bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pd/AlN/Si or SiC Structure for Hydrogen Sensing Device
Authors: Serina Flaminia , Huang C. , Auner G. W. , Naik R. , Ng S. , Rimai L. 
Published: April 2011

ABSTRACTAn AlN (insulator) MIS Hydrogen Sensor was created using plasma source molecular beam epitaxy (PSMBE) deposition on Si (111) and 6H-SiC. A Pd layer was deposited on top of the AlN film via magnetron sputtering technique utilizing a hard mask. Pd was chosen since H2 readily diffuses within its bulk, thus Pd acts not only as a metal electrode of the MIS structure, but also as a catalyst for hydrogen dissociation. To optimize the design structure several sensors with different AlN and Pd thickness have been developed. RHEED and XRD measurements show that AlN film is epitaxial on both Si (111) and 6H-SiC substrates. The sensors were characterized using capacitance versus voltage C(V) and I(V) measurements, at different frequencies ranging from 1kHz to 1 MHz. Shifts in the C-V and I-V curves occurred with the introduction of hydrogen in the chamber. The temperature, hydrogen partial pressure, effects of oxygen and hydrocarbon gases, insulator and metal thicknesses on sensor response were analyzed.
Comprehensive Study of the Electrothermal Operation of SiC Power Devices Using a Fully Coupled Physical Transport Model
Authors: Lades M. , Kaindl W. , Wachutka G. 
Published: April 2011

ABSTRACTBased on an extended electrothermal drift-diffusion model formulated within the framework of phenomenological transport theory, a consistent set of material parameters for 4H- and 6H-SiC is presented. Furthermore we report on detailed numerical studies of the coupled effect between transient impurity kinetics and impact ionization, which alters the reverse blocking characteristics of power devices under short switching conditions.
Implanted Bipolar Technology in 4H-SiC
Authors: Wright N. G. , Johnson C. M. , O'Neill A. G. , Horsfall A. , Ortolland S. , Adachi K. , Knights A. P. , Coleman P.G. 
Published: April 2011

ABSTRACTA simple ion-implanted bipolar transistor technology in 4H-SiC is presented. Suitable for both high-voltage vertical devices and lateral high-temperature transistors (for circuit applications), the technology is based on an implanted boron p-well with nitrogen and boron (or aluminium) implanted n+ and p+ regions respectively. The effects of base doping and carrier lifetime on device performance have been studied using TCAD techniques. It is shown that understanding the strong variation of carrier concentration with temperature (due to deep activation levels) and applied field (so-called field ionization) is critical in device design optimisation. The effects of post-implant anneal conditions on the physical and electrical characteristics of the junctions are investigated. It is shown that annealing can remove much of the damage induced by high dose nitrogen implantation but that residual damage is still present. The electrical characteristics of simple BJT transistors with breakdown voltages in excess of 1000V and common-emitter gains of ∼2 is related to the level of such residual damage.
Low Temperature Lateral Epitaxial Growth of Silicon Carbide on Silicon
Authors: Jacob Chacko , Chung Juyong , Hong Moon-Hi , Pirouz Pirouz , Nishino Shigehiro 
Published: April 2011

ABSTRACTTo reduce the defect density inherent in conventional heteroepitaxial growth of SiC on Si, selective epitaxy followed by lateral epitaxial growth was performed in a conventional atmospheric pressure chemical vapor deposition (APCVD) system. The source gas was primarily hexamethyldisilane (HMDS). Hydrogen was used as the carrier gas and small amounts of hydrogen chloride (HCl) were added to improve the selectivity. Si(001) wafers, with an oxide layer (∼ 700 nm thick) as a mask, were used as substrates. The grown films were analyzed using optical microscopy and scanning electron microscopy (SEM). In earlier work, we had demonstrated the problems associated with the application of this technique – viz., oxide degradation and high growth temperature. Using HMDS, the growth temperature has been considerably reduced allowing the continued use of an oxide mask. Selective growth was demonstrated in films grown at 1250° and below.
GaN based quantum dot heterostructures
Authors: Reshchikov M. A. , Cui J. , Yun F. , Baski A. , Nathan M. I. , Morkoç Hadis 
Published: April 2011

ABSTRACTGaN dots have been grown on c-plane sapphire and (111) Si substrates by reactive molecular beam epitaxy. A new method involving two-dimensional growth followed by a controlled annealing during which dots are formed was employed. Due the dot nature and large dot density, relatively high luminescence efficiencies were obtained on both substrates. Single layer dots were used for AFM analysis whereas 30 layer dots were used for photoluminescence experiments. AlN barrier layers, some too thick for mechanical interaction, some thin enough for vertical coupling were used. Strong polarization effects lead to a sizeable red shift, which depends on the size of the dots.
Characterization of Thin GaN Layers Deposited by Hydride Vapour Phase Epitaxy (HVPE) on 6H- SiC Substrates
Authors: Wolan J.T. , Koshka Y. , Saddow S.E. , Melnik Yu. V. , Dmitriev V. 
Published: April 2011

ABSTRACTIn this study, the near-surface regions of air-exposed thin GaN layers deposited by hydride vapour phase (HVPE) epitaxy on 6H-SiC substrates have been examined. Chemical-state identification and in-depth elemental distribution profiles are evaluated using angle-resolved X-ray photoelectron spectroscopy (ARXPS) and secondary ion mass spectroscopy (SIMS). The epilayers show a high degree of chemical purity as determined by XPS and SIMS. Low temperature photoluminescence (PL) were performed and is dominated by donor-acceptor pairs (DAP) emission. Layer thickness was measured to be ∼ 600-700 nm and an abrupt, well-defined heterointerface is observed using scanning electron microscopy (SEM) and SIMS.
TEM Study of High Quality GaN Grown by OMVPE Using an Intermediate Layer
Authors: Benamara M. , Liliental-Weber Z. , Kellermann S. , Swider W. , Washburn J. , Mazur J.H. , Bourret-Courchesne E. D. 
Published: April 2011

ABSTRACTWe report on high quality GaN layers grown with the use of one intermediate layer. The defect analysis shows that the density of dislocation is only 8×107/cm2 in these layers, compared to over 1010/cm2 for layers grown without the intermediate layer (IL). Electron microscopy on cross-section samples shows that deposition under certain specific conditions of a low- temperature IL directly benefits the quality of the subsequently deposited GaN layer. The growth of the GaN top layer appears to be similar to growth observed for lateral epitaxial overgrowth layers. This first time observation opens the possibility for using standard growth methods of GaN compounds to achieve a dislocation density comparable to that achieved with lateral overgrowth epitaxy.
Channeling defects in group-III nitrides during dry etching processes
Authors: Breitschädel O. , Hsieh J.T. , Kuhn B. , Scholz F. , Schweizer H. 
Published: April 2011

ABSTRACTThe effects of Ar+ ion beam etching (IBE) of AlGaN/GaN heterostructures and GaN/InGaN/GaN quantum well structures were investigated dependent on different ion incidence angles. The AlGaN/GaN heterostructure was measured before and after etching with respect to mobility and sheet resistance. The InGaN quantum well structure was measured with PL to determine the PL intensity and the energy shift, respectively. This experiments show that ion channeling is a significant defect generation phenomena in group- III nitrides at vertical ion incidence angle and can be minimized by tilting the sample against the ion beam.
The Formation and Characterization of Epitaxial Titanium Carbide Contacts to 4H-SiC
Authors: Lee S.-K. , Danielsson E. , Zetterling C.-M. , Östling M. , Palmquist J.-P. , Högberg H. , Jansson U. 
Published: April 2011

ABSTRACTEpitaxial TiC Ohmic and Schottky contacts to 4H-SiC were formed by a new deposition method, UHV co-evaporation with Ti and C60, at low temperature (< 500°C). We achieved a contact resistivity of 2 × 10−5Δcm2 at 25°C for as deposited Ohmic contacts on Al ion implanted 4H-Silicon carbide. The rectifying behavior of TiC Schottky contacts was also investigated using I-V and C-V. The measured Schottky barrier height (SBH) was 1.26 eV for n-type and 1.65 eV for p-type 4H-SiC using C-V measurements for frequencies ranging from 1kHz to 1MHz. LEED, RBS, XPS, and XRD measurements were performed to analyze composition ratio, interface reaction, and structural properties of the TiC epitaxial layer.
The Materials Properties of a Nickel Based Composite Contact to n-Sic for Pulsed Power Switching
Authors: Cole M. W. , Joshi P. C. , Ren F. , Hubbard C. W. , Wood M. C. , Ervin M. H. 
Published: April 2011

ABSTRACTNovel Ni/WSi/Ti/Pt composite Ohmic contacts to n-SiC were investigated as a function of annealing temperatures up to 1000°C. The onset of Ohmic behavior occurred at annealing temperatures of 900°C. Annealing at temperatures between 950°and 1000°C yielded excellent Ohmic behavior. At these temperatures the contact-SiC interface was smooth, defect free and characterized by a narrow Ni2Si reaction region. The annealed contacts possessed atomically smooth surface morphologies and exhibited minimal contact expansion. The residual carbon, resultant from SiC decomposition, was constrained by reaction with the WSi and Ti metallization layers forming carbide phases of W and Ti. The locations of the carbide phases were spatially distant from the metal semiconductor interface. Our results demonstrate that the Ni/WSi/Ti/Pt composite Ohmic contact maintains the desirable electrical properties associated with Ni contacts and possess excellent interfacial, compositional and surface properties which are required for reliable high power and high temperature device operation.
High-Dose Titanium Ion Implantation into Epitaxial Si/3C-SiC/Si Layer Systems for Electrical Contact Formation
Authors: Lindner Jörg K.N. , Wenzel Stephanie , Stritzker Bernd 
Published: April 2011

ABSTRACTHigh-dose titanium implantations have been performed into ion beam synthesized heteroepitaxial layer systems of Si/3C-SiC/Si(100) in order to study the formation of titanium silicide layers in the silicon top layer. The structure and composition of layers was analysed using RBS, XRD, XTEM and EFTEM. The sputtering rates of 180 keV Ti ions were determined using the lower SiC/Si interface as a marker. A homogeneous surface layer with the stoichiometry of TiSi2 was formed by a nearly stoichiometric implantation and subsequent annealing. The formation of more metal-rich silicides was observed at doses where the peak Ti concentration largely exceeds the TiSi2 stoichiometry and where the total amount of Ti atoms in the top layer is greater than the amount needed to convert the entire Si top layer into TiSi2. Under these conditions, strong solid state reactions of the implanted Ti atoms with the buried SiC layer and the silicon substrate are observed.
UV Radiation Effects on the Sol-Gel Processing of Ferroelectric PZT Thin Films
Authors: Brinkman K. S. , Schwartz R. W. , Ballato J. 
Published: April 2011

AbstractSol gel solutions have been modified with hydrogen peroxide to improve the durability of photo-irradiated films to water and acidic solvents for photo-patterning. The solutions used for film fabricati.on are aqueous based and contain acetylacetonate (acac). UV-Vis absorption studies indicate that peroxide modifies the acetylacetonate ligand (in this case the zirconium precursor) creating a new absorbing species at longer wavelength which also affects the response of the acac ligand to UV radiation. Precursor modification and UV treatments have also been shown to impact the texture and improve the microstructure of resulting films. Depth profiling by radio-frequency glow discharge atomic emission spectroscopy indicates reduction in the carbon to hydrogen ratios of films crystallized after exposure to UV radiation.
Ferroelectric Na0.5K0.5NbO3/SiO2/Si Thin Film Structures for Nonvolatile Memory
Authors: Cho C.-R. , Grishin A. M. 
Published: April 2011

AbstractHighly c-axis oriented Na0.5K0.5NbO3 (NKN) films have been prepared on thermally grown thin SiO2 template layer onto Si(001) wafer by pulsed laser deposition technique. X-ray diffraction ø-2ø-scan data show multiple-cell structuring along the polar axis in NKN films grown onto SiO2 with thickness up to 45 nm. On the other hand, the film deposited onto amorphous ceramic (Coming) glass is a mixture of slightly c-axis oriented NKN and pyrochlore phases, while the film onto Pt(lll)/Ti/SiO2/Si(001) shows perfect [111] orientation. This implies small amount of SiO2 crystallites distributed in amorphous silica matrix inherits Si(001) orientation and serves as a key factor in highly oriented growth of NKN films. Au upper electrodes have been defined on the top of NKN(270nm)/SiO2/Si structures to investigate Metal-Ferroelectric-Insulator-Silicon (MFIS) diode characteristics for Field Effect Transistor (MFIS-FET) nonvolatile memory applications. C-V measurements yield memory window of 4.14 V at 10 V of gate voltage.
Fundamental Advances in Transparent Conducting Oxides
Authors: Coutts Timothy J. , Young David L. , Li Xiaonan 
Published: April 2011

AbstractIncreasingly large-volume markets for large-area, flat-panel displays and photovoltaic panels are likely to be established in the early years of the next century and transparent conducting oxides (TCOs) of improved opto-electronic properties will be required to enable some of these applications to be realized. Our work is focusing on improving both the fabrication-limited properties of the materials (extrinsic), and materials-limited properties (intrinsic). The emphasis on achieving improved electrical and optical properties hinges on achieving higher electron mobility via intrinsic and/or extrinsic properties. To this end, we have investigated the properties of several TCOs including cadmium oxide, tin oxide, zinc oxide, cadmium stannate and zinc stannate. These may be deposited by chemical vapor deposition (CVD) or sputtering and we hope to establish the capability to fabricate compounds and alloys in the cadmium oxide, tin oxide, zinc oxide ternary phase diagram.The properties of the materials have been investigated using a wide variety of techniques including high-resolution electron microscopy, atomic force microscopy and X-ray diffraction, as well as Mössbauer, Raman and UV/visible/NIR spectroscopies. We have measured the transport properties (conductivity, Hall, Seebeck and Nernst coefficients) and have obtained the effective mZLss, relaxation time, Fermi energy, and scattering parameter. This information has been obtained as a function of carrier concentration, which depends on the deposition and annealing procedures. We have found that the mobilities of free-electrons in the cadmiumbearing compounds are greatly superior to those in the other materials, because they have much longer electron relaxation times. In the case of cadmium oxide, there is also great benefit from a much lower effective mass. We are gaining a clearer understanding of the fundamental microscopic attributes needed for TCOs, which will be required in more-demanding, and rapidly emerging, applications.
In2O3 Based Multicomponent Oxide Transparent Conducting Films Prepared by R.F. Magnetron Sputtering
Authors: Minami Tadatsugu , Miyata Toshihiro , Toda Hidenobu , Suzuki Shingo 
Published: April 2011

AbstractTransparent and conductive thin films using new multicomponent oxides consisting of a combination of different In2O3 based ternary compounds have been prepared on room temperature substrates by r.f. magnetron sputtering. Transparent and conductive (Ga,In)2O3-MgIn2O4, (Ga,In)2O3-Zn2In2O2, (Ga,In)2O3-In4Sn3O12, Zn2In2O5,-In4Sn3O12 and Zn21n2O5-MgIn2O4 films were prepared over the whole range of compositions in these multicomponent oxides. The electrical and chemical properties of the resulting films could be controlled by varying the composition in the target. The resistivity, band-gap energy, work function and etching rate of the resulting multicomponent oxide films ranged between the properties of the two ternary compound films. This paper also presents a discussion of a significant spatial distribution of resistivity found on the substrate of the multicomponent oxide films as a function of composition. The resistivity distribution is attributable to the oxygen concentration on the substrate surface rather than the bombardment effect of high energy particles.
IR-Transparent Electrically Conductive CuAlxOy Deposited by Reactive Magnetron Co-Sputtering
Authors: Johnson L. F. , Moran M. B. , Savrun E. , Sarikaya M. , Kolega R. R. 
Published: April 2011

AbstractThis paper reports on progress in the fabrication of IR-transparent electrically conductive copper aluminum oxide (CuAlxOy) by reactive magnetron co-sputtering from high-purity-Cu and -Al targets in an argon-oxygen-gas mixture. Recent equipment modifications have resulted in much better control of deposition parameters like forward and reflected power and, consequently, much better control of film composition. Applying the correct amount of power to each target and adjusting the oxygen-partial pressure have significantly reduced the growth of surface-oxide layers on the metal targets. Equipment and process improvements have eliminated the sputterrate inconsistencies and arcing that led to lack of composition control in our earliest films. We now have much better control of film composition and are beginning to understand the relationship between the electro-optical properties and the molecular structure of the films using Fourier transform infrared (FTIR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), inductively coupled plasma (ICP) emission spectroscopy, high resolution electron microscopy (HREM) and electron energy loss spectroscopy (EELS). A pair of weakly intense FTIR absorption bands at 1470 and 1395cm−1 is present in films that have enhanced electrical conductivity and IR transparency. Understanding the origin of these bands could speed development of CuAlO2 as a wide-bandgap-conductive oxide since these bands are clearly associated with enhanced conductivity and carrier mobility. The best film to date transmits about 80% in the mid-wave IR and has a sheet resistance of 160Δ;/sq.
Exploration of New Properties of Oxides by the Growth Control Using Pulsed Laser Epitaxy
Authors: Koinuma Hideomi , Koidal Takashi , Komiyama Daisuke , Lippmaa Mikk , Ohtomo Akira , Kawasaki Masashi 
Published: April 2011

AbstractMetal oxides exhibit a wide variety of properties originating mainly from strong electron correlation. Electronic properties of oxides had been utilized mostly in the bulk form till recently and people frequently observed significant changes in such properties when these materials were converted into thin films. For the electronic application in recent years, hybridization and integration of materials in thin film forms are becoming more and more important. In view of our recent studies on high-Tc superconducting junctions and ZnO light emitting devices, this paper is devoted to stimulate the exploration of oxides as new innovative electronic materials by discussing the control of epitaxial thin film growth.
Growth of ZnO/MgZnO Superlattice on Sapphire
Authors: Muth J.F. , Teng C.W. , Sharma A.K. , Kvit A. , Kolbas R.M. , Narayan J. 
Published: April 2011

AbstractThe optical and structural properties of ZnO/MgZnO superlattices were investigated by transmission electron microscope, transmission measurement and photoluminescence. The uncoupled wells ranged in thickness from ∼ 30 Å to 75 Å Modulation of the Mg content was observed in Z-contrast TEM indicating the alloy composition was periodic. The density of stacking faults in the superlattice was extremely high, however the photoluminescence in the narrowest well case was blue shifted, and substantially brighter than comparable bulk layers of ZnO and MgZnO indicating that the emission was enhanced. Excitonic features were observed in the optical absorption spectra and also revealed that diffusion of Mg from the barrier layers into the well was occurring.
Surface Investigations on Single Crystal Anatase TiO2
Authors: Hengerer R. , Kavan L. , Bolliger B. , Erbudak M. , Tzel M. Gr 
Published: April 2011

AbstractUtilizing a chemical transport reaction, we succeeded in growing large and clean anatase TiO2 single crystals whose surfaces could be characterized by standard physical and electro-chemical techniques. The examination of the structure of the clean (101) and (001) faces by low energy electron diffraction (LEED) and secondary electron imaging (SEI) showed that these surfaces are bulk terminated and thermodynamically stable. Impedance spectroscopy in aqueous solution revealed a slight difference in the flatband potential between the (101) and the (001) faces. This shift is also manifested in a different photocurrent onset potential and can be rationalized by a different water adsorption on the two surface structures. Voltammetry in aprotic solutions showed a different lithium insertion behavior for the two surfaces. This is explained by a different structural transparency of the anatase lattice in the two directions. Both findings favor the (001) over the (101) surface. These orientational dependencies may have some important technological relevance for the mesoscopic TiO2 films used in solar cells and lithium batteries.
Interface Stability in Hybrid Transition Metal-Oxide Magnetic Junctions
Authors: Sun J. Z. , Roche K. P. , Parkin S. S. P. 
Published: April 2011

AbstractRecent experiments revealed an apparently bias-dependent tunneling magnetoresistance between a transition metal (such as Fe, Co) and an oxide barrier such as SrTiO3. We examine the materials issues involved in this type of hybrid transition metal-oxide junctions. The junction interface is shown to be unstable against thermal treatment or high-bias current stress. We conclude that the junction magnetoresistance is largely determined by the formation of an interface oxide layer different from the barrier or the transition metal electrode themselves.
Magnetic and Magneto-Optic Properties of Pulsed Laser Deposited CexY3−xFe5O12 Films
Authors: Kim Hyonju , Grishin Alex , Sbiaa R. , Gall H. Le , Rao K. V. 
Published: April 2011

AbstractWe present experimental studies of crystalline, magnetic, and magneto-optic (MO) properties and their correlation with the processing parameters of Ce-substituted yttrium iron garnet (CexY3−xFe5O12) thin films grown epitaxially onto single crystal Gd3Ga5O12 (111) substrates by Nd:YAG pulsed laser deposition technique. Rutherford backscattering (RBS) analysis and microprobe energy dispersive spectrometry (EDS) prove the background oxygen pressure, used for films growth, control films stoichiometry. Oxygen ambient pressure appears to be an important parameter to grow CexY3−x, Fe5O12 films with good crystallinity, magnetic properties, as well as enhanced MO effect. It is found that the film fabricated at 50 mTorr oxygen pressure exhibits a maximum Faraday rotation (FR) øF = 1.78 deg/νtm at λ = 633 nm, a maximum saturation magnetization 4πMs = 1255 Gauss with a minimum in-plane coercivity Hc = 35 Oe, and the narrowest full width at half maximum FWHM = 0.06° of the (444) Bragg reflection rocking curve. The analog of the Verdet constant V = øF / 4πMs, also found to be dependent on the oxygen ambient pressure, reaches the value as high as 1.4 deg/νm-kG at 633 nm, suggesting that this material is useful for MO applications.