bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cohesive Model of Electromechanical Fatigue for Ferroelectric Materials and Structures
Authors: Serebrinsky Santiago Ariel , Arias Irene , Ortiz Michael 
Published: April 2011

AbstractWe develop a phenomenological model of electro-mechanical ferroelectric fatigue based on a ferroelectric cohesive law that couples mechanical displacement and electric-potential discontinuity to mechanical tractions and surface-charge density. The ferroelectric cohesive law exhibits a monotonic envelope and loading-unloading hysteresis. The model is applicable whenever the changes in properties leading to fatigue are localized in one or more planar-like regions, modelled by the cohesive surfaces. We validate the model against experimental data for a simple test configuration consisting of an infinite slab acted upon by an oscillatory voltage differential across the slab and otherwise stress free. The model captures salient features of the experimental record including: the existence of a threshold nominal field for the onset of fatigue; the dependence of the threshold on the applied-field frequency; the dependence of fatigue life on the amplitude of the nominal field; and the size effect on the coercive field. Our results, although not conclusive, indicate that planar-like regions affected by cycling may lead to the observed fatigue in tetragonal PZT. A particularly appealing feature of the model is that it can be incorporated in a very natural and convenient way into a general finite element analysis of structures and devices for fatigue life assessment.
Deposition of Highly (100) Oriented PZT Film Using Lanthanum Nitrate/Nickel Acetate Buffer Layer
Authors: Choi Jong-Jin , Hahn Byung-Dong , Jang Joo-Hee , Yoon Woon-Ha , Park Dong-Soo , Kim Hyoun-Ee 
Published: April 2011

AbstractHighly (100) oriented Pb(Zr,Ti)O3 [PZT] films were fabricated using lanthanum nitrate/nickel acetate double layers as a buffer layer, regardless of the other deposition conditions, such as the pyrolysis temperature, pyrolysis time, annealing temperature, and heating rate. The buffer layer was also acted as a very effective barrier against Pb-Si interdiffusion, thus allowing for the direct deposition of PZT films on Si, SiO2/Si, and glass substrates. The strong orientation was attributed to the formation of a crystalline intermediate phase between the PZT and lanthanum nitrate during annealing. The lanthanum nitrate/nickel acetate double layers became a lanthanum nickel oxide (LaNiO3), which shows good electrical conductivity, after an annealing process at 650°C. The nature and the role of lanthanum nitrate buffer as a layer for the growth of highly (100) oriented PZT films have been studied. The dielectric, ferroelectric, piezoelectric and electrooptic properties of the highly (100) oriented PZT films with a lanthanum nitrate/nickel acetate buffer layer were measured and compared with the values measured from the (111) and (100) oriented PZT films deposited without buffer layer.
Influence of the lead-compound on PZT 30/70 thin film orientation
Authors: Mandeljc Mira , Malič Barbara , Kosec Marija , Dražič Goran 
Published: April 2011

AbstractFerroelectric thin films based on Pb(Zr0.30Ti0.70)O3 (PZT 30/70) were prepared by Chemical Solution Deposition from lead oxide or lead acetate and transition metal alkoxides in 2-methoxyethanol at 400 °C. The choice of the lead-compound determines the composition of the PZT-sols and as a consequence the course of the thermal decomposition. In the case of PbO the local atmosphere within the bulk of the film during heating is more reducing, i.e. the partial pressure of oxygen is lower, than in the case of Pb(OAc)2 based film. Thus, in the former case a continuous layer of Pt-Pb phase is formed at 400 °C, while in Pb(OAc)2 based film only a low amount of Pt-Pb inclusions could be determined by TEM.
Electrical Properties of Au/Bi4-xLaxTi3O12 Thin Film/Si Structures and Reduction of Interface States
Authors: Kohno Atsushi , Tomari Hiroyuki 
Published: April 2011

AbstractSub-100nm-Thick Polycrystalline Bi4-xLaxTi3O12 (BLT) thin films have been formed on silicon substrates by sol-gel and spin-coating techniques. The analysis of X-ray reflectivity for the BLT/Si structure showed that the BLT film density was slightly lower than the ideal value and the interfacial layer was formed. By Fourier transform infrared spectroscopy (FT-IR) it is confirmed that the formation of the interfacial layer was due to oxidation of Si. Clockwise hysteresis was observed in capacitance-voltage (C-V) characteristics for Au/BLT/p-Si structures at a frequency range between 1 MHz – 1 kHz. The frequency dispersion of the C-V curve was caused by a large amount of interface states at BLT/Si interface. As the film was crystallized at 550°C for 2 h the maximum interface state density was ∼3.4×1011 cm-2ev-1 at 1 kHz. Also, the negative gate-voltage shift of the C-V curve from the ideal curve and the gate-bias dependence of the flat-band voltage were observed, resulting in the presence of undesirable positive charges in the film and the electron injection to the traps near the BLT/Si interface. By post-annealing of the device at 400 °C in oxygen atmosphere the interface states (fast sates) were successfully reduced to a third of the initial value and also the positive charges were significantly diminished.
Ferroelectric Gates for Modulation of 2D Electron Gas at GaN/AlGaN Interfaces
Authors: Stolichnov Igor , Malin Lisa , Muralt Paul , Setter Nava 
Published: April 2011

AbstractThe Pb(Zr,Ti)O3 ferroelectric gate was successfully integrated into the GaN/AlGaN heterostructure with 2D electron gas. The processing conditions were optimized in a way to obtain high quality textured Pb(Zr,Ti)O3 films without destroying the 2D gas situated as close to the interface as 20nm. Study of transport properties in this system demonstrates a possibility to control the 2D gas by switching the spontaneous polarization in the gate. Concentration and mobility of electrons in the 2D gas were monitored using Hall effect and resistivity measurements in a wide temperature range from 4.2K to 300K. The polarization oriented in the direction “from bottom to top” provokes a partial depletion effect in the channel resulting in a conductivity decrease. A correlation between the depletion effect in 2D gas and the change of the spontaneous polarization with temperature has been observed. The depletion effect is found to be reversible so that the initial conductivity in 2D gas can be restored by inversing the spontaneous polarization in the gate. These results suggest that ferroelectric gates integrated into systems with 2D electron gas may be potentially interesting for a number of experiments and applications as a flexible and nondestructive way of making rewritable nanopatterns on semiconductor heterostructures.
Terahertz radiation from multiferroic BiFeO3 thin films as a new approach for ferroelectric memory readout and ferroelectric domain imaging microscopy
Authors: Takahashi Kouhei , Kida Noriaki , Tonouchi Masayoshi 
Published: April 2011

AbstractWe have observed novel terahertz (THz) radiation characteristics of multiferroic BiFeO3 thin films upon illumination of femtosecond laser pulses. The radiated THz pulses from BiFeO3 thin films were shown to originate from an ultrafast modulation of spontaneous polarization, which was introduced by the photoexcited charge carriers. Based on our findings, we briefly present new approaches to nondestructive readout for nonvolatile memory devices and ferroelectric domain imaging microscopy using THz radiation as a sensitive probe.
Three-dimensional observation of nano-scale ferroelectric domain using scanning nonlinear dielectric microscopy
Authors: Cho Yasuo , Sugihara Tomoyuki 
Published: April 2011

AbstractThree-dimensional domain configuration of multi-domain LiTaO3 is revealed by Scanning Nonlinear Dielectric Microscopy (SNDM). SNDM can measure the polarization components both perpendicular and parallel to the surface of the specimen. These techniques are applied to the both congruent and stoichiometric LiTaO3 crystals. The images obtained by SNDM measurements allow us to confirm the various domain features of LiTaO3 and to understand both similarities and differences between the congruent and stoichiometric compositions.
Recent Developments in Thermodynamic Theory of Ferroelectric Thin Films
Authors: Pertsev Nikolay 
Published: April 2011

AbstractThe nonlinear thermodynamic theory of epitaxial ferroelectric films has predicted several important strain-induced phenomena, which have been already observed experimentally. This justifies further development of this theory aiming at the better understanding of the structure/property relationships in thin-film ferroelectrics. To that end, a number of new theoretical studies have been performed recently. First, the thermodynamic formalism has been extended to epitaxial films grown on dissimilar substrates inducing anisotropic strains and a shear deformation in the film plane. Second, the polarization states and dielectric properties were calculated for polydomain Pb(Zr1-xTix)O3 films deposited on cubic substrates. Third, the effect of depolarizing field on the physical properties of strained single-domain films sandwiched between continuous electrodes was described. The results of these studies will be discussed in this paper.
High Growth Rate Process in a SiC Horizontal Reactor with HCl Addition: Structural and Electrical Characterization
Authors: La Via Francesco , Galvagno Giuseppa , Firrincieli Andrea , Di Franco Salvatore , Severino Andrea , Leone Stefano , Mauceri Marco , Pistone Giuseppe , Abbondanza Giuseppe , Portuese Ferdinando , Calcagno Lucia , Foti Gaetano 
Published: April 2011

AbstractThe growth rate of 4H-SiC epitaxial layer has been increased by a factor 19 (up to 112 μm/h) with respect to the standard process with the introduction of HCl in the deposition chamber. The epitaxial layers grown with the addition of HCl have been characterized by electrical, optical and structural characterization methods. The effects of different deposition parameters on the epitaxial growth process have been described in detail. This process can be very promising for high power devices with a breakdown voltage of 10 kV.
Growth of Crystalline Silicon Carbide by CVD Using Chlorosilane Gases
Authors: Loboda Mark , MacMillan M. F. , Wan J. , Chung G. , Carlson E. , Makarov Y. , Galyukov A. , Molnar M. J. 
Published: April 2011

AbstractThe forefront of semiconductor silicon carbide technology now approaches commercialization for both materials and device technology. The commercialization of SiC epitaxy processes requires improvement in defect density, uniformity and repeatability. Especially problematic are graphite particles, gas phase nucleation of particles and the limitations placed on achieving growth rates that can positively impact process costs. When it approached the same historical point of development, silicon epitaxy technology shifted to the use of chlorosilane precursor gases to suppress gas phase nucleation and achieve targeted growth rates. Recent work on SiC epitaxy chemistry now investigates the use of HCl, halocarbons and most recently chlorosilane precursors. This paper will review the original work on gas phase nucleation and its control in silicon epitaxy processes using HCl additives and chlorosilanes. Using established dissociation pathways for chlorosilanes, equilibrium chemical reaction models are used to assess the impact of HCl, halocarbons and chlorosilane precursors on growth rates and particle formation SiC epitaxy. Experimental data is presented on the comparative performance of HCl additive and chlorosilane precursors in SiC epitaxy and film properties.
Effect of Dopant Concentration on High Voltage 4H-SiC Schottky Diodes
Authors: La Via Francesco , Galvagno Giuseppa , Firrincieli Andrea , Di Franco Salvatore , Severino Andrea , Leone Stefano , Mauceri Marco , Pistone Giuseppe , Abbondanza Giuseppe , Portuese Ferdinando , Calcagno Lucia , Foti Gaetano 
Published: April 2011

AbstractPractical design of high-voltage SiC Schottky rectifiers requires the understanding of the influence of the epitaxial dopant concentration on the reverse and forward characteristics. This work analyzes the correlation between the dopant concentration and the I-V characteristics of Schottky diodes for a critical concentration range where the leakage current variations are more evident. The details of how high temperatures affect the properties of junctions have been carefully described to obtain further improvement in the future by proper device optimization. Dopant concentration of about 1.2 × 1016 cm-3 gives the best results in reverse characteristics without great losses in forward currents.
Growth of Epitaxial γ-Al2O3 Dielectrics on 4H-SiC
Authors: Tanner Carey M. , Lu Jun , Blom Hans-Olof , Chang Jane P. 
Published: April 2011

AbstractHighly oriented ?-Al2O3 thin films on 4H-SiC were engineered to demonstrate their potential as a crystalline high-k gate dielectric in SiC power MOSFETs. As-deposited Al2O3 thin films grown on 4H-SiC (0001) by thermal atomic layer deposition (ALD) were amorphous as determined by in-situ reflection high-energy electron diffraction (RHEED). Upon annealing in N2 at 1100°C, the film crystallized to the ?-Al2O3 phase as observed by RHEED, high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Based on Fourier transforms of the HRTEM image, an epitaxial relationship of ?-Al2O3 (111) on 4H-SiC (0001) was observed in which ?-Al2O3 (-110) is oriented with 4H-SiC (-12-10). This orientation was further confirmed by XRD analysis in which only the ?-Al2O3 (111) and (222) peaks were observed. An abrupt interface of both amorphous and crystalline Al2O3 with 4H-SiC was determined by HRTEM.
TiW/TiWN/Pt Ohmic Contacts to n-Type 3C-SiC
Authors: Hofeling Kirk , Rieth Loren , Solzbacher Florian 
Published: April 2011

AbstractTiW(40 nm)/TiWN(80 nm)/Pt(500nm) was investigated as a new high-temperature compatible contact stack to 3C-SiC for harsh environment applications. Performance of TiW/TiWN/Pt contacts deposited on unintentionally doped (8.85×1018 cm-3) 3C-SiC grown by LPCVD to a thickness of ~1μm on (100) Si are reported. The linear transmission line method was used to determine specific contact resistance (ρc) at room temperature and for long-term tests at 300 °C. As deposited contacts were Ohmic with a ρc range of 1×10-4 to 1×10-3 &#61527;cm2. These contacts were annealed for five minutes in forming gas (8% H2 92% Ar), at temperatures from 450 to 950 °C and all retained Ohmic character. Annealing samples at 450, 550 and 950 °C decreased ρc while anneling between 650 and 850 °C generally increased ρc.Auger Electron Spectroscopy (AES) analysis was performed on a sample annealed at 750 °C. The as-received surface was composed of Si and O; after a brief sputter etch a characteristic Pt peak became visible and the O peak decreased substantially. Depth profiles detected Si throughout the Pt capping layer but not in the TiW layers. We suspect that Si diffuses from the SiC substrate into the Pt capping layer and surface Si also reacts with O2 to from an oxide. These reactions, in combination with incomplete SiC/TiW interface reactions, are suspected to cause the increase of ρc for samples annealed between 650 and 850 °C. Annealing at 950 °C gave the lowest contact resistance of 2.3×10-5. Long-term testing at 300 °C for 190 hours, in atmosphere, was performed on contacts annealed at 450 °C. When heated, the contacts initial ρc of 2.1×10-4 &#61527;cm2 increased to ~4×10-3 &#61527;cm2 which remained stable for the test duration. After long-term testing the sample ρc measured at room temperature decreased to 9.8×10-5 &#61527;cm2.
Thermal detection mechanism of SiC-Based Resistive Gas Sensors
Authors: Fawcett Timothy J. , Reyes Meralys , Lloyd Spetz Anita , Saddow Stephen E. , Wolan John T. 
Published: April 2011

AbstractSilicon carbide-based resistive gas sensors from our laboratory have been previously reported to detect hydrogen at concentrations ranging from less than 1% to 100% H2 in Ar and at temperatures ranging from 50°C to 450°C. The gas sensing mechanism for these devices was not well understood, hindering further improvement in this technology. In this report, resistive devices built on a thin 3C-SiC epitaxial layer grown on 150Å thick Si layer wafer bonded to a polycrystalline SiC substrate were studied. The polycrystalline SiC substrate is insulating, allowing the formation of isolated epitaxy resistors on the 3C-SiC layer. The gas sensing devices consisted of rectangular ohmic NiCr contacts with a Au overlayer fabricated on the 3C-SiC surface. Under a constant dc bias, nominally 10V in this study, these sensors demonstrated a decrease in current of up to ~25.4 mA upon the introduction of 100% H2, relative to 100% N2 in the test gas stream. The time constant for this device, estimated as a first-order exponential decay, was ~16-22 sec, with the full response occurring after ~90-120 sec. Upon the introduction of 100% H2 to the sensing environment, the device temperature, as measured by an resistance temperature detector (RTD) in intimate thermal contact with the device, decreased from 400°C to 237°C (&#916;T = ~163°C). This large decrease in device temperature was driven by increased heat transfer coefficient of H2 relative to N2. The sensitivity to CH4 in N2, CO2 in N2 and He in Ar was also tested. Sensitivities, defined as the smallest change in concentration, as low as 300 ppm H2 in N2 were achieved with devices operating at 400°C and 10 V dc. Details of the device performance and a model of the sensing mechanism will be discussed.
Reliability of High Voltage 4H-SiC MOSFET Devices
Authors: Krishnaswami Sumi , Ryu Sei-Hyung , Heath Bradley , Agarwal Anant , Palmour John , Lelis Aivars , Scozzie Charles , Scofield James 
Published: April 2011

AbstractThe commercialization of 4H-SiC MOSFETs will greatly depend on the reliability of gate oxide. Long-term gate oxide reliability and device stability of 1200 V 4H-SiC MOSFETs are being studied, both under the on- and off-states. Device reliability is studied by stressing the device under three conditions: (a) Gate stress - a constant gate voltage of +15 V is applied to the gate at a temperature of 175°C. The forward I-V characteristics and threshold voltage are monitored for device stability, (b) Forward current stress – devices are stressed under a constant drain current of Id = 4 A and Vg = 20 V. The devices were allowed to self-heat to a temperature of Tsink = 125°C and the I-V curves are monitored with time, and (c) High temperature reverse bias testing at 1200 V and 175°C to study the reliability of the devices in the off-state. Our very first measurements on (a) and (b) show very little variation between the pre-stress and post-stress I-V characteristics and threshold voltage up to 1000 hrs of operation at 175°C indicating excellent stability of the MOSFETs in the on-state. In addition, high temperature reverse bias stress test looks very promising with the devices showing very little variation in the reverse leakage current with time.
Nanothick Layer Transfer of Hydrogen-implanted Wafer Using Polysilicon Sacrificial Layer
Authors: Huang C. H. , Chang C. L. , Yang Y. Y. , Suryasindhu T. , Liao W. -C. , Su Y. -H. , Li P. W. , Liu C. -Y. , Lai C. S. , Ting J. -H. , Chu C. S. , Lee C, -S , Lee T. -H. 
Published: April 2011

AbstractAn ion implantation-wafer bonding-layer splitting based 2-D nanostructure material fabrication method using polysilicon sacrificial layer for forming nanothick SOI materials without using post-thinning processes is presented in this paper. Polysilicon layer was initially deposited on the thermal oxidized surface of silicon wafer prior to the ion implantation step to achieve the hydrogen-rich buried layer which depth from the top surface is less than 100 nm in the as-implanted silicon wafer. Before this as-implanted wafer being bonded with a handle wafer, the polysilicon layer was removed by a wet etching method. A nanothick silicon layer was then successfully transferred onto a handle wafer after wafer bonding and layer splitting steps. The thickness of the final transferred silicon layer was 100 nm measured by transmission electron microscopy (TEM).
Damage Effects of Ionizing Radiation in Polymer Film Electrets
Authors: Parada Marco Aurélio , Minamisawa Renato Amaral , Moreira Marcos Vasques , de Almeida Adelaide , Muntele Iulia , Ila Daryush 
Published: April 2011

ABSTRACTElectret sensors or dosimeters can be used to quantify the ionizing radiation dose from charged particles or waves beams (α, β, -e, p etc… γ, X), and with appropriate converters, from fast and slow neutrons. The electret state is reached, by some insulating materials (electrical conductivity lower than 10−8 (Ω m)−1), when once charged, the incorporated charge is quasi-permanent ≈ 109 s. The charge densities are read (before and after the irradiations) and the radiation dose inferred from the difference between them. PFA (Tetrafluoroethylene-per-fluoromethoxyethylene) and FEP (Tetrafluoroethylene-hexa-fluoropropylene) damage mechanisms were studied bombarding these fluoropolymers with: 1 MeV protons at constant current and fluences from 1×1011 tower 1×1016 ions/cm2, 60Co gamma and X-rays, respectively of 1.25 and 0.106 MeV for absorbed doses of 0.5, 1.0, 8,0 and 100 Gy. The emission of chemical species was monitored with a Residual Gas Analyzer (RGA), during proton bombardment and techniques of Optical Absorption Photospectrometry (OAP), Fourier Transform Infrared (FTIR) and Micro-Raman spectroscopy were used to analyze the virgin, exposed and irradiated films.
Metallurgical and Corrosion Studies of Modified T91 Grade steel
Authors: Kumar Pankaj , Maitra Debajyoti , Roy Ajit K 
Published: April 2011

ABSTRACTModified 9Cr-1Mo steels containing different Silicon (Si) content have been tested for evaluation of their metallurgical and corrosion properties. The results of tensile testing indicated reduced failure strain up to 400°C followed by its enhancement at a higher temperature. Stress corrosion cracking tests at constant load did not show any failure in any materials. However, reduced ductility and true failure stress were noted in slow strain rate (SSR) testing, indicating increased cracking susceptibility at elevated temperatures. The corrosion potential became more active with increasing temperature in polarization studies. A combination of intergranular and cleavage failures was observed in specimens tested by the SSR technique.
The Corrosion Behavior of Nickel-base Austenitic Alloys for Nuclear Hydrogen Generation
Authors: Koripelli Rama S , Pal Joydeep , Roy Ajit K 
Published: April 2011

ABSTRACTThree nickel-base austenitic alloys, namely Alloy C-22, Alloy C-276 and Waspaloy have been tested for evaluation of their corrosion resistance in an acidic solution at ambient and elevated temperatures. The results of stress corrosion cracking studies indicate that none of these materials did exhibit any failure at constant load. The cracking susceptibility determined by the slow strain rate technique was gradually enhanced at higher temperatures showing reduced ductility and true failure stress. The critical potentials determined by the polarization technique, became more active (negative) with increasing temperature. The fractograpic evaluations by scanning electron microscopy (SEM) revealed ductile failure in Alloys C-22 and C-276. However, Waspaloy showed brittle failure at elevated temperature.