bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of Transport Through Low-Temperature GaAs Surface Insulator Layers
Authors: Ibbetson J. P. , Yin L.-W. , Hashemi M. , Gossard A. C. , Mishra U. K. 
Published: March 2011

ABSTRACTSince epilayers of GaAs grown at low substrate temperature (LTGaAs) and annealed at 600°C were first demonstrated to be an effective buffer layer for eliminating backgating effects, the material properties and electronic characteristics of bulk LTGaAs have been actively investigated. Less attention has been paid to thin layers of LTGaAs (∼2000Å), although these have been shown to improve gate-to-drain breakdown characteristics when incorporated as the surface insulator layer in GaAs MISFET's. In bulk LTGaAs that has been annealed for 10 minutes at 600°C, the formation of arsenic precipitates with a density of 1018 cm-3 has been observed. These are considered to be at least partially responsible for the high resistivity of LTGaAs2. While the exact mechanism of precipitate formation is currently unknown, it would seem reasonable to expect the availability of the growth surface to have a significant effect on any defect redistribution during the anneal. This surface effect would become increasingly apparent as the LTGaAs layer thickness was decreased. It is desirable for MISFET applications that the LTGaAs gate insulator layer be as thin as possible, whilst maintaining high breakdown, in order to maximize device transconductance. To achieve this, it is important to understand how the observed bulk features (such as ∼60Å size arsenic precipitates) are affected in thin LTGaAs layers
A Gate Breakdown Mechanism in Mesfets and HEMTs
Authors: Trew R. J. , Winslow T. A. , Mishra U. K. 
Published: March 2011

ABSTRACTA model for gate breakdown in MESFETs and HEMTs is proposed. The model is based upon a combination of thermally assisted tunneling and avalanche breakdown. When thermal effects are considered it is demonstrated that the model predicts increasing drain-source breakdown as the gate electrode is biased towards pinch-off, in agreement with experimental data. The model also predicts, for the first time, the gate current versus bias behavior observed in experimental data. The model is consistent with the various reports of breakdown and light emission phenomena reported in the literature.
Picosecond High-Voltage Pulses Generation Using Low-Temperature (LT) GaAs
Authors: Motet T. , Nees J. , Williamson S. , Mourou G. 
Published: March 2011

ABSTRACTWe report on the generation of 825 V electrical pulses with 1.4 ps rise time and 4 ps Full-Width-at-Half-Maximum using pulse biased Low-Temperature-grown GaAs photoconductive switch triggered by submicrojoule, 150 fs laser pulses. Dependence of the temporal pulse shape on both the electric field and the optical energy is observed and discussed.
TEM and HREM Studies of As-Grown Low-Temperature Molecular Beam Epitaxial In0.52Al0.48As/InP Heterolayers
Authors: Claverie A. , Liliental-Weber Z. , Werner P. , Swider W. , Bhatiacharya P. K. , Gupta S. , Mourou G. 
Published: March 2011

ABSTRACTTransmission and High Resolution Electron Microscopy have been used to study the dramatic changes in crystalline quality which occur in As-rich In0.52Al0.48As/InP layers when the growth temperature is lowered. We have found that for temperatures as low as 200°C and for a flux ratio of 20, the layers can be of high quality. For the lowest growth temperature of 150°C, pyramidal defects as well as hexagonal As grains are found which are characteristic of the breakdown of the monocrystalline growth in these layers. A mechanism for the formation of these defects is proposed based on their crystallographic structure. The fast photo response previously observed in these layers must be related to the presence of these defects.
Effect of Growth Conditions on Optical Response of GaAs Grown at Low Substrate Temperature by MBE
Authors: Schaff W. J. , Offsey S. D. , Song X. J. , Eastman L. F. , Norris T. B. , Sha W. J. , Mourou G. A. 
Published: March 2011

ABSTRACTThe effect of growth conditions on the properties of GaAs grown by molecular beam epitaxy at low substrate temperatures has been studied. It has been found that the response time to 100 fsec 830nm light pulses is a function of substrate temperature and arsenic flux. The reason for variation of optical response with growth conditions is related to the nature of the incorporation of excess arsenic. A recent model proposed by Warren and others is invoked to explain the change in optical response with growth conditions. Further substantiation of this model comes from experiments on the annealing of low substrate temperature GaAs which has been doped with silicon.
STM Study of Diamond(001) Surface
Authors: Tsuno Takashi , Imai Takahiro , Nishibayashi Yoshiki , Fujimori Naoji 
Published: March 2011

ABSTRACTUndoped and boron-doped diamond epitaxial films were deposited on diamond(001) substrate by micro-wave plasma assisted chemical vapor deposition and their surfaces were studied by scanning tunneling microscopy in air. An atomic order resolution was confirmed for the observation.For the undoped epitaxial films, which showed 2×1 and 1×2 RHEED patterns, dimer type reconstruction was observed and it was considered that the growth occurs through the dimer row extension. In the case of B-doped films, the dimer reconstruction was also observed. However, 2×2 structure due to the absence of dimer was partially observed.The effect of boron concentration and methane concentration during epitaxial growth on the surface morphology were also studied. The morphology observed by STM became flatter, as the concentration of B-doping and methane concentration, during growth, increased.
Electronic Structure of N-V Centers and Terahertz Spectroscopy of Diamond
Authors: Redman D. A. , Shu Q. , Brown S. W. , Lenef A. , Lrj Y. , Whitaker J. , Rand S. C. , Satoh S. , Tsuji K. , Yazu S. 
Published: March 2011

ABSTRACTWe report an essentially complete characterization of energies and relaxation processes of the lowest seven electronic states of the N-V (nitrogen-vacancy) center in diamond using several different nonlinear laser spectroscopie techniques. We have also applied ultrafast optical techniques to measure dielectric properties of CVD and bulk diamond in the 0.3–1.6 THz range for the first time.
Characterization of ZnS Layers Grown by MOCVD for Thin Film Electroluminescence (TFEL) Devices
Authors: Yu J. E. , Jones K. S. , Fang J. , Holloway P. H. , Pathangey B. , Bretschneider E. , Anderson T. J. 
Published: March 2011

ABSTRACTWe have characterized MOCVD grown ZnS layers for thin film electroluminescence (TFEL) devices. Films with thicknesses ranged from several Å to 2 μm were studied by x-ray diffractometry (XRD), cross-sectional transmission electron microscopy (XTEM), high-resolution transmission electron microscopy (HRTEM), and ultraviolet-visible photospectrometry (UVS). From HRTEM micrographs, it was observed that ZnS films consist of a mixture of hexagonal and cubic phases. Correlation of UV absorption spectra with XRD analysis resulted in a method for quantitative determination of the cubic packing fraction of polymorphic ZnS films. The initial ZnS layer (< 1000 Å) deposited on BaTa2O6 had more hexagonal than cubic phase because of denser crystal defects. However, the fraction of cubic phase increased with the film thickness. In addition to film microstructures, the mean grain size, growth rate, film uniformity, and surface roughness of MOCVD grown ZnS thin films as functions of film thicknesses and substrate temperatures were also calibrated by XTEM results.
OMVPE Growth of ZnSe Utilizing Zinc Amides as Source Compounds: Relevance to the Production of p-Type Material
Authors: Rees William S. , Green David M. , Anderson Timothy J. , Bretschneider Eric 
Published: March 2011

ABSTRACTGrowth of ZnSe on GaAs from H2S9 and Zn[N(TMS)2]2 precursors has been demonstrated. When Et2Zn is used as the zinc precursor a higher quality deposit is obtained. Results of experiments employing Et2Zn as the main zinc source with Zn[N(TMS)2]2 introduced at a dopant level indicate nitrogen has been incorporated. Final thin films were characterized by PL, XRD, SIMS, and Raman.
High Resolution Photoluminescence of EDGE and Near-Edge CdTe
Authors: Carmo M. C. , Soares M. J. 
Published: March 2011

ABSTRACTAmong II-VI semiconductors CdTe is the one that can be grown in better crystal quality. However most of the edge and near edge luminescence properties are still to be clarified. CdTe can be obtained in both n and p type and conductivity type conversion is obtained under heat treatment.In this work we studied the behaviour of a batch of CdTe samples under annealing in different conditions. We observed the growth and destruction of the 1.47 eV band and separated the 1.47 eV and 1.43 eV bands. We also show that these bands are strongly related with the chemical stoi chiometry.
Theoretical Studies of Diamond Surface Chemistry and Diamond-Metal Interfaces
Authors: Pickett W. E. , Pederson M. R. , Jackson K. A. , Erwin S. C. 
Published: March 2011

ABSTRACTAdvances in diamond film growth have prompted us to study the interfaces involved in this process: the interface with the substrate, and the growth interface with the ambient hydrocarbon vapor. Carbon chemistry lies at the heart of the properties of both interfaces, and much of the relevant chemistry is not well understood. We report here the energies involved in some idealized chemical processes that may be important in the growth process. Results (Schottky barriers, interface energies) for diamond/metal interfaces are also reported, and the especially unusual diamond/nickel results we have recently obtained are discussed in some detail.
EPR Investigation of Defects in Boron Nitride thin Films
Authors: Fanciulli M. , Moustakas T. D. 
Published: March 2011

ABSTRACTDefects in BN thin films, produced by reactive sputtering, were investigated by Electron Paramagnetic Resonance (EPR) measurements. The EPR signals of films produced with up to 10% N2in the argon discharge are consistent with films having a cubic structure, and becoming more ordered with nitrogen incorporation in the films. The concentration of spins is in the order of 1019spins/g and they are attributed to nitrogen vacancies with an electron trapped in. Carbon incorporation changes the EPR signal and increases the concentration of spins significantly. This result is consistent with the notion that carbon doping stabilizes the electron in a nitrogen vacancy.
Thermoelectric Properties of Boron and Boron Phosphide Film
Authors: Kumashiro Y. , Yokoyama T. , Nakahura J. , Hatsuda K. , Yoshida H. , Takahashi J. 
Published: March 2011

ABSTRACTThis paper describes the thermoelectric properties of amorphous or polycrystalline boron and boron phosphide films prepared using chemical vapor deposition and molecular beam deposition. The temperature dependencies of electrical conductivity of a-B and distorted B13P2 films obey the Mott's rule of loga vs T-1/4, while those of polycrystalline BP films have linear relationship between loga vs T-1. The a-B and B13P2 films have high electric resistivity and show p-type conductors while BP film shows n-type conductor. The estimated thermoelectric figure of merit of boron phosphide film is compatible to that of sintered specimen, but there remains some problems for a-B to alter.
Modeling of the Formation of Boron Carbide Particles in an Aerosol Flow Reactor
Authors: Xiong Yun , Pratsinis Sotiris E. , Weimer W. 
Published: March 2011

ABSTRACTThe formation of submicron crystals of boron carbide (B4C) by rapid carbothermal reduction of intimately mixed carbon-boron oxide precursor powders in an aerosol flow reactor at temperatures above the boiling point of boron oxide is investigated. The employed high heating rates (105 K/s) of the process force release of gaseous boron oxide and suboxides and rupture of the precursor particles resulting in formation of boron carbide molecular clusters that grow to macroscopic particles by coagulation. Consequently, the formation and growth of B4C particles is described by simultaneous interparticle collision and coalescence using a two-dimensional distribution model that traces the evolution of both size and shape characteristics of the particles through their volume and surface area. Here, in addition to the coagulation term, the governing population balance equation includes a coalescence contribution based on B4C sintering law. The predicted evolution of the two-dimensional particle size distribution leads to a direct characterization of morphology as well as the average size and polydispersity of the powders. Furthermore, model predictions of the volume and surface area of boron carbide particles can be directly compared with experimental data of B4C specific surface area and grain size.
Investigation of Pt Bottom Electrodes for "In-Situ" Deposited Pb(Zr,Ti)O3 (PZT) thin Films
Authors: Bruchhaus Rainer , Pitzer Dana , Eibl Oliver , Scheithauer Uwe , Hoesler Wolfgang 
Published: March 2011

AbstractThe deposition of the bottom electrode plays a key role in the fabrication of ferroelectric capacitors. Processing at elevated temperatures of up to 800°C can give rise to diffusion processes and thereof formation of harmful dielectric layers.In this paper we used Rutherford backscattering spectrometry (RBS), Auger electron spectrometry (AES) and transmission electron microscopy (TEM) to study Pt/Ti/SiO2/Si substrates with various thicknesses of the Ti and Pt layers. During heating up to about 450°C in vacuum the initial layer sequence remains unchanged. However, drastic changes occur when the electrodes are exposed to Ar/O2 atmosphere during heat treatment. Oxidation induced diffusion of Ti into Pt and oxidation of Ti were observed. A Pt electrode with a 100 nm thick Ti adhesion layer proved to be suitable for the "in-situ" deposition of PZT films.
Photoluminescence Investigation of Pb(Zr,Ti)O3 Thin Films
Authors: Zurcher Peter , Jones Raymond P. , Sun Yongchen , Cone R.L. 
Published: March 2011

AbstractPhotoluminescence (PL) excited at 1.7K with a N2-Laser (3.679eV) was used to investigate defect related electron-hole recombination transitions in ferroelectric PZT thin films. The interaction of doping, heat treatment, and hydrogen with the defect related PL spectrum has been studied. Donor/acceptor related transitions between 3.0 and 3.5eV and deep trap transitions between 2.0 and 2.6eV have been found. Certain heat treatments produce high densities of deep trap transitions in Pb(Zr0.48Ti0.52)03 thin films but not in 6% La doped PZT; different treatments are neccessary to produce similar deep trap transitions in the doped films. Hydrogen anneals eliminate the strongest deep trap transition at 2.15eV in both undoped and La-doped PZT films; however the donor/acceptor transitions are affected differently. Correlation with electrical properties seems to indicate the expected result: smaller defect densities are associated with better electrical performance.
Optical Properties of PZT, PLZT, and PNZT Thin Films
Authors: Peng Chien H. , Chang Jhing-Fang , Desu Seshu B. 
Published: March 2011

AbstractOptical properties were investigated for undoped, La-doped, and Nd-doped Pb(ZrxTi1-x)O3 thin films deposited on sapphire substrates by metalorganic decomposition (MOD) process. Refractive index and extinction coefficient of these films were calculated from transmission spectra in the wavelength range of 300 to 2000 nm. The packing densities of these films were calculated from the refractive index data by using the effective medium approximation. Band gap energies of these films were also reported under the assumption of direct band-to-band transition. The refractive index and band gap energy of PZT films showed a linear dependence on Zr/Ti ratio. The refractive index decreased, while the band gap energy increased with increasing zirconium content. It was also found that both La-doped and Nd-doped PZT films had higher refractive indices than those of undoped PZT films with the same Zr/Ti ratio (50/50).
Ferroelectric Thin Films of Bismuth Titanate Prepared by Mocvd
Authors: Wang H. , Fu L. W. , Shang S. X. , Yu S. Q. , Wang X. L. , Lu Z. K. , Jiang M.H. 
Published: March 2011

AbstractThe ferroelectric thin films of bismuth titanate (Bi4Ti3O12) have been prepared by metalorganic chemical vapor deposition ( MOCVD) technique at atmosphere. The triphenyl bismuth (Bi(CaH5 ) 3)and tetrabutyl titanate (C16H36O4Ti) were used as precursors. Dense Bi4Ti3 O12 films with smooth shinning surface have been grown on Si( 100) substrates at 550°C whithout postannealing. The as- grown films were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy dispersion analysis ( EDAX). The films showed well-ordered crystallinity with an (001)preffered orientation. The influence of growth parameters on deposition rate, composition and morphology of as-grown films was also discussed.
BaTiO3 Thin Films Prepared by Organometallic Chemical Vapor Deposition
Authors: Wills L.A. , Wessels B.W. , Schulz D.L. , Marks T.J. 
Published: March 2011

AbstractBaTiO3 thin films have been prepared by low pressure organometallic chemical vapor deposition on (100) MgO and (100) LaAlO3 substrates using the volatile precursors, titanium(IV) tetraisopropoxide and barium (hexafluoroacetylacetonate)2 (tetraglyme). The phase composition and structure of the films depends on the reactant partial pressure, growth temperature, and substrate. High quality, epitaxial BaTiO3 films can be prepared in-situ on LaAlO3 as confirmed by x-ray diffraction measurements. These BaTiO3 films exhibit smooth surface morphologies as evidenced by scanning electron microscopy. Electrical resistivity measurements indicate that the films are semi-insulating.
Chemical Vapor Deposition of Lead-Titanate
Authors: Greenwald Anton C. , Daly James T. , Kalkhoran Nader M. 
Published: March 2011

AbstractThin films of lead-titanate were deposited by chemical vapor deposition (CVD) using tetraethyl lead and titanium isopropoxide. Good high frequency hysteresis curves were obtained with platinum contacts. Low resistance of the material (estimated at 108 ohm-cm) affected low frequency measurements.Optimized experimental parameters (pressure, temperature, gas flows, oxidizer) were derived from a designed experimental matrix using response surface methodology. This approach significantly reduced the number of deposition trials required.
Properties of Pzt Thin Films with 2CdO·B2O3Glass Phase Additive
Authors: Brooks Keith G. , Chen Jiayu , Udayakumar K. R. , Cross L. Eric 
Published: March 2011

AbstractLead zirconate titanate thin films containing 0-4 wt.% of 2CdO·B2O3glass phase additive have been fabricated by sol-gel processing. Smooth dense perovskite films of approximately 3500Å thickness were formed on Si wafers by a multiple layer spin coating process followed by rapid thermal annealing. Remanent polarizations of up to 23μC/cm2were measured. Hysteresis properties were found to be very sensitive to annealing time at 700°C, with remanence being maximized at 100-200 seconds.
Sol-Gel Derived Barium Sodium Niobate and Bismuth Titanate Films
Authors: Boulton J.M. , Teowee G. , Bomnersbach W.M. , Uhlmann D.R. 
Published: March 2011

AbstractSol-gel derived barium sodium niobate and bismuth titanate films were successfully prepared from precursor solutions of chelated Ba[Nb(OEt)6]2 and NaNb(OEt)6 and from bismuth 2-ethyl hexanoate and Ti(OEt)4 respectively. Single phase Ba2NaNb5O15 was formed at 750C on platinized Si and at 850C on fused SiO2. Monoclinic (pseudo-orthorhombic) Bi4Ti3O12 was formed at temperatures as low as 500C. Both film compositions showed significant second harmonic generation. The dielectric constant of the bismuth titanate film was comparable to that of sputtered films.
Fatigue Parameters of Lead Zirconate Titanate Thin Films
Authors: Yoo In K. , Desu Seshu B. 
Published: March 2011

AbstractTemperature and voltage dependence of fatigue parameters were studied for PZT thin film capacitors on the basis of our fatigue model. It was found that the coefficient of dielectric viscosity of PZT and initial internal field difference of PZT capacitors play a key role in determining fatigue rate. Jump distance was calculated from voltage dependence of decay constant, and it turned out to be essentially the same as the lattice parameter. This result indicates that vacancies (oxygen vacancies, mainly) move parallel to the polarization direction during fatigue. Activation energy was calculated from the temperature dependence of the decay constant. It was confirmed that activation energy for domain wall movement determines fatigue rate at various temperatures. This fatigue model can be used to predict the fatigue behavior and can be extended to develop an accelerated test for fatigue.
Volatility and Thermal Stability of Lead bis-Heptafluorodimethyloctadione [Pb(fod)2] and Lead bis-Tetramethylheptadione [Pb(thd)2]
Authors: Nyman May , Desu Seshu B. 
Published: March 2011

AbstractLead bis-heptafluorodimethyloctadione, or Pb(fod)2 and lead bis-tetramethylbeptadione, or Pb(thd)2 are useful precursors for MOCVD of PbO, a component of PZT ferroelectrics. The two compounds differ only by substituents on their respective ligands, and properties such as volatility and thermal stability differ as a function of the substituents. The volatilities and thermal stabilities of Pb(fod)2 and Pb(thd)2 were examined and compared, in order to further determine usefulness as precursors for MOCVD. Pb(fod)2 and Pb(thd)2 were synthesized and purified via a procedure developed in our laboratory, and purity was confirmed by several techniques. Isothermal and dynamic thermogravimetric analysis experiments were carried out. Regions of thermal stability and thermal instability were identified as a function of heating time and temperature. The region of instability was further examined by heating experiments and chemical ionization mass spectrometry. It was proposed that vaporization of the monomeric form of Pb(fod)2 and Pb(thd)2 controls the rate of weight loss observed in the region of thermal stability, and oligomerization controls the observed rate of weight loss in the region of thermal instability. Heat of vaporization was calculated to be 75 KJ/mol for Pb(fod)2 and 86 KJ/mol for Pb(thd)2.
Observation of Structural Defects in Epitaxial Ferroelectric Bismuth Titanate/PrBa2Cu3O7 Superconductor thin Film Heterostructures on LaAlO3
Authors: Ghonge Subodh , Goo Edward , Ramesh R. 
Published: March 2011

AbstractEpitaxial PrBa2Cu3O7 superconductor/ferroelectric bismuth titanate heterostructures grown on [001] oriented LaAlO3 by pulsed laser deposition are being studied. X-ray diffraction studies of the heterostructures have shown that all the layers grow in the c-axis orientation. In this investigation, the early stages of ferroelectric film growth have been studied using transmission electron microscopy (TEM) of crosssectioned samples. High resolution lattice imaging has been carried out to study the atomic structure of the ferroelectric/superconductor growth interface and the defect structure of the ferroelectric film.
Production of Molecular Clusters of Lithium Niobate by Ultraviolet and Visible Laser Ablation
Authors: Haglund R. F. , Tang K. , Chen C. H. 
Published: March 2011

AbstractWe have investigated laser ablation of molecular ions from the ferroelectric LiNbO3 at 532, 355 and 266 nm, comparing the effects of changing wavelength and intensity. The time-of-flight spectra show great sensitivity to the onset of plasma formation. Just below the plasma formation threshold, production of the monomer, dimer and trimer negative molecular ions were observed. Possible implications for thin-film deposition processing are discussed.