dielectric shows better drain characteristics with respect to others. The JNT with Al as gate material gives better current characteristics with respect to others. It is also analysed that under flat-band condition the driving of drain current does not directly depend on the gate-oxide capacitance but depends upon the channel doping concentrations. Thus by choosing the proper gate material and gate dielectric combinations, the desired device characteristics could be obtained for JNT.

  8. Ultra-thin multilayer capacitors.

    SciTech Connect

    Renk, Timothy Jerome; Monson, Todd C.

    2009-06-01

    The fabrication of ultra-thin lanthanum-doped lead zirconium titanate (PLZT) multilayer ceramic capacitors (MLCCs) using a high-power pulsed ion beam was studied. The deposition experiments were conducted on the RHEPP-1 facility at Sandia National Laboratories. The goal of this work was to increase the energy density of ceramic capacitors through the formation of a multilayer device with excellent materials properties, dielectric constant, and standoff voltage. For successful device construction, there are a number of challenging requirements including achieving correct stoichiometric and crystallographic composition of the deposited PLZT, as well as the creation of a defect free homogenous film. This report details some success in satisfying these requirements, although 900 C temperatures were necessary for PLZT perovskite phase formation. These temperatures were applied to a previously deposited multi-layer film which was then post-annealed to this temperature. The film exhibited mechanical distress attributable to differences in the coefficient of thermal expansion (CTE) of the various layers. This caused significant defects in the deposited films that led to shorts across devices. A follow-on single layer deposition without post-anneal produced smooth layers with good interface behavior, but without the perovskite phase formation. These issues will need to be addressed in order for ion beam deposited MLCCs to become a viable technology. It is possible that future in-situ heating during deposition may address both the CTE issue, and result in lowered processing temperatures, which in turn could raise the probability of successful MLCC formation.

  9. Limits of Optical and X-ray Metrology Applied to Thin Gate Dielectrics

    NASA Astrophysics Data System (ADS)

    Zollner, Stefan; Liang, Yong; Gregory, Richard B.; Fejes, Peter L.; Theodore, David; Yu, Z.; Triyoso, D. H.; Curless, J.; Tracy, Clarence

    2005-09-01

    We analyze the limits of optical and x-ray metrology techniques (spectroscopic ellipsometry, x-ray reflectivity, and powder x-ray diffraction) applied to thin films in microelectronics, especially metal oxides used as gate dielectrics. By tilting the substrate from the symmetric scattering geometry, we can enhance the sensitivity of powder diffraction and detect the tetragonal (011) Bragg peak from a 30 Å thick HfO2 layer on Si. We have calculated the Bragg peak positions and intensities of tetragonal hafnia. Vacuum-ultraviolet spectroscopic ellipsometry and grazing-incidence x-ray reflectivity spectra for 50 to 200 Å thick HfO2 layers on Si (001) can be described by a model, which consists of only a single (metal oxide) layer on the Si substrate. These techniques, within the scope of our work, are unable to determine the thickness of the interfacial oxide layer between the metal oxide and the substrate. A method to determine the optical properties (complex dielectric function) of thin insulating layers on Si is described.

  10. Advanced passivation techniques for Si solar cells with high-? dielectric materials

    NASA Astrophysics Data System (ADS)

    Geng, Huijuan; Lin, Tingjui; Letha, Ayra Jagadhamma; Hwang, Huey-Liang; Kyznetsov, Fedor A.; Smirnova, Tamara P.; Saraev, Andrey A.; Kaichev, Vasily V.

    2014-09-01

    Electronic recombination losses at the wafer surface significantly reduce the efficiency of Si solar cells. Surface passivation using a suitable thin dielectric layer can minimize the recombination losses. Herein, advanced passivation using simple materials (Al2O3, HfO2) and their compounds H(Hf)A(Al)O deposited by atomic layer deposition (ALD) was investigated. The chemical composition of Hf and Al oxide films were determined by X-ray photoelectron spectroscopy (XPS). The XPS depth profiles exhibit continuous uniform dense layers. The ALD-Al2O3 film has been found to provide negative fixed charge (-6.4 × 1011 cm-2), whereas HfO2 film provides positive fixed charge (3.2 × 1012 cm-2). The effective lifetimes can be improved after oxygen gas annealing for 1 min. I-V characteristics of Si solar cells with high-? dielectric materials as passivation layers indicate that the performance is significantly improved, and ALD-HfO2 film would provide better passivation properties than that of the ALD-Al2O3 film in this research work.

  11. The composition of ultrathin silicon oxynitrides thermally grown in nitric oxide

    E-print Network

    Gustafsson, Torgny

    The composition of ultrathin silicon oxynitrides thermally grown in nitric oxide E. P. Gusev, H. C for publication 8 April 1997 The thermal oxynitridation of Si 100 in nitric oxide NO has been studied by high oxynitrides (SiOxNy) are the leading candidates to replace conventional oxides (SiO2) as the gate dielectric

  12. High-performance, highly bendable MoS2 transistors with high-k dielectrics for flexible low-power systems.

    PubMed

    Chang, Hsiao-Yu; Yang, Shixuan; Lee, Jongho; Tao, Li; Hwang, Wan-Sik; Jena, Debdeep; Lu, Nanshu; Akinwande, Deji

    2013-06-25

    While there has been increasing studies of MoS2 and other two-dimensional (2D) semiconducting dichalcogenides on hard conventional substrates, experimental or analytical studies on flexible substrates has been very limited so far, even though these 2D crystals are understood to have greater prospects for flexible smart systems. In this article, we report detailed studies of MoS2 transistors on industrial plastic sheets. Transistor characteristics afford more than 100x improvement in the ON/OFF current ratio and 4x enhancement in mobility compared to previous flexible MoS2 devices. Mechanical studies reveal robust electronic properties down to a bending radius of 1 mm which is comparable to previous reports for flexible graphene transistors. Experimental investigation identifies that crack formation in the dielectric is the responsible failure mechanism demonstrating that the mechanical properties of the dielectric layer is critical for realizing flexible electronics that can accommodate high strain. Our uniaxial tensile tests have revealed that atomic-layer-deposited HfO2 and Al2O3 films have very similar crack onset strain. However, crack propagation is slower in HfO2 dielectric compared to Al2O3 dielectric, suggesting a subcritical fracture mechanism in the thin oxide films. Rigorous mechanics modeling provides guidance for achieving flexible MoS2 transistors that are reliable at sub-mm bending radius. PMID:23668386

  13. Dispersion engineering of plasmonic nanocomposite for ultrathin broadband optical absorber.

    PubMed

    Feng, Peng; Li, Wen-Di; Zhang, Weihua

    2015-02-01

    We theoretically study the metal-insulator-metal (MIM) structure based ultrathin broadband optical absorber which consists of a metallic substrate, a dielectric middle layer, and a nanostructured metallic top layer. It is found that, there exists an effective permittivity, ?null, for the top nanostructured metallic layer which leads to unit-absorption (zero-reflection) of the MIM structure. Importantly, this ?null exhibits abnormal dispersion behaviors. Both its real and imaginary parts increase monotonically with the wavelength. To obtain such naturally non-existing permittivity, we investigate the optical properties of two typical types of metal-dielectric nanocomposites, namely, thoroughly mingled composites using Bruggeman's effective medium theory, and more realistic Au nanosphere-in-dielectric structures using numerical permittivity retrieval techniques. We demonstrate that the ?null-type dispersions, and consequently, perfect absorption can be obtained over a broad spectral range when the filling factor of the metal component is close to the percolation threshold. The result not only explains the recently reported broadband absorbers made of randomly deposited Au nanoparticles [M. K. Hedayati, et al, Adv. Mater. 23, 5410 (2011)], but also provides theoretical guidelines for designing ultrathin broadband plasmonic absorbers for a wealthy of important applications. PMID:25836100

  14. Global optimization of omnidirectional wavelength selective emitters/absorbers based on dielectric-filled anti-reflection coated two-dimensional metallic photonic crystals.

    PubMed

    Yeng, Yi Xiang; Chou, Jeffrey B; Rinnerbauer, Veronika; Shen, Yichen; Kim, Sang-Gook; Joannopoulos, John D; Soljacic, Marin; Celanovi?, Ivan

    2014-09-01

    We report the design of dielectric-filled anti-reflection coated (ARC) two-dimensional (2D) metallic photonic crystals (MPhCs) capable of omnidirectional, polarization insensitive, wavelength selective emission/absorption. Using non-linear global optimization methods, optimized hafnium oxide (HfO2)-filled ARC 2D Tantalum (Ta) PhC designs exhibiting up to 26% improvement in emittance/absorptance at wavelengths ? below a cutoff wavelength ?c over the unfilled 2D TaPhCs are demonstrated. The optimized designs possess high hemispherically average emittance/absorptance ?H of 0.86 at ? < ?c and low ?H of 0.12 at ? > ?c. PMID:25321547

  15. GaAs metal-oxide-semiconductor device with HfO2\\/TaN gate stack and thermal nitridation surface passivation

    Microsoft Academic Search

    Fei Gao; S. J. Lee; D. Z. Chi; S. Balakumar; D.-L. Kwong

    2007-01-01

    Oxides induced Fermi level pinning at the interface between the GaAs and high-k gate dielectric is a major obstacle for developing high performance GaAs metal-oxide-semiconductor (MOS) devices. In this letter, thermal nitridation treatment on GaAs surface prior to the high-k deposition is proposed to solve the issue of interface pinning. It is found that an optimized nitride layer formed during

  16. Ultrathin flexible dual band terahertz absorber

    NASA Astrophysics Data System (ADS)

    Shan, Yan; Chen, Lin; Shi, Cheng; Cheng, Zhaoxiang; Zang, Xiaofei; Xu, Boqing; Zhu, Yiming

    2015-09-01

    We propose an ultrathin and flexible dual band absorber operated at terahertz frequencies based on metamaterial. The metamaterial structure consists of periodical split ring resonators with two asymmetric gaps and a metallic ground plane, separated by a thin-flexible dielectric spacer. Particularly, the dielectric spacer is a free-standing polyimide film with thickness of 25 ?m, resulting in highly flexible for our absorber and making it promising for non-planar applications such as micro-bolometers and stealth aircraft. Experimental results show that the absorber has two resonant absorption frequencies (0.41 THz and 0.75 THz) with absorption rates 92.2% and 97.4%, respectively. The resonances at the absorption frequencies come from normal dipole resonance and high-order dipole resonance which is inaccessible in the symmetrical structure. Multiple reflection interference theory is used to analyze the mechanism of the absorber and the results are in good agreement with simulated and experimental results. Furthermore, the absorption properties are studied under various spacer thicknesses. This kind of metamaterial absorber is insensitive to polarization, has high absorption rates (over 90%) with wide incident angles range from 0° to 45° and the absorption rates are also above 90% when wrapping it to a curved surface.

  17. Dirac electron-hole pairing gap in the heterostructure of ultra-thin films of topological insulator bilayer

    NASA Astrophysics Data System (ADS)

    Wang, Zhigang; Fu, Zhen-Guo; Zhang, Ping

    2015-06-01

    The electron-hole pairing gap in a system of topological insulator (TI) ultra-thin film bilayer separated by a dielectric barrier is theoretically investigated beyond the mean-field approximation. We show that the pairing gap ? is dramatically suppressed when accounting for the Coulomb correlation effect as well as the finite-thickness effect of the dielectric barrier. However, ? can be increased by the coupling between the upper and lower surface states of each TI ultra-thin film. In order to observe much larger ? in the present structure experimentally, the dielectric surrounding media materials with much lower dielectric constant, such as SiO2-based xerogel films, may be needed.

  18. Optical Transmission Through Multilayered Ultra-Thin Metal Gratings

    Microsoft Academic Search

    Zhijun Sun; Xiaoliu Zuo; Jie Li

    Optical transmission properties of multilayered ultra-thin metal gratings are numerically studied. The transmission spectrum\\u000a has a broad stop-band with extremely low transmittance compared to that of a single-layer one for TM polarization. The stop-band\\u000a is shown to be formed by multiple-interference tunneling and various plasmon resonance processes in ultra-thin-metal and dielectric\\u000a multilayers. That is on the transmission background of non-apertured

  19. Conformal surface plasmons propagating on ultrathin and flexible films

    PubMed Central

    Shen, Xiaopeng; Cui, Tie Jun; Martin-Cano, Diego; Garcia-Vidal, Francisco J.

    2013-01-01

    Surface plasmon polaritons (SPPs) are localized surface electromagnetic waves that propagate along the interface between a metal and a dielectric. Owing to their inherent subwavelength confinement, SPPs have a strong potential to become building blocks of a type of photonic circuitry built up on 2D metal surfaces; however, SPPs are difficult to control on curved surfaces conformably and flexibly to produce advanced functional devices. Here we propose the concept of conformal surface plasmons (CSPs), surface plasmon waves that can propagate on ultrathin and flexible films to long distances in a wide broadband range from microwave to mid-infrared frequencies. We present the experimental realization of these CSPs in the microwave regime on paper-like dielectric films with a thickness 600-fold smaller than the operating wavelength. The flexible paper-like films can be bent, folded, and even twisted to mold the flow of CSPs. PMID:23248311

  20. Spectroscopic Studies of Electronically Active Defects in Transition Metal Oxides for Advanced Si Devices

    SciTech Connect

    Lucovsky, G.; Luning, J.

    2009-06-04

    Based on spectroscopic studies, and guided by ab initio theory, the electron and hole traps in HfO2 and other transition metal elemental oxides e.g., TiO2, are assigned to O-atom divacancies, clustered at internal grain boundaries. Engineering solutions for defect reduction are identified: (i) deposition of ultra-thin, < 2 nm HfO2 and phase separated Hf silicate dielectrics, in which grain boundary formation is suppressed by effectively eliminating inter-primitive unit cell {pi}-bonding interactions, and (ii) non-crystalline Zr/Hf Si oxynitrides without nanocrystalline grain boundaries.

  1. Printed array of thin-dielectric metal-oxide-metal (MOM) tunneling diodes Mario Barei,1,a)

    E-print Network

    Grundler, Dirk

    of different materials (e.g., metals and insulators8,9 ) was prepared on a stamp and then transferred ontoPrinted array of thin-dielectric metal-oxide-metal (MOM) tunneling diodes Mario Bareiß,1,a) Andreas area array of metal-oxide-metal (MOM) tunneling diodes with an ultrathin dielectric ($3.6 nm aluminum

  2. In-line Quantitative Dose Metrology of Ultra-thin Gate Oxide

    NASA Astrophysics Data System (ADS)

    Jee, Yunjung; Park, Kibeom; Kim, T. K.; Cho, Han-Soo; Eom, T. M.; Cho, Sungchan; Jun, C. S.; Kim, Taesung

    2005-09-01

    In-line quantitative dose monitoring has been successfully performed with the E-beam Induced X-ray fluoresecence technique. Nitrogen and other elemental doses have been quantified for ultra-thin gate oxides with oxynitride and high k dielectrics, and compared with the other analytical tools and electrical elements of non-contact CV method. Nitrogen concentration extracted from Low energy Electron induced X-ray Emission Spectrometry (LEXES) showed good correlation with that of XPS, and the effects of each elemental composition on EOT and leakage current were investigated. The results suggest that the non-destructive dose metrology with LEXES can be used to control and monitor the ultrathin gate-oxide process during CMOS fabrication even for product samples owing to the small analyzing spot size. Moreover, the results of the high k dielectrics suggest that dose monitoring is applicable to other elemental quantification of ULSI thin films.

  3. Ultrathin Silicide Nanowires

    NASA Astrophysics Data System (ADS)

    Dumitrica, Traian; Hua, Ming; Yakobson, Boris I.

    2004-03-01

    Molecular electronics aims at building useful circuits from basic building blocks of nanometer-size dimensions. Along with carbon nanotubes, semiconductor-based nanowires (seamless solid rods with nanometer size widths and micrometer lengths) represent the most critical components of such assemblies. Even though silicon is isovalent to the carbon atom in the periodic table, its behavior in forming bonds is different. For example, it is known that silicon cannot form the stable caged clusters called fullerenes, unless a guest atom (metal) is introduced inside the cage. In this context, we propose new metal (Me)-encapsulated silicon nanoclusters, which can be assembled into ultrathin silicon nanotubes. In comparison with other reported Me@Si structures, the formation energy of our nanotubes is of the same magnitude or lower, as a function of the metal's position in the periodic table. The properties of the proposed wires will be discussed, also in connection with the self-assembled silicide nanowires grown on Si (001) surface.

  4. Ultrathin Planar Graphene Supercapacitors

    SciTech Connect

    Huang, Jingsong [ORNL; Meunier, Vincent [ORNL; Sumpter, Bobby G [ORNL; Ajayan, Pullikel M [Rice University; Yoo, Jung Joon [KAIST, Daejeon, Republic of Korea; Balakrishnan, Kaushik [Rice University; Srivastava, Anchal [Rice University; Conway, Michelle [Rice University; Reddy, Arava Leela Mohan [Rice University; Yu, Jin [Rice University; Vajtai, Robert [Rice University

    2011-01-01

    With the advent of atomically thin and flat layers of conducting materials such as graphene, new designs for thin film energy storage devices with good performance have become possible. Here, we report an in-plane fabrication approach for ultrathin supercapacitors based on electrodes comprised of pristine graphene and multi-layer reduced graphene oxide. The in-plane design is straightforward to implement and exploits efficiently the surface of each graphene layer for energy storage. The open architecture and the effect of graphene edges enable even the thinnest of devices, made from as grown 1-2 graphene layers, to reach specific capacities up to 80 Fcm-2. While, much higher (394 Fcm-2) specific capacities are observed in case of multi-layered graphene oxide electrodes, owing to the better utilization of the available electrochemical surface area. The performances of devices with pristine as well as thicker graphene based structures are examined using a combination of experiments and model calculations. The demonstrated all solid-state supercapacitors provide a prototype for a broad range of thin-film based energy storage devices.

  5. Substrate dielectric effects on graphene field effect transistors

    NASA Astrophysics Data System (ADS)

    Hu, Zhaoying; Prasad Sinha, Dhiraj; Ung Lee, Ji; Liehr, Michael

    2014-05-01

    Graphene is emerging as a promising material for future electronics and optoelectronics applications due to its unique electronic structure. Understanding the graphene-dielectric interaction is of vital importance for the development of graphene field effect transistors (FETs) and other novel graphene devices. Here, we extend the exploration of substrate dielectrics from conventionally used thermally grown SiO2 and hexagonal boron nitride films to technologically relevant deposited dielectrics used in semiconductor industry. A systematic analysis of morphology and optical and electrical properties was performed to study the effects of different substrates (SiO2, HfO2, Al2O3, tetraethyl orthosilicate (TEOS)-oxide, and Si3N4) on the carrier transport of chemical vapor deposition-derived graphene FET devices. As baseline, we use graphene FETs fabricated on thermal SiO2 with a relatively high carrier mobility of 10 000 cm2/(V s). Among the deposited dielectrics studied, silicon nitride showed the highest mobility, comparable to the properties of graphene fabricated on thermal SiO2. We conclude that this result comes from lower long range scattering and short range scattering rates in the nitride compared those in the other deposited films. The carrier fluctuation caused by substrates, however, seems to be the main contributing factor for mobility degradation, as a universal mobility-disorder density product is observed for all the dielectrics examined. The extrinsic doping trend is further confirmed by Raman spectra. We also provide, for the first time, correlation between the intensity ratio of G peak and 2D peak in the Raman spectra to the carrier mobility of graphene for different substrates.

  6. Magnetotransport in ultrathin (Ga,Mn)As channels controlled by a ferroelectric gate

    E-print Network

    Dalang, Robert C.

    Magnetotransport in ultrathin (Ga,Mn)As channels controlled by a ferroelectric gate E.Mikheev1,I.L.Gallagher2,K.Výborný3,T.Jungwirth2,3 and H.J.Trodahl4 1:Ceramics Laboratory,EPFL-Swiss Federal Institute ferroelectric Relatively high spontaneous polarization swing of 18 µC/cm2 Low dielectric constant of ~8 (high

  7. Enzymatically active ultrathin pepsin membranes.

    PubMed

    Raaijmakers, Michiel J T; Schmidt, Thomas; Barth, Monika; Tutus, Murat; Benes, Nieck E; Wessling, Matthias

    2015-05-11

    Enzymatically active proteins enable efficient and specific cleavage reactions of peptide bonds. Covalent coupling of the enzymes permits immobilization, which in turn reduces autolysis-induced deactivation. Ultrathin pepsin membranes were prepared by facile interfacial polycondensation of pepsin and trimesoyl chloride. The pepsin membrane allows for simultaneous enzymatic conversion and selective removal of digestion products. The large water fluxes through the membrane expedite the transport of large molecules through the pepsin layers. The presented method enables the large-scale production of ultrathin, cross-linked, enzymatically active membranes. PMID:25779668

  8. Intercalative poly(carbazole) precursor electropolymerization within hybrid nanostructured titanium oxide ultrathin films.

    PubMed

    Frau, Antonio F; Estillore, Nicel C; Fulghum, Timothy M; Advincula, Rigoberto C

    2010-12-01

    A protocol for nanostructuring and electropolymerization of a hybrid semiconductor polycarbazole-titanium oxide ultrathin film is described. Ultrathin (<100 nm) films based on polycarbazole precursor polyelectrolytes and titanium oxide (TiOx) have been fabricated by combining the layer-by-layer (LbL) and surface sol-gel layering techniques. Film growth was followed and confirmed through UV-vis spectroscopy, ellipsometry and quartz crystal microbalance with dissipation (QCM-D). Subsequent anodic electrochemical oxidation of the carbazole pendant units afforded a conjugated polymer network (CPN) film within intercalating TiOx layers of cross-linked and ?-conjugated carbazole units. Cyclic voltammetry (CV), UV-vis, and fluorescence spectroscopy measurements confirmed this process. The LbL-driven polyelectrolyte deposition process resulted in a quantified electrochemical response, proportional to the number of layers, while the TiOx acted as a dielectric spacer limiting electron transfer kinetics and attenuating energy transfer in fluorescence. Electro-optical properties were compared with other polycarbazole thin film materials with respect to bandgap energy (Eg). The straightforward protocol in film nanostructuring and barrier/dielectric properties of the inorganic oxide slab (denoted here as, TiOx) should enable applications in organic light-emitting diodes (OLEDs), dielectric mirrors, planar waveguides, and photovoltaic devices for these hybrid ultrathin films. PMID:21080659

  9. Dielectric siphons.

    NASA Technical Reports Server (NTRS)

    Jones, T. B.; Perry, M. P.; Melcher, J. R.

    1971-01-01

    The normally weak polarization force density, exerted on insulating dielectric liquids by a nonuniform electric field, is enhanced if high pressures are used. The nonuniform electric field acts as an elastic ?wall' to contain and guide the dielectric fluid. A general theory for these electrohydrodynamic (EHD) conduits has been developed. An illustrative example of the EHD conduits is the dielectric siphon consisting of two U-shaped electrodes held adjacent to each other by insulating nylon screws.

  10. High temperature calorimetric studies of heat of solution of NiO, CuO, La2O3, TiO2, HfO2 in sodium silicate liquids

    NASA Astrophysics Data System (ADS)

    Linard, Yannick; Wilding, Martin C.; Navrotsky, Alexandra

    2008-01-01

    The enthalpies of solution of La2O3, TiO2, HfO2, NiO and CuO were measured in sodium silicate melts at high temperature. When the heat of fusion was available, we derived the corresponding liquid-liquid enthalpies of mixing. These data, combined with previously published work, provide insight into the speciation reactions in sodium silicate melts. The heat of solution of La2O3 in these silicate solvents is strongly exothermic and varies little with La2O3 concentration. The variation of heat of solution with composition of the liquid reflects the ability of La(III) to perturb the transient silicate framework and compete with other cations for oxygen. The enthalpy of solution of TiO2 is temperature-dependent and indicates that the formation of Na-O-Si species is favored over Na-O-Ti at low temperature. The speciation reactions can be interpreted in terms of recent spectroscopic studies of titanium-bearing melts which identify a dual role of Ti4+ as both a network-former end network-modifier. The heats of solution of oxides of transition elements (Ni and Cu) are endothermic, concentration-dependent and reach a maximum with concentration. These indicate a charge balanced substitution which diminishes the network modifying role of Na+ by addition of Ni2+ or Cu2+. The transition metal is believed to be in tetrahedral coordination, charge balanced by the sodium cation in the melts.

  11. X-ray photoemission and X-ray absorption studies of Hf-silicate dielectric layers

    NASA Astrophysics Data System (ADS)

    O'Connor, R.; Hughes, G.; Glans, P.-A.; Learmonth, T.; Smith, K. E.

    2006-12-01

    Photoelectron spectroscopy and X-ray absorption spectroscopy (XAS) measurements have been performed on HfSi xO y and HfSi xO yN z dielectric layers, which are potential candidates as high- k transistor gate dielectrics. The hafnium silicate layers, 3-4 nm thick, were formed by codepositing HfO 2 and SiO 2 (50%:50%) by MOCVD at 485 °C on a silicon substrate following an IMEC clean. Annealing the HfSi xO y layer in a nitrogen atmosphere at 1000 °C resulted in an increase in the Si 4+ chemical shift from 3.5 to 3.9 eV with respect to the Si 0 peak. Annealing the hafnium silicate layer in a NH 3 atmosphere at 800 °C resulted in the incorporation of 10% nitrogen and the decrease in the chemical shift between the Si 4+ and the Si 0 to 3.3 eV. The results suggest that the inclusion of nitrogen in the silicate layer restricts the tendency of the HfO 2 and the SiO 2 to segregate into separate phases during the annealing step. Synchrotron radiation valence band photoemission studies determined that the valence band offsets were of the order of 3 eV. X-ray absorption measurements show that the band gap of these layers is 4.6 eV and that the magnitude of the conduction band offset is as little as 0.5 eV.

  12. Wave manipulation with designer dielectric metasurfaces.

    PubMed

    Cheng, Jierong; Ansari-Oghol-Beig, Davood; Mosallaei, Hossein

    2014-11-01

    The concept of an ultra-thin metasurface made of single layer of only-dielectric disks for successful phase control over a full range is demonstrated. Conduction loss is avoided compared to its plasmonic counterpart. The interaction of the Mie resonances of the first two modes of the dielectric particles, magnetic and electric dipoles, is tailored by the dimensions of the disks, providing required phase shift for the transmitted beam from 0° to 360°, together with high transmission efficiency. The successful performance of a beam-tilting array and a large-scale lens functioning at 195 THz demonstrates the ability of the dielectric metasurface that is thin and has also high efficiency of more than 80%. Such configurations can serve as outstanding alternatives for plasmonic metasurfaces especially that it can be a scalable design. PMID:25361335

  13. Accurate characterization and understanding of interface trap density trends between atomic layer deposited dielectrics and AlGaN/GaN with bonding constraint theory

    NASA Astrophysics Data System (ADS)

    Ramanan, Narayanan; Lee, Bongmook; Misra, Veena

    2015-06-01

    Many dielectrics have been proposed for the gate stack or passivation of AlGaN/GaN based metal oxide semiconductor heterojunction field effect transistors, to reduce gate leakage and current collapse, both for power and RF applications. Atomic Layer Deposition (ALD) is preferred for dielectric deposition as it provides uniform, conformal, and high quality films with precise monolayer control of film thickness. Identification of the optimum ALD dielectric for the gate stack or passivation requires a critical investigation of traps created at the dielectric/AlGaN interface. In this work, a pulsed-IV traps characterization method has been used for accurate characterization of interface traps with a variety of ALD dielectrics. High-k dielectrics (HfO2, HfAlO, and Al2O3) are found to host a high density of interface traps with AlGaN. In contrast, ALD SiO2 shows the lowest interface trap density (<2 × 1012 cm-2) after annealing above 600 °C in N2 for 60 s. The trend in observed trap densities is subsequently explained with bonding constraint theory, which predicts a high density of interface traps due to a higher coordination state and bond strain in high-k dielectrics.

  14. Piezoelectric and dielectric tunabilities of ultra-thin ferroelectric heterostructures

    E-print Network

    Alpay, S. Pamir

    with top and bottom SrRuO3 electrodes were grown onto (001) SrTiO3 substrates via pulsed laser deposition SrRuO3 (SRO) electrodes on (001) SrTiO3 (STO) substrates. Further details on the growth of the films

  15. THE GROWTH MECHANISMS OF ULTRATHIN GATE DIELECTRICS ON SILICON

    E-print Network

    Gustafsson, Torgny

    . Medium energy ion scattering (MEIS) is used in combination with an isotopic labeling technique (16 O2, isotopic mixture during the further oxidation of very thin (14 Å) SiO2 films in 18 O2, and the existence

  16. Elasticity theory of ultrathin nanofilms

    NASA Astrophysics Data System (ADS)

    Li, Jiangang; Narsu, B.; Yun, Guohong; Yao, Haiyan

    2015-07-01

    A self-consistent theoretical scheme for describing the elastic behavior of ultrathin nanofilms (UTNFs) was proposed. Taking into account the lower symmetry of an UTNF compared to its bulk counterpart, additional elastic and magnetoelastic parameters were introduced to model the elasticity rigorously. The applications of current theory to several elastic and magnetoelastic systems gave excellent agreement with experiments. More importantly, the surface elastic and magnetoelastic parameters used to fit the experimental results are physically reasonable and in close agreement with those obtained from experiment and simulation. This fact suggests that the additional elastic (magnetoelastic) constants due to symmetry breaking are of great importance in theoretical description of the mechanical properties of UTNFs. And we proved that the elasticity of UTNFs should be described by a three-dimensional model just including the intrinsic surface and bulk parameters, but not the effective surface parameters. It is believed that the theory reported here is a universal strategy for elasticity and magnetoelasticity of ultrathin films.

  17. Dielectric gradient metasurface optical elements.

    PubMed

    Lin, Dianmin; Fan, Pengyu; Hasman, Erez; Brongersma, Mark L

    2014-07-18

    Gradient metasurfaces are two-dimensional optical elements capable of manipulating light by imparting local, space-variant phase changes on an incident electromagnetic wave. These surfaces have thus far been constructed from nanometallic optical antennas, and high diffraction efficiencies have been limited to operation in reflection mode. We describe the experimental realization and operation of dielectric gradient metasurface optical elements capable of also achieving high efficiencies in transmission mode in the visible spectrum. Ultrathin gratings, lenses, and axicons have been realized by patterning a 100-nanometer-thick Si layer into a dense arrangement of Si nanobeam antennas. The use of semiconductors can broaden the general applicability of gradient metasurfaces, as they offer facile integration with electronics and can be realized by mature semiconductor fabrication technologies. PMID:25035488

  18. Electron tunneling through ultrathin boron nitride crystalline barriers.

    PubMed

    Britnell, Liam; Gorbachev, Roman V; Jalil, Rashid; Belle, Branson D; Schedin, Fred; Katsnelson, Mikhail I; Eaves, Laurence; Morozov, Sergey V; Mayorov, Alexander S; Peres, Nuno M R; Neto, Antonio H Castro; Leist, Jon; Geim, Andre K; Ponomarenko, Leonid A; Novoselov, Kostya S

    2012-03-14

    We investigate the electronic properties of ultrathin hexagonal boron nitride (h-BN) crystalline layers with different conducting materials (graphite, graphene, and gold) on either side of the barrier layer. The tunnel current depends exponentially on the number of h-BN atomic layers, down to a monolayer thickness. Conductive atomic force microscopy scans across h-BN terraces of different thickness reveal a high level of uniformity in the tunnel current. Our results demonstrate that atomically thin h-BN acts as a defect-free dielectric with a high breakdown field. It offers great potential for applications in tunnel devices and in field-effect transistors with a high carrier density in the conducting channel. PMID:22380756

  19. Simple method for the fabrication of a high dielectric constant metal-oxide-semiconductor capacitor embedded with Pt nanoparticles

    NASA Astrophysics Data System (ADS)

    Sargentis, Ch.; Giannakopoulos, K.; Travlos, A.; Boukos, N.; Tsamakis, D.

    2006-02-01

    We present a simple method for the fabrication of Pt nanoparticles embedded in a high-k dielectric. The nanoparticles are formed during the first deposition stages of a thin Pt layer on a 30Å SiO2 tunneling layer, at room temperature, performed with electron-beam (e-beam) evaporation of metallic Pt. Then, the nanoparticles are covered, in situ, by a thicker HfO2 layer, which forms a control oxide. The fabricated nanoparticles have an average diameter of 4.9nm, sheet density of 3.2×1012cm-2 and they present high uniformity in their size. High-frequency capacitance-voltage (C-V ) measurements demonstrate that this structure operates as a memory device.

  20. Metal mirrors with metal-dielectric HR-coating for ultrashort laser pulses applied in scanner applications

    NASA Astrophysics Data System (ADS)

    Schürmann, M.; Risse, S.; Kämmer, H.; Franke, C.; Schlegel, R.; Müller, S.; Damm, C.; Steinkopf, R.; Dreisow, F.; Nolte, S.; Eberhardt, R.; Kaiser, N.

    2015-03-01

    Metal mirrors are an attractive solution for scan mirrors working with ultra-short pulse lasers. Small mechanical inertia and a small mirror mass are required. Therefore, the mirrors have to be very stiff and a high quality optical surface has to be provided. This can be achieved with lightweight AlSi based mirrors with diamond-turned NiP polishable plating. Different coating options were evaluated in order to provide the necessary high reflectivity and a satisfactory laser damage threshold for ultrashort laser pulses in the few ps to fs regime at ? = 1030 nm. High-reflective metal layers enhanced by dielectric HfO2/SiO2 stacks were found to be the most advantageous coating option due to their comparatively small thickness and measured damage thresholds above 1 J/cm2@8ps.

  1. Making silicon nitride film a viable gate dielectric

    Microsoft Academic Search

    T. P. Ma

    1998-01-01

    To extend the scaling limit of thermal SiO2 in the ultrathin regime when the direct tunneling current becomes significant, members of this author's research team at Yale University, in collaboration with the Jet Process Corporation, embarked on a program to explore the potential of silicon nitride as an alternative gate dielectric. In this paper, high-quality silicon nitride (or oxynitride) films

  2. Ultrathin silicon solar cell for space application

    NASA Astrophysics Data System (ADS)

    Matsutani, T.; Saga, T.; Ueyama, H.; Hagihara, Y.; Hirano, T.; Suzuki, A.

    1982-01-01

    Ultrathin silicon (Si) solar cells for space application were fabricated on an experimental basis and the electrical characteristics were investigated for three kinds of cells (Black, BSFR and Conventional cells). Under 135.3 mW sq cm (AM0) illumination, ultrathin Black cells showed 67.7 mW output, which is equal to 89 percent output of 280 micron Black cells. The power to mass ratio of bare ultrathin Black cells was 3.6 times high compared with 280 micron thick Black cells. 1 MeV electron irradiation test was carried out to evaluate the radiation resistance. Ultrathin cells showed superior radiation resistance compared with that of 280 micron thick cells, and it was comparable to that of a GaAs solar cell which had been recognized as a radiation resistive cell. The results suggest that ultrathin solar cells have high potential for space application.

  3. Transition metal oxides and silicates as high-? dielectrics: a first-principles investigation

    NASA Astrophysics Data System (ADS)

    Rignanese, Gian-Marco; Gonze, Xavier; Pasquarello, Alfredo

    2003-03-01

    Using first-principles calculations, we investigate the structural, vibrational and dielectric properties of the Hf-Si-O and Zr-Si-O systems which have drawn considerable attention as alternative high-? materials. For the oxides, both the cubic and tetragonal phases of hafnia (HfO_2) and zirconia (ZrO_2) are studied. For the silicates, we analyze first the crystalline phases: hafnon (HfSiO_4) and zircon (ZrSiO_4). Then, the amorphous silicates are considered. We introduce a scheme which relates the dielectric constants to the local bonding of Si and M=(Hf, Zr) atoms. This scheme is based on the definition of parameters characteristic of the basic structural units (SUs) formed by Si and M=(Hf, Zr) atoms and their nearest neighbours, and allows us to avoid heavy large-scale calculations, which are beyond current computational capabilities. Applied to amorphous Zr silicates, our scheme provides a good description of the measured dielectric constants, and highlights the role of sixfold coordinated M=(Hf, Zr) atoms.

  4. Silicon nanowires with high-k hafnium oxide dielectrics for sensitive detection of small nucleic acid oligomers.

    PubMed

    Dorvel, Brian R; Reddy, Bobby; Go, Jonghyun; Duarte Guevara, Carlos; Salm, Eric; Alam, Muhammad Ashraful; Bashir, Rashid

    2012-07-24

    Nanobiosensors based on silicon nanowire field effect transistors offer advantages of low cost, label-free detection, and potential for massive parallelization. As a result, these sensors have often been suggested as an attractive option for applications in point-of-care (POC) medical diagnostics. Unfortunately, a number of performance issues, such as gate leakage and current instability due to fluid contact, have prevented widespread adoption of the technology for routine use. High-k dielectrics, such as hafnium oxide (HfO(2)), have the known ability to address these challenges by passivating the exposed surfaces against destabilizing concerns of ion transport. With these fundamental stability issues addressed, a promising target for POC diagnostics and SiNWFETs has been small oligonucleotides, more specifically, microRNA (miRNA). MicroRNAs are small RNA oligonucleotides which bind to mRNAs, causing translational repression of proteins, gene silencing, and expressions are typically altered in several forms of cancer. In this paper, we describe a process for fabricating stable HfO(2) dielectric-based silicon nanowires for biosensing applications. Here we demonstrate sensing of single-stranded DNA analogues to their microRNA cousins using miR-10b and miR-21 as templates, both known to be upregulated in breast cancer. We characterize the effect of surface functionalization on device performance using the miR-10b DNA analogue as the target sequence and different molecular weight poly-l-lysine as the functionalization layer. By optimizing the surface functionalization and fabrication protocol, we were able to achieve <100 fM detection levels of the miR-10b DNA analogue, with a theoretical limit of detection of 1 fM. Moreover, the noncomplementary DNA target strand, based on miR-21, showed very little response, indicating a highly sensitive and highly selective biosensing platform. PMID:22695179

  5. Low-temperature deposition of ultrathin SiO2 films on Si substrates

    NASA Astrophysics Data System (ADS)

    Vitanov, P.; Harizanova, A.; Ivanova, T.; Dikov, H.

    2014-05-01

    We present a detailed investigation of the properties of silicon dioxide deposited at a low temperature. The advantages of this process include its low thermal requirements (about 200 °C), the absence of corrosive by-products and the lack of need of vacuum equipment. Sol solutions were prepared for the deposition of ultrathin SiO2 films by spin-coating at the low annealing temperature of 200 °C. The layers' thickness was 24 nm and 5 nm. We describe in detail the material properties of this novel low-temperature SiO2 layers obtained by extensive characterization using Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), XPS spectroscopy, capacitance-voltage (C-V) and current-voltage (I-V) measurements. The ultrathin oxide layers on Si substrates show good dielectric properties.

  6. Fundamental Limits of Ultrathin Metasurfaces

    E-print Network

    Arbabi, Amir

    2014-01-01

    We present universal theoretical limits on the operation and performance of non-magnetic passive ultrathin metasurfaces. In particular, we prove that their local transmission, reflection, and polarization conversion coefficients are confined to limited regions of the complex plane. As a result, full control over the phase of the light transmitted through such metasurfaces cannot be achieved if the polarization of the light is not to be affected at the same time. We also establish fundamental limits on the maximum polarization conversion efficiency of these metasurfaces, and show that they cannot achieve more than 25% polarization conversion efficiency in transmission.

  7. Dielectric surface-controlled low-voltage organic transistors via n-alkyl phosphonic acid self-assembled monolayers on high-k metal oxide.

    PubMed

    Acton, Orb; Acton, By Orb; Ting, Guy G; Shamberger, Patrick J; Ohuchi, Fumio S; Ma, Hong; Jen, Alex K-Y

    2010-02-01

    In this paper, we report on n-alkyl phosphonic acid (PA) self-assembled monolayer (SAM)/hafnium oxide (HfO(2)) hybrid dielectrics utilizing the advantages of SAMs for control over the dielectric/semiconductor interface with those of high-k metal oxides for low-voltage organic thin film transistors (OTFTs). By systematically varying the number of carbon atoms of the n-alkyl PA SAM from six to eighteen on HfO(2) with stable and low leakage current density, we observe how the structural nature of the SAM affects the thin-film crystal structure and morphology, and subsequent device performance of low-voltage pentacene based OTFTs. We find that two primary structural factors of the SAM play a critical role in optimizing the device electrical characteristics, namely, the order/disorder of the SAM and its physical thickness. High saturation-field-effect mobilities result at a balance between disordered SAMs to promote large pentacene grains and thick SAMs to aid in physically buffering the charge carriers in pentacene from the adverse effects of the underlying high-k oxide. Employing the appropriate n-alkyl PA SAM/HfO(2) hybrid dielectrics, pentacene-based OTFTs operate under -2.0 V with low hysteresis, on-off current ratios above 1 x 10(6), threshold voltages below -0.6 V, subthreshold slopes as low as 100 mV dec(-1), and field-effect mobilities as high as 1.8 cm(2) V(-1) s(-1). PMID:20356199

  8. Hybrid gate dielectric materials for unconventional electronic circuitry.

    PubMed

    Ha, Young-Geun; Everaerts, Ken; Hersam, Mark C; Marks, Tobin J

    2014-04-15

    Recent advances in semiconductor performance made possible by organic ?-electron molecules, carbon-based nanomaterials, and metal oxides have been a central scientific and technological research focus over the past decade in the quest for flexible and transparent electronic products. However, advances in semiconductor materials require corresponding advances in compatible gate dielectric materials, which must exhibit excellent electrical properties such as large capacitance, high breakdown strength, low leakage current density, and mechanical flexibility on arbitrary substrates. Historically, conventional silicon dioxide (SiO2) has dominated electronics as the preferred gate dielectric material in complementary metal oxide semiconductor (CMOS) integrated transistor circuitry. However, it does not satisfy many of the performance requirements for the aforementioned semiconductors due to its relatively low dielectric constant and intransigent processability. High-k inorganics such as hafnium dioxide (HfO2) or zirconium dioxide (ZrO2) offer some increases in performance, but scientists have great difficulty depositing these materials as smooth films at temperatures compatible with flexible plastic substrates. While various organic polymers are accessible via chemical synthesis and readily form films from solution, they typically exhibit low capacitances, and the corresponding transistors operate at unacceptably high voltages. More recently, researchers have combined the favorable properties of high-k metal oxides and ?-electron organics to form processable, structurally well-defined, and robust self-assembled multilayer nanodielectrics, which enable high-performance transistors with a wide variety of unconventional semiconductors. In this Account, we review recent advances in organic-inorganic hybrid gate dielectrics, fabricated by multilayer self-assembly, and their remarkable synergy with unconventional semiconductors. We first discuss the principals and functional importance of gate dielectric materials in thin-film transistor (TFT) operation. Next, we describe the design, fabrication, properties, and applications of solution-deposited multilayer organic-inorganic hybrid gate dielectrics, using self-assembly techniques, which provide bonding between the organic and inorganic layers. Finally, we discuss approaches for preparing analogous hybrid multilayers by vapor-phase growth and discuss the properties of these materials. PMID:24428627

  9. Physicochemically functional ultrathin films by interfacial polymerization

    DOEpatents

    Lonsdale, H.K.; Babcock, W.C.; Friensen, D.T.; Smith, K.L.; Johnson, B.M.; Wamser, C.C.

    1990-08-14

    Interfacially-polymerized ultrathin films containing physicochemically functional groups are disclosed, both with and without supports. Various applications are disclosed, including membrane electrodes, selective membranes and sorbents, biocompatible materials, targeted drug delivery, and narrow band optical absorbers. 3 figs.

  10. Physicochemically functional ultrathin films by interfacial polymerization

    DOEpatents

    Lonsdale, Harold K. (Bend, OR); Babcock, Walter C. (Bend, OR); Friensen, Dwayne T. (Bend, OR); Smith, Kelly L. (Bend, OR); Johnson, Bruce M. (Bend, OR); Wamser, Carl C. (West Linn, OR)

    1990-01-01

    Interfacially-polymerized ultrathin films containing physicochemically functional groups are disclosed, both with and without supports. Various applications are disclsoed, including membrane electrodes, selective membranes and sorbents, biocompatible materials, targeted drug delivery, and narrow band optical absorbers.

  11. Advancing quasi-freestanding epitaxial graphene electronics through integration of wafer scale hexagonal boron nitride dielectrics

    NASA Astrophysics Data System (ADS)

    Bresnehan, Michael S.; Hollander, Matthew J.; Marucci, Rebecca L.; LaBella, Michael; Trumbull, Kathleen A.; Cavalero, Randal; Snyder, David W.; Robinson, Joshua A.

    2012-09-01

    A key limitation to graphene based electronics is graphene's interaction with dielectric interfaces. SiO2 and various high-k gate dielectrics can introduce scattering from charged surface states, impurities, and surface optical phonons; degrading the transport properties of graphene. Hexagonal boron nitride (h-BN) exhibits an atomically smooth surface that is expected to be free of dangling bonds, leading to an interface that is relatively free of surface charge traps and adsorbed impurities. Additionally, the decreased surface optical phonon interaction from h-BN is expected to further reduce scattering. While h-BN gated graphene FETs have been demonstrated on a small scale utilizing CVD grown or exfoliated graphene, integrating quasi-freestanding epitaxial graphene (QFEG) with h-BN gate dielectrics on a wafer scale has not been explored. We present results from the first large scale CVD growth of h-BN and its subsequent transfer to a 75mm QFEG wafer. The effects of growth conditions on the thickness and quality of the h-BN film and its potential and limitations as a gate dielectric to QFEG are discussed. The introduction of charged impurities during the transfer process resulted in an average degradation in mobility of only 9%. Despite the slight degradation, we show that h-BN is highly beneficial compared to high-k dielectrics when the charged impurity concentration of QFEG is below 5x1012cm-2. Here we show improvements in mobility of >3x and intrinsic cutoff frequency of >2x compared to HfO2.

  12. Magnetization dynamics in ultrathin magnetic films

    Microsoft Academic Search

    Oleksandr Mosendz

    2008-01-01

    Ultrathin magnetic multilayer structures are prepared by Molecular Beam Epitaxy (MBE) on GaAs(001) substrates. Growth was monitored and characterized by Reflection High Energy Electron Diffraction (RHEED), Auger Electron Spectroscopy (AES), X-Ray Photoelectron Spectroscopy (XPS) and Scanning Tunneling Microscopy (STM). The Fe\\/GaAs interface and its influence on the static magnetic properties in magnetic ultrathin films was studied by means of Ferromagnetic

  13. Ultrathin silicon solar cell for space application

    Microsoft Academic Search

    T. Matsutani; T. Saga; H. Ueyama; Y. Hagihara; T. Hirano; A. Suzuki

    1982-01-01

    Ultrathin silicon (Si) solar cells for space application were fabricated on an experimental basis and the electrical characteristics were investigated for three kinds of cells (Black, BSFR and Conventional cells). Under 135.3 mW sq cm (AM0) illumination, ultrathin Black cells showed 67.7 mW output, which is equal to 89 percent output of 280 micron Black cells. The power to mass

  14. Ultrathin films as photomechanical transducers

    NASA Technical Reports Server (NTRS)

    Sarbolouki, M. N.; Fedors, R. F.

    1979-01-01

    In order to investigate the photomechanical effect in ultrathin films, several commercially available polymers of various structure and properties have been studied experimentally below the glass transition temperature. In the experiments using an Instron test machine equipped with a 200-g load cell and a microscope stage illuminator as the light source, the load at the fixed strain was recorded as a function of time. Plots of the steady-state change in stress as a function of the intensity of the incident radiation are presented for several of the materials studied. The response is found to be linear; the greater the intensity of the incident radiation, the greater is the change in stress.

  15. High-k dielectric characterization by VUV spectroscopic ellipsometry and X-ray reflection

    NASA Astrophysics Data System (ADS)

    Boher, P.; Evrard, P.; Piel, J. P.; Defranoux, C.; Fouere, J. C.; Bellandi, E.; Bender, H.

    2003-09-01

    In this study, we use vacuum UV spectroscopic ellipsometry (VUVSE) to characterize new high dielectric materials. Indeed, all the candidates for high k dielectrics become strongly absorbent when the wavelength is reduced down to 140nm. So, the correlation between thickness and refractive index is reduced in the VUV range and much more precise structural information can be deduced. HfO2, Al2O3 and mixed HfAlOx layers have been studied with and without thin SiO2 oxide at the interface. X-ray reflectometry (XRR) has been used to measure precisely the layer thickness and roughness. The two techniques are included in the same automated metrology system dedicated to 300mm technology which is also presented. We show in particular that VUVSE can detect the crystalline character of the layers and their composition can be measured in addition to the layer thickness. Results are compared to those obtained by transmission electron microscopy (TEM), x-ray fluorescence analysis (XRF) and x-ray photoemission (XPS).

  16. Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

    NASA Astrophysics Data System (ADS)

    Yang, Jialing; Eller, Brianna S.; Nemanich, Robert J.

    2014-09-01

    The effects of surface pretreatment, dielectric growth, and post deposition annealing on interface electronic structure and polarization charge compensation of Ga- and N-face bulk GaN were investigated. The cleaning process consisted of an ex-situ wet chemical NH4OH treatment and an in-situ elevated temperature NH3 plasma process to remove carbon contamination, reduce oxygen coverage, and potentially passivate N-vacancy related defects. After the cleaning process, carbon contamination decreased below the x-ray photoemission spectroscopy detection limit, and the oxygen coverage stabilized at ˜1 monolayer on both Ga- and N-face GaN. In addition, Ga- and N-face GaN had an upward band bending of 0.8 ± 0.1 eV and 0.6 ± 0.1 eV, respectively, which suggested the net charge of the surface states and polarization bound charge was similar on Ga- and N-face GaN. Furthermore, three dielectrics (HfO2, Al2O3, and SiO2) were prepared by plasma-enhanced atomic layer deposition on Ga- or N-face GaN and annealed in N2 ambient to investigate the effect of the polarization charge on the interface electronic structure and band offsets. The respective valence band offsets of HfO2, Al2O3, and SiO2 with respect to Ga- and N-face GaN were 1.4 ± 0.1, 2.0 ± 0.1, and 3.2 ± 0.1 eV, regardless of dielectric thickness. The corresponding conduction band offsets were 1.0 ± 0.1, 1.3 ± 0.1, and 2.3 ± 0.1 eV, respectively. Experimental band offset results were consistent with theoretical calculations based on the charge neutrality level model. The trend of band offsets for dielectric/GaN interfaces was related to the band gap and/or the electronic part of the dielectric constant. The effect of polarization charge on band offset was apparently screened by the dielectric-GaN interface states.

  17. An ultrathin sectioning alignment tool with application to cell monolayers.

    PubMed

    Cramer, C T

    1989-02-01

    Details are given concerning the construction and use of a simple tool to help align a specimen block face in the vertical axis for subsequent ultrathin sectioning. Further instructions are given for the preparation of cell monolayers for ultrathin sectioning. The advantage is simple, repetitive and quick alignment of the specimen block face for ultrathin sectioning. PMID:2709137

  18. Chemically tunable ultrathin silsesquiazane interlayer for n-type and p-type organic transistors on flexible plastic.

    PubMed

    Lee, Wi Hyoung; Lee, Seung Goo; Kwark, Young-Je; Lee, Dong Ryeol; Lee, Shichoon; Cho, Jeong Ho

    2014-12-24

    In organic field-effect transistors (OFETs), surface modification of the gate-dielectric is a critical technique for enhancing the electrical properties of the device. Here, we report a simple and versatile method for fabricating an ultrathin cross-linked interlayer (thickness ?3 nm) on an oxide gate dielectric by using polymeric silsesquiazane (SSQZ). The fabricated siloxane film exhibited an ultrasmooth surface with minimal hydroxyl groups; the properties of the surface were chemically tuned by introducing phenyl and phenyl/fluorine pendent groups into the SSQZ. The growth characteristics of two semiconductors-pentacene (p-type) and N,N'-ditridecyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C13, n-type)-on this ultrathin film were systematically investigated according to the type of pendent groups in the SSQZ-treated gate dielectric. Pentacene films on phenyl/fluorine groups exhibited large grains and excellent crystalline homogeneity. By contrast, PTCDI-C13 films exhibited greater crystalline order and perfectness when deposited on phenyl groups rather than on phenyl/fluorine groups. These microstructural characteristics of the organic semiconductors, as well as the dipole moment of the pendent groups, determined the electrical properties of FETs based on pentacene or PTCDI-C13. Importantly, compared to FETs in which the gate dielectric was treated with a silane-coupling agent (a commonly used surface treatment), the FETs fabricated using the tunable SSQZ treatment showed much higher field-effect mobilities. Finally, surface treatment with an ultrathin SSQZ layer was also utilized to fabricate flexible OFETs on a plastic substrate. This was facilitated by the facile SSQZ deposition process and the compatibility of SSQZ with the plastic substrate. PMID:25459690

  19. Ultrathin core-sheath fibers for liposome stabilization.

    PubMed

    Li, Zhuang; Kang, Hongliang; Li, Qinmei; Che, Ning; Liu, Zhijing; Li, Pingping; Zhang, Chao; Liu, Ruigang; Huang, Yong

    2014-10-01

    Ultrathin core-sheath fibers with small unilamellar vesicles (SUVs) in the core were prepared by coaxial electrospinning. SUVs/sodium hyaluranate (HA-Na)/water and polyvinylpyrrolidone (PVP)/ethanol solutions were used as core and sheath fluid in electrospinning, respectively. The ultrathin fibers were characterized by scanning and transmission electron microscopy (SEM and TEM) and laser scanning confocal microscopy (LSCM). The SUVs were successfully encapsulated in the core HA-Na matrix of the ultrathin fibers and are in the elliptic shape. The SUVs encapsulated in the core matrix of the ultrathin fibers have an excellent stability. The SUVs embedded in the ultrathin fibers are stable. When the ultrathin fibers were re-dissolved in water after one-month storage at room temperature, the rehydrated SUVs have the similar size and size distribution as the as-prepared SUVs. The liposome-loaded ultrathin fiber mats have the promising applications in wound healing materials. PMID:25130418

  20. Low field leakage current and soft breakdown in ultra-thin gate oxides after heavy ions, electrons or X-ray irradiation

    Microsoft Academic Search

    M. Ceschia; A. Paccagnella; S. Sandrin; G. Ghidini; J. Wyss; M. Lavale; O. Flament

    1999-01-01

    The excess leakage current across ultra-thin dielectrics has been studied for different ionizing radiation sources. Namely, X-rays, 8 MeV electrons, and three ion beams with different LETs values have been used on large area MOS capacitors with 4-nm thick oxides. Small oxide fields were applied during irradiation, reaching 3 MV\\/cm at most. For ionizing radiation with relatively low LET (<10

  1. Low field leakage current and soft breakdown in ultra-thin gate oxides after heavy ions, electron or X-ray irradiation

    Microsoft Academic Search

    M. Ceschia; A. Paccagnella; S. Sandrin; G. Ghidini; J. Wyss; M. Lavale; O. Flament

    2000-01-01

    The excess leakage current across ultra-thin dielectrics has been studied for different ionizing radiation sources. X-rays, 8 MeV electrons, and three ion beams with different LETs values have been used on large area MOS capacitors with 4-nm thick oxides. Small oxide fields were applied during irradiation, reaching 3 MV\\/cm at most. For ionizing radiation with relatively low LET (<10 MeV

  2. A study on the evolution of dielectric function of ZnO thin films with decreasing film thickness

    SciTech Connect

    Li, X. D.; Chen, T. P., E-mail: echentp@ntu.edu.sg; Liu, P. [School of Electrical and Electronic Engineering, Nanyang Technological University, 639798 Singapore (Singapore); Liu, Y. [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology, Chengdu 610054 (China); Liu, Z. [School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006 (China); Leong, K. C. [GLOBALFOUNDRIES Singapore Pte Ltd, 738406 Singapore (Singapore)

    2014-03-14

    Dielectric function, band gap, and exciton binding energies of ultrathin ZnO films as a function of film thickness have been obtained with spectroscopic ellipsometry. As the film thickness decreases, both real (?{sub 1}) and imaginary (?{sub 2}) parts of the dielectric function decrease significantly, and ?{sub 2} shows a blue shift. The film thickness dependence of the dielectric function is shown related to the changes in the interband absorption, discrete-exciton absorption, and continuum-exciton absorption, which can be attributed to the quantum confinement effect on both the band gap and exciton binding energies.

  3. Performance and reliability of low-temperature polysilicon TFT with a novel stack gate dielectric and stack optimization using PECVD nitrous oxide plasma

    Microsoft Academic Search

    Kow-Ming Chang; Wen-Chih Yang; Chiu-Pao Tsai

    2004-01-01

    This paper proposes a novel tetraethylorthosilicate (TEOS)\\/oxynitride stack gate dielectric for low-temperature poly-Si thin-film transistors, composed of a plasma-enhanced chemical vapor deposition (PECVD) thick TEOS oxide\\/ultrathin oxynitride grown by PECVD N2O plasma. The novel stack gate dielectric exhibits a very high electrical breakdown field of 8.5 MV\\/cm, which is approximately 3 MV\\/cm higher than traditional PECVD TEOS oxide. The novel

  4. Gas leak through ultrathin radiation entrance windows

    Microsoft Academic Search

    Veli-Pekka Viitanen; Heini Harvela

    1995-01-01

    The permeation rates through an ultrathin radiation entrance window membrane have been measured for several common detector gas components, as well as for some atmospheric gases, by collecting the permeated gas into a clean volume equipped with an absolute pressure transducer. The dependence of the leak rate on the differential pressure (1.0 bar in most of the measurements) has also

  5. Glass Transition Measurements of Ultrathin Polystyrene Films

    E-print Network

    1 Glass Transition Measurements of Ultrathin Polystyrene Films Cynthia Buenviaje, Franco Dinelli. Measurements taken on polystyrene surfaces of various film thickness provide insight into how the glass of polymers have been studied extensively, many properties of thin films, specifically the glass transition

  6. Ultrathin FBG Pressure Sensor With Enhanced Responsivity

    Microsoft Academic Search

    W. T. Zhang; F. Li; Y. L. Liu; L. H. Liu

    2007-01-01

    An ultrathin fiber Bragg grating pressure sensor with enhanced sensitivity is demonstrated. A novel piston-like diaphragm with a hard core in the center is used as the sensing element to enhance the responsivity. Both the theoretical analysis and the experimental results show that the Young's modulus of the diaphragm and the radius of the hard core have significant effect on

  7. YBCO film growth on ultrathin Ag layers

    SciTech Connect

    Zhong, C.; Ruggiero, S.T. (Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States)); Fletcher, R.; Moser, E. (Wright Laboratory, Materials Directorate, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States))

    1994-11-01

    We discuss our results on the growth of YBCO thin films on ultrathin (1--10 nm) Ag underlayers. Substrates were LaAlO[sub 3]. YBCO was sputter deposited and Ag thermally evaporated. It was observed that [ital T][sub [ital c

  8. Electrical characteristics of low temperature polysilicon TFT with a novel TEOS\\/oxynitride stack gate dielectric

    Microsoft Academic Search

    Kow-Ming Chang; Wen-Chih Yang; Chiu-Pao Tsai

    2003-01-01

    This investigation is the first to demonstrate a novel tetraethylorthosilicate (TEOS)\\/oxynitride stack gate dielectric for low-temperature poly-Si (LTPS) thin film transistors (TFTs), composed of a plasma-enhanced chemical vapor deposition (PECVD) thick TEOS oxide\\/ultrathin oxynitride grown by PECVD N2O-plasma. The stack oxide shows a very high electrical breakdown field of 8.4 MV\\/cm, which is approximately 3 MV\\/cm larger than traditional PECVD

  9. Pattern formation in dielectric barrier discharges with different dielectric materials

    Microsoft Academic Search

    L. F. Dong; W. L. Fan; S. Wang; Y. F. Ji; Z. W. Liu; Q. Chen

    2011-01-01

    The influence of dielectric material on the bifurcation and spatiotemporal dynamics of the patterns in dielectric barrier discharge in argon\\/air at atmospheric pressure is studied. It is found that pattern bifurcation sequences are different with different dielectric materials. The spatiotemporal dynamics of the hexagonal pattern in dielectric barrier discharge depends on the dielectric material. The hexagon pattern with glass dielectric

  10. Gate stack dielectric degradation of rare-earth oxides grown on high mobility Ge substrates

    NASA Astrophysics Data System (ADS)

    Shahinur Rahman, Md.; Evangelou, E. K.; Konofaos, N.; Dimoulas, A.

    2012-11-01

    We report on the reliability characteristics and their analysis, of rare-earth oxides (REOs) dielectric degradation, when used as interfacial buffer layers together with HfO2 high-k films (REOs/HfO2) on high mobility Ge substrates. Metal-oxide-semiconductor (MOS) devices with these stacks, show dissimilar charge trapping phenomena under varying levels of constant-voltage-stress (CVS) conditions, influencing the measured densities of the interface (Nit) and border (NBT) traps. In the present study, we report on C-Vg hysteresis curves related to both Nit and NBT. We propose a new model based on the Maxwell-Wagner mechanism, and this model explains the current decay transient observed under CVS bias from low to higher fields of MOS gate stack devices grown on Ge substrates. The proposed model is unlike to those used for other MOS devices. Finally, CVS measurements for very long times at moderate fields reveal an initial current decay due to relaxation, followed by charge trapping and generation of stress-induced leakage which eventually lead to hard breakdown.

  11. Thickness dependent properties of magnetic ultrathin films

    NASA Astrophysics Data System (ADS)

    Cong, Bach Thanh; Thao, Pham Huong

    2013-10-01

    The dependence of magnetic properties on the thickness of few-layer thin films is investigated at finite temperature using the functional integral method for solving the Heisenberg spin model. The temperature dependence of the ultra-thin film's magnetization and Curie temperature are calculated in terms of the mean field theory and of the Gaussian spin fluctuation approximations. It has been shown that both Curie temperature and temperature interval, where the magnetization is non-zero, are strongly reduced with the thickness reduction by using the spin fluctuation approximations in comparison with the mean field results. Curie temperature dependence on the film thickness calculated numerically well agrees with the experimental data for Ni/Cu(1 0 0) and Ni/Cu(1 1 1) ultrathin films.

  12. Hybridization and magnetism in ultrathin Mn films

    Microsoft Academic Search

    H. A. Dürr; G. van der Laan; D. Spanke; F. U. Hillebrecht; N. B. Brookes; J. B. Goedkoop

    1997-01-01

    We have studied the electronic and magnetic structure of ultrathin Mn films grown on 3d transition metal surfaces using X-ray absorption and resonant photoemission. At submonolayer coverages Mn deposition leads to a highly localized 3d5-like ground state. A delocalized metallic ground state is formed upon increasing Mn?Mn 3d orbital overlap after percolation of the film. A similar state can also

  13. Spin Damping in Ultrathin Magnetic Films

    Microsoft Academic Search

    Douglas L. Mills; Sergio M. Rezende

    This chapter reviews the origin of the damping of spin motions in ultra-thin ferromagnetic films and multilayer structures,\\u000a with focus on the linear response regime probed by ferromagnetic resonance or Brillouin light scattering. We begin with a\\u000a description of the spin response provided by the Landau-Lifshitz equation, which ascribes damping to dissipative processes\\u000a of intrinsic origin. It is noted that

  14. Monte Carlo Simulations of Ultrathin Magnetic Dots

    E-print Network

    M. Rapini; R. A. Dias; D. P. Landau; B. V. Costa

    2006-04-10

    In this work we study the thermodynamic properties of ultrathin ferromagnetic dots using Monte Carlo simulations. We investigate the vortex density as a function of the temperature and the vortex structure in monolayer dots with perpendicular anisotropy and long-range dipole interaction. The interplay between these two terms in the hamiltonian leads to an interesting behavior of the thermodynamic quantities as well as the vortex density.

  15. An ultrathin wide-band planar metamaterial absorber based on a fractal frequency selective surface and resistive film

    NASA Astrophysics Data System (ADS)

    Fan, Yue-Nong; Cheng, Yong-Zhi; Nie, Yan; Wang, Xian; Gong, Rong-Zhou

    2013-06-01

    We propose an ultrathin wide-band metamaterial absorber (MA) based on a Minkowski (MIK) fractal frequency selective surface and resistive film. This absorber consists of a periodic arrangement of dielectric substrates sandwiched with an MIK fractal loop structure electric resonator and a resistive film. The finite element method is used to simulate and analyze the absorption of the MA. Compared with the MA-backed copper film, the designed MA-backed resistive film exhibits an absorption of 90% at a frequency region of 2 GHz-20 GHz. The power loss density distribution of the MA is further illustrated to explain the mechanism of the proposed MA. Simulated absorptions at different incidence cases indicate that this absorber is polarization-insensitive and wide-angled. Finally, further simulated results indicate that the surface resistance of the resistive film and the dielectric constant of the substrate can affect the absorbing property of the MA. This absorber may be used in many military fields.

  16. Structural and electrical characterization of ultrathin Er2O3 films grown on Si(001) by reactive evaporation

    NASA Astrophysics Data System (ADS)

    Fang, Z. B.; Chen, S.; Zhu, Y. Y.; Wu, Y. Q.; Fan, Y. L.; Wang, Y. Y.; Jiang, Z. M.

    2007-04-01

    Stoichiometric, amorphous, uniform Er2O3 films are deposited on Si(001) substrates by reactive evaporation using a metallic Er source at room temperature in an oxygen ambient pressure of 9 × 10-6 Torr. Transmission electron microscopic measurement shows that the film possesses good thermal stability and forms a sharp interface with its Si substrate after annealing at 700 °C for 30 min in ultrahigh vacuum. The effective dielectric constant (k) of the film is measured to be 12.6, and its effective oxide thickness (EOT) can reach 1.4 nm, with a low leakage current density of 8 × 10-4 A cm-2 at an electric field of 1 MV cm-1 after annealing. The characteristics obtained indicate that ultrathin amorphous Er2O3 film could be a promising candidate for a high-k gate dielectric in Si microelectronic devices.

  17. Photoresponsive properties of ultrathin silicon nanowires

    NASA Astrophysics Data System (ADS)

    Tran, Duy P.; Macdonald, Thomas J.; Wolfrum, Bernhard; Stockmann, Regina; Nann, Thomas; Offenhäusser, Andreas; Thierry, Benjamin

    2014-12-01

    Functional silicon nanowires (SiNWs) are promising building blocks in the design of highly sensitive photodetectors and bio-chemical sensors. We systematically investigate the photoresponse properties of ultrathin SiNWs (20 nm) fabricated using a size-reduction method based on e-beam lithography and tetramethylammonium hydroxide wet-etching. The high-quality SiNWs were able to detect light from the UV to the visible range with excellent sensitivity (˜1 pW/array), good time response, and high photoresponsivity (R ˜ 2.5 × 104 A/W). Improvement of the ultrathin SiNWs' photoresponse has been observed in comparison to 40 nm counter-part nanowires. These properties are attributable to the predominance surface-effect due to the high surface-to-volume ratio of ultrathin SiNWs. Long-term measurements at different temperatures in both the forward and reverse bias directions demonstrated the stability and reliability of the fabricated device. By sensitizing the fabricated SiNW arrays with cadmium telluride quantum dots (QDs), hybrid QD SiNW devices displayed an improvement in photocurrent response under UV light, while preserving their performance in the visible light range. The fast, stable, and high photoresponse of these hybrid nanostructures is promising towards the development of optoelectronic and photovoltaic devices.

  18. Microwave absorptions of ultrathin conductive films and designs of frequency-independent ultrathin absorbers

    SciTech Connect

    Li, Sucheng; Anwar, Shahzad; Lu, Weixin; Hang, Zhi Hong; Hou, Bo, E-mail: houbo@suda.edu.cn, E-mail: phyhoubo@gmail.com; Shen, Mingrong [School of Physical Science and Technology, Soochow University, 1 Shizi Street, Suzhou 215006 (China)] [School of Physical Science and Technology, Soochow University, 1 Shizi Street, Suzhou 215006 (China); Wang, Chin-Hua [Institute of Modern Optical Technologies and Collaborative Innovation Center of Suzhou Nano Science and Technology, Jiangsu Key Lab of Advanced Optical Manufacturing Technologies, Soochow University, 1 Shizi Street, Suzhou 215006 (China)] [Institute of Modern Optical Technologies and Collaborative Innovation Center of Suzhou Nano Science and Technology, Jiangsu Key Lab of Advanced Optical Manufacturing Technologies, Soochow University, 1 Shizi Street, Suzhou 215006 (China)

    2014-01-15

    We study the absorption properties of ultrathin conductive films in the microwave regime, and find a moderate absorption effect which gives rise to maximal absorbance 50% if the sheet (square) resistance of the film meets an impedance matching condition. The maximal absorption exhibits a frequency-independent feature and takes place on an extremely subwavelength scale, the film thickness. As a realistic instance, ?5 nm thick Au film is predicted to achieve the optimal absorption. In addition, a methodology based on metallic mesh structure is proposed to design the frequency-independent ultrathin absorbers. We perform a design of such absorbers with 50% absorption, which is verified by numerical simulations.

  19. Broadband Frequency-Selective Spoof Surface Plasmon Polaritons on Ultrathin Metallic Structure

    PubMed Central

    Yin, Jia Yuan; Ren, Jian; Zhang, Hao Chi; Pan, Bai Cao; Cui, Tie Jun

    2015-01-01

    We propose an ultrathin metallic structure to produce frequency-selective spoof surface plasmon polaritons (SPPs) in the microwave and terahertz frequencies. Designed on a thin dielectric substrate, the ultrathin metallic structure is composed of two oppositely oriented single-side corrugated strips, which are coupled to two double-side corrugated strips. The structure is fed by a traditional coplanar waveguide (CPW). To make a smooth conversion between the spatial modes in CPW and SPP modes, two transition sections are also designed. We fabricate and measure the frequency-selective spoof SPP structure in microwave frequencies. The measurement results show that the reflection coefficient is less than -10?dB with the transmission loss around 1.5?dB in the selective frequency band from 7 to 10?GHz, which are in good agreements with numerical simulations. The proposed structure can be used as an SPP filter with good performance of low loss, high transmission, and wide bandwidth in the selective frequency band. PMID:25641730

  20. Semitransparent ultrathin CdTe solar cells Semitransparent ultrathin CdTe solar cells and durabilityand durability

    E-print Network

    Rollins, Andrew M.

    Semitransparent ultrathin CdTe solar cells Semitransparent ultrathin CdTe solar cells PV coatings based on CdTe. ...for transparent window PV:...for transparent window PV: , p g · The X26 core technology is built around · sputter deposition · CdS/CdTe cell structure · Extensive IP

  1. Effect of film properties for non-linear DPL model in a nanoscale MOSFET with high-k material: ZrO2/HfO2/La2O3

    NASA Astrophysics Data System (ADS)

    Shomali, Zahra; Ghazanfarian, Jafar; Abbassi, Abbas

    2015-07-01

    Numerical simulation of non-linear non-Fourier heat conduction within a nano-scale metal-oxide-semiconductor field-effect transistor (MOSFET) is presented under the framework of Dual-Phase-Lag model including the boundary phonon scattering. The MOSFET is modeled in four cases of: (I) thin silicon slab, (II) including uniform heat generation, (III) double-layered buried oxide MOSFET with uniform heat generation in silicon-dioxide layer, and (IV) high-k/metal gate transistor. First, four cases are studied under four conditions of (a) constant bulk and (b) constant film thermal properties, (c) temperature-dependent properties of bulk silicon, and (d) temperature-dependent thermal properties of film silicon. The heat source and boundary conditions are similar to what existed in a real MOSFET. It is concluded that in all cases, considering the film properties lowers the temperature jump due to the reduction of the Knudsen number. Furthermore, the speed of heat flux penetration for film properties is less than that of the cases concerning bulk properties. Also, considering the temperature-dependent properties drastically changes the temperature and heat flux distributions within the transistor, which increases the diffusion speed and more, decreases the steady state time. Calculations for case (III) presents that all previous studies have underestimated the value of the peak temperature rise by considering the constant bulk properties of silicon. Also, it is found that among the high-k dielectrics investigated in case (IV), zirconium dioxide shows the least peak temperature rise. This presents that zirconium dioxide is a good candidate as far as the thermal issues are concerned.

  2. Flexible low-voltage organic complementary circuits: finding the optimum combination of semiconductors and monolayer gate dielectrics.

    PubMed

    Kraft, Ulrike; Sejfi?, Mirsada; Kang, Myeong Jin; Takimiya, Kazuo; Zaki, Tarek; Letzkus, Florian; Burghartz, Joachim N; Weber, Edwin; Klauk, Hagen

    2015-01-14

    Low-voltage p-channel and n-channel organic transistors with channel lengths down to 0.5 ?m using four small-molecule semiconductors and ultra-thin dielectrics based on two different phosphonic acid monolayers are fabricated on plastic substrates and studied in terms of effective mobility, intrinsic mobility and contact resistance. For the optimum materials combination, flexible complementary circuits have signal delays of 3.1 ?s at 5 V. PMID:25330764

  3. Resonant dielectric metamaterials

    DOEpatents

    Loui, Hung; Carroll, James; Clem, Paul G; Sinclair, Michael B

    2014-12-02

    A resonant dielectric metamaterial comprises a first and a second set of dielectric scattering particles (e.g., spheres) having different permittivities arranged in a cubic array. The array can be an ordered or randomized array of particles. The resonant dielectric metamaterials are low-loss 3D isotropic materials with negative permittivity and permeability. Such isotropic double negative materials offer polarization and direction independent electromagnetic wave propagation.

  4. Comparative study of CNT, silicon nanowire and fullerene embedded multilayer high-k gate dielectric MOS memory devices

    NASA Astrophysics Data System (ADS)

    Sengupta, Amretashis; Sarkar, Chandan Kumar; Requejo, Felix G.

    2011-10-01

    Here, we present a comparative theoretical study on stacked (multilayer) gate dielectric MOS memory devices, having a metallic/semiconducting carbon nanotube (CNT), silicon nanowire (Si NW) and fullerene (C60) embedded nitride layer acting as a floating gate. Two types of devices, one with HfO2-SiO2 stack (stack-1) and the other with La2O3-SiO2 stack (stack-2) as the tunnel oxide were compared. We evaluated the effective barrier height, the dielectric constant and the effective electron mobility in the composite gate dielectric with the Maxwell-Garnett effective medium theory. Thereafter applying the WKB approximation, we simulated the Fowler-Nordheim (F-N) tunnelling/writing current and the direct tunnelling/leakage current in these devices. We evaluated the I-V characteristics, the charge decay and also the impact of CNT/Si NW aspect ratio and the volume fraction on the effective barrier height and the write voltage, respectively. We also simulated the write time, retention time and the erase time of these MOS devices. Based on the simulation results, it was concluded that the metallic CNT embedded stack-1 device offered the best performance in terms of higher F-N tunnelling current, lower direct tunnelling current and lesser write voltage and write time compared with the other devices. In case of direct tunnelling leakage and retention time it was found that the met CNT embedded stack-2 device showed better characteristics. For erasing, however, the C60 embedded stack-1 device showed the smallest erase time. When compared with earlier reports, it was seen that CNT, C60 and Si NW embedded devices all performed better than nanocrystalline Si embedded MOS non-volatile memories.

  5. Ultrathin inorganic molecular nanowire based on polyoxometalates.

    PubMed

    Zhang, Zhenxin; Murayama, Toru; Sadakane, Masahiro; Ariga, Hiroko; Yasuda, Nobuhiro; Sakaguchi, Norihito; Asakura, Kiyotaka; Ueda, Wataru

    2015-01-01

    The development of metal oxide-based molecular wires is important for fundamental research and potential practical applications. However, examples of these materials are rare. Here we report an all-inorganic transition metal oxide molecular wire prepared by disassembly of larger crystals. The wires are comprised of molybdenum(VI) with either tellurium(IV) or selenium(IV): {(NH4)2[XMo6O21]}n (X=tellurium(IV) or selenium(IV)). The ultrathin molecular nanowires with widths of 1.2?nm grow to micrometre-scale crystals and are characterized by single-crystal X-ray analysis, Rietveld analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, thermal analysis and elemental analysis. The crystals can be disassembled into individual molecular wires through cation exchange and subsequent ultrasound treatment, as visualized by atomic force microscopy and transmission electron microscopy. The ultrathin molecular wire-based material exhibits high activity as an acid catalyst, and the band gap of the molecular wire-based crystal is tunable by heat treatment. PMID:26139011

  6. Ultrathin inorganic molecular nanowire based on polyoxometalates

    PubMed Central

    Zhang, Zhenxin; Murayama, Toru; Sadakane, Masahiro; Ariga, Hiroko; Yasuda, Nobuhiro; Sakaguchi, Norihito; Asakura, Kiyotaka; Ueda, Wataru

    2015-01-01

    The development of metal oxide-based molecular wires is important for fundamental research and potential practical applications. However, examples of these materials are rare. Here we report an all-inorganic transition metal oxide molecular wire prepared by disassembly of larger crystals. The wires are comprised of molybdenum(VI) with either tellurium(IV) or selenium(IV): {(NH4)2[XMo6O21]}n (X=tellurium(IV) or selenium(IV)). The ultrathin molecular nanowires with widths of 1.2?nm grow to micrometre-scale crystals and are characterized by single-crystal X-ray analysis, Rietveld analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible spectroscopy, thermal analysis and elemental analysis. The crystals can be disassembled into individual molecular wires through cation exchange and subsequent ultrasound treatment, as visualized by atomic force microscopy and transmission electron microscopy. The ultrathin molecular wire-based material exhibits high activity as an acid catalyst, and the band gap of the molecular wire-based crystal is tunable by heat treatment. PMID:26139011

  7. MMIC capacitor dielectric reliability

    Microsoft Academic Search

    H. Cramer; J. Oliver; G. Dix

    1998-01-01

    Field strength and leakage are intrinsic dielectric properties which alone are not sufficient to ensure high reliability. To analyze lifetime, one also needs to consider “charge to breakdown” failure caused by defects and their effect on the dielectric thinning. The linear field model was used to explain the aging effects of electric field and temperature on capacitors. This model shows

  8. Characterization of ultrathin oxide prepared by low-temperature wafer loading and nitrogen preannealing before oxidation

    NASA Astrophysics Data System (ADS)

    Wu, S. L.; Lee, C. L.; Lei, T. F.; Liang, M. S.

    1992-08-01

    In this study, we report a high-performance ultrathin oxide (?80 Å) prepared by a low-temperature wafer loading and N2 preannealing before oxidation. This recipe can reduce native oxide thickness and thermal stress compared to the conventional oxidation recipe. The high-resolution transmission electron microscopy reveals that the SiO2/Si interface is atomically flat, and a thin crystalline-like oxide layer about 7 Å exists at the interface. Oxides prepared by the proposed recipe show a very high dielectric breakdown field (?16 MV/cm) and a very low interface state density (Nit ? 3 × 109 eV-1 cm-2 at midgap). The effective barrier height at cathode derived from the slopes of log(Jg/E2ox) vs 1/Eox and tbd vs 1/Eox plots is about 3.9 eV, instead of 3.2 eV for the control sample. It also shows a better immunity to the charge trapping and interface state generation under high-field stressing, and superior time-dependent dielectric breakdown characteristics.

  9. Ultrathin Optical Panel And A Method Of Making An Ultrathin Optical Panel.

    DOEpatents

    Biscardi, Cyrus (Bellport, NY); Brewster, Calvin (North Patchogue, NY); DeSanto, Leonard (Patchogue, NY); Veligdan, James T. (Manorville, NY)

    2005-05-17

    An ultrathin optical panel, and a method of producing an ultrathin optical panel, are disclosed, including stacking a plurality of glass sheets, which sheets may be coated with a transparent cladding substance or may be uncoated, fastening together the plurality of stacked coated glass sheets using an epoxy or ultraviolet adhesive, applying uniform pressure to the stack, curing the stack, sawing the stack to form an inlet face on a side of the stack and an outlet face on an opposed side of the stack, bonding a coupler to the inlet face of the stack, and fastening the stack, having the coupler bonded thereto, within a rectangular housing having an open front which is aligned with the outlet face, the rectangular housing having therein a light generator which is optically aligned with the coupler. The light generator is preferably placed parallel to and proximate with the inlet face, thereby allowing for a reduction in the depth of the housing.

  10. Ultrathin optical panel and a method of making an ultrathin optical panel

    DOEpatents

    Biscardi, Cyrus (Bellport, NY); Brewster, Calvin (North Patchogue, NY); DeSanto, Leonard (Patchogue, NY); Veligdan, James T. (Manorville, NY)

    2001-10-09

    An ultrathin optical panel, and a method of producing an ultrathin optical panel, are disclosed, including stacking a plurality of glass sheets, which sheets may be coated with a transparent cladding substance or may be uncoated, fastening together the plurality of stacked coated glass sheets using an epoxy or ultraviolet adhesive, applying uniform pressure to the stack, curing the stack, sawing the stack to form an inlet face on a side of the stack and an outlet face on an opposed side of the stack, bonding a coupler to the inlet face of the stack, and fastening the stack, having the coupler bonded thereto, within a rectangular housing having an open front which is aligned with the outlet face, the rectangular housing having therein a light generator which is optically aligned with the coupler. The light generator is preferably placed parallel to and proximate with the inlet face, thereby allowing for a reduction in the depth of the housing.

  11. Ultrathin optical panel and a method of making an ultrathin optical panel

    DOEpatents

    Biscardi, Cyrus (Bellport, NY); Brewster, Calvin (North Patchogue, NY); DeSanto, Leonard (Patchogue, NY); Veligdan, James T. (Manorville, NY)

    2002-01-01

    An ultrathin optical panel, and a method of producing an ultrathin optical panel, are disclosed, including stacking a plurality of glass sheets, which sheets may be coated With a transparent cladding substance or may be uncoated, fastening together the plurality of stacked coated glass sheets using an epoxy or ultraviolet adhesive, applying uniform pressure to the stack, curing the stack, sawing the stack to form an inlet face on a side of the stack and an outlet face on an opposed side of the stack, bonding a coupler to the inlet face of the stack, and fastening the stack, having the coupler bonded thereto, within a rectangular housing having an open front which is aligned with the outlet face, the rectangular housing having therein a light generator which is optically aligned with the coupler. The light generator is preferably placed parallel to and proximate with the inlet face, thereby allowing for a reduction in the depth of the housing.

  12. Ultrathin Optical Panel And A Method Of Making An Ultrathin Optical Panel.

    DOEpatents

    Biscardi, Cyrus (Bellport, NY); Brewster, Calvin (North Patchoque, NY); DeSanto, Leonard (Patchoque, NY); Veligdan, James T. (Manorville, NY)

    2005-02-15

    An ultrathin optical panel, and a method of producing an ultrathin optical panel, are disclosed, including stacking a plurality of glass sheets, which sheets may be coated with a transparent cladding substance or may be uncoated, fastening together the plurality of stacked coated glass sheets using an epoxy or ultraviolet adhesive, applying uniform pressure to the stack, curing the stack, sawing the stack to form an inlet face on a side of the stack and an outlet face on an opposed side of the stack, bonding a coupler to the inlet face of the stack, and fastening the stack, having the coupler bonded thereto, within a rectangular housing having an open front which is aligned with the outlet face, the rectangular housing having therein a light generator which is optically aligned with the coupler. The light generator is preferably placed parallel to and proximate with the inlet face, thereby allowing for a reduction in the depth of the housing.

  13. Ultrathin optical panel and a method of making an ultrathin optical panel

    DOEpatents

    Biscardi, Cyrus (Bellport, NY); Brewster, Calvin (North Patchogue, NY); DeSanto, Leonard (Patchogue, NY); Veligdan, James T. (Manorville, NY)

    2003-02-11

    An ultrathin optical panel, and a method of producing an ultrathin optical panel, are disclosed, including stacking a plurality of glass sheets, which sheets may be coated with a transparent cladding substance or may be uncoated, fastening together the plurality of stacked coated glass sheets using an epoxy or ultraviolet adhesive, applying uniform pressure to the stack, curing the stack, sawing the stack to form an inlet face on a side of the stack and an outlet face on an opposed side of the stack, bonding a coupler to the inlet face of the stack, and fastening the stack, having the coupler bonded thereto, within a rectangular housing having an open front which is aligned with the outlet face, the rectangular housing having therein a light generator which is optically aligned with the coupler. The light generator is preferably placed parallel to and proximate with the inlet face, thereby allowing for a reduction in the depth of the housing.

  14. Lifetimes of Confined Acoustic Phonons in Ultrathin Silicon Membranes

    E-print Network

    Cuffe, John

    We study the relaxation of coherent acoustic phonon modes with frequencies up to 500 GHz in ultrathin free-standing silicon membranes. Using an ultrafast pump-probe technique of asynchronous optical sampling, we observe ...

  15. Nanopyramid structure for ultrathin c-Si tandem solar cells.

    PubMed

    Li, Guijun; Li, He; Ho, Jacob Y L; Wong, Man; Kwok, Hoi Sing

    2014-05-14

    Recently, ultrathin crystalline silicon solar cells have gained tremendous interest because they are deemed to dramatically reduce material usage. However, the resulting conversion efficiency is still limited by the incomplete light absorption in such ultrathin devices. In this letter, we propose ultrathin a-Si/c-Si tandem solar cells with an efficient light trapping design, where a nanopyramid structure is introduced between the top and bottom cells. The superior light harvesting results in a 48% and 35% remarkable improvement of the short-circuit current density for the top and bottom cells, respectively. Meanwhile, the use of SiOx mixed-phase nanomaterial helps to provide the maximum light trapping without paying the price of reduced electrical performance, and conversion efficiencies of up to 13.3% have been achieved for the ultrathin tandem cell employing only 8 ?m of silicon, which is 29% higher than the result obtained for the planar cell. PMID:24730470

  16. Improved Performance of Dye-Sensitized Solar Cells Fabricated from a Coumarin NKX-2700 Dye-Sensitized TiO2/MgO Core-Shell Photoanode with an HfO2 Blocking Layer and a Quasi-Solid-State Electrolyte

    NASA Astrophysics Data System (ADS)

    Maheswari, D.; Venkatachalam, P.

    2015-03-01

    Dye sensitized solar cells (DSSC) were fabricated from a coumarin NKX-2700 dye-sensitized core-shell photoanode and a quasi-solid-state electrolyte, sandwiched together, with a cobalt sulfide-coated counter electrode. The core-shell photoanode consisted of a composite mixture of 90% TiO2 nanoparticles and 10% TiO2 nanowires (TNPW) as core layer and MgO nanoparticles (MNP) as shell layer. Hafnium oxide (HfO2) was applied to the core-shell photoanode film as a blocking layer. TiO2 nanoparticles, TiO2 nanowires, and TNPW/MNP were characterized by x-ray diffractometry, scanning electron microscopy, and transmission electron microscopy. It was apparent from the UV-visible spectrum of the sensitizing dye coumarin NKX-2700 that its absorption was maximum at 525 nm. Power conversion efficiency (PCE) was greater for DSSC-1, fabricated with a core-shell TNPW/MNP/HfO2 photoanode, than for the other DSSC; its photovoltaic properties were: short circuit photocurrent J sc = 19 mA/cm2, open circuit voltage ( V oc) = 720 mV, fill factor ( FF) = 66%, and PCE ( ?) = 9.02%. The charge-transport and charge-recombination behavior of the DSSC were investigated by electrochemical impedance spectroscopy; the results showed that the composite core-shell film resulted in the lowest charge-transfer resistance ( R CE) and the longest electron lifetime ( ? eff). Hence, the improved performance of DSSC-1 could be ascribed to the core-shell photoanode with blocking layer, which increased electron transport and suppressed recombination of charge carriers at the photoanode/dye/electrolyte interface.

  17. Characterization of the ultrathin vertical channel CMOS technology

    Microsoft Academic Search

    Haitao Liu; Johnny K. O. Sin; Peiqi Xuan; Jeffrey Bokor

    2004-01-01

    In this paper, an ultrathin vertical channel (UTVC) CMOS with self-aligned asymmetric lightly doped drain is experimentally demonstrated. In the structure, the UTVC was obtained using solid phase epitaxy, and the midgap material, boron-doped poly-Si0.5Ge0.5, was used as the gate electrode to obtain symmetrical threshold voltages for both the NMOS and PMOS devices. Due to the ultrathin channel, the fabricated

  18. Improved Dielectric Films For Capacitors

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S.; Lewis, Carol R.; Cygan, Peter J.; Jow, T. Richard

    1994-01-01

    Dielectric films made from blends of some commercially available high-dielectric-constant cyanoresins with each other and with cellulose triacetate (CTA) have both high dielectric constants and high breakdown strengths. Dielectric constants as high as 16.2. Films used to produce high-energy-density capacitors.

  19. Ultra-thin microporous/hybrid materials

    DOEpatents

    Jiang, Ying-Bing (Albuquerque, NM); Cecchi, Joseph L. (Albuquerque, NM); Brinker, C. Jeffrey (Albuquerque, NM)

    2012-05-29

    Ultra-thin hybrid and/or microporous materials and methods for their fabrication are provided. In one embodiment, the exemplary hybrid membranes can be formed including successive surface activation and reaction steps on a porous support that is patterned or non-patterned. The surface activation can be performed using remote plasma exposure to locally activate the exterior surfaces of porous support. Organic/inorganic hybrid precursors such as organometallic silane precursors can be condensed on the locally activated exterior surfaces, whereby ALD reactions can then take place between the condensed hybrid precursors and a reactant. Various embodiments can also include an intermittent replacement of ALD precursors during the membrane formation so as to enhance the hybrid molecular network of the membranes.

  20. Electric field effect in ultrathin black phosphorus

    SciTech Connect

    Koenig, Steven P.; Schmidt, Hennrik [Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Doganov, Rostislav A.; Castro Neto, A. H.; Özyilmaz, Barbaros [Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore, 28 Medical Drive, Singapore 117456 (Singapore)

    2014-03-10

    Black phosphorus exhibits a layered structure similar to graphene, allowing mechanical exfoliation of ultrathin single crystals. Here, we demonstrate few-layer black phosphorus field effect devices on Si/SiO{sub 2} and measure charge carrier mobility in a four-probe configuration as well as drain current modulation in a two-point configuration. We find room-temperature mobilities of up to 300 cm{sup 2}/Vs and drain current modulation of over 10{sup 3}. At low temperatures, the on-off ratio exceeds 10{sup 5}, and the device exhibits both electron and hole conduction. Using atomic force microscopy, we observe significant surface roughening of thin black phosphorus crystals over the course of 1 h after exfoliation.

  1. Cast dielectric composite linear accelerator

    DOEpatents

    Sanders, David M. (Livermore, CA); Sampayan, Stephen (Manteca, CA); Slenes, Kirk (Albuquerque, NM); Stoller, H. M. (Albuquerque, NM)

    2009-11-10

    A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.

  2. Broadband Liquid Dielectric Spectrometer

    NASA Astrophysics Data System (ADS)

    Chandra, Satyan; Arellano, Jesus; Mazzeo, Brian

    2009-10-01

    A dielectric spectrometer was built to measure the dielectric relaxation of proteins in solution. The dielectric cell consisted of two parallel stainless-steel electrodes (separation of 8.5 mm) embedded in PTFE. To provide temperature stability, thermally regulated water flowed through both electrodes. The cell was connected to a 4294A Precision Impedance Analyzer, providing impedance measurements from 40Hz to 110 MHz. Due to electrode polarization and high frequency parasitics, useful measurements were obtained for frequencies ranging from 10 kHz to 10 MHz. Calibration was performed using air, iso-propanol and deionized water. Experiments were also conducted on buffers and salt solutions. The dielectric relaxation of the protein beta-lactoglobulin was measured at mg/ml concentrations.

  3. High performance organic field-effect transistors with ultra-thin HfO{sub 2} gate insulator deposited directly onto the organic semiconductor

    SciTech Connect

    Ono, S., E-mail: shimpei@criepi.denken.or.jp [Central Research Institute of Electric Power Industry, Komae, Tokyo 201-8511 (Japan); Häusermann, R. [Central Research Institute of Electric Power Industry, Komae, Tokyo 201-8511 (Japan) [Central Research Institute of Electric Power Industry, Komae, Tokyo 201-8511 (Japan); Laboratory for Solid State Physics, ETH Zurich, Zurich 8093 (Switzerland); Chiba, D. [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan) [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 322-0012 (Japan); Department of Applied Physics, University of Tokyo, Tokyo 113-8656 (Japan); Shimamura, K.; Ono, T. [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)] [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Batlogg, B. [Laboratory for Solid State Physics, ETH Zurich, Zurich 8093 (Switzerland)] [Laboratory for Solid State Physics, ETH Zurich, Zurich 8093 (Switzerland)

    2014-01-06

    We have produced stable organic field-effect transistors (OFETs) with an ultra-thin HfO{sub 2} gate insulator deposited directly on top of rubrene single crystals by atomic layer deposition (ALD). We find that ALD is a gentle deposition process to grow thin films without damaging rubrene single crystals, as results these devices have a negligibly small threshold voltage and are very stable against gate-bias-stress, and the mobility exceeds 1 cm{sup 2}/V s. Moreover, the devices show very little degradation even when kept in air for more than 2 months. These results demonstrate thin HfO{sub 2} layers deposited by ALD to be well suited as high capacitance gate dielectrics in OFETs operating at small gate voltage. In addition, the dielectric layer acts as an effective passivation layer to protect the organic semiconductor.

  4. Electrical and reliability characteristics of Mn-doped nano BaTiO3-based ceramics for ultrathin multilayer ceramic capacitor application

    NASA Astrophysics Data System (ADS)

    Gong, Huiling; Wang, Xiaohui; Zhang, Shaopeng; Tian, Zhibin; Li, Longtu

    2012-12-01

    Nano BaTiO3-based dielectric ceramics were prepared by chemical coating approach, which are promising for ultrathin multilayer ceramic capacitor (MLCC) applications. The doping effects of Mn element on the microstructures and dielectric properties of the ceramics were investigated. The degradation test and impedance spectroscopy were employed to study the resistance degradation and the conduction mechanism of Mn-doped nano-BaTiO3 ceramic samples. It has been found that the reliability characteristics greatly depended on the Mn-doped content. Moreover, the BaTiO3 ceramic with grain size in nanoscale is more sensitive to the Mn-doped content than that in sub-micron scale. The addition of 0.3 mol. % Mn is beneficial for improving the reliability of the nano BaTiO3-based ceramics, which is an important parameter for MLCC applications. However, further increasing the addition amount will deteriorate the performance of the ceramic samples.

  5. An air spacer technology for improving short-channel immunity of MOSFETs with raised source\\/drain and high-? gate dielectric

    Microsoft Academic Search

    Chunshan Yin; Philip C. H. Chan; Mansun Chan

    2005-01-01

    An air-spacer technology with raised source\\/drain (S\\/D) for ultrathin-body (UTB) silicon-on-insulator MOSFETs is developed. The results show that the poly raised S\\/D can effectively reduce the series resistance and the air spacer can effectively reduce the fringing capacitance. The air spacer is particularly useful when combined with high-? gate dielectric. The improved device characteristics are demonstrated experimentally and by extensive

  6. Interfacial diffusion behavior in Ni-BaTiO 3 MLCCs with ultra-thin active layers

    NASA Astrophysics Data System (ADS)

    Gong, Huiling; Wang, Xiaohui; Tian, Zhibin; Zhang, Hui; Li, Longtu

    2014-03-01

    The interfacial structure and diffusion behavior between the dielectric layers (BaTiO3) and internal electrode layers (Ni) in X5R-type multilayer ceramic capacitors (MLCCs, from -55°C to 85°C, at a temperature capacitance coefficient within ±15%) with ultra-thin active layers ( T = 1-3 µm) have been investigated by several microstructural techniques (SEM/TEM/HRTEM) with energy-dispersive x-ray spectroscopy (EDS). In the MLCC samples with different active layer thicknesses (1-3 µm), weak interfacial diffusion was observed between BaTiO3 and Ni. It was also found that the diffusion capability of Ni into the BaTiO3 layer was stronger than that of BaTiO3 to the Ni electrode, which indicated that the diffusion of Ni was the dominant factor for the interfacial diffusion behavior in the ultra-thin layered MLCCs. The mechanism of Ni diffusion is discussed in this study as well.

  7. Achieving wide-band linear-to-circular polarization conversion using ultra-thin bi-layered metasurfaces

    NASA Astrophysics Data System (ADS)

    Li, Yongfeng; Zhang, Jieqiu; Qu, Shaobo; Wang, Jiafu; Zheng, Lin; Pang, Yongqiang; Xu, Zhuo; Zhang, Anxue

    2015-01-01

    In this paper, we propose to achieve wideband linear-to-circular (LTC) polarization conversion by ultra-thin bi-layered metasurfaces. As an example, an LTC polarization conversion metasurface operating in 11.4-14.3 GHz is designed and fabricated, which is composed of two layers of metallic pattern arrays separated by a 1.5 mm-thick dielectric spacer. When linearly polarized waves impinge on the bi-layered metasurface, LTC polarization conversion transmission is greater than 90% over a wide frequency range from 11.0 GHz to 18.3 GHz. Meanwhile, the axis ratio is lower than 3 dB in 9.8-18.3 GHz. This wide-band and highly efficient LTC polarization conversion transmission is analyzed theoretically. The measured LTC polarization conversion transmissions are well consistent with the simulated results.

  8. PREFACE: Dielectrics 2011

    NASA Astrophysics Data System (ADS)

    Vaughan, Alun; Lewin, Paul

    2011-08-01

    In 2011, the biennial meeting of the Dielectrics Group of the IOP, Dielectrics 2011, was held for the first time in a number of years at the University of Kent at Canterbury. This conference represents the most recent in a long standing series that can trace its roots back to a two-day meeting that was held in the spring of 1968 at Gregynog Hall of the University of Wales. In the intervening 43 years, this series of meetings has addressed many topics, including dielectric relaxation, high field phenomena, biomaterials and even molecular electronics, and has been held at many different venues within the UK. However, in the early 1990s, a regular venue was established at the University of Kent at Canterbury and, it this respect, this year's conference can be considered as "Dielectrics coming home". The format for the 2011 meeting followed that established at Dielectrics 2009, in breaking away from the concept of a strongly themed event that held sway during the mid 2000s. Rather, we again adopted a general, inclusive approach that was based upon four broad technical areas: Theme 1: Insulation/HV Materials Theme 2: Dielectric Spectroscopy Theme 3: Modelling Dielectric Response Theme 4: Functional Materials The result was a highly successful conference that attracted more than 60 delegates from eight countries, giving the event a truly international flavour, and which included both regular and new attendees; it was particularly pleasing to see the number of early career researchers at the meeting. Consequently, the organizing committee would like to thank our colleagues at the IOP, the invited speakers, our sponsors and all the delegates for making the event such a success. Finally, we look forward to convening again in 2013, when we will be returning to The University of Reading. Prof Alun Vaughan and Prof Paul Lewin, Editors

  9. Resilience of ultra-thin oxynitride films to percolative wear-out and reliability implications for high-? stacks at low voltage stress

    NASA Astrophysics Data System (ADS)

    Raghavan, Nagarajan; Padovani, Andrea; Li, Xiang; Wu, Xing; Lip Lo, Vui; Bosman, Michel; Larcher, Luca; Leong Pey, Kin

    2013-09-01

    Localized progressive wear-out and degradation of ultra-thin dielectrics around the oxygen vacancy percolation path formed during accelerated time dependent dielectric breakdown tests is a well-known phenomenon documented for silicon oxynitride (SiON) based gate stacks in metal oxide semiconductor field effect transistors. This progressive or post breakdown stage involves an initial phase characterized by "digital" random telegraph noise fluctuations followed by the wear-out of the percolation path, which results in an "analog" increase in the leakage current, culminating in a thermal runaway and hard breakdown. The relative contribution of the digital and analog phases of degradation at very low voltage stress in ultra-thin SiON (16 Å´) is yet to be fully investigated, which represents the core of this study. We investigate the wear-out process by combining electrical and physical analysis evidences with modeling and simulation results using Kinetic Monte Carlo defect generation and multi-phonon trap assisted tunneling (PTAT) models. We show that the transition from the digital to the analog regime is governed by a critical voltage (VCRIT), which determines the reliability margin in the post breakdown phase. Our results have a significant impact on the post-breakdown operational reliability of SiON and advanced high-?-SiOx interfacial layer gate stacks, wherein the SiOx layer seems to be the weakest link for percolation event.

  10. Non-Destructive Characterization and Metrology for Ultra-Thin High-k Dielectric Layers

    NASA Astrophysics Data System (ADS)

    Champaneria, R.; Mack, P.; White, R.; Wolstenholme, J.

    2003-09-01

    Angle-resolved X-ray photoelectron spectroscopy (ARXPS) has been used to characterize non-destructively silicon oxynitride and high-k film samples. The ARXPS data have been processed to provide accurate and precise measurements of thickness of surface and interface layers. Concentration depth profiles have been reconstructed from the ARXPS data to provide elemental and chemical state distribution information. For silicon oxynitride samples, nitrogen doses have been calculated from the concentration profiles, thereby accounting for the distribution of the nitrogen within the oxynitride layer. A comparison of ARXPS with modeled single-angle XPS experiments illustrate the potential errors in calculation of both thickness and dose using the latter technique. Sputter depth profiles are also shown to contain potentially misleading information when compared to reconstructed ARXPS depth profiles.

  11. Ultrathin, ultrasmooth gold layer on dielectrics without the use of additional metallic adhesion layers.

    PubMed

    Leandro, Lorenzo; Malureanu, Radu; Rozlosnik, Noemi; Lavrinenko, Andrei

    2015-03-18

    With advances in the plasmonics and metamaterials research field, it has become more and more important to fabricate thin and smooth Au metal films in a reliable way. Here, by thin films we mean that their average height is below 10 nm and their average roughness is below 5% of the total thickness. In this article, we investigated the use of amino- and mercaptosilanes to increase the adhesion of Au on Si wafers, thus obtaining a smooth and thin layer. This method does not include the use of other metals to improve the adhesion of gold, like Ti or Cr, since they would reduce the optical characteristics of the structure. Our results show that layers having 6 nm thickness and below 0.3 nm roughness can be reproducibly obtained using aminosilanes. Layers having a nominal thickness of 5 nm have a yield of 58%; thus, this thickness is the limit for the process that we investigated. PMID:25723253

  12. Substrate-assisted nucleation of ultra-thin dielectric layers on graphene by atomic layer deposition

    E-print Network

    Dlubak, Bruno; Kidambi, Piran R.; Weatherup, Robert S.; Hofmann, Stephan; Robertson, John

    2012-04-26

    , A. F. Young, N. Baklitskaya, N. J. Tremblay, C. Nuckolls, P. Kim, and K. L. Shepard, Nano Lett. 11, 1093 (2011). 14. X. Wang, S. M. Tabakman, and H. J. Dai, J. Am. Chem. Soc. 130, 8152 (2008). 15. T. Yamaguchi, S. Masubuchi, K. Iguchi, R. Moriya... , and T. Machida, J. Magn. Magn. Mater. 324, 849 (2011). 16. Y. Xuan, Y. Q. Wu, T. Shen, M. Qi, M. A. Capano, J. A. Cooper, and P. D. Ye, Appl. Phys. Lett. 92, 013101 (2008). 17. B. Lee, S. Y. Park, H. C. Kim, K. J. Cho, E. M. Vogel, M. J. Kim, R. M...

  13. Nanoscale Buckling of Ultrathin Low-k Dielectric Lines during Hard-Mask Patterning.

    PubMed

    Stan, Gheorghe; Ciobanu, Cristian V; Levin, Igor; Yoo, Hui J; Myers, Alan; Singh, Kanwal; Jezewski, Christopher; Miner, Barbara; King, Sean W

    2015-06-10

    Commonly known in macroscale mechanics, buckling phenomena are now also encountered in the nanoscale world as revealed in today's cutting-edge fabrication of microelectronics. The description of nanoscale buckling requires precise dimensional and elastic moduli measurements, as well as a thorough understanding of the relationships between stresses in the system and the ensuing morphologies. Here, we analyze quantitatively the buckling mechanics of organosilicate fins that are capped with hard masks in the process of lithographic formation of deep interconnects. We propose an analytical model that quantitatively describes the morphologies of the buckled fins generated by residual stresses in the hard mask. Using measurements of mechanical properties and geometric characteristics, we have verified the predictions of the analytical model for structures with various degrees of buckling, thus putting forth a framework for guiding the design of future nanoscale interconnect architectures. PMID:25950850

  14. Ultrathin, ordered oxide films on metal surfaces

    NASA Astrophysics Data System (ADS)

    Chen, M. S.; Goodman, D. W.

    2008-07-01

    Metal oxides and oxide thin films are extensively used as active catalysts and catalytic supports, as well as in many other important technical applications. Unlike TiO2, which is a semiconductor and can be investigated using a variety of surface science techniques, most metal oxides are insulators, which seriously restricts their use as model surfaces with modern surface science techniques. This difficulty can be circumvented by synthesizing ultrathin oxide films a few nanometers in thickness with well-defined structures, that mimic the corresponding bulk oxides yet are thin enough to be sufficiently conducting. In this review, preparations, structures, electronic and chemical properties of four representative oxides, alumina, magnesium oxide, silica, and titania, are addressed. Of these MgO is found to grow in a layer-by-layer fashion, allowing preparation of crystalline thin film structures with varying thicknesses. Crystalline TiO2 and Ti2O3 can also be synthesized, whereas SiO2 and Al2O3, although amenable to synthesis as well-defined monolayer structures, have only been grown to date as amorphous multilayers.

  15. Versatile ultrathin nanoporous silicon nitride membranes

    PubMed Central

    Vlassiouk, Ivan; Apel, Pavel Y.; Dmitriev, Sergey N.; Healy, Ken; Siwy, Zuzanna S.

    2009-01-01

    Single- and multiple-nanopore membranes are both highly interesting for biosensing and separation processes, as well as their ability to mimic biological membranes. The density of pores, their shape, and their surface chemistry are the key factors that determine membrane transport and separation capabilities. Here, we report silicon nitride (SiN) membranes with fully controlled porosity, pore geometry, and pore surface chemistry. An ultrathin freestanding SiN platform is described with conical or double-conical nanopores of diameters as small as several nanometers, prepared by the track-etching technique. This technique allows the membrane porosity to be tuned from one to billions of pores per square centimeter. We demonstrate the separation capabilities of these membranes by discrimination of dye and protein molecules based on their charge and size. This separation process is based on an electrostatic mechanism and operates in physiological electrolyte conditions. As we have also shown, the separation capabilities can be tuned by chemically modifying the pore walls. Compared with typical membranes with cylindrical pores, the conical and double-conical pores reported here allow for higher fluxes, a critical advantage in separation applications. In addition, the conical pore shape results in a shorter effective length, which gives advantages for single biomolecule detection applications such as nanopore-based DNA analysis. PMID:19948951

  16. Phase structures and stability in barium titanate ferroelectric ultrathin films

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Yin, Zhen; Zhang, Ming-Sheng

    2003-04-01

    Under taking into account both stress and surface effects, an extended Landau-Devonshire theory is developed to investigate the phase structures and ferroelectric stability in barium titanate ultrathin films. The phase diagrams of temperature-stress, film thickness-stress and polarization-film thickness are calculated. For the surface polarization smaller than the bulk, the paraelectric phase starts at temperature below the bulk Curie temperature under small stresses and the ferroelectric phases can be stabilized in the ultrathin films under large stresses. For the surface polarization larger than the bulk, the paraelectric phase appears at temperature above the bulk Curie temperature and the ferroelectricity can be sustained in the ultrathin films by the “superpolarized” surface layer.

  17. Engineering curvature in graphene ribbons using ultrathin polymer films.

    PubMed

    Li, Chunyu; Koslowski, Marisol; Strachan, Alejandro

    2014-12-10

    We propose a method to induce curvature in graphene nanoribbons in a controlled manner using an ultrathin thermoset polymer in a bimaterial strip setup and test it via molecular dynamics (MD) simulations. Continuum mechanics shows that curvature develops to release the residual stress caused by the chemical and thermal shrinkage of the polymer during processing and that this curvature increases with decreasing film thickness; however, significant deformation is only achieved for ultrathin polymer films. Quite surprisingly, explicit MD simulations of the curing and annealing processes show that the predicted trend not just continues down to film thicknesses of 1-2 nm but that the curvature development is enhanced significantly in such ultrathin films due to surface tension effects. This combination of effects leads to very large curvatures of over 0.14 nm(-1) that can be tuned via film thickness. This provides a new avenue to engineer curvature and, thus, electromagnetic properties of graphene. PMID:25375290

  18. Cellulose as biodegradable high-k dielectric layer in organic complementary inverters

    NASA Astrophysics Data System (ADS)

    Petritz, A.; Wolfberger, A.; Fian, A.; Irimia-Vladu, M.; Haase, A.; Gold, H.; Rothländer, T.; Griesser, T.; Stadlober, B.

    2013-10-01

    We report on the natural source based and biodegradable material cellulose on Al2O3 as ultrathin hybrid high-k dielectric layer for applications in green electronics. Dielectric films of 16 nm cellulose (? ? 8.4) and 8 nm Al2O3 (? ? 9) exhibit low leakage currents up to electric fields of 1.5 MV/cm. Pentacene and C60 based organic thin film transistors show a well-balanced performance with operation voltages around 2 V. They are implemented in complementary inverters with excellent switching behavior, a small-signal gain up to 60 and with exceptionally high and balanced noise margin values of 82% at ultralow operation voltage (VDD = 2.5 V).

  19. A dielectric affinity microbiosensor

    NASA Astrophysics Data System (ADS)

    Huang, Xian; Li, Siqi; Schultz, Jerome S.; Wang, Qian; Lin, Qiao

    2010-01-01

    We present an affinity biosensing approach that exploits changes in dielectric properties of a polymer due to its specific, reversible binding with an analyte. The approach is demonstrated using a microsensor comprising a pair of thin-film capacitive electrodes sandwiching a solution of poly(acrylamide-ran-3-acrylamidophenylboronic acid), a synthetic polymer with specific affinity to glucose. Binding with glucose induces changes in the permittivity of the polymer, which can be measured capacitively for specific glucose detection, as confirmed by experimental results at physiologically relevant concentrations. The dielectric affinity biosensing approach holds the potential for practical applications such as long-term continuous glucose monitoring.

  20. Thermally switchable dielectrics

    DOEpatents

    Dirk, Shawn M.; Johnson, Ross S.

    2013-04-30

    Precursor polymers to conjugated polymers, such as poly(phenylene vinylene), poly(poly(thiophene vinylene), poly(aniline vinylene), and poly(pyrrole vinylene), can be used as thermally switchable capacitor dielectrics that fail at a specific temperature due to the non-conjugated precursor polymer irreversibly switching from an insulator to the conjugated polymer, which serves as a bleed resistor. The precursor polymer is a good dielectric until it reaches a specific temperature determined by the stability of the leaving groups. Conjugation of the polymer backbone at high temperature effectively disables the capacitor, providing a `built-in` safety mechanism for electronic devices.

  1. Ultrathin metallic coatings can induce quantum levitation between nanosurfaces

    NASA Astrophysics Data System (ADS)

    Boström, Mathias; Ninham, Barry W.; Brevik, Iver; Persson, Clas; Parsons, Drew F.; Sernelius, Bo E.

    2012-06-01

    There is an attractive Casimir-Lifshitz force between two silica surfaces in a liquid (bromobenze or toluene). We demonstrate that adding an ultrathin (5-50 Å) metallic nanocoating to one of the surfaces results in repulsive Casimir-Lifshitz forces above a critical separation. The onset of such quantum levitation comes at decreasing separations as the film thickness decreases. Remarkably, the effect of retardation can turn attraction into repulsion. From that we explain how an ultrathin metallic coating may prevent nanoelectromechanical systems from crashing together.

  2. Method for laser welding ultra-thin metal foils

    DOEpatents

    Pernicka, John C. (Fort Collins, CO); Benson, David K. (Golden, CO); Tracy, C. Edwin (Golden, CO)

    1996-01-01

    A method for simultaneously cutting and welding ultra-thin foils having a thickness of less than 0.002 inches wherein two ultra-thin films are stacked and clamped together. A pulsed laser such as of the Neodymium: YAG type is provided and the beam of the laser is directed onto the stacked films to cut a channel through the films. The laser is moved relative to the stacked foils to cut the stacked foils at successive locations and to form a plurality of connected weld beads to form a continuous weld.

  3. Method for laser welding ultra-thin metal foils

    DOEpatents

    Pernicka, J.C.; Benson, D.K.; Tracy, C.E.

    1996-03-26

    A method for simultaneously cutting and welding ultra-thin foils having a thickness of less than 0.002 inches wherein two ultra-thin films are stacked and clamped together. A pulsed laser such as of the Neodymium: YAG type is provided and the beam of the laser is directed onto the stacked films to cut a channel through the films. The laser is moved relative to the stacked foils to cut the stacked foils at successive locations and to form a plurality of connected weld beads to form a continuous weld. 5 figs.

  4. Preparation and characterization of ultrathin free-standing carbon films

    NASA Astrophysics Data System (ADS)

    Lee, Hoikwan; Rajagopalan, Ramakrishnan

    2013-11-01

    Ultrathin free-standing carbon films with thicknesses of ˜8-14 nm were prepared by peeling from glass after pyrolization of the polyfurfuryl alcohol precursor at 700 °C. The carbon films were characterized by using optical profilometry, confocal Raman spectroscopy, transmission electron microscopy, UV-vis spectroscopy, and a two-point probe I - V station measurement. The results confirmed the formation of ultrathin free-standing carbon films with a polyaromatic domain structure. Those films had up to a 90% transmittance with respect to air and had an ohmic behavior. In this work, we also suggest that the most likely peeling mechanism of carbon films results from glass corrosion.

  5. Advanced gate dielectric materials for sub-100 nm CMOS

    Microsoft Academic Search

    H. Iwai; S. Ohmi; S. Akama; C. Ohshima; A. Kikuchi; I. Kashiwagi; J. Taguchi; H. Yamamoto; J. Tonotani; Y. Kim; I. Ueda; A. Kuriyama; Y. Yoshihara

    2002-01-01

    Properties of lanthanide oxides for gate insulators are studied with comparison to ZrO2 and HfO2. Molecular beam epitaxy (MBE) was used for the deposition of the 'amorphous' high-k films on n-type [100] Si substrates. The deposited films were annealed in N2 or O2 ambient at different temperatures and Al electrodes were deposited to fabricate MIS capacitors. Our La2O3 results showed

  6. Folded dielectric elastomer actuators

    Microsoft Academic Search

    Federico Carpi; Claudio Salaris; Danilo DeRossi

    2007-01-01

    Polymer-based linear actuators with contractile ability are currently demanded for several types of applications. Within the class of dielectric elastomer actuators, two basic configurations are available today for such a purpose: the multi-layer stack and the helical structure. The first consists of several layers of elementary planar actuators stacked in series mechanically and parallel electrically. The second configuration relies on

  7. Dielectric Properties Of Nanoferrites

    Microsoft Academic Search

    Stevan B. Jankov; Zeljka N. Cvejic; Srdjan Rakic; Vladimir Srdic

    2007-01-01

    Dielectric properties: permittivity, loss factor, tan delta and ionic conductivity of nanostructured ferrites have been measured. Samples used were nickel, zinc and yttrium doped ferrites mixed in various ratios. The synthesis has been performed using precipitation method and obtained powders were pressed in pellets under varying pressure. X-ray diffractography approach for the refinement of structure and microstructural analysis has been

  8. Molds for cable dielectrics

    DOEpatents

    Roose, L.D.

    1996-12-10

    Molds for use in making end moldings for high-voltage cables are described wherein the dielectric insulator of a cable is heated and molded to conform to a desired shape. As a consequence, high quality substantially bubble-free cable connectors suitable for mating to premanufactured fittings are made. 5 figs.

  9. Dielectric elastomer memory

    NASA Astrophysics Data System (ADS)

    O'Brien, Benjamin M.; McKay, Thomas G.; Xie, Sheng Q.; Calius, Emilio P.; Anderson, Iain A.

    2011-04-01

    Life shows us that the distribution of intelligence throughout flexible muscular networks is a highly successful solution to a wide range of challenges, for example: human hearts, octopi, or even starfish. Recreating this success in engineered systems requires soft actuator technologies with embedded sensing and intelligence. Dielectric Elastomer Actuator(s) (DEA) are promising due to their large stresses and strains, as well as quiet flexible multimodal operation. Recently dielectric elastomer devices were presented with built in sensor, driver, and logic capability enabled by a new concept called the Dielectric Elastomer Switch(es) (DES). DES use electrode piezoresistivity to control the charge on DEA and enable the distribution of intelligence throughout a DEA device. In this paper we advance the capabilities of DES further to form volatile memory elements. A set reset flip-flop with inverted reset line was developed based on DES and DEA. With a 3200V supply the flip-flop behaved appropriately and demonstrated the creation of dielectric elastomer memory capable of changing state in response to 1 second long set and reset pulses. This memory opens up applications such as oscillator, de-bounce, timing, and sequential logic circuits; all of which could be distributed throughout biomimetic actuator arrays. Future work will include miniaturisation to improve response speed, implementation into more complex circuits, and investigation of longer lasting and more sensitive switching materials.

  10. Silicon-ion-implanted PMMA with nanostructured ultrathin layers for plastic electronics

    NASA Astrophysics Data System (ADS)

    Hadjichristov, G. B.; Ivanov, Tz E.; Marinov, Y. G.

    2014-12-01

    Being of interest for plastic electronics, ion-beam produced nanostructure, namely silicon ion (Si+) implanted polymethyl-methacrylate (PMMA) with ultrathin nanostructured dielectric (NSD) top layer and nanocomposite (NC) buried layer, is examined by electric measurements. In the proposed field-effect organic nanomaterial structure produced within the PMMA network by ion implantation with low energy (50 keV) Si+ at the fluence of 3.2 × 1016 cm?2 the gate NSD is ion-nanotracks-modified low-conductive surface layer, and the channel NC consists of carbon nanoclusters. In the studied ion-modified PMMA field-effect configuration, the gate NSD and the buried NC are formed as planar layers both with a thickness of about 80 nm. The NC channel of nano-clustered amorphous carbon (that is an organic semiconductor) provides a huge increase in the electrical conduction of the material in the subsurface region, but also modulates the electric field distribution in the drift region. The field effect via the gate NSD is analyzed. The most important performance parameters, such as the charge carrier field-effect mobility and amplification of this particular type of PMMA- based transconductance device with NC n-type channel and gate NSD top layer, are determined.

  11. Gate Last Indium-Gallium-Arsenide MOSFETs with Regrown Source-Drain Regions and ALD Dielectrics

    NASA Astrophysics Data System (ADS)

    Carter, Andrew Daniel

    III-V-based MOSFETs have the potential to exceed the performance of silicon-based MOSFETs due to the semiconductor's small electron effective mass. Modern silicon-based MOSFETs with 22 nm gate lengths utilize high-k gate insulators and non-planar device geometries to optimize device performance. III-V HEMT technology has achieved similar gate lengths, but large source-drain access resistances and the lack of high-quality gate insulators prevent further device performance scaling. Sub-22 nm gate length III-V MOSFETs require metal-semiconductor contact resistivity to be less than 1 ohm-micron squared, gate insulators with less than 1 nm effective oxide thickness, and semiconductor-insulator interface trap densities less than 2E12 per square centimeter per electron volt. This dissertation presents InGaAs-based III-V MOSFET process flows and device results to assess their use in VLSI circuits. Previous III-V MOSFET results focused on long (>100 nm) gate lengths and ion implantation for source-drain region formation. Scaling III-V MOSFETs to shorter gate lengths requires source-drain regions that have low sheet resistance, high mobile charge densities, and low metal-semiconductor contact resistance. MBE- and MOCVD-based raised epitaxial source-drain regrowth meet these requirements. MBE InAs source-drain regrowth samples have shown 0.5 to 2 ohm-micron squared metal semiconductor contact resistivities. MOCVD InGaAs source-drain regrowth samples have shown < 100 ohm-micron single-sided access resistance to InGaAs MOSFETs. Gate insulators on III-V materials require large conduction band offsets to the channel, high dielectric permittivities, and low semiconductor-insulator interface trap densities. An in-situ hydrogen plasma / trimethylaluminum treatment has been developed to lower the gate semiconductor-insulator interface trap density. This treatment, done immediately before gate insulator deposition, has been shown to lower MOS capacitor interface trap densities by more than a factor of two. Devices using gate-first MBE regrowth, gate-last MBE regrowth, and gate-last MOCVD regrowth were fabricated and resulting devices characterized. 65 nm gate length gate-first MBE regrowth devices employing a 2.2 nm EOT Al 2O3 gate insulator show peak transconductances of 0.3 mS/micron at 1 V Vds. Gate-first FET performance scaling is limited by processed-induced damage and ungated access regions. 64 nm gate length gate-last MBE regrowth devices employing a 1.21 nm EOT Al2O 3 / HfO2 bi-layer gate insulator show peak transconductances of 1.4 mS/micron at 0.5 V Vds. Other gate-last MBE samples had long channel subthreshold swings as low as 117 mV/dec. 48 nm gate length gate-last MOCVD MOSFETs employing a 0.8 nm EOT HfO2 gate insulator and digital channel etching show peak transconductances of 2 mS/micron at 0.5 V Vds, with long channel devices having 97 mV/dec subthreshold swing.

  12. Dynamic response of ultrathin highly dense ZIF-8 nanofilms.

    PubMed

    Cookney, Joanna; Ogieglo, Wojciech; Hrabanek, Pavel; Vankelecom, Ivo; Fila, Vlastimil; Benes, Nieck E

    2014-10-11

    Ultrathin ZIF-8 nanofilms are prepared by facile step-by-step dip coating. A critical withdrawal speed allows for films with a very uniform minimum thickness. The high refractive index of the films denotes the absence of mesopores. The dynamic response of the films to CO2 exposure resembles behaviour observed for non-equilibrium organic polymers. PMID:25142780

  13. Growth, characterization and properties of ultrathin magnetic films and multilayers

    Microsoft Academic Search

    B. T. Jonker; J. P. Heremans; E. E. Marinero

    1989-01-01

    This book is a collection of invited and contributed papers presented at the Symposium on Growth, Characterization and Properties of Ultrathin Magnetic Films and Multilayers, held during the Spring Meeting of the Materials Research Society in San Diego, April 25-29, 1989. This symposium comprised 11 invited talks and 42 contributed papers, ran over 3 1\\/2 days, and provided a unique

  14. Performance of Ultrathin Silicon Solar Microcells with Nanostructures of Relief

    E-print Network

    Rogers, John A.

    , Urbana, Illinois 61801 ABSTRACT Recently developed classes of monocrystalline silicon solar microcells with monocrystalline silicon. Several emerging strategies exist for using this form of silicon in ways that offerPerformance of Ultrathin Silicon Solar Microcells with Nanostructures of Relief Formed by Soft

  15. Structure of Ultrathin MgO Films on Mo(001)

    SciTech Connect

    Gallagher, Marc C.; Fyfield, Margaret S.; Bumm, Lloyd A.; Cowin, James P.; Joyce , Stephen A.

    2003-11-24

    We have studied the structure of ultrathin MgO films grown on a single crystal Mo(001) surface. Scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) were used to investigate the effect of substrate temperature and oxygen partial pressure on the growth and morphology of these films.

  16. Acoustic scattering cancellation via ultrathin pseudo-surface

    Microsoft Academic Search

    Pai-Yen Chen; Mohamed Farhat; Se´bastien Guenneau; Stefan Enoch

    2011-01-01

    We propose the use of an ultrathin cloak made of an acoustic surface impedance that leads to invisibility for acoustic waves. Unlike current acoustic cloaks that require volumetric metamaterials and a significant shell thickness, the mantle cloak presented here is based on a patterned acoustic metasurface that produces similar effects in a thinner geometry. We show that by covering a

  17. Ultrathin Thermoelectric Devices for On-Chip Peltier Cooling

    Microsoft Academic Search

    Man Prakash Gupta; Min-Hee Sayer; Saibal Mukhopadhyay; Satish Kumar

    2011-01-01

    The efficient usage of thermoelectric (TE) devices for microelectronics cooling application requires investigation and remedy of various obstacles such as integration of these devices with electronic package, parasitic contact resistances, and utilization of appropriate current pulses. We develop a computational model to investigate the effect of steady state and transient mode of operation of ultrathin thermoelectric cooler (TEC) devices on

  18. A New Fabrication and Assembly Process for Ultrathin Chips

    Microsoft Academic Search

    Joachim N. Burghartz; Wolfgang Appel; Horst D. Rempp; Martin Zimmermann

    2009-01-01

    A new ultrathin chip fabrication and assembly process, consisting of a preprocess module Chipfilm and a postprocess module Pick, Crack, and Place, is presented. In contrast to the established wafer thinning technique, the preprocessed wafer substrates are prepared with extremely narrow buried cavities beneath the chip areas at a well-defined distance from the wafer surface, thus precisely defining the chip

  19. Ultrathin micropatterned porphyrin films assembled via zirconium phosphonate chemistry

    E-print Network

    Ultrathin micropatterned porphyrin films assembled via zirconium phosphonate chemistry Aaron M of a phosphonic-acid-functionalized porphyrin is presented and a procedure for the reproducible assembly of the porphyrins into thin films on glass or conductive glass surfaces is described. The assembly scheme, which

  20. ANALYSIS AND DESIGN OF AN ULTRA-THIN METAMATERIAL ABSORBER

    Microsoft Academic Search

    Ruifeng Huang; Zheng-Wen Li; Ling Bing Kong; Lie Liu; Serguei Matitsine

    2009-01-01

    This paper presents a class of ultra-thin metamaterial absorbers, which consists of periodic microstrip lines on top of a planar lossy substrate backed by a conducting metallic plate. A highly efficient full-wave analysis method was developed to solve the electromagnetic response of the absorbers. The influence of electromagnetic properties of the substrate and physical dimensions of the microstrip lines were

  1. Anisotropic effective permittivity of an ultrathin gold coating on optical fiber in air, water and saline solutions.

    PubMed

    Zhou, Wenjun; Mandia, David J; Barry, Seán T; Albert, Jacques

    2014-12-29

    The optical properties of an ultrathin discontinuous gold film in different dielectric surroundings are investigated experimentally by measuring the polarization-dependent wavelength shifts and amplitudes of the cladding mode resonances of a tilted fiber Bragg grating. The gold film was prepared by electron-beam evaporation and had an average thickness of 5.5 nm ( ± 1 nm). Scanning electron imaging was used to determine that the film is actually formed of individual particles with average lateral dimensions of 28 nm ( ± 8 nm). The complex refractive indices of the equivalent uniform film in air at a wavelength of 1570 nm were calculated from the measurements to be 4.84-i0.74 and 3.97-i0.85 for TM and TE polarizations respectively (compared to the value for bulk gold: 0.54-i10.9). Additionally, changes in the birefringence and dichroism of the films were measured as a function of the surrounding medium, in air, water and a saturated NaCl (salt) solution. These results show that the film has stronger dielectric behavior for TM light than for TE, a trend that increases with increasing surrounding index. Finally, the experimental results are compared to predictions from two widely used effective medium approximations, the generalized Maxwell-Garnett and Bruggeman theories for gold particles in a surrounding matrix. It is found that both of these methods fail to predict the observed behavior for the film considered. PMID:25607137

  2. Dielectric coated wire antennas

    NASA Technical Reports Server (NTRS)

    Richmond, J. H.; Newman, E. H.

    1976-01-01

    An electrically thin dielectric insulating shell on an antenna composed of electrically thin circular cylindrical wires is examined. A moment method solution is obtained, and the insulating shell is modeled by equivalent volume polarization currents. These polarization currents are related in a simple manner to the surface charge density on the wire antenna. In this way the insulating shell causes no new unknowns to be introduced, and the size of the impedance matrix is the same as for the uninsulated wires. The insulation is accounted for entirely through a modification of the symmetric impedance matrix. This modification influences the current distribution, impedance, efficiency, field patterns, and scattering properties. The theory is compared with measurement for dielectric coated antennas in air.

  3. Dielectric fluid motors

    SciTech Connect

    Otsubo, Y. [Center of Cooperative Research, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba-shi 263 (Japan)] [Center of Cooperative Research, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba-shi 263 (Japan); Edamura, K. [New Technology Management Co., Higashi-Shinkoiwa 2-9-1-306, Katsushika-ku, Tokyo 124 (Japan)] [New Technology Management Co., Higashi-Shinkoiwa 2-9-1-306, Katsushika-ku, Tokyo 124 (Japan)

    1997-07-01

    On the application of high electric fields to a dielectric fluid, a convective motion of the fluid is induced. By controlling the fluid motion in nonuniform dc fields, a new type of fluid motor is developed. An angular velocity of more than 15s{sup {minus}1} (150 rpm) can be achieved at a dc voltage of 5 kV for a motor with a rotor radius of 10 mm. The efficiency of energy transformation from electric to kinetic energy is about 4{percent}. Since magnetic fields and switching circuits are not required, the advantage of the fluid motor will be enhanced by size reduction. The dielectric fluid motor is attractive as a source of mechanical energy in a micromachine. {copyright} {ital 1997 American Institute of Physics.}

  4. Ultra-Thin Coatings Beautify Art

    NASA Technical Reports Server (NTRS)

    2013-01-01

    The craftsmen in the Roman Empire who constructed the Lycurgus Cup 17 centuries ago probably didn't think their artifact would survive for nearly 2,000 years as a prized possession. And they certainly couldn't have known that the technology they used to make it would eventually become an important part of space exploration. Carved from one solid mass, the cup is one of the few complete glass objects from that period, and the only one made from dichroic glass. Meaning "two-colored" in Greek, dichroic glass was originally created by adding trace amounts of gold and silver to a large volume of glass melt. The resulting medium partially reflects the light passing through it, causing an observer to see different colors depending on the direction of the light source. The Lycurgus Cup, for example, is famous for appearing green in daylight and red when lit at night, symbolic of the ripening grapes used to fill it with wine. NASA revitalized the production of dichroic glass in the 1950s and 1960s as a means of protecting its astronauts. Ordinary clear substances cannot protect human vision from the harsh rays of unfiltered sunlight, and everything from the human body to spacecraft sensors and computers are at risk if left unprotected from the radiation that permeates space. The microscopic amounts of metal present in dichroic glass make it an effective barrier against such harmful radiation. While the ancient manufacturing technique called for adding metals to glass melt, NASA developed a process in which metals are vaporized by electron beams in a vacuum chamber and then applied directly to surfaces in an ultra-thin film. The vapor condenses in the form of crystal structures, and the process is repeated for up to several dozen coatings. The resulting material, still only about 30 millionths of an inch thick, is sufficient to reflect radiation even while the glass, or polycarbonate, as in the case of space suit helmets, remains transparent to the human eye.

  5. Morphology and structure of polymers in ultrathin films and constrained geometries

    NASA Astrophysics Data System (ADS)

    Gullerud, Steven Olaf

    We have explored the organization of polycaprolactone (PCL) constrained in ultrathin films and nanometer-scale domains. Specifically, PCL functionalized with triethoxysilane functional groups was used to create tethered ultrathin films on silicon (100) substrates through silanization, and a sol-gel reaction was used to produce PCL/silsesquioxane composites with nanoscale phase-separated domains. In the first case, analysis by AFM and ellipsometry showed the existence of an amorphous sublayer up to 4 nm thick. Above this, physisorbed PCL formed heterogeneous surface features, up to 7 nm thick, with the morphology dependent on the polymer solution concentration during the deposition process. Low PCL solution concentration produced amorphous globular domains, while higher polymer concentrations allowed the growth of dendritic crystalline features. We report the results of in situ thermal analysis of grafted PCL by AFM, which show the melting of the surface structures at the film surface as well as growth of new dendritic structures upon recrystallization. High tapping forces applied by the AFM tip revealed the presence of crystalline lamellae buried below an amorphous layer in the dendritic structures, as well as in the PCL sublayer when the film was cooled below room temperature. PCL phase separation behavior and morphology in sol-gel organic/inorganic nanocomposites with methylsilsesquioxane (MSSQ) or phenylsilsesquioxane (PSSQ) was probed using TEM, FTIR, and fluorescence spectroscopy of dansyl and pyrene-labeled PCL. Star-like and linear PCL were used to study the effects of molecular weight, endgroup functionality, and polymer geometry on the phase separation behavior in these materials. PCL crystallinity, as detected through FTIR, served to detect the presence of macroscopic phase separation, as well as the critical PCL loading amount at which this occurs, for a given PCL/SSQ system. Fluorescence spectroscopy of dansyl-labeled PCL detected the presence of an immobilized interfacial layer for PCL domains in MSSQ composites. While most PCL molecules proved to be highly compatible with PSSQ, linear PCL/MSSQ composites exhibited nanoscale phase separation only with low polymer content and low molecular weight. By contrast, star-like PCL/MSSQ nanocomposites possessed nanoscale domains with significant polymer loading, and hold the most promise for potential applications in the area of low-k dielectric insulators.

  6. Slow DNA transport through nanopores in hafnium oxide membranes.

    PubMed

    Larkin, Joseph; Henley, Robert; Bell, David C; Cohen-Karni, Tzahi; Rosenstein, Jacob K; Wanunu, Meni

    2013-11-26

    We present a study of double- and single-stranded DNA transport through nanopores fabricated in ultrathin (2-7 nm thick) freestanding hafnium oxide (HfO2) membranes. The high chemical stability of ultrathin HfO2 enables long-lived experiments with <2 nm diameter pores that last several hours, in which we observe >50 000 DNA translocations with no detectable pore expansion. Mean DNA velocities are slower than velocities through comparable silicon nitride pores, providing evidence that HfO2 nanopores have favorable physicochemical interactions with nucleic acids that can be leveraged to slow down DNA in a nanopore. PMID:24083444

  7. Organic ultrathin film adhesion on compliant substrate using scratch test technique

    E-print Network

    Paris-Sud XI, Université de

    Organic ultrathin film adhesion on compliant substrate using scratch test technique X. Boddaerta Thin Film Transistor (OTFT) on compliant substrate. Since these devices are flexible, they will undergo

  8. Seeding Atomic Layer Deposition of High-k Dielectrics on Epitaxial Graphene with Organic Self-assembled Monolayers

    SciTech Connect

    Alaboson, Justice M. P.; Wang, Qing Hua; Emery, J.D.; Lipson, Albert L; Bedzyk, M.J.; Elam, Jeffrey W.; Pellin, Michael J.; Hersam, Mark C.

    2011-06-28

    The development of high-performance graphene-based nanoelectronics requires the integration of ultrathin and pinhole-free high-k dielectric films with graphene at the wafer scale. Here, we demonstrate that self-assembled monolayers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) act as effective organic seeding layers for atomic layer deposition (ALD) of HfO? and Al?O? on epitaxial graphene on SiC(0001). The PTCDA is deposited via sublimation in ultrahigh vacuum and shown to be highly ordered with low defect density by molecular-resolution scanning tunneling microscopy. Whereas identical ALD conditions lead to incomplete and rough dielectric deposition on bare graphene, the chemical functionality provided by the PTCDA seeding layer yields highly uniform and conformal films. The morphology and chemistry of the dielectric films are characterized by atomic force microscopy, ellipsometry, cross-sectional scanning electron microscopy, and X-ray photoelectron spectroscopy, while high-resolution X-ray reflectivity measurements indicate that the underlying graphene remains intact following ALD. Using the PTCDA seeding layer, metal-oxide-graphene capacitors fabricated with a 3 nm Al?O? and 10 nm HfO? dielectric stack show high capacitance values of ?700 nF/cm² and low leakage currents of ?5 × 10{sup –9} A/cm² at 1 V applied bias. These results demonstrate the viability of sublimated organic self-assembled monolayers as seeding layers for high-k dielectric films in graphene-based nanoelectronics.

  9. Langevin simulations of a model for ultrathin magnetic films

    E-print Network

    Lucas Nicolao; Daniel A. Stariolo

    2007-08-31

    We show results from simulations of the Langevin dynamics of a two-dimensional scalar model with competing interactions for ultrathin magnetic films. We find a phase transition from a high temperature disordered phase to a low temperature phase with both positional and orientational orders. Both kinds of order emerge at the same temperature, probably due to the isotropy of the model Hamiltonian. In the low temperature phase orientational correlations show long range order while positional correlations show only quasi-long-range order in a wide temperature range. The orientational correlation length and the associated susceptibility seem to diverge with power laws at the transition. While at zero temperature the system exhibits stripe long range order, as temperature grows we observe the proliferation of different kinds of topological defects that ultimately drive the system to the disordered phase. The magnetic structures observed are similar to experimental results on ultrathin ferromagnetic films.

  10. Ultrathin and lightweight organic solar cells with high flexibility

    PubMed Central

    Kaltenbrunner, Martin; White, Matthew S.; G?owacki, Eric D.; Sekitani, Tsuyoshi; Someya, Takao; Sariciftci, Niyazi Serdar; Bauer, Siegfried

    2012-01-01

    Application-specific requirements for future lighting, displays and photovoltaics will include large-area, low-weight and mechanical resilience for dual-purpose uses such as electronic skin, textiles and surface conforming foils. Here we demonstrate polymer-based photovoltaic devices on plastic foil substrates less than 2??m thick, with equal power conversion efficiency to their glass-based counterparts. They can reversibly withstand extreme mechanical deformation and have unprecedented solar cell-specific weight. Instead of a single bend, we form a random network of folds within the device area. The processing methods are standard, so the same weight and flexibility should be achievable in light emitting diodes, capacitors and transistors to fully realize ultrathin organic electronics. These ultrathin organic solar cells are over ten times thinner, lighter and more flexible than any other solar cell of any technology to date. PMID:22473014

  11. Ultrathin and lightweight organic solar cells with high flexibility.

    PubMed

    Kaltenbrunner, Martin; White, Matthew S; G?owacki, Eric D; Sekitani, Tsuyoshi; Someya, Takao; Sariciftci, Niyazi Serdar; Bauer, Siegfried

    2012-01-01

    Application-specific requirements for future lighting, displays and photovoltaics will include large-area, low-weight and mechanical resilience for dual-purpose uses such as electronic skin, textiles and surface conforming foils. Here we demonstrate polymer-based photovoltaic devices on plastic foil substrates less than 2 ?m thick, with equal power conversion efficiency to their glass-based counterparts. They can reversibly withstand extreme mechanical deformation and have unprecedented solar cell-specific weight. Instead of a single bend, we form a random network of folds within the device area. The processing methods are standard, so the same weight and flexibility should be achievable in light emitting diodes, capacitors and transistors to fully realize ultrathin organic electronics. These ultrathin organic solar cells are over ten times thinner, lighter and more flexible than any other solar cell of any technology to date. PMID:22473014

  12. Magnetoelectric transport and quantum interference effect in ultrathin manganite films

    SciTech Connect

    Wang, Cong; Jin, Kui-juan, E-mail: kjjin@iphy.ac.cn; Gu, Lin; Lu, Hui-bin; Li, Shan-ming; Zhou, Wen-jia; Zhao, Rui-qiang; Guo, Hai-zhong; He, Meng; Yang, Guo-zhen [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-04-21

    The magnetoelectric transport behavior with respect to the thicknesses of ultrathin La{sub 0.9}Sr{sub 0.1}MnO{sub 3} films is investigated in detail. The metal-insulator phase transition, which has never been observed in bulk La{sub 0.9}Sr{sub 0.1}MnO{sub 3}, is found in ultrathin films with thicknesses larger than 6 unit cells. Low-temperature resistivity minima appeared in films with thicknesses less than 10 unit cells. This is attributed to the presence of quantum interference effects. These data suggest that the influence of the weak localization becomes much pronounced as the film thickness decreases from 16 to 8 unit cells.

  13. Magnetic excitations in ultrathin magnetic films: Temperature effects

    NASA Astrophysics Data System (ADS)

    Zakeri, Kh.; Prokop, J.; Zhang, Y.; Kirschner, J.

    2014-12-01

    The idea of investigating large wave-vector magnetic excitations in ultrathin films by spin-polarized electron spectroscopy is briefly reviewed. The historical background of the paper is based on the personal experience of the authors who collaborated and discussed with Douglas Mills regarding this subject. Douglas Mills' impact on the understanding of fundamental mechanisms involved in the excitation process and the development of the theory of magnetic excitations is outlined. In addition, the temperature effects on the large wave-vector magnetic excitations in ultrathin Fe films are addressed. The experimental results of magnon excitations in the pseudomorphic Fe monolayer on W(110) are presented. The temperature dependence of the magnon dispersion relation is discussed.

  14. Tunable ultrathin mantle cloak via varactor-diode-loaded metasurface.

    PubMed

    Liu, Shuo; Xu, He-Xiu; Zhang, Hao Chi; Cui, Tie Jun

    2014-06-01

    We propose a tunable strategy for the ultrathin mantle cloak via metasurface. The tunable cloak is implemented by loading varactor diodes between two neighboring horizontal metallic strips which constitute the metasurface. We demonstrate that the varactor diodes enable the capacitive reactance of the metasurface to be tunable from -157 ? to -3 ? when the DC bias voltage is properly changed. The active metasurface is then explored to cloak conformally a conducting cylinder. Both numerical and experiment results show that the cloaking frequency can be continuously controlled from 2.3 GHz to 3.7 GHz by appropriately adjusting the bias voltage. The flexible tunability and good cloaking performance are further examined by the measured field distributions. The advanced features of tunability, low profile, and conformal ability of the ultrathin cloak pave the way for practical applications of cloaking devices. PMID:24921534

  15. Thermoelectric properties of an ultra-thin topological insulator.

    PubMed

    Islam, S K Firoz; Ghosh, T K

    2014-04-23

    Thermoelectric coefficients of an ultra-thin topological insulator are presented here. The hybridization between top and bottom surface states of a topological insulator plays a significant role. In the absence of a magnetic field, the thermopower increases and thermal conductivity decreases with an increase in the hybridization energy. In the presence of a magnetic field perpendicular to the ultra-thin topological insulator, thermoelectric coefficients exhibit quantum oscillations with inverse magnetic field, whose frequency is strongly modified by the Zeeman energy and whose phase factor is governed by the product of the Landé g-factor and the hybridization energy. In addition to the numerical results, the low-temperature approximate analytical results for the thermoelectric coefficients are also provided. It is also observed that for a given magnetic field these transport coefficients oscillate with hybridization energy, at a frequency that depends on the Landé g-factor. PMID:24694878

  16. Evolution of the electronic structure in ultrathin Bi(111) films

    NASA Astrophysics Data System (ADS)

    Miao, Lin; Yao, Meng-Yu; Ming, Wenmei; Zhu, Fengfeng; Han, C. Q.; Wang, Z. F.; Guan, D. D.; Gao, C. L.; Liu, Canhua; Liu, Feng; Qian, Dong; Jia, Jin-Feng

    2015-05-01

    By combining angle-resolved photoemission spectroscopy and first-principles calculations, we systematically studied the electronic structures of ultrathin Bi(111) films (?5 bilayers) epitaxially grown on Bi2Te3. High-resolution low-energy band dispersions and Fermi surfaces of ultrathin Bi (111 )/Bi2Te3 films as a function of thickness were experimentally determined. Our results also indicate that the electronic structures of epitaxial Bi films are strongly influenced by the substrate compared with freestanding films. The substrate effects mainly include two aspects. First, the in-plane lattice constant of Bi(111) films is compressed, which increases the bandwidth of the surface-state-like bands. Furthermore, the band dispersion near the ? ¯ point is significantly modified as well. Second, there exists a strong hybridization at the Bi /Bi2Te3 interface, and the hybridization effects spatially extend to three Bi bilayers.

  17. Ultrathin septuple layered PbBi2Se4 nanosheets.

    PubMed

    Chatterjee, Arindom; Guin, Satya N; Biswas, Kanishka

    2014-07-28

    Layered lead bismuth selenide, PbBi2Se4, an intergrowth compound of PbSe (rocksalt) and Bi2Se3 (hexagonal), is a topological insulator in the bulk phase. We present a simple solution based synthesis of two dimensional (2D) few seven atomic (septuple) layered PbBi2Se4 nanosheets (4-7 nm thick) for the first time. The excellent electrical transport in ultrathin PbBi2Se4 is attributed to the presence of dominant surface states that offer high electrical mobility (?153 cm(2) V(-1) s(-1)) and scattering resistant carriers. Ultrathin 3-5 SLs PbBi2Se4 shows an n-type semiconducting behaviour with a band gap of ?0.6 eV, which is confirmed by optical spectroscopy and thermopower measurements. PMID:24916418

  18. Ultrathin GaAs space solar cell devices

    Microsoft Academic Search

    C. Hardingham; C. R. Huggins; J. W. Simpson; T. A. Cross

    1996-01-01

    This paper reports the continued development of ultrathin (6 ?m) GaAs solar cells (UTCs) for application in space. Previously, the authors reported the development of 20×20 mm GaAs UTCs, made by the etchback or sacrificial substrate technique, with efficiencies up to 19.7% (1 sun AM0 aperture area). Further, they have reported the use of direct, adhesive-free coverglass bonding to enhance

  19. Corrosion of Ultrathin Iron Layers and Titanium Nitride Coated Iron

    Microsoft Academic Search

    J. F. Marco; M. Gracia; J. R. Gancedo; A. Agudelo; W. Exel; W. Meisel; D. Hanzel

    2001-01-01

    In this paper results are presented on the corrosion resistance against SO2-polluted atmospheres of ultrathin Fe layers (2\\/Si wafers by two methods: vacuum evaporation and Langmuir–Blodgett (LB) technique. It is shown that the corrosion resistance\\u000a of the evaporated films is similar to that shown by massive iron while the corrosion resistance of the LB films is remarkably\\u000a higher. We also

  20. Square wells, quantum wells and ultra-thin metallic films

    E-print Network

    Victor Barsan

    2013-07-09

    The eigenvalue equations for the energy of bound states of a particle in a square well are solved, and the exact solutions are obtained, as power series. Accurate analytical approximate solutions are also given. The application of these results in the physics of quantum wells are discussed,especially for ultra-thin metallic films, but also in the case of resonant cavities, heterojunction lasers, revivals and super-revivals.

  1. Confined carrier quantum states in ultrathin semiconductor heterostructures

    Microsoft Academic Search

    Raymond Dingle

    1975-01-01

    New effects associated with the quantization of confined carrier motion in ultrathin semiconductor heterostructures have recently\\u000a been observed. Optical and electrical studies of molecular-beam grown AlxGa1?xAs-GaAs structures consisting of to 100 layers with layers as thin as 10 Å have revealed discrete structures which are difficelt\\u000a to analyze with usual bulk crystal methods. A complete understanding can be achieved with

  2. Ultra-thin bifacial CdTe solar cell

    Microsoft Academic Search

    S. Marsillac; V. Y. Parikh; A. D. Compaan

    2007-01-01

    Developing a high-quality transparent back contact, while maintaining efficient light transmission through the top absorber layer, are key components for achieving high-efficiency II–VI polycrystalline thin-film tandem solar cells. Combining these two elements, we fabricated ultra-thin bifacial CdTe solar cells (0.68?m) with ZnTe:N\\/ITO transparent back contact and achieved efficiencies of 5.7% and 5.0% with illumination from the glass and the contact

  3. Processing and characterization of Ultrathin carbon coatings on glass

    Microsoft Academic Search

    Hoikwan Lee; Ramakrishnan Rajagopalan; Joshua Robinson; Carlo G. Pantano

    2009-01-01

    Ultrathin carbon layers, on the order of 3-6 nm in thickness, were formed on glass substrates by spin coating and pyrolysis of polymer precursors. The organic precursors used were poly(furfuryl alcohol), coal tar pitch, and a photoresist. The carbon coatings were characterized by ellipsometry, optical profilometry, water contact angle, confocal Raman spectroscopy, UV-vis spectroscopy, and atomic force microscopy. We also

  4. Automated microwave dielectric constant measurement

    Microsoft Academic Search

    Brian C. Glancy; Albert Krall

    1987-01-01

    The tedious and often difficult measurement of dielectric constants as a function of microwave frequency has been simplified using an automated testing apparatus. This automated procedure is based on the use of a slotted line to take measurements. It also includes the automatic application of a numeric solution to a transcendental equation to determine the dielectric constant. The computer program

  5. Degradation Of Reflectors And Dielectrics

    NASA Technical Reports Server (NTRS)

    Bouquet, Frank L.; Cuddihy, Edward F.; Maag, Carl R., Jr.

    1987-01-01

    Report describes important degrading effects of atmosphere and outer-space environments on reflective surfaces and dielectrics. For reflective surfaces, terrestrial effects include soiling on glass surfaces and changing with time. Space effects include ultraviolet enhancement of contamination and possible surface erosion due to solar radiation, impact of debris, and interactions with atomic oxygen. Dielectrics similarly affected in both environments.

  6. Dielectric Breakdown of Polymer Films

    Microsoft Academic Search

    J. Blok; D. G. Legrand

    1969-01-01

    Strong electric fields have been applied to dielectric polymer films to study field-induced mechanical stresses. For voltages near breakdown the mechanical forces are sufficient to cause localized deformation in some polymer films. Considerable field enhancement can occur at the deformation sites, leading to reduced nominal dielectric strength for the samples. Experimental evidence for electromechanical deformation is presented as a possible

  7. Extremely low distortion dielectric ceramics

    Microsoft Academic Search

    Youhei Ishikawa; Hiroshi Tamura; Toshio Nishikawa; Kikuo Wakino

    1992-01-01

    High Q and linear dielectric resonator materials are required in high power circuits of multi channel transmitters. Distortion (due to nonlinear dielectric constant of resonators) of less than – 150 dBc is required to prevent cross talk between transmitter and receiver channels. A new measurement method and a test fixture design to measure very weak 3rd harmonic distortion are proposed.

  8. GaAs metal-oxide-semiconductor based non-volatile flash memory devices with InAs quantum dots as charge storage nodes

    NASA Astrophysics Data System (ADS)

    Islam, Sk Masiul; Chowdhury, Sisir; Sarkar, Krishnendu; Nagabhushan, B.; Banerji, P.; Chakraborty, S.; Mukherjee, Rabibrata

    2015-06-01

    Ultra-thin InP passivated GaAs metal-oxide-semiconductor based non-volatile flash memory devices were fabricated using InAs quantum dots (QDs) as charge storing elements by metal organic chemical vapor deposition technique to study the efficacy of the QDs as charge storage elements. The grown QDs were embedded between two high-k dielectric such as HfO2 and ZrO2, which were used for tunneling and control oxide layers, respectively. The size and density of the QDs were found to be 5 nm and 1.8×1011 cm-2, respectively. The device with a structure Metal/ZrO2/InAs QDs/HfO2/GaAs/Metal shows maximum memory window equivalent to 6.87 V. The device also exhibits low leakage current density of the order of 10-6 A/cm2 and reasonably good charge retention characteristics. The low value of leakage current in the fabricated memory device is attributed to the Coulomb blockade effect influenced by quantum confinement as well as reduction of interface trap states by ultra-thin InP passivation on GaAs prior to HfO2 deposition.

  9. Room Temperature Ferroelectricity in Ultrathin SnTe Films

    NASA Astrophysics Data System (ADS)

    Chang, Kai; Liu, Junwei; Lin, Haicheng; Zhao, Kun; Zhong, Yong; Ji, Shuai-Hua; He, Ke; Wang, Lili; Ma, Xucun; Fu, Liang; Chen, Xi; Xue, Qi-Kun

    2015-03-01

    The ultrathin SnTe films with several unit cell thickness grown on graphitized SiC(0001) surface have been studied by the scanning tunneling microscopy and spectroscopy (STM/S). The domain structures, local lattice distortion and the electronic band bending at film edges induced by the in-plane spontaneous polarization along < 110 > have been revealed at atomic scale. The experiments at variant temperature show that the Curie temperature Tc of the one unit cell thick (two atomic layers) SnTe film is as high as 280K, much higher than that of the bulk counterpart (~100K) and the 2-4 unit cell thick films even indicate robust ferroelectricity at room temperature. This Tc enhancement is attributed to the stress-free interface, larger electronic band gap and greatly reduced Sn vacancy concentration in the ultrathin films. The lateral domain size varies from several tens to several hundreds of nanometers, and the spontaneous polarization direction could be modified by STM tip. Those properties of ultrathin SnTe films show the potential application on ferroelectric devices. The work was financially supported by Ministry of Science and Technology of China, National Science Foundation and Ministry of Education of China.

  10. Magnetism and surface structure of atomically controlled ultrathin metal films.

    SciTech Connect

    Shiratsuchi, Yu.; Yamamoto, M.; Bader, S. D.; Materials Science Division; Osaka Univ.

    2007-01-01

    We review the correlation of magnetism and surface structure in ultrathin metal films, including the tailoring of novel magnetic properties using atomic scale control of the nanostructure. We provide an overview of modern fabrication and characterization techniques used to create and explore these fascinating materials, and highlight important phenomena of interest. We also discuss techniques that control and characterize both the magnetic and structural properties on an atomic scale. Recent advances in the development and applications of these techniques allow nanomagnetism to be investigated in an unprecedented manner. A system cannot necessarily retain a two-dimensional structure as it enters the ultrathin region, but it can transform into a three-dimensional, discontinuous structure due to the Volmer-Weber growth mechanism. This structural transformation can give rise to superparamagnetism. During this evolution, competing factors such as interparticle interactions and the effective magnetic anisotropy govern the magnetic state. These magnetic parameters are influenced by the nanostructure of the film. In particular, controlling the magnetic anisotropy is critical for determining the magnetic properties. Surface effects play especially important roles in influencing both the magnitude and direction of the magnetic anisotropy in ultrathin films. By properly altering the surface structure, the strength and direction of the magnetic anisotropy are controlled via spin-orbit and/or dipole interactions.

  11. Electric field effect in ultrathin zigzag graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Zhang, Wen-Xing; Liu, Yun-Xiao; Tian, Hua; Xu, Jun-Wei; Feng, Lin

    2015-07-01

    The electric field effect in ultrathin zigzag graphene nanoribbons containing only three or four zigzag carbon chains is studied by first-principles calculations, and the change of conducting mechanism is observed with increasing in-plane electric field perpendicular to the ribbon. Wider zigzag graphene nanoribbons have been predicted to be spin-splitted for both valence band maximum (VBM) and conduction band minimum (CBM) with an applied electric field and become half-metal due to the vanishing band gap of one spin with increasing applied field. The change of VBM for the ultrathin zigzag graphene nanoribbons is similar to that for the wider ones when an electric field is applied. However, in the ultrathin zigzag graphene nanoribbons, there are two kinds of CBMs, one is spin-degenerate and the other is spin-splitted, and both are tunable by the electric field. Moreover, the two CBMs are spatially separated in momentum space. The conducting mechanism changes from spin-degenerate CBM to spin-splitted CBM with increasing applied electric field. Our results are confirmed by density functional calculations with both LDA and GGA functionals, in which the LDA always underestimates the band gap while the GGA normally produces a bigger band gap than the LDA. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204201 and 11147142) and the Natural Science Foundation for Young Scientists of Shanxi Province, China (Grant No. 2013021010-1).

  12. Low dielectric polyimide fibers

    NASA Technical Reports Server (NTRS)

    Dorogy, William E., Jr. (inventor); St.clair, Anne K. (inventor)

    1994-01-01

    A high temperature resistant polyimide fiber that has a dielectric constant of less than 3 is presented. The fiber was prepared by first reacting 2,2-bis (4-(4aminophenoxy)phenyl) hexafluoropropane with 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride in an aprotic solvent to form a polyamic acid resin solution. The polyamic acid resin solution is then extruded into a coagulation medium to form polyamic acid fibers. The fibers are thermally cured to their polyimide form. Alternatively, 2,2-bis(4-(4-aminophenoxy)phenyl) hexafluoropropane is reacted with 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride to form a polyamic acid, and the polyamic acid is chemically converted to its polyimide form. The polyimide is then dissolved in a solvent to form a polyimide resin solution, and the polyimide resin is extruded into a coagulation medium to form a polyimide wet gel filament. In order to obtain polyimide fibers of increased tensile properties, the polyimide wet gel filaments are stretched at elevated temperatures. The tensile properties of the fibers were measured and found to be in the range of standard textile fibers. Polyimide fibers obtained by either method will have a dielectric constant similar to that of the corresponding polymer, viz., less than 3 at 10 GHz.

  13. Dielectric laser accelerators

    NASA Astrophysics Data System (ADS)

    England, R. Joel; Noble, Robert J.; Bane, Karl; Dowell, David H.; Ng, Cho-Kuen; Spencer, James E.; Tantawi, Sami; Wu, Ziran; Byer, Robert L.; Peralta, Edgar; Soong, Ken; Chang, Chia-Ming; Montazeri, Behnam; Wolf, Stephen J.; Cowan, Benjamin; Dawson, Jay; Gai, Wei; Hommelhoff, Peter; Huang, Yen-Chieh; Jing, Chunguang; McGuinness, Christopher; Palmer, Robert B.; Naranjo, Brian; Rosenzweig, James; Travish, Gil; Mizrahi, Amit; Schachter, Levi; Sears, Christopher; Werner, Gregory R.; Yoder, Rodney B.

    2014-10-01

    The use of infrared lasers to power optical-scale lithographically fabricated particle accelerators is a developing area of research that has garnered increasing interest in recent years. The physics and technology of this approach is reviewed, which is referred to as dielectric laser acceleration (DLA). In the DLA scheme operating at typical laser pulse lengths of 0.1 to 1 ps, the laser damage fluences for robust dielectric materials correspond to peak surface electric fields in the GV /m regime. The corresponding accelerating field enhancement represents a potential reduction in active length of the accelerator between 1 and 2 orders of magnitude. Power sources for DLA-based accelerators (lasers) are less costly than microwave sources (klystrons) for equivalent average power levels due to wider availability and private sector investment. Because of the high laser-to-particle coupling efficiency, required pulse energies are consistent with tabletop microJoule class lasers. Combined with the very high (MHz) repetition rates these lasers can provide, the DLA approach appears promising for a variety of applications, including future high-energy physics colliders, compact light sources, and portable medical scanners and radiative therapy machines.

  14. Mode Evolution and Transmission Suppression in a Perforated Ultrathin Metallic Film with a Triangular Array of Holes

    E-print Network

    Mode Evolution and Transmission Suppression in a Perforated Ultrathin Metallic Film in a perforated ultrathin metallic film (PUMF) with a periodic triangular array of holes. It is found for the future studies in PUMF-based structures and devices. Keywords Surface plasmon . Perforated ultrathin

  15. Modeling and characterization of direct tunneling hole current through ultrathin gate oxide in p-metal{endash}oxide{endash}semiconductor field-effect transistors

    SciTech Connect

    Hou, Y. T.; Li, M. F.; Lai, W. H.; Jin, Y.

    2001-06-18

    We report the calculation of hole direct tunneling (DT) current from the inversion layer in a p-metal{endash}oxide{endash}semiconductor field-effect transistor based on a solid physical background. Our results are in good agreement with those obtained from carrier separation measurements over a wide range of oxide thicknesses in the ultrathin regime. The effect of valence band mixing on hole quantization in an inversion layer in a Si substrate is properly accounted for by an improved one-band effective mass approximation. A modified Wentzel{endash}Kramers{endash}Brillouin approximation to calculate the hole transmission probability is used by adopting a more accurate dispersion equation in the oxide gap. Our method is general, simple, and computationally efficient. It may even be used to calculate the hole DT current in other gate dielectric materials. {copyright} 2001 American Institute of Physics.

  16. Design and fabrication of photonic crystals in epitaxial free silicon for ultrathin solar cells

    E-print Network

    Paris-Sud XI, Université de

    Design and fabrication of photonic crystals in epitaxial free silicon for ultrathin solar cells photovoltaic solar cell. Optical simulations performed on a complete solar cell revealed that patterning to obtain ultrathin patterned solar cells. Keywords: Photonic crystals; Epitaxial crystalline silicon; Thin

  17. Physical Review B 66, 024419 (2002) Anisotropy of ultrathin ferromagnetic films and the spin reorientation transition

    E-print Network

    Usadel, K. D.

    2002-01-01

    Physical Review B 66, 024419 (2002) Anisotropy of ultrathin ferromagnetic films and the spin relative to the film. These coefficients are then studied experimentally (for a review see Ref. 6 on the direction of the magne- tization of ultrathin ferromagnetic films in the ground-state is studied. The ground

  18. Ultrathin, ultrasmooth, and low-loss silver films via wetting and annealing K. P. Chen,1

    E-print Network

    Shalaev, Vladimir M.

    deposited sequentially on the initial substrates without breaking the chamber vacuum. First, a 10 nm SiO2 demonstrated that a thermal annealing treatment can reduce the optical losses in ultrathin, ultrasmooth, silver thermal annealing treatment to reduce the ultrathin SF losses significantly by enlarging the internal

  19. Ultrathin Topological Insulator Bi2Se3 Nanoribbons Exfoliated by Atomic Force

    E-print Network

    Cui, Yi

    Ultrathin Topological Insulator Bi2Se3 Nanoribbons Exfoliated by Atomic Force Microscopy Seung Sae, Stanford University, Stanford, California 94305 ABSTRACT Ultrathin topological insulator nanostructures), the layered bismuth selenide (Bi2Se3), a single Dirac-cone topological insulator with a large bulk gap, can

  20. TiO2 nanotubes with ultrathin walls for enhanced water splitting.

    PubMed

    Mohamed, Ahmad M; Aljaber, Amina S; AlQaradawi, Siham Y; Allam, Nageh K

    2015-07-23

    We demonstrate, for the first time, the synthesis of titania nanotubes with ultrathin (3-5 nm) wall thickness. As revealed by the incident photon-to-current collection efficiency (IPCE) and electrochemical impedance spectroscopy measurements, the ultrathin walls, less than the charge carrier diffusion length, were essential to ensure fast and efficient charge carrier collection. PMID:26158790

  1. Profiling nitrogen in ultrathin silicon oxynitrides with angle-resolved x-ray photoelectron spectroscopy

    E-print Network

    Gustafsson, Torgny

    Profiling nitrogen in ultrathin silicon oxynitrides with angle-resolved x-ray photoelectron­XPS is utilized in this work to accurately and nondestructively determine the nitrogen concentration and profile of nitrogen is incorporated in the ultrathin ( 4 nm oxide films. Additional nitrogen can be incorporated

  2. Ballistic transport in ultrathin films and channels with random rough walls

    E-print Network

    Meyerovich, Alex

    Ballistic transport in ultrathin films and channels with random rough walls A.E.Meyerovich y and S: Ballistic transport in ultrathin films and channels with random rough walls December 4, 1996 y To whom.Mathews Ave., Urbana, IL 61801, USA #12; 2 1. Introduction Repeated collisions of ballistic particles

  3. Reliability of ultra-thin insulation coatings for long-term electrophysiological recordings

    NASA Astrophysics Data System (ADS)

    Hooker, S. A.

    2006-03-01

    Improved measurement of neural signals is needed for research into Alzheimer's, Parkinson's, epilepsy, strokes, and spinal cord injuries. At the heart of such instruments are microelectrodes that measure electrical signals in the body. Such electrodes must be small, stable, biocompatible, and robust. However, it is also important that they be easily implanted without causing substantial damage to surrounding tissue. Tissue damage can lead to the generation of immune responses that can interfere with the electrical measurement, preventing long-term recording. Recent advances in microfabrication and nanotechnology afford the opportunity to dramatically reduce the physical dimensions of recording electrodes, thereby minimizing insertion damage. However, one potential cause for concern is the reliability of the insulating coatings, applied to these ultra-fine-diameter wires to precisely control impedance. Such coatings are often polymeric and are applied everywhere but the sharpened tips of the wires, resulting in nominal impedances between 0.5 MOhms and 2.0 MOhms. However, during operation, the polymer degrades, changing the exposed area and the impedance. In this work, ultra-thin ceramic coatings were deposited as an alternative to polymer coatings. Processing conditions were varied to determine the effect of microstructure on measurement stability during two-electrode measurements in a standard buffer solution. Coatings were applied to seven different metals to determine any differences in performance due to the surface characteristics of the underlying wire. Sintering temperature and wire type had significant effects on coating degradation. Dielectric breakdown was also observed at relatively low voltages, indicating that test conditions must be carefully controlled to maximize reliability.

  4. Physical and dielectric properties of pharmaceutical powders

    Microsoft Academic Search

    C. M McLoughlin; W. A. M McMinn; T. R. A Magee

    2003-01-01

    The limited availability of published physical and dielectric property data for pharmaceutical powders hinders the design of processing systems, particularly dryers. In this study, the physical properties (solubility and boiling point) and dielectric properties, in terms of temperature rise, dielectric constant, and dielectric loss factor, of selected pharmaceutical powders were measured. The pharmaceutical actives, paracetamol and aspirin, and selected common

  5. PREFACE: Dielectrics 2009: Measurement Analysis and Applications

    Microsoft Academic Search

    Alun Vaughan; Graham Williams

    2009-01-01

    The conference Dielectrics 2009: Measurements, Analysis and Applications represents a significant milestone in the evolution of dielectrics research in the UK. It is reasonable to state that the academic study of dielectrics has led to many fundamental advances and that dielectric materials underpin the modern world in devices ranging from field effect transistors, which operate at extremely high fields, albeit

  6. The electrical characteristics of a 4H—silicon carbide metal—insulator—semiconductor structure with Al2O3 as the gate dielectric

    NASA Astrophysics Data System (ADS)

    Liu, Li; Yang, Yin-Tang; Ma, Xiao-Hua

    2011-12-01

    A 4H—silicon carbide metal—insulator—semiconductor structure with ultra-thin Al2O3 as the gate dielectric, deposited by atomic layer deposition on the epitaxial layer of a 4H—SiC (0001) 80N-/N+ substrate, has been fabricated. The experimental results indicate that the prepared ultra-thin Al2O3 gate dielectric exhibits good physical and electrical characteristics, including a high breakdown electrical field of 25 MV/cm, excellent interface properties (1×1014 cm-2) and low gate-leakage current (IG = 1 × 10-3 A/cm-2@Eox = 8 MV/cm). Analysis of the current conduction mechanism on the deposited Al2O3 gate dielectric was also systematically performed. The confirmed conduction mechanisms consisted of Fowler—Nordheim (FN) tunneling, the Frenkel—Poole mechanism, direct tunneling and Schottky emission, and the dominant current conduction mechanism depends on the applied electrical field. When the gate leakage current mechanism is dominated by FN tunneling, the barrier height of SiC/Al2O3 is 1.4 eV, which can meet the requirements of silicon carbide metal—insulator—semiconductor transistor devices.

  7. Dielectric microscopy with submillimeter resolution

    E-print Network

    Nathan S. Greeney; John A. Scales

    2007-06-20

    In analogy with optical near-field scanning methods, we use tapered dielectric waveguides as probes for a millimeter wave vector network analyzer. By scanning thin samples between two such probes we are able to map the spatially varying dielectric properties of materials with sub-wavelength resolution; using a 150 GHz probe in transmision mode we see spatial resolution of around 500 microns. We have applied this method to a variety of highly heterogeneous materials. Here we show dielectric maps of granite and oil shale.

  8. Effective dielectric constant of electrolytes

    NASA Astrophysics Data System (ADS)

    Barbero, G.; Lelidis, I.

    2014-05-01

    We show that in the framework of the Poisson-Nernst-Planck model, where the ions are assumed point-like particles, the dielectric constant of the electrolyte coincides with that of the solvent in which the ions are dispersed. Only in the case where the ions are considered polarizable particles, their presence can contribute to the effective dielectric constant of the electrolyte and can play a role in the non-linear version of the Poisson-Nernst-Planck model. From this observation, it follows that generalizations of the linear Poisson-Nernst-Planck model in which the dielectric constant of the solution is considered depending on the ionic distributions are questionable.

  9. Nonlinear Dielectric Losses and Dynamics of Intrinsic Conductivity of Dielectrics

    Microsoft Academic Search

    J. A. Ma?ecki

    The phenomenological approach to dynamics of the intrinsic electric conductivity of dielectrics in the electric field was\\u000a used for analyzing the respective contribution to dielectric losses. The proposed differential equation contains only two\\u000a parameters — the effective time ?F of conductivity decay in electric field, and time ?R describing the rate of conductivity recovery after switching field off. The proposed

  10. Towards all-dielectric metamaterials and nanophotonics

    E-print Network

    Krasnok, Alexander; Petrov, Mikhail; Savelev, Roman; Belov, Pavel; Kivshar, Yuri

    2015-01-01

    We review a new, rapidly developing field of all-dielectric nanophotonics which allows to control both magnetic and electric response of structured matter by engineering the Mie resonances in high-index dielectric nanoparticles. We discuss optical properties of such dielectric nanoparticles, methods of their fabrication, and also recent advances in all-dielectric metadevices including couple-resonator dielectric waveguides, nanoantennas, and metasurfaces.

  11. Electrolytes near structured dielectric interfaces

    NASA Astrophysics Data System (ADS)

    Wu, Huanxin; Jing, Yufei; Solis, Francisco; Olvera de La Cruz, Monica; Luijten, Erik

    2015-03-01

    The ion distribution in an electrolyte near a dielectric interface has important consequences for numerous applications. To date, most studies have focused on planar interfaces, where, e.g., simulations can take advantage of the image-charge method. However, for surfaces that display structure on the nanoscale, dielectric effects may be significantly different. Here, we investigate such interfaces via a combination of computer simulations and Poisson-Boltzmann theory. We demonstrate how, even for systems with piecewise uniform dielectric constant, surface structure affects the induced polarization charge as well as the ion distribution near the interface, in particular for asymmetric salts. We explore the role of ion concentration, dielectric mismatch and characteristic length scale of the surface structure.

  12. Generalized dielectric permittivity of ice

    NASA Astrophysics Data System (ADS)

    Klyuev, A. V.; Ryzhkin, I. A.; Ryzhkin, M. I.

    2015-01-01

    The generalized dielectric permittivity describes the electric response of both bound charges (normal dielectric constant) and free charges (conductivity). The generalized dielectric permittivity of ice (water) has been calculated within the model of classical quasiparticles as a function of the wave vector and frequency ?( q, ?). At zero wave vector and nonzero frequency, this function describes the response to a uniform alternating electric field, whereas at nonzero wave vector and zero frequency, it describes the screening of a static electric field. At simultaneously nonzero wave vector and frequency, it can be used to study electromagnetic waves in ice. In addition, the generalized dielectric permittivity allows the calculation of the dynamic correlation function of the electric polarization in terms of the fluctuation-dissipation theorem.

  13. Fractal Dimension of Dielectric Breakdown

    Microsoft Academic Search

    L. Niemeyer; L. Pietronero; H. J. Wiesmann

    1984-01-01

    It is shown that the simplest nontrivial stochastic model for dielectric breakdown naturally leads to fractal structures for the discharge pattern. Planar discharges are studied in detail and the results are compared with properly designed experiments.

  14. Infrared cubic dielectric resonator metamaterial.

    SciTech Connect

    Sinclair, Michael B.; Brener, Igal; Peters, David William; Ginn, James Cleveland, III; Ten Eyck, Gregory A.

    2010-06-01

    Dielectric resonators are an effective means to realize isotropic, low-loss optical metamaterials. As proof of this concept, a cubic resonator is analytically designed and then tested in the long-wave infrared.

  15. Dielectric phantoms for electromagnetic radiation

    SciTech Connect

    Broadhurst, M.G.; Chiang, C.K.; Davis, G.T.

    1986-03-01

    The report describes the design and performance of a synthetic material that has the same dielectric-heating characteristics as living muscle in the 1-1000 MHz frequency range. The dielectric phantom is a combination of four components: (1) a 50/50 solution of ethylene carbonate and propylene carbonate chosen to have the same dielectric constant as water, (2) an organic salt to provide the same conductivity as biological electrolytes, (3) flakes of polyethylene terephthalate to provide the interfacial polarization that occurs at cell walls in biological tissue and (4) an inorganic and a polymeric gelling agents to provide mechanical rigidity. The resulting composite material is more stable to biological attack and drying than are existing aqueous-based phantom materials, and its dielectric properties are more closely matched to those of natural tissues over most of the frequency range of interest.

  16. Dielectric screening in inversion layers

    Microsoft Academic Search

    G. Srinivasan; M. Jonson

    1975-01-01

    The authors have investigated the dielectric response of carriers in inversion layers in a MISFET. Particular attention has been paid to the Anderson-localized regime (where the carriers are localized by disorder) and the possible Wigner lattice. In the Anderson-localized regime, it is found that the long-wavelength dielectric function is given by a Thomas-Fermi function. The most interesting feature of the

  17. Nonvolatile memory characteristics of WSi2 nanocrystals embedded in SiO2 dielectrics.

    PubMed

    Seo, Ki Bong; Lee, Dong Uk; Han, Seung Jong; Kim, Seon Pil; Kim, Eun Kyu

    2011-01-01

    A nano-floating gate capacitor with WSi2 nanocrystals embedded in SiO2 dielectrics was fabricated. The WSi2 nanocrystals were created from ultrathin WSi2 film during rapid thermal annealing process and their average size and density were about 2.5 nm and 3.59 x 10(12) cm(-2), respectively. The flat-band voltage shift due to the carrier charging effect of WSi2 nanocrystals were measured up to 5.9 V when the gate voltage sweep in the range of +/- 9 V. The memory window was decreased from 3.7 V to 1.9 V after 1 h and remained about 3.7 V after 10(5) programming/erasing cycles. These results show that there is a possibility for the WSi2 nanocrystals to be applied to nonvolatile memory devices. PMID:21446472

  18. Enhanced performance using an SU-8 dielectric interlayer in a bulk heterojunction organic solar cell.

    PubMed

    Pang, Christina; Chellappan, Vijila; Yim, Jong Hyuk; Tan, Mein Jin; Goh, Glen Tai Wei; Lee, Soonil; Zhang, Jie; de Mello, John

    2015-03-11

    The effect of inserting an SU-8 dielectric interlayer into inverted bulk heterojunction (BHJ) organic solar cells (OSCs) was studied. Insertion of an ultrathin layer of SU-8 between the zinc oxide (ZnO) electron transport layer and the photoactive layer resulted in a smoother interface and a 14% enhancement in power conversion efficiency. The properties of devices with and without an SU-8 interlayer were investigated using transient photovoltage (TPV) and double injection (DoI) techniques, and it was found that devices with SU-8 show longer carrier lifetimes and greater mobility-lifetime (?-?) products than those without. Devices with SU-8 were also found to have improved stability. The results indicate that the insertion of an SU-8 interlayer reduces the recombination rate for photogenerated carriers without affecting the charge transport properties, improving overall performance and stability. PMID:25658649

  19. Parity-time symmetry from stacking purely dielectric and magnetic slabs

    NASA Astrophysics Data System (ADS)

    Gear, James; Liu, Fu; Chu, S. T.; Rotter, Stefan; Li, Jensen

    2015-03-01

    We show that parity-time symmetry in matching electric permittivity to magnetic permeability can be established by considering an effective parity operator involving both mirror symmetry and coupling between electric and magnetic fields. This approach extends the discussion of parity-time symmetry to the situation with more than one material potential. We show that the band structure of a one-dimensional photonic crystal with alternating purely dielectric and purely magnetic slabs can undergo a phase transition between propagation modes and evanescent modes when the balanced gain or loss parameter is varied. The cross matching between different material potentials also allows exceptional points of the constitutive matrix to appear in the long-wavelength limit where they can be used to construct ultrathin metamaterials with unidirectional reflection.

  20. Water absorption and interface reactivity of yttrium oxide gate dielectrics on silicon

    NASA Astrophysics Data System (ADS)

    Niu, D.; Ashcraft, R. W.; Parsons, G. N.

    2002-05-01

    High dielectric constant insulators deposited at low temperatures rapidly absorb water during exposure to the atmosphere, and the resulting OH leads to detrimental interface reactions. We report the effect of atmospheric exposure on ultrathin yttrium oxide, and details of silicon substrate reactions during postdeposition anneals. Infrared absorption analysis indicates significant absorption of water vapor during atmospheric exposure, even for very short times (<15 min). X-ray photoelectron spectroscopy demonstrates that after OH absorption, a thermally activated interface reaction proceeds with an activation energy of 0.33 eV, consistent with substrate reaction with OH present in the film. The OH absorption rate is reduced for annealed films or when capping layers are deposited in situ. Similar oxidation processes are expected to occur in other high-k materials of interest, where the rate of OH absorption will depend on the deposition process and material thermal history.

  1. LETTER TO THE EDITOR: Electrical properties of crystalline YSZ films on silicon as alternative gate dielectrics

    NASA Astrophysics Data System (ADS)

    Wang, S. J.; Ong, C. K.; Xu, S. Y.; Chen, P.; Tjiu, W. C.; Huan, ACH; Yoo, W. J.; Lim, J. S.; Feng, W.; Choi, W. K.

    2001-03-01

    Crystalline yttria-stabilized zirconia oxide (YSZ) film was successfully deposited on a silicon wafer without an interfacial amorphous SiO2 layer. The film with equivalent oxide thickness teox down to 1.77 nm shows negligible hysteresis and low interface state density, less than 3×1011 cm-2 eV-1. The leakage current density for teox = 1.77 nm film, 1.5×10-5 A cm-2 at 1 V bias voltage, is five orders of magnitude lower than that for SiO2 with the same equivalent oxide thickness. The results demonstrate that an ultra-thin YSZ film has sufficient resistivity against the formation of an underlying amorphous layer, and can be a promising gate dielectric replacing SiO2 to reduce the feature size of devices.

  2. Structural advantage for the EOT scaling and improved electron channel mobility by incorporating dysprosium oxide (Dy\\/sub 2\\/O\\/sub 3\\/) into HfO\\/sub 2\\/ n-MOSFETs

    Microsoft Academic Search

    Tackhwi Lee; Se Jong Rhee; Chang Yong Kang; Feng Zhu; Hyoung-sub Kim; Changhwan Choi; Manhong Zhang; S. Krishnan; G. Thareja; J. C. Lee

    2006-01-01

    A structural approach of fabricating laminated Dy2O3-incorporated HfO2 multimetal oxide dielectric has been developed for high-performance CMOS applications. Top Dy2O3 laminated HfO2 bilayer structure shows the thinnest equivalent oxide thickness (EOT) with a reduced leakage current compared to HfO2. This structure shows a great advantage for the EOT scaling CMOS technology. Excellent electrical performances of the Dy2O3\\/HfO 2 multimetal stack

  3. Breathing modes of confined skyrmions in ultrathin magnetic dots

    NASA Astrophysics Data System (ADS)

    Kim, Joo-Von; Garcia-Sanchez, Felipe; Sampaio, João; Moreau-Luchaire, Constance; Cros, Vincent; Fert, Albert

    2014-08-01

    The dynamics of individual magnetic skyrmions confined in ultrathin film dots is studied theoretically. The systems considered are transition-metal ferromagnets possessing perpendicular magnetic anisotropy and particular attention is given to the dynamic response of the skyrmions to perpendicular ac fields. By using micromagnetics simulations, it is shown that breathing modes can hybridize with geometrically quantized spin wave eigenmodes of the circular dots, leading to distinct features in the power spectrum that differ from the behavior expected for uniformly magnetized systems. The static field dependence of the breathing mode frequency offers a direct means of detecting and characterizing such skyrmion states in experiment.

  4. Experimental phase diagram of perpendicularly magnetized ultrathin ferromagnetic films.

    PubMed

    Saratz, N; Lichtenberger, A; Portmann, O; Ramsperger, U; Vindigni, A; Pescia, D

    2010-02-19

    We image the domain patterns in perpendicularly magnetized ultrathin Fe films on Cu(100) as a function of the temperature T and the applied magnetic field H. Between the low-field stripe phase and the high-field uniform phase we find a bubble phase, consisting of reversed circular domains in a homogeneous background. The curvature of the transition lines in the H-T parameter space is in contrast to the general expectations. The pattern transformations show yet undetected scaling properties. PMID:20366912

  5. Low thermal conductivity in ultrathin carbon nanotube (2, 1).

    PubMed

    Zhu, Liyan; Li, Baowen

    2014-01-01

    Molecular dynamic simulations reveal that the ultrathin carbon nanotube (CNT) (2, 1) with a reconstructed structure exhibits a surprisingly low thermal conductivity, which is only ~16-30% of those in regular CNTs, e.g. CNT (2, 2) and (5, 5). Detailed lattice dynamic calculations suggest that the acoustic phonon modes greatly soften in CNT (2, 1) as compared to regular CNTs. Moreover, both phonon group velocities and phonon lifetimes strikingly decrease in CNT (2, 1), which result in the remarkable reduction of thermal conductivity. Besides, isotope doping and chemical functionalization enable the further reduction of thermal conductivity in CNT (2, 1). PMID:24815003

  6. Anomalous polarization conversion in arrays of ultrathin ferromagnetic nanowires

    E-print Network

    Stashkevich, Andrey A; Poddubny, Alexander N; Chérif, S -M; Zheng, Y; Vidal, Franck; Yagupov, Ilya V; Slobozhanyuk, Alexei P; Belov, Pavel A; Kivshar, Yuri S

    2015-01-01

    We study optical properties of arrays of ultrathin nanowires by means of the Brillouin scattering of light on magnons. We employ the Stokes/anti-Stokes scattering asymmetry to probe the circular polarization of a local electric field induced inside nanowires by linearly polarized light waves. We observe the anomalous polarization conversion of the opposite sign than that in a bulk medium or thick nanowires with a great enhancement of the degree of circular polarization attributed to an unconventional refraction in the nanowire medium.

  7. Asymmetric orbital-lattice interactions in ultrathin correlated oxide films.

    PubMed

    Chakhalian, J; Rondinelli, J M; Liu, Jian; Gray, B A; Kareev, M; Moon, E J; Prasai, N; Cohn, J L; Varela, M; Tung, I C; Bedzyk, M J; Altendorf, S G; Strigari, F; Dabrowski, B; Tjeng, L H; Ryan, P J; Freeland, J W

    2011-09-01

    Using resonant x-ray spectroscopies combined with density functional calculations, we find an asymmetric biaxial strain-induced d-orbital response in ultrathin films of the correlated metal LaNiO3 which are not accessible in the bulk. The sign of the misfit strain governs the stability of an octahedral "breathing" distortion, which, in turn, produces an emergent charge-ordered ground state with an altered ligand-hole density and bond covalency. Control of this new mechanism opens a pathway to rational orbital engineering, providing a platform for artificially designed Mott materials. PMID:22026694

  8. Asymmetric orbital-lattice interactions in ultrathin correlated oxide films

    SciTech Connect

    Chakalian, J. [University of Arkansas; Rondinelli, J. [University of California; Gray, B [University of Arkansas; Kareev, M [University of Arkansas; Moon, E.J. [University of Arkansas; Cohn, J. [University of Arkansas; Varela del Arco, Maria [ORNL; Altendorf, S. J. [University of Arkansas; Strigari, F. [University of Arkansas; Dabrowski, B. [Argonne National Laboratory (ANL); Tjeng, L. H. [Universitat zu Koln, Koln, Germany; Ryan, P.J. [Argonne National Laboratory (ANL); Freeland, J. W. [Argonne National Laboratory (ANL)

    2011-01-01

    Using resonant x-ray spectroscopies combined with density functional calculations, we find an asymmetric biaxial strain-induced d-orbital response in ultrathin films of the correlated metal LaNiO{sub 3} which are not accessible in the bulk. The sign of the misfit strain governs the stability of an octahedral 'breathing' distortion, which, in turn, produces an emergent charge-ordered ground state with an altered ligand-hole density and bond covalency. Control of this new mechanism opens a pathway to rational orbital engineering, providing a platform for artificially designed Mott materials.

  9. Slowing Down of Accelerated Structural Relaxation in Ultrathin Polymer Films

    NASA Astrophysics Data System (ADS)

    Tang, Qiyun; Hu, Wenbing; Napolitano, Simone

    2014-04-01

    We demonstrate with molecular simulation that the acceleration of structural relaxation, also known as physical aging, commonly experimentally observed in thin polymer films slows down at extremely small thicknesses. This phenomenon can be attributed to an inversed free volume diffusion process caused by the sliding motion of chain molecules. Our findings provide direct evidence of the relationship between the sliding motion of short chain fragments and the structural relaxation of ultrathin polymer films, and also verify the existence of a new confinement effect at the nanoscale.

  10. Very low loss ultrathin Co-based amorphous ribbon cores

    Microsoft Academic Search

    M. Yagi; T. Sato; Y. Sakaki; T. Sawa; K. Inomata

    1988-01-01

    Ultrathin Co-based amorphous ribbons with a thickness of 6–10 ?m were fabricated by a single roller quenching method in vacuum. The compositions of the alloys were zero magnetostrictive: Fe4.7Co70.3Si15B10 and (Fe0.05Co0.95)71(Si0.5B0.5)29. The ribbons obtained had good smoothness and dimensional uniformity. The core loss of toroidal samples 15 mm in diameter was measured after annealing. The loss decreased with decreasing ribbon

  11. Extracellular ultrathin fibers sensitive to intracellular reactive oxygen species: Formation of intercellular membrane bridges

    SciTech Connect

    Jung, Se-Hui; Park, Jin-Young; Joo, Jung-Hoon; Kim, Young-Myeong; Ha, Kwon-Soo, E-mail: ksha@kangwon.ac.kr

    2011-07-15

    Membrane bridges are key cellular structures involved in intercellular communication; however, dynamics for their formation are not well understood. We demonstrated the formation and regulation of novel extracellular ultrathin fibers in NIH3T3 cells using confocal and atomic force microscopy. At adjacent regions of neighboring cells, phorbol 12-myristate 13-acetate (PMA) and glucose oxidase induced ultrathin fiber formation, which was prevented by Trolox, a reactive oxygen species (ROS) scavenger. The height of ROS-sensitive ultrathin fibers ranged from 2 to 4 nm. PMA-induced formation of ultrathin fibers was inhibited by cytochalasin D, but not by Taxol or colchicine, indicating that ultrathin fibers mainly comprise microfilaments. PMA-induced ultrathin fibers underwent dynamic structural changes, resulting in formation of intercellular membrane bridges. Thus, these fibers are formed by a mechanism(s) involving ROS and involved in formation of intercellular membrane bridges. Furthermore, ultrastructural imaging of ultrathin fibers may contribute to understanding the diverse mechanisms of cell-to-cell communication and the intercellular transfer of biomolecules, including proteins and cell organelles.

  12. Ultrathin Si buffer layers to improve the exchange bias between Ni-Fe and FeMn layers

    NASA Astrophysics Data System (ADS)

    Nakagawa, S.; Nishimura, K.; Shimizu, Y.; Naoe, M.

    1999-04-01

    Ni-Fe/FeMn bilayers were deposited by using dual ion beam sputtering apparatus. In order to promote (111) orientation in ?-FeMn layers and to exhibit exchange bias field Hex, Si and/or silicon nitride (Si3N4) layers were deposited as buffer layers. Although silicon nitride (Si3N4) buffer layers did not improve (111) orientation in FeMn layers, as well as in Ni-Fe layers, an amorphous Si buffer layer only 1 nm thick improved (111) orientation in FeMn layers and increased Hex to above 100 Oe. FeMn/Ni-Fe bilayers deposited on Si(0.5 nm)/Si3N4(1 nm) bilayered buffer layer also exhibited high Hex of about 130 Oe. This result implies that the ultrathin a-Si buffer layer was effective in improving (111) orientation in Ni-Fe layers. Very thin Si/Si3N4 bilayers may be applicable as dielectric layers in tunneling magnetoresistive spin valve devices.

  13. Do dielectrics attract streamer discharges?

    NASA Astrophysics Data System (ADS)

    Dubinova, Anna; Teunissen, Jannis; Ebert, Ute; Multiscale Dynamics Team

    2013-09-01

    Streamer discharges developing near dielectric materials can cause sparks and surface flashovers. This effect is to be avoided in high voltage technology. Dielectric materials tend to attract the discharge due to polarization effects resulting in the modification of the local electric field. Other mechanisms known for influencing streamer discharge propagation include photoionization, background ionization, accumulation of surface charge on the dielectrics and secondary electron emission. However, the actual physical mechanisms responsible for the surface flashovers are still under discussion. Developing advanced simulation tools, we aim at getting insight into the nature of streamer discharges in the presence of dielectrics in full 3D. We report the results of our simulations showing essential differences between a positive streamer propagating due to background ionization and due to photoionization. We compare our numerical results with experiments. We also describe a numerical method (a generalized Ghost Fluid Method) which allowed us to include dielectric interfaces into our streamer models, in an accurate and fast manner. Streamer discharges developing near dielectric materials can cause sparks and surface flashovers. This effect is to be avoided in high voltage technology. Dielectric materials tend to attract the discharge due to polarization effects resulting in the modification of the local electric field. Other mechanisms known for influencing streamer discharge propagation include photoionization, background ionization, accumulation of surface charge on the dielectrics and secondary electron emission. However, the actual physical mechanisms responsible for the surface flashovers are still under discussion. Developing advanced simulation tools, we aim at getting insight into the nature of streamer discharges in the presence of dielectrics in full 3D. We report the results of our simulations showing essential differences between a positive streamer propagating due to background ionization and due to photoionization. We compare our numerical results with experiments. We also describe a numerical method (a generalized Ghost Fluid Method) which allowed us to include dielectric interfaces into our streamer models, in an accurate and fast manner. A.Dubinova is supported by STW-project 12119, partly funded by ABB. She also acknowledges fruitful discussions with Thomas Christen.

  14. Dielectric and permeability

    NASA Technical Reports Server (NTRS)

    Cole, K. D.

    1982-01-01

    Using the unabridged Maxwell equations (including vectors D, E and H) new effects in collisionless plasmas are uncovered. In a steady state, it is found that spatially varying energy density of the electric field (E perpendicular) orthogonal to B produces electric current leading, under certain conditions, to the relationship P perpendicular+B(2)/8 pi-epsilon E perpendicular(2)/8 pi = constant, where epsilon is the dielectric constant of the plasma for fields orthogonal to B. In steady state quasi-two-dimensional flows in plasmas, a general relationship between the components of electric field parallel and perpendicular to B is found. These effects are significant in goephysical and astrophysical plasmas. The general conditions for a steady state in collisionless plasma are deduced. With time variations in a plasma, slow compared to ion-gyroperiod, there is a general current, (j*), which includes the well-known polarisation current, given by J*=d/dt (ExM)+(PxB)xB B(-2) where M and P are the magnetization and polarization vectors respectively.

  15. Study of transport properties in graphene monolayer flakes on SiO[sub 2] substrates

    E-print Network

    Tirado, J. M.

    We investigate the carrier mobility in monolayer and bilayer graphene with a top HfO2dielectric, as a function of the HfO2film thickness and temperature. The results show that the carrier mobility decreases during the ...

  16. Deswelling of ultrathin molecular layer-by-layer polyamide water desalination membranes.

    PubMed

    Chan, Edwin P

    2014-05-01

    The selective layer of pressure-induced water desalination membranes is an ultrathin and highly crosslinked aromatic polyamide (PA) film that separates salt from water based on differences in permeability, which is a product of diffusivity and solubility. Characterizing the transport properties of the selective layer is necessary in understanding its permselective performance. However, measuring transport of ultrathin films in general is nontrivial. Here, Poroelastic Relaxation Indentation (PRI) is employed as a simple deswelling technique for measuring the transport properties of these ultrathin selective layers. PMID:24658339

  17. Spatial confinement effects on ultrathin semiconducting polymer heterojunction thin films

    SciTech Connect

    Xuejun Zhang; Jenekhe, S.A. [Univ. of Rochester, NY (United States)

    1996-12-31

    Thin and ultrathin films of electroactive and photoactive polymers are of growing interest for applications in electronic and optoelectronic devices such as thin film transistors, light emitting diodes, solar cells, and xerographic photoreceptors. Although spatial confinement effects on the electronic, optical, optoelectronic, magnetic, and mechanical properties of inorganic semiconductors, metals, oxides, and ceramics are well known and understood, very little is currently known about nanoscale size effects in electroactive and photoactive polymers. Therefore, we recently initiated studies aimed at the understanding of spatial confinement effects on electroactive and photoactive nanostructured polymers and related thin film devices. We have extensively investigated layered nanoscale semiconducting polymer heterojunctions by applying several experimental techniques including photoluminescence, optical absorption, transient absorption, electroluminescence, cyclic voltammetry, and current-voltage measurements. Our findings reveal clear evidence of spatial confinement effects, including: dramatic enhancement of photoconductivity in ultrathin films; enhancement of electroluminescence efficiency and performance characteristics in nanoscale heterojunction devices; observation of novel phenomena in nanoscale devices. These spatial confinement effects in nanostructured semiconducting polymers can be understood in terms of classical charge transport and interfacial processes without invoking quantum size effects.

  18. Thickness-driven spin reorientation transition in ultrathin films

    NASA Astrophysics Data System (ADS)

    Miao, BingFeng; Millev, YonkeTimtchev; Sun, Liang; You, Biao; Zhang, Wei; Ding, HaiFeng

    2013-01-01

    We review recent studies by different experimental means of ultrathin films, exhibiting thickness-driven spin reorientation transitions (SRTs). The stage is set by determining, via phenomenological thermodynamic description, of the relevant phase diagrams for the possible types of SRT with and without applied magnetic field. Suitable representation may be chosen such that best use is made of the linear character (under thickness variation) of the system's path in anisotropy space. The latter involves higher-order bulk and surface anisotropies in a substantial way. We examine sensitive experimental techniques for the detection and quantification of SRTs, such as hysteresis measurements with magneto-optical Kerr effect (MOKE), micromagnetic studies utilizing scanning electron microscopy with polarization analysis (SEMPA), photoemission electron microscopy (PEEM) and spin-polarized low-energy electron microscopy (SPLEEM) as well as ac magnetic susceptibility measurements via MOKE. Key issues are conclusively discussed including the identification of reliable experimental fingerprints about whether a given SRT proceeds via a phase of coexistence or via a cone (canted) phase. We demonstrate how the application of the general theoretical ideas to carefully designed measurements leads to the determination of the most important material parameters in any ultrathin-film SRT, namely, the surface (interface) magnetic anisotropy constants. The review concludes by our personal outline for future promising work on SRTs.

  19. Ultrathin TiOx films on Pt(111)

    NASA Astrophysics Data System (ADS)

    Granozzi, Gaetano; Sedona, Francesco; Schierbaum, Klaus

    2006-03-01

    Ultrathin ordered titanium oxide films on Pt(111) surface were prepared by reactive evaporation of Ti in oxygen. By varying the Ti dose and the annealing conditions, several long-range ordered phases were obtained and characterized by means of LEED, XPS, UPS, photoelectron diffraction, STM and XAS. XPS and photoelectron diffraction data indicate that all the phases, except two, are one-monolayer thick and composed of a Ti-O bilayer with interfacial Ti. Atomically resolved STM images of all the prepared phases have been obtained. At a low Ti dose (0.4 MLE), an incommensurate kagom'e-like low density phase is observed where hexagons are sharing their vertices. At a higher Ti dose (0.8 MLE) two denser phases are found, both characterized by a zigzag motif, but with distinct rectangular unit cells. When the post-annealing of the 0.8 MLE deposit is carried out at high temperatures and oxygen partial pressures, an incommensurate non-wetting fully oxidized phase is found, whose symmetry and lattice dimensions are almost identical with those observed in the system VOx/Pd(111). At higher coverage, two commensurate hexagonal phases are formed, which show wagon-wheel-like structures and have slightly different lattice dimensions. Competitively to the formation of ultrathin films, nanosized TiO2 crystallites can grow on top of the surface. They predominate the entire morphology only for large initial Ti deposits.

  20. Mechanical constraints enhance electrical energy densities of soft dielectrics

    E-print Network

    Ferrari, Silvia

    Mechanical constraints enhance electrical energy densities of soft dielectrics Lin Zhang, Qiming, the dielectric will breakdown electrically. The breakdown limits the electrical energy density of the dielectric including high dielectric strength, fast charging rate, and mechanical flexibility and conformability. Soft

  1. A novel numerical technique for dielectric measurement of generally lossy dielectrics

    Microsoft Academic Search

    Stoyan I. Ganchev; Sasan Bakhtiari; Reza Zoughi

    1992-01-01

    A method for determining the dielectric properties of infinite half-space of generally lossy dielectric materials is described. This method utilizes the measurement of the admittance of a rectangular waveguide radiating into such dielectrics. It is shown that the real part of the admittance is relatively insensitive to the variations of the imaginary part of the dielectric constant. A numerical procedure

  2. Dielectric Breakdown in High-K Gate Dielectrics - Mechanism and Lifetime Assessment

    Microsoft Academic Search

    Kenji OKADA; Hiroyuki OTA; Toshihide NABATAME; A. Toriumi

    2007-01-01

    Dielectric breakdown in high-k gate dielectrics is discussed from the viewpoints of its mechanism and accurate TDDB lifetime assessment. As for the dielectric breakdown mechanism, we have proposed the generated subordinate carrier injection (GSCI) model. The GSCI model considers that injected subordinate carriers degrade the dielectrics and that breakdown occurs when their number reaches a threshold value. Due to the

  3. Dielectric Bow-tie Nanocavity

    E-print Network

    Lu, Qijing; Zou, Chang-Ling

    2013-01-01

    We propose a novel dielectric bow-tie nanocavity consisting of two tip-to-tip opposite triangle semiconductor nanowires, whose end faces are coated by silver nanofilms. Based on the advantages of the dielectric slot and tip structures, and the high reflectivity from the silver mirror, light can be confined in this nanocavity with low loss. We demonstrate that the mode excited in this nanocavity has a deep subwavelength mode volume of 2.8*10^-4 um3 and a high quality factor of 4.9*10^4 (401.3), consequently an ultrahigh Purcell factor of 1.6*10^7 (1.36*10^5), at 4.5 K (300 K) around the resonance wavelength of 1550 nm. This dielectric bow-tie nanocavity may find applications for integrated nanophotonic circuits, such as high-efficiency single photon source, thresholdless nanolaser, and cavity QED strong coupling experiments.

  4. Langevin simulations of a model for ultrathin magnetic films Lucas Nicolao* and Daniel A. Stariolo

    E-print Network

    Stariolo, Daniel Adrián

    Langevin simulations of a model for ultrathin magnetic films Lucas Nicolao* and Daniel A. Stariolo show results from simulations of the Langevin dynamics of a two-dimensional scalar model with competing

  5. Well-defined ultrathin Pd films on Pt(111): electrochemical preparation and interfacial chemistry 

    E-print Network

    Park, Yeon Su

    2005-08-29

    Well-defined ultrathin films of palladium, with coverages ranging from submonolayer, ?Pd = 0.5 monolayer (ML), to multilayer, ?P d = 8 ML, were electrochemically deposited on Pt(111) using potentiostatic and ...

  6. Supporting Information: Si Photoanode Protected by Metal Modified ITO with Ultrathin

    E-print Network

    Wang, Deli

    Supporting Information: Si Photoanode Protected by Metal Modified ITO with Ultrathin NiOx for Solar catalyst, a stabilized n-Si photoanode that is chemically inert to the alkaline environment is required

  7. Near-Infrared Surface Plasmon Resonance Measurements of Ultrathin Films. 2. Fourier

    E-print Network

    Near-Infrared Surface Plasmon Resonance Measurements of Ultrathin Films. 2. Fourier Transform SPR Place, Madison, Wisconsin, 53711 The application of surface plasmon resonance (SPR) measurements otherwise interfere with the analysis. Surface plasmon resonance (SPR) measurements are surface- sensitive

  8. Atomistic calculations of the electronic, thermal, and thermoelectric properties of ultra-thin Si layers

    E-print Network

    nanostructures are promising candidates for next generation thermoelectric (TE) applications because1 Atomistic calculations of the electronic, thermal, and thermoelectric properties of ultra-thin Si are considered promising candidates for thermoelectric applications with enhanced performance because

  9. Efficiency enhancement of a dielectric barrier plasma discharge by dielectric barrier optimization.

    PubMed

    Meiners, Annette; Leck, Michael; Abel, Bernd

    2010-11-01

    The characteristic feature of a dielectric barrier discharge (DBD) is the dielectric barrier placed between the electrodes. In the present work, the influence of the dielectric barrier to the properties of a DBD in air was investigated. Spectroscopic characterization of the DBD and electrical measurements were carried out. It was shown that the efficiency of a DBD can be considerably improved by optimizing the dielectric barrier. The dielectric material should possess an appropriate relative permittivity and thickness. For thin dielectric barriers, a high secondary emission coefficient becomes important. Additionally, the use of only one dielectric barrier is advantageous. PMID:21133471

  10. CVD Diamond Dielectric Accelerating Structures

    NASA Astrophysics Data System (ADS)

    Schoessow, P.; Kanareykin, A.; Gat, R.

    2009-01-01

    The electrical and mechanical properties of diamond make it an ideal candidate material for use in dielectric accelerating structures: high RF breakdown field, extremely low dielectric losses and the highest available thermoconductive coefficient. Using chemical vapor deposition (CVD) cylindrical diamond structures have been manufactured with dimensions corresponding to fundamental TM01 mode frequencies in the GHz to THz range. Surface treatments are being developed to reduce the secondary electron emission (SEE) coefficient below unity to reduce the possibility of multipactor. The diamond CVD cylindrical waveguide technology developed here can be applied to a variety of other high frequency, large-signal applications.

  11. Quantum-well effect in magnetic tunnel junctions with ultrathin single-crystal Fe(100) electrodes

    NASA Astrophysics Data System (ADS)

    Nagahama, T.; Yuasa, S.; Suzuki, Y.; Tamura, E.

    2001-12-01

    We studied the tunnel spectra of magnetic tunnel junctions with a single-crystal ultrathin Fe(100) electrode. The tunnel spectra show oscillations of the differential conductivity and the differential tunnel magnetoresistance. The positions of the maxima of the oscillations move systematically with the change in the Fe(100) electrode's thickness, indicating that the oscillations originate from the quantum-well states in the ultrathin Fe(100) electrode. This effect provides us with an opportunity to create voltage-controlled spin functional devices.

  12. Ultrathin pancharatnam-berry metasurface with maximal cross-polarization efficiency.

    PubMed

    Ding, Xumin; Monticone, Francesco; Zhang, Kuang; Zhang, Lei; Gao, Dongliang; Burokur, Shah Nawaz; de Lustrac, Andre; Wu, Qun; Qiu, Cheng-Wei; Alù, Andrea

    2015-02-18

    Novel ultrathin dual-functional metalenses are proposed, fabricated, tested, and verified in the microwave regime for the first time. The significance is that their anomalous transmission efficiency almost reaches the theoretical limit of 25%, showing a remarkable improvement compared with earlier ultrathin metasurface designs with less than 5% coupling efficiency. The planar metalens proposed empowers significant reduction in thickness, versatile focusing behavior, and high transmission efficiency simultaneously. PMID:25545285

  13. Local study of ultrathin silicon dioxide\\/silicon for nanoelectronics by scanning probe microscopy

    Microsoft Academic Search

    Kun Xue

    2005-01-01

    Systematical local studies of ultrathin SiO2\\/Si properties are carried out by scanning probe microscopy (SPM) with nanometer resolution. By exploiting the advantages of scanning tunneling spectroscopy (STS) studies with the exactly same tip and same sample, monolayer-resolved local electronic properties of ultrathin SiO2 are scrutinized. It shows that an electronically transitional instead of abrupt region (3 monolayers) existed near silicon

  14. Development of an ultra-thin DC brushless motor for a hybrid car

    Microsoft Academic Search

    Akiyoshi Shimada; Hirohisa Ogawa; Minoru Nakajima

    2001-01-01

    Use of an ultra-thin design for this motor overcomes restrictions of the layout construction between the engine and the transmission. The ultra-thin design was achieved using a concentrated winding for the salient-pole of the split stator and a centralized distribution bus ring. In addition, since the use of this arrangement for the motor subjects it to the effects of water

  15. SOME APPLICATIONS FOR DIELECTRIC SPECTROSCOPY IN AGRICULTURE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of agricultural products are of interest for several reasons. These include the sensing of moisture content through its correlation with the dielectric properties, or permittivities, of cereal grain and oilseed crops, the influence of permittivity on the dielectric heating of ...

  16. DIELECTRIC MEASUREMENTS ON THE RING MAGNET COILS

    Microsoft Academic Search

    Vogel

    1963-01-01

    Causes of failure of the dielectric in the ring magnet coils are briefly ; examined. Measures taken to prevent breakdown due to insufficient intrinsic ; dielectric strength and breakdown initiated by thermal runaway are described. ; The effects of gas discharges (ionization and atomic interactions) are discussed ; more fully, and a device and procedure for testing the dielectric against

  17. Cellulose Triacetate Dielectric Films For Capacitors

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S.; Jow, T. Richard

    1994-01-01

    Cellulose triacetate investigated for use as dielectric material in high-energy-density capacitors for pulsed-electrical-power systems. Films of cellulose triacetate metalized on one or both sides for use as substrates for electrodes and/or as dielectrics between electrodes in capacitors. Used without metalization as simple dielectric films. Advantages include high breakdown strength and self-healing capability.

  18. Dielectric material degradation monitoring of dielectric barrier discharge plasma actuators

    NASA Astrophysics Data System (ADS)

    Hanson, Ronald E.; Houser, Nicole M.; Lavoie, Philippe

    2014-01-01

    It is a known phenomenon that some dielectric materials used to construct plasma actuators degrade during operation. However, the rate at which this process occurs, to what extent, as well as a method to monitor is yet to be established. In this experimental study, it is shown that electrical measurements can be used to monitor changes in the material of the plasma actuators. The procedure we introduce for monitoring the actuators follows from the work of Kriegseis, Grundmann, and Tropea [Kriegseis et al., J. Appl. Phys. 110, 013305 (2011)], who used Lissajous figures to measure actuator power consumption and capacitance. In the present study, we quantify changes in both the power consumption and capacitance of the actuators over long operating durations. It is shown that the increase in the effective capacitance of the actuator is related to degradation (thinning) of the dielectric layer, which is accompanied by an increase in actuator power consumption. For actuators constructed from layers of Kapton® polyimide tape, these changes are self-limiting. Although the polyimide film degrades relatively quickly, the underlying adhesive layer appears to remain intact. Over time, the effective capacitance was found to increase by up to 36%, 25%, and 11% for actuators constructed with 2, 3, and 4 layers of Kapton tape, respectively. A method is presented to prevent erosion of the Kapton dielectric layer using a coating of Polydimethylsiloxane oil. It is shown the application of this treatment can delay the onset of degradation of the Kapton dielectric material.

  19. Thickness dependent dielectric strength of a low-permittivity dielectric film

    Microsoft Academic Search

    H. K. Kim; F. G. Shi

    2001-01-01

    The dielectric strength of a promising interlevel low relative permittivity dielectric is investigated for various film thicknesses and temperatures by using I-V measurements with metal-insulator-semiconductor (MIS) structures. It is found that the dielectric breakdown mechanism also depends on thickness. For relatively thick films (thickness >500 nm), the dielectric breakdown is electromechanical in origin, i.e. the dielectric strength is proportional to

  20. PHYSICAL REVIEW B 83, 195305 (2011) Enhanced spin relaxation in an ultrathin metal film by the Rashba-type surface

    E-print Network

    Hasegawa, Shuji

    2011-01-01

    PHYSICAL REVIEW B 83, 195305 (2011) Enhanced spin relaxation in an ultrathin metal film/Ag-terminated ultrathin Ag(111) films by the micro-four-point probe method as a function of the applied magnetic field in the ultrathin film significantly. DOI: 10.1103/PhysRevB.83.195305 PACS number(s): 73.63.Hs, 72.15.Rn, 79.60.-i

  1. MoS2 ultrathin nanosheets obtained under a high magnetic field for lithium storage with stable and high capacity.

    PubMed

    Hu, Lin; Feng, Xuyong; Wei, Lingzhi; Zhang, Kejun; Dai, Jianming; Wu, Yucheng; Chen, Qianwang

    2015-07-01

    A new strategy, namely a high magnetic field-induced method, has been designed to enhance lithium storage properties of MoS2 ultrathin nanosheets. The MoS2 ultrathin nanosheets obtained under 8 T exhibit improved cycling stability at high currents, better rate performance and reduced electrochemical impedance, compared to MoS2 ultrathin nanosheets obtained without a high magnetic field. PMID:26054306

  2. Nonideal ultrathin mantle cloak for electrically large conducting cylinders.

    PubMed

    Liu, Shuo; Zhang, Hao Chi; Xu, He-Xiu; Cui, Tie Jun

    2014-09-01

    Based on the concept of the scattering cancellation technique, we propose a nonideal ultrathin mantle cloak that can efficiently suppress the total scattering cross sections of an electrically large conducting cylinder (over one free-space wavelength). The cloaking mechanism is investigated in depth based on the Mie scattering theory and is simultaneously interpreted from the perspective of far-field bistatic scattering and near-field distributions. We remark that, unlike the perfect transformation-optics-based cloak, this nonideal cloaking technique is mainly designed to minimize simultaneously several scattering multipoles of a relatively large geometry around considerably broad bandwidth. Numerical simulations and experimental results show that the antiscattering ability of the metasurface gives rise to excellent total scattering reduction of the electrically large cylinder and remarkable electric-field restoration around the cloak. The outstanding cloaking performance together with the good features of and ultralow profile, flexibility, and easy fabrication predict promising applications in the microwave frequencies. PMID:25401449

  3. Ultrathin nanostructured metals for highly transmissive plasmonic subtractive color filters.

    PubMed

    Zeng, Beibei; Gao, Yongkang; Bartoli, Filbert J

    2013-01-01

    Plasmonic color filters employing a single optically-thick nanostructured metal layer have recently generated considerable interest as an alternative to colorant-based color filtering technologies, due to their reliability, ease of fabrication, and high color tunability. However, their relatively low transmission efficiency (~30%) needs to be significantly improved for practical applications. The present work reports, for the first time, a novel plasmonic subtractive color filtering scheme that exploits the counter-intuitive phenomenon of extraordinary low transmission (ELT) through an ultrathin nanostructured metal film. This approach relies on a fundamentally different color filtering mechanism than that of existing plasmonic additive color filters, and achieves unusually high transmission efficiencies of 60 ~ 70% for simple architectures. Furthermore, owing to short-range interactions of surface plasmon polaritons at ELT resonances, our design offers high spatial resolution color filtering with compact pixel size close to the optical diffraction limit (~?/2), creating solid applications ranging from imaging sensors to color displays. PMID:24100869

  4. Selective and efficient electrochemical biosensing of ultrathin molybdenum disulfide sheets

    NASA Astrophysics Data System (ADS)

    Narayanan, Tharangattu N.; Vusa, Chiranjeevi S. R.; Alwarappan, Subbiah

    2014-08-01

    Atomically thin molybdenum disulfide (MoS2) sheets were synthesized and isolated via solvent-assisted chemical exfoliation. The charge-dependent electrochemical activities of these MoS2 sheets were studied using positively charged hexamine ruthenium (III) chloride and negatively charged ferricyanide/ferrocyanide redox probes. Ultrathin MoS2 sheet-based electrodes were employed for the electrochemical detection of an important neurotransmitter, namely dopamine (DA), in the presence of ascorbic acid (AA). MoS2 electrodes were identified as being capable of distinguishing the coexistence of the DA and the AA with an excellent stability. Moreover, the enzymatic detection of the glucose was studied by immobilizing glucose oxidase on the MoS2. This study opens enzymatic and non-enzymatic electrochemical biosensing applications of atomic MoS2 sheets, which will supplement their established electronic applications.

  5. Multilevel conductance and memory in ultrathin organic films

    NASA Astrophysics Data System (ADS)

    Mukherjee, Biswanath; Pal, Amlan J.

    2004-09-01

    The present letter reports conductance switching in Langmuir-Blodgett films of an organic semiconductor. We have achieved multiple conducting levels in devices based on ultrathin films for increased density of memory bits in the same space. We have shown that multiple conducting levels in a device can be achieved by controlling the density of high-conducting molecules in the structures. We have observed one low- and three high-conducting states of the devices. All four states have associated memory for data-storage applications. Any of the four states, namely 00, 01, 10, and 11, can be "read" for several hours for read-only memory applications. We could "erase" a state, "write" another, and "read" the state for multibit random-access-memory applications.

  6. Reflected wavefront manipulation based on ultrathin planar acoustic metasurfaces

    PubMed Central

    Li, Yong; Liang, Bin; Gu, Zhong-ming; Zou, Xin-ye; Cheng, Jian-chun

    2013-01-01

    The introduction of metasurfaces has renewed the Snell's law and opened up new degrees of freedom to tailor the optical wavefront at will. Here, we theoretically demonstrate that the generalized Snell's law can be achieved for reflected acoustic waves based on ultrathin planar acoustic metasurfaces. The metasurfaces are constructed with eight units of a solid structure to provide discrete phase shifts covering the full 2? span with steps of ?/4 by coiling up the space. By careful selection of the phase profiles in the transverse direction of the metasurfaces, some fascinating wavefront engineering phenomena are demonstrated, such as anomalous reflections, conversion of propagating waves into surface waves, planar aberration-free lens and nondiffracting Bessel beam generated by planar acoustic axicon. Our results could open up a new avenue for acoustic wavefront engineering and manipulations. PMID:23986034

  7. Dendrimer-mediated hydrothermal synthesis of ultrathin gold nanowires

    PubMed Central

    Liu, Hui; Cao, Xiaoming; Yang, Jianmao; Gong, Xue-Qing; Shi, Xiangyang

    2013-01-01

    We report the use of poly(amidoamine) dendrimers as stabilizers to synthesize ultrathin Au nanowires (NWs) with a diameter of 1.3?nm via a hydrothermal approach. The formation of uniform Au NWs was optimized by varying the Au/Ag salt molar ratio, dendrimer stabilizers, and reaction solvent, temperature, and time. A novel growth mechanism involving a synergic facet-dependent deposition/reduction of Ag(I) and oriented migration of Au atoms is proposed based on density functional theory calculations and the experimental results. This work can significantly expand the scope of dendrimers as stabilizers to generate metal NWs in aqueous solution that may be further functionalized for different applications. PMID:24212329

  8. Low-reflection beam refractions by ultrathin Huygens metasurface

    NASA Astrophysics Data System (ADS)

    Jia, Sheng Li; Wan, Xiang; Fu, Xiao Jian; Zhao, Yong Jiu; Cui, Tie Jun

    2015-06-01

    We propose a Huygens source unit cell to develop an ultrathin low-reflection metasurface, which could provide extreme controls of phases of the transmitted waves. Both electric and magnetic currents are supported by the proposed unit cell, thus leading to highly efficient and full controls of phases. The coupling between electric and magnetic responses is negligible, which will significantly reduce the difficulty of design. Since the unit cell of metasurface is printed on two bonded boards, the fabrication process is simplified and the thickness of metasurface is reduced. Based on the proposed unit cell, a beam-refracting metasurface with low-reflection is designed and manufactured. Both near-field and far-field characteristics of the beam-refracting metasurface are investigated by simulations and measurements, which indicate that the proposed Huygens metasurface performs well in controlling electromagnetic waves.

  9. Ultrathin porous carbon films as amperometric transducers for biocatalytic sensors

    SciTech Connect

    Wang, J.; Chen, Q. (New Mexico State Univ., Las Cruces, NM (United States)); Renschler, C.L.; White, C. (Sandia National Lab., Albuquerque, NM (United States))

    1994-07-01

    Novel ultrathin (0.4 [mu]m) porous carbon films are employed as transducers for amperometric biosensors. Such foamlike nanoscopic films couple the advantages of high enzyme loadings (within the micropore hosts) and large microscopic area with a small geometric area. Both electropolymerization and metalization are used to entrap the enzyme within the micropores. Scanning electron microscopy sheds useful insights into the unique morphology of the growing enzyme layer. The greatly enhanced sensitivity is coupled with a fast and stable response. Factors influencing the performance of porous-film-based biosensors are examined and discussed. The improved performance is illustrated in connection with glucose and phenol sensors. The latter offers a remarkably low detection limit of 2.5 x 10[sup [minus]8] M. The new nanoscopic foams should prove useful for many other electroanalytical applications. 11 refs., 7 figs.

  10. Transport properties of ultrathin black phosphorus on hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Doganov, Rostislav A.; Koenig, Steven P.; Yeo, Yuting; Watanabe, Kenji; Taniguchi, Takashi; Özyilmaz, Barbaros

    2015-02-01

    Ultrathin black phosphorus, or phosphorene, is a two-dimensional material that allows both high carrier mobility and large on/off ratios. Similar to other atomic crystals, like graphene or layered transition metal dichalcogenides, the transport behavior of few-layer black phosphorus is expected to be affected by the underlying substrate. The properties of black phosphorus have so far been studied on the widely utilized SiO2 substrate. Here, we characterize few-layer black phosphorus field effect transistors on hexagonal boron nitride—an atomically smooth and charge trap-free substrate. We measure the temperature dependence of the field effect mobility for both holes and electrons and explain the observed behavior in terms of charged impurity limited transport. We find that in-situ vacuum annealing at 400 K removes the p-doping of few-layer black phosphorus on both boron nitride and SiO2 substrates and reduces the hysteresis at room temperature.

  11. Polar compensation in ultrathin films of a perovskite nickelate

    NASA Astrophysics Data System (ADS)

    Middey, S.; Rivero, P.; Meyers, D.; Kareev, M.; Liu, X.; Cao, Y.; Freeland, J. W.; Barraza-Lopez, S.; Chakhalian, J.

    2014-03-01

    The effect of strong polarity mismatch at the heterointerface, grown along the pseudo cubic [111] direction between the correlated metal LaNiO3 and band insulator SrTiO3 has been considered. While the metallic LaNiO3 film can itself screen this polarity mismatch, additional reconstruction mechanisms are needed in ultrathin films which are insulating in nature. The reflection high energy electron diffraction patterns recorded during growth highlighted the evolution of nucleation of an additional phase during the first few unit cells of deposition, which are found to be oxygen deficient phase LaNiO3-x by x ray diffraction and x-ray resonant spectroscopy measurement. The amount of oxygen vacancies decreases ABRUPTLY with the increase of film thickness due to the increase electrical conductivity, which acts in a partial screening of the polar catastrophe.

  12. Electrostatically Directed Self-Assembly of Ultrathin Supramolecular Polymer Microcapsules

    PubMed Central

    Parker, Richard M; Zhang, Jing; Zheng, Yu; Coulston, Roger J; Smith, Clive A; Salmon, Andrew R; Yu, Ziyi; Scherman, Oren A; Abell, Chris

    2015-01-01

    Supramolecular self-assembly offers routes to challenging architectures on the molecular and macroscopic scale. Coupled with microfluidics it has been used to make microcapsules—where a 2D sheet is shaped in 3D, encapsulating the volume within. In this paper, a versatile methodology to direct the accumulation of capsule-forming components to the droplet interface using electrostatic interactions is described. In this approach, charged copolymers are selectively partitioned to the microdroplet interface by a complementary charged surfactant for subsequent supramolecular cross-linking via cucurbit[8]uril. This dynamic assembly process is employed to selectively form both hollow, ultrathin microcapsules and solid microparticles from a single solution. The ability to dictate the distribution of a mixture of charged copolymers within the microdroplet, as demonstrated by the single-step fabrication of distinct core–shell microcapsules, gives access to a new generation of innovative self-assembled constructs.

  13. Pattern-Directed Dewetting of Ultrathin Polymer Films

    NSDL National Science Digital Library

    Sehgal, Amit

    2002-03-09

    We utilize chemically patterned substrates with arrays of progressively narrower stripes (1-15 mm) to investigate the influence of pattern size on the morphology of ultrathin dewetting polystyrene films. The scale and orientation of the spinodal-like height fluctuations of the dewetting patterns are coupled to the imposed substrate chemical frequency, providing a powerful means of morphological control. Dewetting patterns are correlated to the substrate pattern period leading to the formation of droplet arrays. The measurements confirm recent numerical simulations by Kargupta and Sharma of the existence of upper and lower cutoff scales for pattern recognition of a dewetting fluid. For pattern dimensions less than the characteristic scale on nonpatterned substrates, the droplets become anisotropic as they coarsen to a scale comparable to the stripe width, and then undergo a morphological transition to circular droplets that cross multiple stripes. This leads to quantization of droplet size and contact angles, as indicated by theory.

  14. Stability and capping of magnetite ultra-thin films

    NASA Astrophysics Data System (ADS)

    Fleischer, K.; Mauit, O.; Shvets, I. V.

    2014-05-01

    Ultrathin films of Fe3O4 have been grown epitaxially on nearly lattice matched MgO(001). The stability of 4 nm thick films in ambient air and under annealing in an oxygen atmosphere at 200 °C has been studied. By magneto optical and Raman measurements, we can confirm the presence of the Fe3O4 phase and the formation of a maghemite top layer passivating the Fe3O4 thin film. In a second step, we are able to demonstrate that this top layer oxidation in ambient air can be prevented by a 2 nm thick magnesium ferrite passivation layer, while a thicker 20 nm MgO layer prevents oxidation even at elevated temperatures.

  15. Ultrathin Nanostructured Metals for Highly Transmissive Plasmonic Subtractive Color Filters

    PubMed Central

    Zeng, Beibei; Gao, Yongkang; Bartoli, Filbert J.

    2013-01-01

    Plasmonic color filters employing a single optically-thick nanostructured metal layer have recently generated considerable interest as an alternative to colorant-based color filtering technologies, due to their reliability, ease of fabrication, and high color tunability. However, their relatively low transmission efficiency (~30%) needs to be significantly improved for practical applications. The present work reports, for the first time, a novel plasmonic subtractive color filtering scheme that exploits the counter-intuitive phenomenon of extraordinary low transmission (ELT) through an ultrathin nanostructured metal film. This approach relies on a fundamentally different color filtering mechanism than that of existing plasmonic additive color filters, and achieves unusually high transmission efficiencies of 60 ~ 70% for simple architectures. Furthermore, owing to short-range interactions of surface plasmon polaritons at ELT resonances, our design offers high spatial resolution color filtering with compact pixel size close to the optical diffraction limit (~?/2), creating solid applications ranging from imaging sensors to color displays. PMID:24100869

  16. Efficient laser-ion acceleration from closely stacked ultrathin foils

    SciTech Connect

    Kluge, T.; Kraft, S. D.; Schramm, U.; Zeil, K.; Cowan, T. E.; Sauerbrey, R.; Bussmann, M. [Forschungszentrum Dresden-Rossendorf e.V., D-01328 Dresden (Germany); Enghardt, W. [OncoRay, Technische Universitaet Dresden, D-01307 Dresden (Germany); Sentoku, Y. [University of Nevada, Reno, Nevada 89557 (United States)

    2010-07-15

    A new scheme to efficiently accelerate protons by a single linear polarized high-intensity ultrashort laser pulse using multiple ultrathin foils is proposed. The foils are stacked at a spacing comparable to their thickness and subsequently irradiated by the same laser pulse. The foil thicknesses are chosen such that the laser light pressure can displace all electrons out of the foil. The authors present a simple, yet precise dynamical model of the acceleration process from which both optimum foil thickness and spacing can be derived. Extensive two-dimensional (2D) particle-in-cell simulations verify the model predictions and suggest an enhancement of the maximum proton kinetic energy by 30% for the two-foil case compared to a single foil.

  17. Efficient laser-ion acceleration from closely stacked ultrathin foils.

    PubMed

    Kluge, T; Enghardt, W; Kraft, S D; Schramm, U; Sentoku, Y; Zeil, K; Cowan, T E; Sauerbrey, R; Bussmann, M

    2010-07-01

    A new scheme to efficiently accelerate protons by a single linear polarized high-intensity ultrashort laser pulse using multiple ultrathin foils is proposed. The foils are stacked at a spacing comparable to their thickness and subsequently irradiated by the same laser pulse. The foil thicknesses are chosen such that the laser light pressure can displace all electrons out of the foil. The authors present a simple, yet precise dynamical model of the acceleration process from which both optimum foil thickness and spacing can be derived. Extensive two-dimensional (2D) particle-in-cell simulations verify the model predictions and suggest an enhancement of the maximum proton kinetic energy by 30% for the two-foil case compared to a single foil. PMID:20866745

  18. Efficient laser-ion acceleration from closely stacked ultrathin foils

    NASA Astrophysics Data System (ADS)

    Kluge, T.; Enghardt, W.; Kraft, S. D.; Schramm, U.; Sentoku, Y.; Zeil, K.; Cowan, T. E.; Sauerbrey, R.; Bussmann, M.

    2010-07-01

    A new scheme to efficiently accelerate protons by a single linear polarized high-intensity ultrashort laser pulse using multiple ultrathin foils is proposed. The foils are stacked at a spacing comparable to their thickness and subsequently irradiated by the same laser pulse. The foil thicknesses are chosen such that the laser light pressure can displace all electrons out of the foil. The authors present a simple, yet precise dynamical model of the acceleration process from which both optimum foil thickness and spacing can be derived. Extensive two-dimensional (2D) particle-in-cell simulations verify the model predictions and suggest an enhancement of the maximum proton kinetic energy by 30% for the two-foil case compared to a single foil.

  19. Dielectric properties and microstructure of sintered BaTiO3 fabricated by using mixed 150-nm and 80-nm powders with various additives

    NASA Astrophysics Data System (ADS)

    Oh, Min Wook; Kang, Jae Won; Yeo, Dong Hun; Shin, Hyo Soon; Jeong, Dae Yong

    2015-04-01

    Recently, the use of small-sized BaTiO3 particles for ultra-thin MLCC research has increased as a method for minimizing the dielectric layer's thickness in thick film process. However, when particles smaller than 100 nm are used, the reduced particle size leads to a reduced dielectric constant. The use of nanoparticles, therefore, requires an increase in the amount of additive used due to the increase in the specific surface area, thus increasing the production cost. In this study, a novel method of coating 150-nm and 80-nm BaTiO3 powders with additives and mixing them together was employed, taking advantage of the effect obtained through the use of BaTiO3 particles smaller than 100 nm, to conveniently obtain the desired dielectric constant and thermal characteristics. Also, the microstructure and the dielectric properties were evaluated. The additives Dy, Mn, Mg, Si, and Cr were coated on a 150-nm powder, and the additives Dy, Mn, Mg, and Si were coated on 80-nm powder, followed by mixing at a ratio of 1:1. As a result, the microstructure revealed grain formation according to the liquid-phase additive Si; additionally, densification was well realized. However, non-reducibility was not obtained, and the material became a semiconductor. When the amount of added Mn in the 150-nm powder was increased to 0.2 and 0.3 mol%, insignificant changes in the microstructure were observed, and the bulk density after mixing was found to have increased drastically in comparison to that before mixing. Also, non-reducibility was obtained for certain conditions. The dielectric property was found to be consistent with the densification and the grain size. The mixed composition #1-0.3 had a dielectric constant over 2000, and the result somewhat satisfied the dielectric constant temperature dependency for X6S.

  20. Soft Dielectrics: Heterogeneity and Instabilities

    NASA Astrophysics Data System (ADS)

    Rudykh, Stephan; Debotton, Gal; Bhattacharya, Kaushik

    2012-02-01

    Dielectric Elastomers are capable of large deformations in response to electrical stimuli. Heterogeneous soft dielectrics with proper microstructures demonstrate much stronger electromechanical coupling than their homogeneous constituents. In turn, the heterogeneity is an origin for instability developments leading to drastic change in the composite microstructure. In this talk, the electromechanical instabilities are considered. Stability of anisotropic soft dielectrics is analyzed. Ways to achieve giant deformations and manipulating extreme material properties are discussed. 1. S. Rudykh and G. deBotton, ``Instabilities of Hyperelastic Fiber Composites: Micromechanical Versus Numerical Analyses.'' Journal of Elasticity, 2011. http://dx.doi.org/2010.1007/s10659-011-9313-x 2. S. Rudykh, K. Bhattacharya and G. deBotton, ``Snap-through actuation of thick-wall electroactive balloons.'' International Journal of Non-Linear Mechanics, 2011. http://dx.doi.org/10.1016/j.ijnonlinmec.2011.05.006 3. S. Rudykh and G. deBotton, ``Stability of Anisotropic Electroactive Polymers with Application to Layered Media.'' Zeitschrift f"ur angewandte Mathematik und Physik, 2011. http://dx.doi.org/10.1007/s00033-011-0136-1 4. S. Rudykh, A. Lewinstein, G. Uner and G. deBotton, ``Giant Enhancement of the Electromechanical Coupling in Soft Heterogeneous Dielectrics.'' 2011 http://arxiv.org/abs/1105.4217v1

  1. Polarization of Dielectrics by Acceleration

    E-print Network

    L. A. Melnikovsky

    2006-08-23

    We argue that acceleration induces electric polarization in usual dielectrics. Both accelerations in superfluid participate in the medium polarization. Excitations contribution to the polarization is calculated at low temperatures. Estimates of the effect show order of magnitude agreement with recent experimental results on electric effect of superflow.

  2. Dielectric nanocomposites with insulating properties

    Microsoft Academic Search

    Toshikatsu Tanaka

    2005-01-01

    Polymer nanocomposites possess promising high performances as engineering materials, if they are prepared and fabricated properly. Some work has been recently done on such polymer nanocomposites as dielectrics and electrical insulation. This was reviewed in 2004 based on the literatures published up to 2003. New significant findings have been added since then. Furthermore, a multi-core model with the far-distance effect,

  3. Dielectric breakdown model for composite materials.

    PubMed

    Peruani, F; Solovey, G; Irurzun, I M; Mola, E E; Marzocca, A; Vicente, J L

    2003-06-01

    This paper addresses the problem of dielectric breakdown in composite materials. The dielectric breakdown model was generalized to describe dielectric breakdown patterns in conductor-loaded composites. Conducting particles are distributed at random in the insulating matrix, and the dielectric breakdown propagates according to new rules to take into account electrical properties and particle size. Dielectric breakdown patterns are characterized by their fractal dimension D and the parameters of the Weibull distribution. Studies are carried out as a function of the fraction of conducting inhomogeneities, p. The fractal dimension D of electrical trees approaches the fractal dimension of a percolation cluster when the fraction of conducting particles approximates the percolation limit. PMID:16241318

  4. Energy Storage via Polyvinylidene Fluoride Dielectric on the Counterelectrode of Dye-Sensitized Solar Cells.

    PubMed

    Huang, Xuezhen; Zhang, Xi; Jiang, Hongrui

    2014-02-15

    To study the fundamental energy storage mechanism of photovoltaically self-charging cells (PSCs) without involving light-responsive semiconductor materials such as Si powder and ZnO nanowires, we fabricate a two-electrode PSC with the dual functions of photocurrent output and energy storage by introducing a PVDF film dielectric on the counterelectrode of a dye-sensitized solar cell. A layer of ultrathin Au film used as a quasi-electrode establishes a shared interface for the I(-)/I3 (-) redox reaction and for the contact between the electrolyte and the dielectric for the energy storage, and prohibits recombination during the discharging period because of its discontinuity. PSCs with a 10-nm-thick PVDF provide a steady photocurrent output and achieve a light-to-electricity conversion efficiency (?) of 3.38%, and simultaneously offer energy storage with a charge density of 1.67 C g(-1). Using this quasi-electrode design, optimized energy storage structures may be used in PSCs for high energy storage density. PMID:24327797

  5. Energy storage via polyvinylidene fluoride dielectric on the counterelectrode of dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Huang, Xuezhen; Zhang, Xi; Jiang, Hongrui

    2014-02-01

    To study the fundamental energy storage mechanism of photovoltaically self-charging cells (PSCs) without involving light-responsive semiconductor materials such as Si powder and ZnO nanowires, we fabricate a two-electrode PSC with the dual functions of photocurrent output and energy storage by introducing a PVDF film dielectric on the counterelectrode of a dye-sensitized solar cell. A layer of ultrathin Au film used as a quasi-electrode establishes a shared interface for the I-/I3- redox reaction and for the contact between the electrolyte and the dielectric for the energy storage, and prohibits recombination during the discharging period because of its discontinuity. PSCs with a 10-nm-thick PVDF provide a steady photocurrent output and achieve a light-to-electricity conversion efficiency (?) of 3.38%, and simultaneously offer energy storage with a charge density of 1.67 C g-1. Using this quasi-electrode design, optimized energy storage structures may be used in PSCs for high energy storage density.

  6. Optical dielectric function of silver

    NASA Astrophysics Data System (ADS)

    Yang, Honghua U.; D'Archangel, Jeffrey; Sundheimer, Michael L.; Tucker, Eric; Boreman, Glenn D.; Raschke, Markus B.

    2015-06-01

    The dielectric function of silver is a fundamental quantity related to its electronic structure and describes its optical properties. However, results published over the past six decades are in part inconsistent and exhibit significant discrepancies. The measurement is experimentally challenging with the values of dielectric function spanning over five orders of magnitude from the mid-infrared to the visible/ultraviolet spectral range. Using broadband spectroscopic ellipsometry, we determine the complex-valued dielectric function of evaporated and template stripped polycrystalline silver films from 0.05 eV (? =25 ? m ) to 4.14 eV (? =300 nm) with a statistical uncertainty of less than 1 % . From Drude analysis of the 0.1-3 eV range, values of the plasma frequency ? ?p=8.9 ±0.2 eV, dielectric function at infinite frequency ??=5 ±2 , and relaxation time ? =1 /? =17 ±3 fs are obtained, with the absolute uncertainties estimated from systematic errors and experimental repeatability. Further analysis based on the extended Drude model reveals an increase in ? with decreasing frequency in agreement with Fermi liquid theory, and extrapolates to ? ?22 fs for zero frequency. A deviation from simple Fermi liquid behavior is suggested at energies below 0.1 eV (? =12 ? m ) with the onset of a further increase in ? connecting to the DC value from transport measurements of ˜40 fs. The results are consistent with a wide range of optical and plasmonic experiments throughout the infrared and visible/ultraviolet spectral range. However, due to the polycrystalline nature of our sample, the values measured are not likely reaching the intrinsic limit of silver. The influence of grain boundaries, defect scattering, and surface oxidation is discussed. The results are compared with our previous measurements of the dielectric function of gold [Olmon et al., Phys. Rev. B 86, 235147 (2012)], 10.1103/PhysRevB.86.235147.

  7. Mechanical properties of high porosity low-k dielectric nano-films determined by Brillouin light scattering

    NASA Astrophysics Data System (ADS)

    Bailey, S.; Mays, E.; Michalak, D. J.; Chebiam, R.; King, S.; Sooryakumar, R.

    2013-01-01

    Integrating nanometre sized pores into hybrid organic-inorganic interconnect layers is one of the key approaches being undertaken by the semiconductor industry to sustain the continued scale down of micro-electronic devices. While increasing porosity of the layers achieves the desirable lowering of the dielectric constant (k), it also has the potential to reduce mechanical and thermal stability and degrade device functionality. We report on Brillouin light scattering to measure the independent elastic constants, and thus the mechanical properties, of ultrathin dielectric films with porosity levels up to 45%, the highest in the industry. Longitudinal and transverse acoustic standing mode type excitations were observed from sub 200 nm thick low-k thin films, and their frequency dispersion and associated light scattering intensities were utilized to determine Poisson's ratio (?) and Young's modulus (E). In comparison with SiO2 and non-porous low-k materials, significant modifications were found in ? and E of these highly porous carbon-doped SiO2 (Si-O-C-H) and amorphous carbon (a-C?:?H) low-k interlayer dielectrics.

  8. Intrinsic microwave dielectric loss of lanthanum aluminate.

    PubMed

    Shimada, Takeshi; Ichikawa, Koji; Minemura, Tetsuro; Yamauchi, Hiroki; Utsumi, Wataru; Ishii, Yoshinobu; Breeze, Jonathan; Alford, Neil McN

    2010-10-01

    The intrinsic dielectric properties of LaAlO? were investigated to understand the microwave properties of several materials containing LaAlO?. In this study, LaAlO? single crystals were prepared by the Czochralski method. The temperature dependence of the dielectric properties and neutron inelastic scattering of the single crystals were measured. From these data, the intrinsic dielectric properties were evaluated and it was found that the dielectric loss of the LaAlO? includes two types of dielectric loss. One is a phonon absorption-related loss and the other is a component of the loss arising from Debye- type orientation polarization. The latter affects the room temperature dielectric loss in materials containing LaAlO?. The present study suggests that avoiding this polarization loss is an important goal in decreasing the total dielectric loss. PMID:20889412

  9. DIELECTRIC RELAXATIONS IN ULTRA-THIN FILMS OF PMMA: ASSESSING THE LENGTH SCALE OF COOPERATIVITY IN THE

    E-print Network

    Dutcher, John

    Tg by up to 10K was observed for a film thickness L REE), indicated below REE. Introduction The idea of cooperatively-rearranging regions (CRR), as first proposed by Adam, also on the end-to-end distance REE of the polymer [8]. In contrast, much lower Tg reductions or even

  10. Tailoring dielectric properties of ferroelectric-dielectric multilayers

    NASA Astrophysics Data System (ADS)

    Kesim, M. T.; Cole, M. W.; Zhang, J.; Misirlioglu, I. B.; Alpay, S. P.

    2014-01-01

    We develop a nonlinear thermodynamic model for multilayer ferroelectric heterostructures that takes into account electrostatic and electromechanical interactions between layers. We concentrate on the effect of relative layer fractions and in-plane thermal stresses on dielectric properties of Ba0.6Sr0.4TiO3-, BaTiO3-, and PbZr0.2Ti0.8O3 (PZT)-SrTiO3 (STO) multilayers on Si and c-sapphire. We show that dielectric properties of such multilayers can be significantly enhanced by tailoring the growth/processing temperature and the STO layer fraction. Our computations show that large tunabilities (˜90% at 400 kV/cm) are possible in carefully designed barium strontium titanate-STO and PZT-STO even on Si for which there exist substantially large in-plane strains.

  11. Dielectric breakdown of cell membranes.

    PubMed

    Zimmermann, U; Pilwat, G; Riemann, F

    1974-11-01

    With human and bovine red blood cells and Escherichia coli B, dielectric breakdown of cell membranes could be demonstrated using a Coulter Counter (AEG-Telefunken, Ulm, West Germany) with a hydrodynamic focusing orifice. In making measurements of the size distributions of red blood cells and bacteria versus increasing electric field strength and plotting the pulse heights versus the electric field strength, a sharp bend in the otherwise linear curve is observed due to the dielectric breakdown of the membranes. Solution of Laplace's equation for the electric field generated yields a value of about 1.6 V for the membrane potential at which dielectric breakdown occurs with modal volumes of red blood cells and bacteria. The same value is also calculated for red blood cells by applying the capacitor spring model of Crowley (1973. Biophys. J. 13:711). The corresponding electric field strength generated in the membrane at breakdown is of the order of 4 . 10(6) V/cm and, therefore, comparable with the breakdown voltages for bilayers of most oils. The critical detector voltage for breakdown depends on the volume of the cells. The volume-dependence predicted by Laplace theory with the assumption that the potential generated across the membrane is independent of volume, could be verified experimentally. Due to dielectric breakdown the red blood cells lose hemoglobin completely. This phenomenon was used to study dielectric breakdown of red blood cells in a homogeneous electric field between two flat platinum electrodes. The electric field was applied by discharging a high voltage storage capacitor via a spark gap. The calculated value of the membrane potential generated to produce dielectric breakdown in the homogeneous field is of the same order as found by means of the Coulter Counter. This indicates that mechanical rupture of the red blood cells by the hydrodynamic forces in the orifice of the Coulter Counter could also be excluded as a hemolysing mechanism. The detector voltage (or the electric field strength in the orifice) depends on the membrane composition (or the intrinsic membrane potential) as revealed by measuring the critical voltage in E. coli B harvested from the logarithmic and stationary growth phases. The critical detector voltage increased by about 30% for a given volume on reaching the stationary growth phase. PMID:4611517

  12. Dielectric properties of insect tissues.

    PubMed

    Ondrácek, J; Brunnhofer, V

    1984-06-01

    In order to explain some effects of microwave irradiation on insects it is necessary to consider a mathematical model. The knowledge of dielectric properties of a typical insect tissue is crucial for such a model. A method based on shift of resonant frequency and of quality factor measurement in a resonator both before and after the insertion of samples was used. The method (measurements at a frequency of 2375 MHz) has been described in detail. A large number of measurements were performed on different kinds of typical insect tissues (cuticle, fat body, muscles, reproductive organs and eggs) for their dielectric properties. The values obtained compare well to those reported in the literature for some mammals. Differences seemed to depend on different water-to-fat content ratios. However, no simple dependence on the water content was found. Values obtained from insect tissue material have been discussed in detail. PMID:6479581

  13. Optomechanics of Levitated Dielectric Particles

    E-print Network

    Yin, Zhang-qi; Li, Tongcang

    2013-01-01

    We review recent works on optomechanics of optically trapped microspheres and nanoparticles in vacuum, which provide an ideal system for studying macroscopic quantum mechanics and ultrasensitive force detection. An optically trapped particle in vacuum has an ultrahigh mechanical quality factor as it is well-isolated from the thermal environment. Its oscillation frequency can be tuned in real time by changing the power of the trapping laser. Furthermore, an optically trapped particle in vacuum may rotate freely, a unique property that does not exist in clamped mechanical oscillators. In this review, we will introduce the current status of optical trapping of dielectric particles in air and vacuum, Brownian motion of an optically trapped particle at room temperature, Feedback cooling and cavity cooling of the Brownian motion. We will also discuss about using optically trapped dielectric particles for studying macroscopic quantum mechanics and ultrasensitive force detection. Applications range from creating macr...

  14. Radiation Resistances of Dielectric Liquids

    NASA Technical Reports Server (NTRS)

    Bouquet, Frank L.; Somoano, Robert B.

    1987-01-01

    Report presents data on effects of ionizing radiation on dielectric liquids for high-energy-density, pulsed-power capacitors. Based on Jet Propulsion Laboratory test results, search of NASA and Department of Energy computer files, survey of open literature, and contacts with manufacturers and suppliers. Covers 22 organic liquids, although detailed data found for only one compound, polydimethyl siloxane. Generic data on effects of radiation on compounds with similar chemical structures provided where data on specific compounds lacking.

  15. Investigations of novel high dielectric materials and new mechanisms

    Microsoft Academic Search

    Meng Guo

    2009-01-01

    A high dielectric constant material with excellent dielectric properties is highly desirable for a wide range of applications, such as high energy density capacitors and optical limiting materials. High dielectric constant materials used for embedded capacitors require characteristics such as a high dielectric constant (>7), a low dielectric loss (<0.01) as well as good thermal stability. Some success has been

  16. Ultra-thin Titanium Oxide Films on Accession #s 00936, 00937,00938 Mo(112), Measured by XPS Technique: XPS

    E-print Network

    Goodman, Wayne

    Ultra-thin Titanium Oxide Films on Accession #s 00936, 00937,00938 Mo(112), Measured by XPS preparation methods were employed to grow a well-ordered ultra-thin titanium oxide film on Mo(J (2), The tirst: photoemission; titanium oxide; tllin film PACS: 81.15.Gh. 79,60.Dp SPECIMEN DESCRIPTION (Accession #00936) Host

  17. ENS'05 Paris, France, 14-16 December 2005 Electrical Characterisation of Ultra-thin SAM Structures

    E-print Network

    Paris-Sud XI, Université de

    Electrical characterization of ultra-thin SAM structures Fig.2: Schottky diode schematic structure. JVERTENS'05 Paris, France, 14-16 December 2005 Electrical Characterisation of Ultra-thin SAM Structures electrical measurements of Schottky diode (Fig.2), for which native oxide is formed on silicon substrate

  18. IEEE ELECTRON DEVICE LETTERS, VOL. 24, NO. 1, JANUARY 2003 31 Low-Frequency Noise Characteristics of Ultrathin

    E-print Network

    Bokor, Jeffrey

    gate, molybdenum, nitrogen implantation, oxide trap density, silicon-on-insulator (SOI), thin-body. I. INTRODUCTION ULTRATHIN body (UTB) silicon-on-insulator (SOI) MOSFET devices are promising for sub-50-nm CMOS of Ultrathin Body p-MOSFETs With Molybdenum Gate Jeong-Soo Lee, Daewon Ha, Yang-Kyu Choi, Tsu-Jae King

  19. Optical dielectric function of gold

    NASA Astrophysics Data System (ADS)

    Olmon, Robert L.; Slovick, Brian; Johnson, Timothy W.; Shelton, David; Oh, Sang-Hyun; Boreman, Glenn D.; Raschke, Markus B.

    2012-12-01

    In metal optics gold assumes a special status because of its practical importance in optoelectronic and nano-optical devices, and its role as a model system for the study of the elementary electronic excitations that underlie the interaction of electromagnetic fields with metals. However, largely inconsistent values for the frequency dependence of the dielectric function describing the optical response of gold are found in the literature. We performed precise spectroscopic ellipsometry measurements on evaporated gold, template-stripped gold, and single-crystal gold to determine the optical dielectric function across a broad spectral range from 300 nm to 25 ?m (0.05-4.14 eV) with high spectral resolution. We fit the data to the Drude free-electron model, with an electron relaxation time ?D=14±3 fs and plasma energy ??p=8.45 eV. We find that the variation in dielectric functions for the different types of samples is small compared to the range of values reported in the literature. Our values, however, are comparable to the aggregate mean of the collection of previous measurements from over the past six decades. This suggests that although some variation can be attributed to surface morphology, the past measurements using different approaches seem to have been plagued more by systematic errors than previously assumed.

  20. Scattering from thin dielectric disks

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  1. Microwave dielectric spectrum of rocks

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.; Bengal, T.; East, J.; Dobson, M. C.; Garvin, J.; Evans, D.

    1988-01-01

    A combination of several measurement techniques was used to investigate the dielectric properties of 80 rock samples in the microwave region. The real part of the dielectric constant, epsilon', was measured in 0.1 GHz steps from 0.5 to 18 GHz, and the imaginary part, epsilon'', was measured at five frequencies extending between 1.6 and 16 GHz. In addition to the dielectric measurements, the bulk density was measured for all the samples and the bulk chemical composition was determined for 56 of the samples. The study shows that epsilon' is frequency-dependent over the 0.5 to 18 GHz range for all rock samples, and that the bulk density rho accounts for about 50 percent of the observed variance of epsilon'. For individual rock types (by genesis), about 90 percent of the observed variance may be explained by the combination of density and the fractional contents of SiO2, Fe2O3, MgO, and TiO2. For the loss factor epsilon'', it was not possible to establish statistically significant relationships between it and the measured properties of the rock samples (density and chemical composition).

  2. Ultrathin Nickel Hydroxide and Oxide Nanosheets: Synthesis, Characterizations and Excellent Supercapacitor Performances

    PubMed Central

    Zhu, Youqi; Cao, Chuanbao; Tao, Shi; Chu, Wangsheng; Wu, Ziyu; Li, Yadong

    2014-01-01

    High-quality ultrathin two-dimensional nanosheets of ?-Ni(OH)2 are synthesized at large scale via microwave-assisted liquid-phase growth under low-temperature atmospheric conditions. After heat treatment, non-layered NiO nanosheets are obtained while maintaining their original frame structure. The well-defined and freestanding nanosheets exhibit a micron-sized planar area and ultrathin thickness (<2?nm), suggesting an ultrahigh surface atom ratio with unique surface and electronic structure. The ultrathin 2D nanostructure can make most atoms exposed outside with high activity thus facilitate the surface-dependent electrochemical reaction processes. The ultrathin ?-Ni(OH)2 and NiO nanosheets exhibit enhanced supercapacitor performances. Particularly, the ?-Ni(OH)2 nanosheets exhibit a maximum specific capacitance of 4172.5?F g?1 at a current density of 1?A g?1. Even at higher rate of 16?A g?1, the specific capacitance is still maintained at 2680?F g?1 with 98.5% retention after 2000 cycles. Even more important, we develop a facile and scalable method to produce high-quality ultrathin transition metal hydroxide and oxide nanosheets and make a possibility in commercial applications. PMID:25168127

  3. Finite element analysis of deflection and residual stress on machined ultra-thin silicon wafers

    NASA Astrophysics Data System (ADS)

    Tian, Y. B.; Zhou, L.; Zhong, Z. W.; Sato, H.; Shimizu, J.

    2011-10-01

    The demand for ultra-thin silicon wafers has escalated in recent years with the rapid development of miniaturized electronic devices. Residual stress generated in the thinning process has a great influence on the machining quality of ultra-thin wafers. This work has developed a 2D axisymmetric finite element (FE) model to predict the deflection and full-field residual stress of ground ultra-thin wafers. The FE model consists of two-layer structures, i.e. a damage layer induced by the thinning process and a bulk silicon crystal layer without defects. A series of uniform in-plane strains is applied to the damage layer to simulate machining-generated initial stress. A full-field residual stress distribution in a machined ultra-thin wafer is predicted with the developed FE model after the initial stress is released. Based on the FE model, effects of wafer geometrical dimensions and loaded initial strain (or stress) on the maximum compressive/tensile residual stress and the maximum wafer deflection are revealed. The model is finally verified by comparing the simulated wafer deflection with the measured value. Based on this work, the deflection and residual stress of a machined ultra-thin wafer can be conveniently predicted.

  4. Crystallization of thin and ultra-thin polymer films

    NASA Astrophysics Data System (ADS)

    Wang, Yantian

    Thin and ultra-thin polymer films have received great interest due to their technological applications in the modern micro-electronic devices. It has been demonstrated that the presence of the interface and the confined geometry greatly affect configuration of the chains, segmental mobility and thermal transitions in the polymer thin films. In the semi-crystalline polymer thin films, the degree of crystallinity, crystallization dynamics, crystal morphology and lamellar orientation are different from their bulk counterparts. In this dissertation, a comprehensive study in the crystallization and melting of spun-coated thin and ultra-thin films of polyethylene-vinyl acetate)(EVA), linear low and medium density polyethylene (LLDPE and LMDPE) on selected substrates was made. The morphology, the lamellar orientation and the melting point of the films were found to have strong dependence on the film thickness and the substrate. On the strongly attractive substrate such as silicon, the film crystallized as spherulite with densely organized edge-on lamellae for the films thicker than 100nm, the lamellae packed more loosely as the film thickness decreased, until finally exhibited a dense branching morphology with mainly flat-on lamellae when the film is thinner than 15nm. A large degree of crystallinity was observed in the film as thin as 15nm. On the less absorbent substrate such as polyimide, the films crystallized in a randomly organized lamellae structure, which showed little dependence on the film thickness. On all the substrates, the melting point of the film decreased with the film thickness decrease when the film was thinner than a critical thickness, the value of which varied for different substrates. The biggest Tm depression observed was between 12°C and 38°C, depending on the substrates. The finite size effect and the reduced melting entropy caused by the confined movement of the polymer chains due to the substrate absorption were suggested to be the main reasons for the sharp Tm depression. The chain orientation inside the crystals was measured by near edge X-ray absorption fine structure (NEXAFS) spectroscopy, which showed that on the silicon substrate, the chains oriented parallel to the substrate with b axis in the radiation direction of the fibrils of the spherulite, a axis perpendicular to the film surface.

  5. Competing weak localization and weak antilocalization in ultrathin topological insulators

    NASA Astrophysics Data System (ADS)

    Lang, Murong; He, Liang; Kou, Xufeng; Upadhyaya, Pramey; Fan, Yabin; Chu, Hao; Yeh, Nai-Chang; Wang, Kang

    2013-03-01

    We demonstrate the evidences of a surface gap opening in (Bi0.57Sb0.43)2 Te3 samples for film thickness below 6 quintuple layers, through magnetotransport and scanning tunneling spectroscopy measurements. By tuning Fermi level position relative to the gap, the striking crossover between weak antilocalization and weak localization is observed in nonmagnetic 4 and 5 QL films at low field region, a characteristic feature of quantum interferences competition, possibly owing to the change of net Berry phase. Furthermore, when the Fermi level is swept into the surface gap, the overall unitary behaviors are revealed at higher magnetic field, which are in contrast to the pure WAL signals obtained in thicker films. Besides, the surface bandgap of ultrathin film is also determined by low temperature STS measurements. Our findings show an exotic phenomenon characterizing the gapped TI surface states and point to the future realization of quantum spin Hall effect and dissipationless TI-based applications. We demonstrate the evidences of a surface gap opening in (Bi0.57Sb0.43)2 Te3 samples for film thickness below 6 quintuple layers, through magnetotransport and scanning tunneling spectroscopy measurements. By tuning Fermi level position relative to the gap, the striking crossover between weak antilocalization and weak localization is observed in nonmagnetic 4 and 5 QL films at low field region, a characteristic feature of quantum interferences competition, possibly owing to the change of net Berry phase. Furthermore, when the Fermi level is swept into the surface gap, the overall unitary behaviors are revealed at higher magnetic field, which are in contrast to the pure WAL signals obtained in thicker films. Besides, the surface bandgap of ultrathin film is also determined by low temperature STS measurements. Our findings show an exotic phenomenon characterizing the gapped TI surface states and point to the future realization of quantum spin Hall effect and dissipationless TI-based applications. This work was in part supported by Defense Advanced Research Projects Agency (DARPA), Focus Center Research Program-Center on Functional Engineered Nano Architectonics (FENA).

  6. Ultra-thin solid oxide fuel cells: Materials and devices

    NASA Astrophysics Data System (ADS)

    Kerman, Kian

    Solid oxide fuel cells are electrochemical energy conversion devices utilizing solid electrolytes transporting O2- that typically operate in the 800 -- 1000 °C temperature range due to the large activation barrier for ionic transport. Reducing electrolyte thickness or increasing ionic conductivity can enable lower temperature operation for both stationary and portable applications. This thesis is focused on the fabrication of free standing ultrathin (<100 nm) oxide membranes of prototypical O 2- conducting electrolytes, namely Y2O3-doped ZrO2 and Gd2O3-doped CeO2. Fabrication of such membranes requires an understanding of thin plate mechanics coupled with controllable thin film deposition processes. Integration of free standing membranes into proof-of-concept fuel cell devices necessitates ideal electrode assemblies as well as creative processing schemes to experimentally test devices in a high temperature dual environment chamber. We present a simple elastic model to determine stable buckling configurations for free standing oxide membranes. This guides the experimental methodology for Y 2O3-doped ZrO2 film processing, which enables tunable internal stress in the films. Using these criteria, we fabricate robust Y2O3-doped ZrO2 membranes on Si and composite polymeric substrates by semiconductor and micro-machining processes, respectively. Fuel cell devices integrating these membranes with metallic electrodes are demonstrated to operate in the 300 -- 500 °C range, exhibiting record performance at such temperatures. A model combining physical transport of electronic carriers in an insulating film and electrochemical aspects of transport is developed to determine the limits of performance enhancement expected via electrolyte thickness reduction. Free standing oxide heterostructures, i.e. electrolyte membrane and oxide electrodes, are demonstrated. Lastly, using Y2O3-doped ZrO2 and Gd2O 3-doped CeO2, novel electrolyte fabrication schemes are explored to develop oxide alloys and nanoscale compositionally graded membranes that are thermomechanically robust and provide added interfacial functionality. The work in this thesis advances experimental state-of-the-art with respect to solid oxide fuel cell operation temperature, provides fundamental boundaries expected for ultrathin electrolytes, develops the ability to integrate highly dissimilar material (such as oxide-polymer) heterostructures, and introduces nanoscale compositionally graded electrolyte membranes that can lead to monolithic materials having multiple functionalities.

  7. Electromechanics of dielectric particles in dielectric liquids acted on by a microelectrode array 

    E-print Network

    Seo, Cheong Soo

    2006-04-12

    Arrays of microelectrodes were used to apply forces to dielectric (soda lime glass) spheres in a thin (200 micrometer thick) layer of a dielectric liquid polymer (EOPN 8021). The microelectrodes were fabricated using ...

  8. Dielectric relaxation of high-k oxides

    PubMed Central

    2013-01-01

    Frequency dispersion of high-k dielectrics was observed and classified into two parts: extrinsic cause and intrinsic cause. Frequency dependence of dielectric constant (dielectric relaxation), that is the intrinsic frequency dispersion, could not be characterized before considering the effects of extrinsic frequency dispersion. Several mathematical models were discussed to describe the dielectric relaxation of high-k dielectrics. For the physical mechanism, dielectric relaxation was found to be related to the degree of polarization, which depended on the structure of the high-k material. It was attributed to the enhancement of the correlations among polar nanodomain. The effect of grain size for the high-k materials' structure mainly originated from higher surface stress in smaller grain due to its higher concentration of grain boundary. PMID:24180696

  9. A self-healing dielectric elastomer actuator

    NASA Astrophysics Data System (ADS)

    Hunt, Stacy; McKay, Thomas G.; Anderson, Iain A.

    2014-03-01

    Dielectric elastomer actuators that can provide muscle-like actuation are unable to self-heal like real muscle tissue. This severely limits dielectric elastomer reliability and robustness. This paper describes a way to instill self-healing into the DE by using a two-phase dielectric consisting of an open-cell silicone sponge saturated with silicone oil. When the dielectric is breached, the oil is able to flow back into any void, re-establishing the dielectric structure. The sponge holds the oil in place and provides dimensional stability, while the oil ensures the integrity of the dielectric layer. The operation of this has been demonstrated in a prototype DE actuator that continued to function despite being perforated multiple times with a sharp object.

  10. Intrinsic microwave dielectric loss of lanthanum aluminate

    Microsoft Academic Search

    T. Shimada; K. Ichikawa; T. Minemura; H. Yamauchi; W. Utsumi; Y. Ishii; J. Breeze; N. M. Alford

    2010-01-01

    The intrinsic dielectric properties of LaAlO3 were investigated to understand the microwave properties of several materials containing LaAlO3. In this study, LaAlO3 single crystals were prepared by the Czochralski method. The temperature dependence of the dielectric properties and neutron inelastic scattering of the single crystals were measured. From these data, the intrinsic dielectric properties were evaluated and it was found

  11. Intrinsic microwave dielectric loss of lanthanum aluminate

    Microsoft Academic Search

    T. Shimada; K. Ichikawa; T. Minemura; H. Yamauchi; W. Utsumi; Y. Ishii; J. Breeze; N. M. Alford

    2009-01-01

    The intrinsic dielectric properties of LaAlO3 were investigated in order to understand the microwave properties for several material containing LaAlO3. LaAlO3 single crystal was the prepared by Czochralski method. The temperature dependence of the dielectric properties and neutron inelastic scattering of the single crystal were measured. From these data, the intrinsic dielectric properties were evaluated and it was found that

  12. Fano resonances in all-dielectric oligomers.

    PubMed

    Miroshnichenko, Andrey E; Kivshar, Yuri S

    2012-12-12

    We demonstrate that light scattering by all-dielectric oligomers exhibits well-pronounced Fano resonances with strong suppression of the scattering cross section. Our analysis reveals that this type of the Fano resonance originates from the optically induced magnetic dipole modes of individual high-dielectric nanoparticles. By comparing to the plasmonic analogues, we observe that Fano resonances in all-dielectric oligomers are less sensitive to structural variations, which makes them promising for future applications in nanophotonics. PMID:23170879

  13. Dielectric elastomer actuators with elastomeric electrodes

    NASA Astrophysics Data System (ADS)

    Bozlar, Michael; Punckt, Christian; Korkut, Sibel; Zhu, Jian; Chiang Foo, Choon; Suo, Zhigang; Aksay, Ilhan A.

    2012-08-01

    For many applications of dielectric elastomer actuators, it is desirable to replace the carbon-grease electrodes with stretchable, solid-state electrodes. Here, we attach thin layers of a conducting silicone elastomer to prestrained films of an acrylic dielectric elastomer and achieve voltage-actuated areal strains over 70%. The influence of the stiffness of the electrodes and the prestrain of the dielectric films is studied experimentally and theoretically.

  14. Dielectric behavior of semiconductors at microwave frequencies

    NASA Technical Reports Server (NTRS)

    Dahiya, Jai N.

    1992-01-01

    A cylindrical microwave resonant cavity in TE(011) (Transverse Electric) mode is used to study the dielectric relaxation in germanium and silicon. The samples of these semiconductors are used to perturb the electric field in the cavity, and Slater's perturbation equations are used to calculate the real and imaginary parts of the dielectric constant. The dielectric loss of germanium and silicon is studied at different temperatures, and Debye's equations are used to calculate the relaxation time at these temperatures.

  15. Study of dielectric relaxation spectra of composite materials by the dielectric spectroscopy method

    Microsoft Academic Search

    O. S. Gefle; S. M. Lebedev; Y. P. Pokholkov; S. N. Tkachenko; V. A. Volokhin; E. I. Cherkashina

    2005-01-01

    In this paper composite solid dielectrics were studied by using the dielectric spectroscopy method in frequency domain. Dielectric relaxation spectra of composite materials on the basis of natural and synthetic rubbers and LDPE filled with a ferroelectric ceramic powder PZT (lead zirconate titanate) were studied. The filled composites with high permittivity were used in HV insulation for the electric field

  16. Twisted ultrathin silicon nanowires: A possible torsion electromechanical nanodevice

    NASA Astrophysics Data System (ADS)

    Garcia, J. C.; Justo, J. F.

    2014-11-01

    Nanowires have been considered for a number of applications in nanometrology. In such a context, we have explored the possibility of using ultrathin twisted nanowires as torsion nanobalances to probe forces and torques at molecular level with high precision, a nanoscale system analogous to the Coulomb's torsion balance electrometer. In order to achieve this goal, we performed a first-principles investigation on the structural and electronic properties of twisted silicon nanowires, in their pristine and hydrogenated forms. The results indicated that wires with pentagonal and hexagonal cross-sections are the thinnest stable silicon nanostructures. Additionally, all wires followed a Hooke's law behavior for small twisting deformations. Hydrogenation leads to spontaneous twisting, but with angular spring constants considerably smaller than the ones for the respective pristine forms. We observed considerable changes on the nanowire electronic properties upon twisting, which allows to envision the possibility of correlating the torsional angular deformation with the nanowire electronic transport. This could ultimately allow a direct access to measurements on interatomic forces at molecular level.

  17. Transepithelial corneal collagen cross-linking in ultrathin keratoconic corneas

    PubMed Central

    Spadea, Leopoldo; Mencucci, Rita

    2012-01-01

    Background The purpose of this paper was to report the results of transepithelial corneal collagen cross-linking (CXL) with modified riboflavin and ultraviolet A irradiation in patients affected by keratoconus, each with thinnest pachymetry values of less than 400 ?m (with epithelium) and not treatable using standard de-epithelialization techniques. Methods Sixteen patients affected by progressive keratoconus with thinnest pachymetry values ranging from 331 ?m to 389 ?m underwent transepithelial CXL in one eye using a riboflavin 0.1% solution in 15% Dextran T500 containing ethylenediamine tetra-acetic acid 0.01% and trometamol to enhance epithelial penetration. The patients underwent complete ophthalmological examination, including endothelial cell density measurements and computerized videokeratography, before CXL and at one day, one week, and one, 6, and 12 months thereafter. Results Epithelial healing was complete in all patients after one day of use of a soft bandage contact lens. No side effects or damage to the limbal region was observed during the follow-up period. All patients showed slightly improved uncorrected and spectacle-corrected visual acuity; keratometric astigmatism showed reductions (up to 5.3 D) and apical ectasia power decreased (Kmax values reduced up to 4.3 D). Endothelial cell density was unchanged. Conclusion Application of transepithelial CXL using riboflavin with substances added to enhance epithelial permeability was safe, seemed to be moderately effective in keratoconic eyes with ultrathin corneas, and applications of the procedure could be extended to patients with advanced keratoconus. PMID:23152657

  18. Superconducting single-photon ultrathin NbN film detector

    SciTech Connect

    Korneev, A A; Minaeva, O V; Rubtsova, Inna A; Milostnaya, I I; Chulkova, G M; Voronov, B M; Smirnov, K V; Seleznev, V A; Gol'tsman, G N [Moscow State Pedagogical University, Moscow (Russian Federation); Pearlman, A; Slysz, W; Cross, A; Alvarez, P; Verevkin, A; Sobolewski, R [University of Rochester, Rochester (United States)

    2005-08-31

    Superconducting single-photon ultrathin NbN film detectors are studied. The development of manufacturing technology of detectors and the reduction of their operating temperature down to 2 K resulted in a considerable increase in their quantum efficiency, which reached in the visible region (at 0.56 {mu}m) 30%-40%, i.e., achieved the limit determined by the absorption coefficient of the film. The quantum efficiency exponentially decreases with increasing wavelength, being equal to {approx}20% at 1.55 {mu}m and {approx}0.02% at 5 {mu}m. For the dark count rate of {approx}10{sup -4}s{sup -1}, the experimental equivalent noise power was 1.5x10{sup -20} W Hz{sup -1/2}; it can be decreased in the future down to the record low value of 5x10{sup -21} W Hz{sup -1/2}. The time resolution of the detector is 30 ps. (fourth seminar to the memory of d.n. klyshko)

  19. Growth of Ordered Ultrathin Tungsten Oxide Films on Pt(111)

    SciTech Connect

    Li, Zhenjun; Zhang, Zhenrong; Kim, Yu Kwon; Smith, R. Scott; Netzer, Falko; Kay, Bruce D.; Rousseau, Roger J.; Dohnalek, Zdenek

    2011-04-07

    Ordered tungsten oxide ultra-thin films were prepared on a Pt(111) substrate at 700 K via direct sublimation of monodispersed cyclic (WO3)3 trimers. The surface composition, structure and morphology were determined using a combination of atomically resolved imaging, ensemble-averaged surface-sensitive spectroscopies, and density functional theory (DFT). We find that half of the (WO3)3 tungsten atoms get partially reduced to the (5+) oxidation state in the first layer at the Pt(111) interface. The opening of the (WO3)3 ring leads to the formation of a tungsten oxide layer with a zig-zag chain structure with a c(4×2) periodicity. In the second layer, the (WO3)3 clusters remain intact and form an ordered (3×3) array of molecularly-bound (WO3)3. DFT calculations provide a detailed understanding of the structure, oxidation states, and the vibrational frequencies for both the c(4×2) and (3×3) overlayers.

  20. Three-dimensional Ultrathin Planar Lenses by Acoustic Metamaterials

    NASA Astrophysics Data System (ADS)

    Li, Yong; Yu, Gaokun; Liang, Bin; Zou, Xinye; Li, Guangyun; Cheng, Su; Cheng, Jianchun

    2014-10-01

    Acoustic lenses find applications in various areas ranging from ultrasound imaging to nondestructive testing. A compact-size and high-efficient planar acoustic lens is crucial to achieving miniaturization and integration, and should have deep implication for the acoustic field. However its realization remains challenging due to the trade-off between high refractive-index and impedance-mismatch. Here we have designed and experimentally realized the first ultrathin planar acoustic lens capable of steering the convergence of acoustic waves in three-dimensional space. A theoretical approach is developed to analytically describe the proposed metamaterial with hybrid labyrinthine units, which reveals the mechanism of coexistence of high refractive index and well-matched impedance. A hyperbolic gradient-index lens design is fabricated and characterized, which can enhance the acoustic energy by 15 dB at the focal point with very high transmission efficiency. Remarkably, the thickness of the lens is only approximately 1/6 of the operating wavelength. The lens can work within a certain frequency band for which the ratio between the bandwidth and the center frequency reaches 0.74. By tailoring the structure of the metamaterials, one can further reduce the thickness of the lens or even realize other acoustic functionalities, opening new opportunity for manipulation of low-frequency sounds with versatile potential.

  1. Lateral manipulation of atomic vacancies in ultrathin insulating films.

    PubMed

    Li, Zhe; Chen, Hsin-Yi Tiffany; Schouteden, Koen; Lauwaet, Koen; Janssens, Ewald; Van Haesendonck, Chris; Pacchioni, Gianfranco; Lievens, Peter

    2015-05-26

    During the last 20 years, using scanning tunneling microscopy (STM) and atomic force microscopy, scientists have successfully achieved vertical and lateral repositioning of individual atoms on and in different types of surfaces. Such atom manipulation allows the bottom-up assembly of novel nanostructures that can otherwise not be fabricated. It is therefore surprising that controlled repositioning of virtual atoms, i.e., atomic vacancies, across atomic lattices has not yet been achieved experimentally. Here we use STM at liquid helium temperature (4.5 K) to create individual Cl vacancies and subsequently to laterally manipulate them across the surface of ultrathin sodium chloride films. This allows monitoring the interactions between two neighboring vacancies with different separations. Our findings are corroborated by density functional theory calculations and STM image simulations. The lateral manipulation of atomic vacancies opens up a new playground for the investigation of fundamental physical properties of vacancy nanostructures of any size and shape and their coupling with the supporting substrate, and of the interaction of various deposits with charged vacancies. PMID:25769024

  2. Laterally assembled nanowires for ultrathin broadband solar absorbers.

    PubMed

    Song, Kyung-Deok; Kempa, Thomas J; Park, Hong-Gyu; Kim, Sun-Kyung

    2014-05-01

    We studied optical resonances in laterally oriented Si nanowire arrays by conducting finite-difference time-domain simulations. Localized Fabry-Perot and whispering-gallery modes are supported within the cross section of each nanowire in the array and result in broadband light absorption. Comparison of a nanowire array with a single nanowire shows that the current density (J(SC)) is preserved for a range of nanowire morphologies. The J(SC) of a nanowire array depends on the spacing of its constituent nanowires, which indicates that both diffraction and optical antenna effects contribute to light absorption. Furthermore, a vertically stacked nanowire array exhibits significantly enhanced light absorption because of the emergence of coupled cavity-waveguide modes and the mitigation of a screening effect. With the assumption of unity internal quantum efficiency, the J(SC) of an 800-nm-thick cross-stacked nanowire array is 14.0 mA/cm², which yields a ~60% enhancement compared with an equivalent bulk film absorber. These numerical results underpin a rational design strategy for ultrathin solar absorbers based on assembled nanowire cavities. PMID:24922405

  3. Magnetic and structural instabilities of ultrathin Fe(100) wedges

    SciTech Connect

    Bader, S.D.; Li, Dongqi; Qiu, Z.Q.

    1994-05-01

    An overview is provided of recent efforts to explore magnetic and related structural issues for ultrathin Fe films grown epitaxially as wedge structures onto Ag(100) and Cu(100). Experiments were carried out utilizing the surface magneto-optic Kerr effect (SMOKE). Ordinary bcc Fe is lattice-matched to the primitive unit cell of the Ag(100) surface. Fe wedges on Ag(100) can be fabricated whose thick end has in-plane magnetic easy axes due to the shape anisotropy, and whose thin end has perpendicular easy axes due to the surface magnetic anisotrophy. A spin-reorientation transition can thus be studied in the center of the wedge where the competing anisotropies cancel. The goal is to test the Mermin-Wagner theorem which states that long-range order is lost at finite temperatures in an isotropic two-dimensional Heisenberg system. Fe wedges on Cu(100) can be studied in like manner, but the lattice matching permits fcc and tetragonally-distorted fcc phases to provide structural complexity in addition to the interplay of competing magnetic anisotropies. The results of these studies are new phase identifications that help both to put previous work into perspective and to define issues to pursue in the future.

  4. Concentration mediated structural transition of triblock copolymer ultrathin films.

    PubMed

    Bal, Jayanta K; Mukherjee, Manabendra; Delorme, Nicolas; Sanyal, Milan K; Gibaud, Alain

    2014-05-27

    X-ray reflectivity, atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle measurement techniques are used to study the structural changeover as a function of concentration of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer diluted in toluene spin-coated as ultrathin films on hydrophilic Si substrate. A lamellar structure made of three alternating incomplete bilayers is observed until the concentration of copolymer solution attains a threshold value of about 3.6-4 g/L. Around this concentration and beyond, the entanglement of polymer chains takes place during drying and the growth of a homogeneous film made of complete bilayers on Si substrate is observed. The strong hydrophilic nature of the Si substrate dictates the growth of this amphiphilic copolymer. We evidence that the lower part of the films is made of hydrophilic PEO blocks attached to the substrate while the hydrophobic PPO blocks are directed toward air. PMID:24785195

  5. Transient coexisting nanophases in ultrathin films confined between corrugated walls

    SciTech Connect

    Curry, J.E.; Zhang, F.; Cushman, J.H. (Lilly Hall of Life Sciences, Purdue University, West Lafayette, Indiana 47907 (United States)); Schoen, M. (Institut fuer Theoretische Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)); Diestler, D.J. (Department of Agronomy, Keim Hall, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0915 (United States))

    1994-12-15

    Grand-canonical Monte Carlo and microcanonical molecular dynamics methods have been used to simulate an ultrathin monatomic film confined to a slit-pore [i.e., between solid surfaces (walls)]. Both walls comprise atoms rigidly fixed in the face centered cubic (100) configuration; one wall is smooth on a nanoscale and the other is corrugated (i.e., scored with regularly spaced rectilinear grooves one to several nanometers wide). Properties of the film have been computed as a function of the lateral alignment (registry), with the temperature, chemical potential, and distance between the walls kept constant. Changing the registry carries the film through a succession of equilibrium states, ranging from all solid at one extreme to all fluid at the other. Over a range of intermediate registries the film consists of fluid and solid portions in equilibrium, that is fluid-filled nanocapillaries separated by solid strips. The range of registries over which such fluid--solid equilibria exist depends upon the width of the grooves and the frequency of the corrugation. For grooves of width comparable to the range of the interatomic potential, fluid and solid phases cease to coexist. In the limit of very wide grooves the character of the film is similar to that of the film confined by strictly smooth walls. The rich phase behavior of the confined film due to the coupling between molecular (registry) and nano (corrugation) scales has obvious implications for boundary lubrication.

  6. Large and Reversible Plasmon Tuning using Ultrathin Responsive Polymer film

    NASA Astrophysics Data System (ADS)

    Singamaneni, Srikanth; Nergiz, Saide

    2011-03-01

    We demonstrate reversible linear and branched aggregation of gold nanoparticles adsorbed on an ultrathin responsive polymer ((poly(4-vinyl pyridine), P4VP) film. P4VP is a weak cationic polymer, which exhibits a reversible coil to globule transition with change in external pH. Atomic force microscopy revealed that in the coiled state (below the isoelectric point of the polymer) of the polymer chains, gold nanoparticles adsorbed on the polymer layer existed as primarily individual nanoparticles. On the other hand, lowering the pH caused the polymer chains to transition from coil to globule state, resulting in aggregation of the nanoparticles into linear and branched chains. Reversible aggregation of the nanoparticles results in a dramatic change in the optical properties of the metal nanostructures. Apart from the large redistribution of the intensity between the individual (530 nm) and coupled (650 nm) plasmon bands, the coupled plasmon band exhibits a shift of nearly 60 nm with change in external pH. The pH triggered aggregation of the nanoparticles and the dramatic change in the optical properties associated with the same can form an excellent platform for colorimetric sensing. The work reported here is supported by the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine.

  7. Very low loss ultrathin Co-based amorphous ribbon cores

    NASA Astrophysics Data System (ADS)

    Yagi, M.; Sato, T.; Sakaki, Y.; Sawa, T.; Inomata, K.

    1988-11-01

    Ultrathin Co-based amorphous ribbons with a thickness of 6-10 ?m were fabricated by a single roller quenching method in vacuum. The compositions of the alloys were zero magnetostrictive: Fe4.7Co70.3Si15B10 and (Fe0.05Co0.95)71(Si0.5B0.5)29. The ribbons obtained had good smoothness and dimensional uniformity. The core loss of toroidal samples 15 mm in diameter was measured after annealing. The loss decreased with decreasing ribbon thickness. In the case of 6.4-?m-thick (Fe,Co)71(Si,B)29 amorphous ribbon, the values at 100 kHz and 1 MHz were 40 mW/cm3 and 1.8 W/cm3 for Bm=0.1 T, respectively. The former was 1/4 that of Mn-Zn ferrites or 1/2 that of 5-?m-thick Supermalloy tape wound core loss. The latter was (2)/(3) that of 5-?m Supermalloy tape wound core loss. In addition, the initial permeability beyond 100 kHz was also markedly improved by thickness reduction. The values of 6.4-?m-thick (Fe,Co)71(Si,B)29 ribbon measured at 1 and 10 MHz were about 7000 and 1000 for Hm=2 mOe, respectively.

  8. Unusual magnetic phases of ultrathin MnCo, MnNi and MnFe alloys.

    NASA Astrophysics Data System (ADS)

    Banerjee, S.; O'Brien, W. L.; Tonner, B. P.

    1998-03-01

    For nearly 30 years the MnCo magnetic phase diagram has been controversial. Even the sign of exchange coupling between Mn and Co atoms is not agreed upon. Contrary to the latest accepted result using neutron scattering, we find that the Mn and Co moments are coupled parallel for dilute Mn concentrations using X-ray Magnetic Circular Dichroism (XMCD). For MnNi alloys, the 1:1 ordered MnNi bulk alloy is antiferromagnetic. However, ordered MnNi ultrathin alloys are ferromagnetic with parallel coupling between Mn and Ni. Bulk FeMn alloys with dilute Mn concentration are ferromagnetic with a parallel coupling between Fe and Mn. We show that ultrathin alloys of same composition have an antiparallel coupling between Mn and Fe. We discuss the potential influence of surface, interface, atomic environment and epitaxy upon the change in magnetism between bulk and ultrathin Mn alloys.

  9. Laser cutting of ultra-thin glasses based on a nonlinear laser interaction effect

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Wu, Zhouling

    2013-07-01

    Glass panel substrates have been widely used in consumer electronics such as in flat panel TVs, laptops, and cell phones. With the advancement in the industry, the glass substrates are becoming thinner and stronger for reduced weight and volume, which brings great challenges for traditional mechanical processes in terms of cut quality, yield, and throughput. Laser glass cutting provides a non-contact process with minimum impact and superior quality compared to the mechanical counterparts. In this paper, we presented recent progresses in advanced laser processing of ultra-thin glass substrates, especially laser-cutting of ultra-thin glasses by a high power laser through a nonlinear interaction effect. Our results indicate that this technique has great potential of application for mass production of ultra-thin glass substrates.

  10. Dispersion compensation for an ultrathin metal film using LCD—CCD system

    NASA Astrophysics Data System (ADS)

    Dai, Yu; Zhang, Jian-Xu

    2012-10-01

    A dispersion compensation method is introduced to correct the distorted image passing through an ultrathin metal film. An LCD—CCD system is modeled by the back propagation network and used to evaluate the transmittance of the ultrathin metal film. Training samples for the network come from 729 images captured by shooting test patches, in which the RGB values are uniformity distributed between 0 and 255. The RGB value of the original image that will be distorted by the dispersion is first transformed by mapping from the LCD to the CCD, multiplied by the inverse matrix of the transmittance matrix, and finally transformed by mapping from the CCD to the LCD, then the corrected image is obtained. In order to verify the effectiveness of the proposed method, ultrathin aluminum films with different thicknesses are evaporated on glass substrates and laid between the CCD and LCD. Experimental results show that the proposed method compensates for the dispersion successfully.

  11. The dielectric behavior of polycrystalline ferroelectric films with fiber textures

    E-print Network

    Li, Jiangyu

    The dielectric behavior of polycrystalline ferroelectric films with fiber textures Quangen Du of crystallographic symmetry, texture, and internal strain on the dielectric properties of polycrystalline ferroelec- tric thin films with fiber textures, including spontaneous polarization, coercivity, dielectric

  12. Atomic layer deposition of hafnium oxide on germanium substrates

    Microsoft Academic Search

    Annelies Delabie; Riikka L. Puurunen; Bert Brijs; Matty Caymax; Thierry Conard; Bart Onsia; Olivier Richard; Wilfried Vandervorst; Chao Zhao; Marc M. Heyns; Marc Meuris; Minna M. Viitanen; Hidde H. Brongersma; Marco de Ridder; Lyudmila V. Goncharova; Eric Garfunkel; Torgny Gustafsson; Wilman Tsai

    2005-01-01

    Germanium combined with high-kappa dielectrics has recently been put forth by the semiconductor industry as potential replacement for planar silicon transistors, which are unlikely to accommodate the severe scaling requirements for sub-45-nm generations. Therefore, we have studied the atomic layer deposition (ALD) of HfO2 high-kappa dielectric layers on HF-cleaned Ge substrates. In this contribution, we describe the HfO2 growth characteristics,

  13. Polarization relaxation induced by a depolarization field in ultrathin ferroelectric capacitors.

    PubMed

    Kim, D J; Jo, J Y; Kim, Y S; Chang, Y J; Lee, J S; Yoon, Jong-Gul; Song, T K; Noh, T W

    2005-12-01

    Time-dependent polarization relaxation behavior induced by a depolarization field E(d) was investigated on high-quality ultrathin SrRuO3/BaTiO3/SrRuO3 capacitors. The E(d) values were determined experimentally from an applied external field to stop the net polarization relaxation. These values agree with those from the electrostatic calculations, demonstrating that a large E(d) inside the ultrathin ferroelectric layer could cause severe polarization relaxation. For numerous ferroelectric devices of capacitor configuration, this effect will set a stricter size limit than the critical thickness issue. PMID:16384347

  14. Copper-Based Ultrathin Nickel Nanocone Films with High-Efficiency Dropwise Condensation Heat Transfer Performance.

    PubMed

    Zhao, Ye; Luo, Yuting; Zhu, Jie; Li, Juan; Gao, Xuefeng

    2015-06-10

    We report a type of copper-based ultrathin nickel nanocone films with high-efficiency dropwise condensation heat transfer (DCHT) performance, which can be fabricated by facile electrodeposition and low-surface-energy chemistry modification. Compared with flat copper samples, our nanosamples show condensate microdrop self-propelling (CMDSP) function and over 89% enhancement in the DCHT coefficient. Such remarkable enhancement may be ascribed to the cooperation of surface nanostructure-induced CMDSP function as well as in situ integration and ultrathin nature of nanofilms. These findings are very significant to design and develop advanced DCHT materials and devices, which help improve the efficiency of thermal management and energy utilization. PMID:26011021

  15. Coexistence of colossal stress and texture gradients in sputter deposited nanocrystalline ultra-thin metal films

    NASA Astrophysics Data System (ADS)

    Kuru, Yener; Welzel, Udo; Mittemeijer, Eric J.

    2014-12-01

    This paper demonstrates experimentally that ultra-thin, nanocrystalline films can exhibit coexisting colossal stress and texture depth gradients. Their quantitative determination is possible by X-ray diffraction experiments. Whereas a uniform texture by itself is known to generally cause curvature in so-called sin2? plots, it is shown that the combined action of texture and stress gradients provides a separate source of curvature in sin2? plots (i.e., even in cases where a uniform texture does not induce such curvature). On this basis, the texture and stress depth profiles of a nanocrystalline, ultra-thin (50 nm) tungsten film could be determined.

  16. Dimensional-Crossover-Driven Metal-Insulator Transition in SrVO3 Ultrathin Films

    SciTech Connect

    Yoshimatsu, K [University of Tokyo, Tokyo, Japan; Okabe, K [University of Tokyo, Tokyo, Japan; Kumigashira, H [University of Tokyo, Tokyo, Japan; Okamoto, Satoshi [ORNL; Aizaki, S [University of Tokyo, Tokyo, Japan; Fujimori, A [University of Tokyo, Tokyo, Japan; Oshima, M [University of Tokyo, Tokyo, Japan

    2010-01-01

    We have investigated the changes occurring in the electronic structure of digitally controlled SrVO3 ultrathin films across the dimensionality-controlled metal-insulator transition (MIT) by in situ photoemission spectroscopy. With decreasing film thickness, a pseudogap is formed at EF through spectral weight transfer from the coherent part to the incoherent part. The pseudogap finally evolves into an energy gap that is indicative of the MIT in a SrVO3 ultrathin film. The observed spectral behavior is reproduced by layer dynamical-mean-field-theory calculations, and it indicates that the observed MIT is caused by the reduction in the bandwidth due to the dimensional crossover.

  17. Excited states at interfaces of a metal-supported ultrathin oxide film

    NASA Astrophysics Data System (ADS)

    Jaouen, T.; Razzoli, E.; Didiot, C.; Monney, G.; Hildebrand, B.; Vanini, F.; Muntwiler, M.; Aebi, P.

    2015-04-01

    We report layer-resolved measurements of the unoccupied electronic structure of ultrathin MgO films grown on Ag(001). The metal-induced gap states at the metal/oxide interface, the oxide band gap, and a surface core exciton involving an image-potential state of the vacuum are revealed through resonant Auger spectroscopy of the Mg K L23L23 Auger transition. Our results demonstrate how to obtain new insights on empty states at interfaces of metal-supported ultrathin oxide films.

  18. Dielectric relaxations in aliphatic polyesters

    NASA Astrophysics Data System (ADS)

    Sen, Sudeepto

    2001-07-01

    The dielectric technique was used to study the relaxation processes of five linear aliphatic polyesters. The polyesters studied were poly (ethylene succinate/adipate) or PESA, poly (trimethylene succinate/adipate) or PTSA, poly (butylene succinate/adipate) or PBSA, poly (ethylene succinate) or PES, and poly (ethylene adipate) or PEA. Three of the polyesters were copolymers (PESA, PTSA, and PBSA), and the remaining two (PES and PEA) were homopolymers. Two of the five were amorphous (PESA and PTSA), and the remaining three (PBSA, PES, and PEA) were semicrystalline. All the five polyesters were synthesized in the laboratory using a poly-condensation reaction between a series of aliphatic diols and diesters. The succinic and adipic groups in the copolymers are in equimolar amounts. The polymers were characterized by differential scanning calorimetry and density measurements. Elemental analysis done on the polymers confirmed that their compositions matched theoretical estimates. The relaxation processes were studied dielectrically using an IMASS time domain dielectric spectrometer (TDS) and an HP 4284A LCR meter. Together they allowed a frequency range from 0.001 Hz to 1 MHz. Typically in the subglass region, good data were obtained between 0.01 Hz and 100 kHz. In the glass transition region, good data were occasionally available over the entire range. Two relaxation processes were detected in the subglass temperature region for all the polymers, and in the case of the copolymers PTSA and PBSA, they were also well resolved. Both the processes showed Arrhenius behavior with modest activation energies characteristic of subglass processes in general. They also progressively merged with increasing temperature, which implies a lower activation energy for the faster process which is consistent with the current understanding of relaxation phenomena. The glass transition region of all the polymers also showed a merging of the dominant alpha relaxation with the subglass processes which had appeared in this region in a coalesced form. This feature has previously been noted mostly in polymers with bulky side-groups.

  19. High-? Dielectric Layers for Bioelectronic Applications

    NASA Astrophysics Data System (ADS)

    Borstlap, Dirk; Schubert, Jürgen; Zander, Willi; Offenhäusser, Andreas; Ingebrandt, Sven

    In many different bioelectronic applications silicon field-effect devices such as transistors or nanowires are used. Usually native or thermally grown silicon oxides serve as interfacing layer to the liquid. For an effective voltage to current conversion of the devices, the main demands for interface layers are low leakage current, low defect density, and high input capacitance. In this article we describe the fabrication and characterization of ultra-thin silicon oxide/high-? material stacks for bioelectronics. A combination of ultra-thin silicon oxide and DyScO3 revealed the best results. This material stack is particularly interesting for future fabrication of field-effect devices for bioelectronic applications.

  20. Superbackscattering from single dielectric particles

    NASA Astrophysics Data System (ADS)

    Liberal, Iñigo; Ederra, Iñigo; Gonzalo, Ramón; Ziolkowski, Richard W.

    2015-07-01

    We demonstrate that superbackscattering responses can be excited in subwavelength dielectric particles with simple geometries. The superbackscattering response arises from the simultaneous, coherent excitation of electric dipole and magnetic quadrupole resonances. Its signature is a superdirective scattering pattern simultaneously pointing towards both the forward and backward directions. The practical implementation of this effect with Tellurium particles operating in the thermal infrared is also addressed. The examples presented reveal that spherical resonators outperform array-based superbackscatterers in terms of the backscattering peak, compact size, robustness against losses and isotropic response.

  1. Casimir Interaction of Dielectric Gratings

    SciTech Connect

    Lambrecht, Astrid [Laboratoire Kastler Brossel, CNRS, ENS, UPMC, Campus Jussieu case 74, 75252 Paris (France); Marachevsky, Valery N. [Laboratoire Kastler Brossel, CNRS, ENS, UPMC, Campus Jussieu case 74, 75252 Paris (France); V. A. Fock Institute of Physics, St. Petersburg State University, 198504 St. Petersburg (Russian Federation)

    2008-10-17

    We derive an exact solution for the Casimir force between two arbitrary periodic dielectric gratings and illustrate our method by applying it to two nanostructured silicon gratings. We also reproduce the Casimir force gradient measured recently [H. B. Chan, Y. Bao, J. Zou, R. A. Cirelli, F. Klemens, W. M. Mansfield, and C. S. Pai, Phys. Rev. Lett. 101, 030401 (2008)] between a silicon grating and a gold sphere taking into account the material dependence of the force. We find good agreement between our theoretical results and the measured values both in absolute force values and the ratios between the exact force and proximity force approximation predictions.

  2. Dielectric cure monitoring: Preliminary studies

    NASA Technical Reports Server (NTRS)

    Goldberg, B. E.; Semmel, M. L.

    1984-01-01

    Preliminary studies have been conducted on two types of dielectric cure monitoring systems employing both epoxy resins and phenolic composites. An Audrey System was used for 23 cure monitoring runs with very limited success. Nine complete cure monitoring runs have been investigated using a Micromet System. Two additional measurements were performed to investigate the Micromet's sensitivity to water absorption in a post-cure carbon-phenolic material. While further work is needed to determine data significance, the Micromet system appears to show promise as a feedback control device during processing.

  3. Stretch dependence of the electrical breakdown strength and dielectric constant of dielectric elastomers

    NASA Astrophysics Data System (ADS)

    Tröls, Andreas; Kogler, Alexander; Baumgartner, Richard; Kaltseis, Rainer; Keplinger, Christoph; Schwödiauer, Reinhard; Graz, Ingrid; Bauer, Siegfried

    2013-10-01

    Dielectric elastomers are used for electromechanical energy conversion in actuators and in harvesting mechanical energy from renewable sources. The electrical breakdown strength determines the limit of a dielectric elastomer for its use in actuators and energy harvesters. We report two experimental configurations for the measurement of the stretch dependence of the electrical breakdown strength of dielectric elastomers, and compare the electrical breakdown fields for compliant and rigid electrodes on the elastomer. We show that the electrode configuration strongly influences the electrical breakdown field strength. Further, we compare the stretch dependent dielectric function and breakdown of the acrylic elastomer VHB 4910™ from 3M™, and of the natural rubber ZruElast™ A1040™ from Zrunek rubber technology. While the dielectric permittivity of VHB decreases with increasing stretch ratio, the dielectric constant of rubber is insensitive to stretch. Our results suggest natural rubber as a versatile material for dielectric elastomer energy harvesting.

  4. DIELECTRIC SPECTROSCOPY OF HARD RED WINTER WHEAT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The dielectric properties (components of the complex permittivity relative to free space) of ground hard red winter wheat of 11 to 25 percent moisture content were determined by dielectric spectroscopy measurements with an open-ended coaxial-line probe and impedance analyzer over the frequency range...

  5. Characterization of Polyurethane Foam Dielectric Strength

    Microsoft Academic Search

    M. Argin; G. G. Karady

    2008-01-01

    Internal flashovers in hollow insulation systems can produce serious damage. Frequently, SF6 or N2 is used to eliminate this problem, but possible gas leakage may endanger the insulation. This paper proposes the use of polyurethane foams to fill the hollow spaces in insulation systems. Thus far, few publications deal with the dielectric properties of foams. This paper demonstrates the dielectric

  6. Thin film dielectric materials for microelectronics

    Microsoft Academic Search

    KARL H. ZAININGER; Chih-Chun Wang

    1969-01-01

    Important applications of dielectric films used in modern integrated circuit technology include dielectric insulation, surface passivation, diffusion masking, radiation resistance, and hermetic seal. These many functional applications pose stringent requirements on the various properties of the insulating films and the methods used for their preparation. To date silicon dioxide (SiO2) has been used almost exclusively because of 1) its ease

  7. Charge accumulation in dielectrics irradiated by protons

    SciTech Connect

    Boev, S.G.; Paderin, V.A.

    1987-11-01

    A phenomenological analysis of the electric charging of dielectrics irradiated by accelerated protons is performed. It is shown that the energy of the particles and their range in the material affect the accumulation of volume charge. The results of an experimental study of the charging of a number of dielectrics with different structures and properties are presented.

  8. Unified presentation of magnetic and dielectric materials

    Microsoft Academic Search

    O. Mata-Mendez

    1992-01-01

    As is well known, time-independent fields generated by dielectric and magnetic materials can be described by real polarization charges and fictitious magnetic charges, respectively. In addition, magnetic materials can also be studied by means of real currents, but no equivalent-current formulation has been given for dielectric materials. In this paper, a compact formulation of Maxwell equations is presented which shows

  9. Discrete charge dielectric model of electrostatic energy

    Microsoft Academic Search

    Tim LaFave

    2011-01-01

    Studies on nanoscale materials merit careful development of an electrostatics model concerning discrete point charges within dielectrics. The discrete charge dielectric model treats three unique interaction types derived from an external source: Coulomb repulsion among point charges, direct polarization between point charges and their associated surface charge elements, and indirect polarization between point charges and surface charge elements formed by

  10. Force relaxation in charged dielectric elastomer actuators

    Microsoft Academic Search

    H. Ragusch; A. Becker; G. Kofod

    2010-01-01

    A new method for the investigation of dielectric elastomer actuators is developed, in which the relaxation of actuation force is observed under constant strain condition in an open-circuit regime. Independent isothermal surface potential decay measurements were employed to study the charge storage properties of the same elastomer materials. The following materials were used for dielectric elastomer actuators fabrication: VHB (adhesive

  11. Area Scaling for Backend Dielectric Breakdown

    Microsoft Academic Search

    Linda Milor; Changsoo Hong

    2010-01-01

    Backend dielectric breakdown is an increasingly important issue for advanced CMOS processes due to the use of progressively lower k dielectrics in the backend. This paper presents area-scaling formulas to enable full chip failure rate projection from test structure data. The area-scaling formulas are based on the negative binomial defect distribution, which in the limit is equivalent to models based

  12. Dielectric Spectroscopy of Fresh Chicken Breast Meat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Technical abstract The dielectric properties of fresh chicken breast meat were measured at temperatures from 5 to 85 degrees °C over the frequency range from 10 MHz to 1.8 GHz by dielectric spectroscopy techniques with an open-ended coaxial-line probe and impedance analyzer. Samples were cut from ...

  13. Graphene-Dielectric Integration for Graphene Transistors

    PubMed Central

    Liao, Lei; Duan, Xiangfeng

    2010-01-01

    Graphene is emerging as an interesting electronic material for future electronics due to its exceptionally high carrier mobility and single-atomic thickness. Graphene-dielectric integration is of critical importance for the development of graphene transistors and a new generation of graphene based electronics. Deposition of dielectric materials onto graphene is of significant challenge due to the intrinsic material incompatibility between pristine graphene and dielectric oxide materials. Here we review various strategies being researched for graphene-dielectric integration. Physical vapor deposition (PVD) can be used to directly deposit dielectric materials on graphene, but often introduces significant defects into the monolayer of carbon lattice; Atomic layer deposition (ALD) process has also been explored to to deposit high-? dielectrics on graphene, which however requires functionalization of graphene surface with reactive groups, inevitably leading to a significant degradation in carrier mobilities; Using naturally oxidized thin aluminum or polymer as buffer layer for dielectric deposition can mitigate the damages to graphene lattice and improve the carrier mobility of the resulted top-gated transistors; Lastly, a physical assembly approach has recently been explored to integrate dielectric nanostructures with graphene without introducing any appreciable defects, and enabled top-gated graphene transistors with the highest carrier mobility reported to date. We will conclude with a brief summary and perspective on future opportunities. PMID:21278913

  14. Low jitter, low inductance solid dielectric switches

    Microsoft Academic Search

    A. H. Guenther; D. M. Strickland; J. R. Bettis

    1979-01-01

    It has been shown that the use of graded solid dielectric sandwiches in laser-triggered spark gaps (LTS) can lead to highly desirable multichannel operations while maintaining the low delay and jitter performance characteristics of LTS. As many as ten separate breakdown channels were observed when small circular or hexagonal aluminum inserts were inserted between two Mylar dielectric sheets stressed at

  15. Diamond-Based Dielectric Loaded Accelerating Structures

    NASA Astrophysics Data System (ADS)

    Antipov, Sergey; Schoessow, Paul; Kanareykin, Alexei; Jing, Chunguang; Altmark, Alexander; Gai, Wei

    2010-11-01

    Diamond is an excellent material for dielectric loaded accelerating structures. It has a high breakdown threshold, very low dielectric losses and an extremely high coefficient of thermal conductance. In this paper we review progress on the design and development of diamond—based accelerating structures in the GHz—THz frequency range.

  16. Analysis of electron interactions in dielectric gases

    SciTech Connect

    Olivet, Aurelio; Duque, Daniel; Vega, Lourdes F. [Institut de Ciencia de Materials de Barcelona, Consejo Superior de Investigaciones Cientificas (ICMAB-CSIC), Campus de la U.A.B., 08193 Bellaterra (Spain)

    2007-01-15

    We present and discuss results concerning electron interactions processes of dielectric gases and their relationship with the macroscopic behavior of these gases, in particular, with their dielectric strength. Such analysis is based on calculating energies of reactions for molecular ionization, dissociative ionization, parent negative ion formation, and dissociative electron attachment processes. We hypothesize that the estimation of the required energy for a reduced number of processes that take place in electrically stressed gases could be related to the gas' capability to manage the electron flow during an electrical discharge. All calculations were done with semiempirical quantum chemistry methods, including an initial optimization of molecular geometry and heat of formation of the dielectric gases and all of species that appear during electron interaction reactions. The performance of semiempirical methods Austin model 1 and Parametric model 3 (PM3) was compared for several compounds, PM3 being superior in most cases. Calculations performed for a sample of nine dielectric gases show that electron attachment and detachment processes occur in different energy bands that do not overlap for any value of the dielectric strength. We have also analyzed the relationship between dielectric strength and two physical properties: electron affinity and ionization energy. Calculations performed for 43 dielectric gases show no clear correlation between them, although certain guidelines for the qualitative estimation of dielectric strength can still be assessed.

  17. Dielectric Relaxation of Aqueous Trimethylamineoxide Solutions

    Microsoft Academic Search

    Toshiyuki Shikata; Shyuji Itatani

    2002-01-01

    Dielectric relaxation was examined for aqueous trimethylamineoxide (TMAO) solutions over a wide concentration (c) range. The dielectric relaxation of TMAO was described by a Debye-type function with a relaxation time of about 3 × 10-11 s, with the strength proportional to c. The number of water molecules tightly hydrated to unprotonated TMAO was estimated to be two. Ab initio calculations

  18. Ultra-thin resistive switching oxide layers self-assembled by field-induced oxygen migration (FIOM) technique.

    PubMed

    Lee, Sangik; Hwang, Inrok; Oh, Sungtaek; Hong, Sahwan; Kim, Yeonsoo; Nam, Yoonseung; Lee, Keundong; Yoon, Chansoo; Kim, Wondong; Park, Bae Ho

    2014-01-01

    High-performance ultra-thin oxide layers are required for various next-generation electronic and optical devices. In particular, ultra-thin resistive switching (RS) oxide layers are expected to become fundamental building blocks of three-dimensional high-density non-volatile memory devices. Until now, special deposition techniques have been introduced for realization of high-quality ultra-thin oxide layers. Here, we report that ultra-thin oxide layers with reliable RS behavior can be self-assembled by field-induced oxygen migration (FIOM) at the interface of an oxide-conductor/oxide-insulator or oxide-conductor/metal. The formation via FIOM of an ultra-thin oxide layer with a thickness of approximately 2-5 nm and 2.5% excess oxygen content is demonstrated using cross-sectional transmission electron microscopy and secondary ion mass spectroscopy depth profile. The observed RS behavior, such as the polarity dependent forming process, can be attributed to the formation of an ultra-thin oxide layer. In general, as oxygen ions are mobile in many oxide-conductors, FIOM can be used for the formation of ultra-thin oxide layers with desired properties at the interfaces or surfaces of oxide-conductors in high-performance oxide-based devices. PMID:25362933

  19. Rectangular Dielectric-lined Accelerator Structure

    SciTech Connect

    Wang Changbiao; Yakovlev, V.P. [Omega-P, Inc., 199 Whitney Ave., New Haven, CT 06511 (United States); Hirshfield, J.L. [Omega-P, Inc., 199 Whitney Ave., New Haven, CT 06511 (United States); Beam Physics Laboratory, Yale University, 272 Whitney Ave., New Haven, CT 06511 (United States)

    2004-12-07

    Results are reported from analysis of a rectangular X-band dielectric-lined accelerator structure operating in the symmetric LSM-11 mode that has a number of favorable attributes, by comparison with dielectric-lined cylindrical structures. These attributes include use of two planar one-piece precision-ground TiN coated dielectric slabs free of joints, open slots along two opposing metallic faces to suppress all anti-symmetric higher-order modes and to facilitate high-speed pumping, and significant reduction of wall losses by use of evanescent vacuum gaps beyond the dielectric slabs. It is shown that a structure operating at 11.424 GHz can be built with a shunt impedance > 60 M{omega}/m using low-loss alumina as the dielectric.

  20. Rectangular Dielectric-lined Accelerator Structure

    NASA Astrophysics Data System (ADS)

    Wang, Changbiao; Yakovlev, V. P.; Hirshfield, J. L.

    2004-12-01

    Results are reported from analysis of a rectangular X-band dielectric-lined accelerator structure operating in the symmetric LSM-11 mode that has a number of favorable attributes, by comparison with dielectric-lined cylindrical structures. These attributes include use of two planar one-piece precision-ground TiN coated dielectric slabs free of joints, open slots along two opposing metallic faces to suppress all anti-symmetric higher-order modes and to facilitate high-speed pumping, and significant reduction of wall losses by use of evanescent vacuum gaps beyond the dielectric slabs. It is shown that a structure operating at 11.424 GHz can be built with a shunt impedance > 60 M?/m using low-loss alumina as the dielectric.