bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of an NEA Diamond Vacuum Microtriode Array
Authors: Hatfield C. W. , Bilbro G. L. , Morris A. S. , Baumann P. K. , Ward B. L. , Nemanich R. J. 
Published: April 2011

AbstractThe properties and characteristics of vacuum microtriodes based on NEA diamond surfaces were modelled. Specifically, an NEA diamond vacuum microtriode array was investigated using electrical measurements, electron optics software, and microwave circuit simulation. Data for emission current versus applied voltage for various anode-to-cathode distances for diamond NEA surfaces was analyzed and various parameters were extracted. Electron optics software was used to determine Fowler-Nordheim and space-charge-limited DC I-V characteristics for each microtriode. Microwave circuit simulation was done to determine the behavior of arrays of these vacuum microtriodes in an RF amplifier circuit.
Growth and Characterization of AlGaN/GaN Heterostructures with Multiple Quantum Wells by PAMBE
Authors: Shim K. H. , Myoung J. M. , Gluschenkov O. V. , Kim C. , Kim K. , Yoo M. C. , Kim S. , Turnbull D. A. , Bishop S. G. 
Published: April 2011

AbstractAlGaN/GaN heterostructures with multiple quantum wells were grown by plasmaassisted molecular beam epitaxy (PAMBE). Structural and optical properties of the heterostructures were analyzed using x-ray diffraction, cathodoldminescence, and photoluminescence. Interband transitions were clearly observed in the GaN quantum wells at both room- and liquid-helium temperatures. The efficiency of the interband recombination due to the confinement effect was greatly enhanced in the thinner quantum wells. The functional dependence of the interband peaks on the well thickness is shown to be in good agreement with the calculated positions of the quantized levels in the wells.
Deposition Of Adherent Diamond Films On Sapphire Substrates
Authors: Gilbert Donald R. , Singh Rajiv K. 
Published: April 2011

AbstractSapphire is an important material for infrared-transmission applications and SOI device structures. The use of diamond as a protective coating for sapphire is a desirable, yet elusive process. The primary obstacle to the successful deposition of diamond on sapphire is the large mismatch in thermal expansion characteristics between the two materials. To overcome this problem, we have used a low temperature deposition process involving an electron cyclotron resonance (ECR) assisted plasma CVD system. Continuous, adherent diamond films have been deposited over 1 to 2 cm2 areas. These films have been characterized for structural quality using Raman spectroscopy and x-ray diffraction.
ESR and LESR Studies in CVD Diamond
Authors: Graeff C. F. O. , Rohrer E. , Nebel C. E. , Stutzmann M. , GUttler H. , Zachai R. 
Published: April 2011

AbstractCVD diamond films with nitrogen content varying from 10 ppm to 132 ppm have been studied by electron spin resonance (ESR), light-induced ESR (LESR) as well as spin-dependent conductivity (SDC). Two characteristic signals have been observed. A carbon-related defect line with g = 2.0029 ± 0.0002 and width 4 ± 1 G, is observed in ESR, LESR and SDC. The intensity of this line measured by ESR increases linearly with nitrogen content. For low-defect-density samples, or after illuminating the high-defect-density samples with UV light, a second signal is observed both in ESR and LESR, but not in SDC, with a central line at g = 2.0024 ± 0.001 and width 0.2 ± 0.1 G and related hyperfine satellites ≈30 G away from the central line. This line is assigned to isolated substitutional nitrogen, the so-called P1 center. The density of N-related paramagnetic states is strongly affected by illumination and heat treatments. Spin-dependent conductivity measurements show that the dark conductivity at room temperature in CVD-diamond is dominated by hopping at the g = 2.0029 defects.
Characterization of Deep Level Defects in 4h and 6H SIC Via DLTS, SIMS And MEV E-Beam Irradiation
Authors: Doyle J. P. , Aboelfotoh M. O. , Linnarsson M. K. , Svensson B. G. , Schöner A. , Nordell N. , Harris C. , Lindström J. L. , Janzén E. , Hemrnmingsson C. 
Published: April 2011

AbstractElectrically active defects in both 4H and 6H polytypes of SiC have been observed through the use of deep level transient spectroscopy (DLTS). Schottky contacts were grown by vapor phase epitaxy (VPE) with doping concentrations, the epitaxial layer having a doping concentration in the range of 1014 cm−3 to 1017cm−3. Numerous levels have been found in the as-grown n-type 6H-SiC samples and secondary ion mass spectrometry (SIMS) and MeV electron irradiation have been employed to corrrelate the defect levels to impurities or structural defects. In contrast, only a single level is observed in the as-grown 4H-SiC samples.
Morphology of Optically Transparent Cubic Silicon Carbide Prepared by Chemical Vapor Deposition
Authors: Russell Michael W. , Freitas Jaime A. , Butler James E. 
Published: April 2011

AbstractCrystals of cubic silicon carbide (3C-SiC) were grown in an RF-induction furnace on graphite substrates by atmospheric pressure chemical vapor deposition (APCVD) from a single precursor, methyltrichlorosilane (MTS) in hydrogen. The deposits were characterized by micro-Raman spectroscopy, x-ray diffraction, and atomic force and scanning electron microscopies. Above ˜1600°C preferential 〈110〉 growth directions were identified for the majority of the crystals. At intermediate deposition temperatures (1600–1700°C) the dominant morphology consisted of yellow prismatic crystals heavily twinned along {111 }and {111} At substrate temperatures exceeding ˜1750°C hexagonally-shaped {1111} oriented 3C-SiC platelets were formed with alternating {001 }/{ 101} edges. The dependence of nucleation density, film morphology and film orientation on deposition conditions will be discussed with emphasis on the growth of high quality single crystals of 3C-SiC.
Dopant incorporation efficiencies of SiC crystals grown on {1100}-face
Authors: Sugiyama Naohiro , Okamoto Atsuto , Tani Toshihiko , Kamiya Nobuo 
Published: April 2011

AbstractThe dopant incorporation efficiencies of SiC bulk single crystals were investigated by the measurement of optical absorption coefficients and chemical analysis by Glow Discharge Mass Spectroscopy. The SiC crystals were grown on the seed with the {1100} face by a sublimation method. The grown ingot consisted of approximately three parts, which were the regions grown with the {1100} face (I), the {110n} face (II) and the {110n} face (III) as a growing front. The nitrogen concentrations in these parts were in the order of II>I>III. The wafers exhibited the color distributions in the c-plane due to the difference of the growing facet. The nitrogen incorporation efficiencies were discussed in terms of atomic structure on the surface. The aluminum concentration in the crystal grown on a {1100}-faced seed was in the medium between those in crystals grown on Si-face and C-face. On the other hand, the boron concentration was similar to that of Si-face grown crystal, and higher than that of C-face grown crystal.
Activation of Acceptors in Mg-Doped, p-Type GaN
Authors: Götz W. , Johnson N. M. , Walker J. , Bour D. P. 
Published: April 2011

AbstractThe activation of acceptors was investigated for Mg-doped, heteroepitaxial layers of GaN grown by metalorganic chemical vapor deposition. After growth the samples were exposed to isochronal rapid thermal anneals in the temperature range from 500°C to 775°C. The samples were studied by variable temperature Hall effect measurements and photoluminescence (PL) spectroscopy in the as-grown condition and after each temperature step. The thermal treatment leads to the formation of acceptors which are characterized by an activation energy for ionization in the range between 165 meV and 182 meV. These acceptors are attributed to Mg atoms substituting for Ga in the GaN lattice. The experimental results for the acceptor activation are consistent with the dissociation of electrically inactive acceptor-hydrogen complexes. The reversibility of this process is investigated by the exposure of the activated, p-type GaN samples to atomic hydrogen in a remote-plasma hydrogenation system at 600°C and reactivating at 850°C.
Role Of Hydrogen And Hydrogen Complexes In Doping Of Gan
Authors: Neugebauer Jörg , Van de wallei Chris G. 
Published: April 2011

AbstractWe have calculated electronic structure, energetics and migration for hydrogen and hydrogen complexes in GaN employing state-of-the-art first-principles calculations. Using these results in combination with previous detailed investigations about native defects we have calculated the concentration of hydrogen and dopants for different growth conditions. Our results reveal a fundamental difference in the behavior of hydrogen in p-type and n-type material. In particular, we explain why hydrogen has little effect on donor impurities and why H concentrations are low in n-type GaN. We discuss why hydrogen is beneficial for acceptor incorporation in GaN, and identify the limitations of this process.
Electronic Structure of Beryllium, Magnesium and Silicon Impurity in Cubic Gallium Nitride
Authors: Gubanov V. A. , Pentaleri E. , Fong C. Y. , Klein B. M. 
Published: April 2011

AbstractBeryllium (Be), magnesium (Mg) and silicon (Si) impurities in zinc-blende galliumnitride (c-GaN) are investigated by the tight binding-linear combination muffin-tin orbitals (TBLMTO) method using a 64-atom supercell. Be and Mg impurities at a Ga site, respectively induce partially empty acceptor-like bands at the valence band edge, which result in p-type conductivity of doped c-GaN. Si impurity in the Ga sublattice creates a partially occupied impurity subband overlapping with the conduction band edge and is responsible for the measured n-type conductivity. The impurity levels of a Si at a N site are located deep in the gap and do not influence much the conductivity of c-GaN. The shell-projected, total and partial densities of states and the charge density maps are used to elucidate the energy and spatial localizations of the impurity states
Formation and High Frequency CV-Measurements of Aluminum / Aluminum Nitride / 6H Silicon Carbide Structures
Authors: Zetterling C. -M. , Wongchotigul K. , Spencer M. G. , Harris C. I. , Wong S. S. , Östling M. 
Published: April 2011

AbstractUndoped single crystalline aluminum nitride films were grown by metal organic chemical vapor deposition (MOCVD) at 1200 °C. The precursors used were trimethylaluminium (TMA) and ammonia (NH3) in a hydrogen carrier flow, at a pressure of 10 Torr. Silicon carbide substrates of the 4H or the 6H polytype with an epilayer on the silicon face, were used to grow the 200 nm thick A1N films. Aluminum was evaporated and subsequently patterned to form MIS capacitors for high frequency (400 kHz) capacitance voltage measurements at room temperature. It was possible to measure the structure and characterize accumulation, depletion and deep depletion. However, it was not possible to invert the low doped SiC epilayer at room temperature. From an independent optical thickness measurement the relative dielectric constant of aluminum nitride was calculated to be 8.4. The films were stressed up to 50 Volts (2.5 MV/cm) without breakdown or excessive leakage currents. These results indicate the possibility to replace silicon dioxide with aluminum nitride in SiC field effect transistors.
Radiative Recombination Rates in GaN, InN, AlN and their Solid Solutions
Authors: Dmitriev A. V. , Oruzheinikov A. L. 
Published: April 2011

AbstractThe radiative recombination rates have been calculated for the first time in the wide band gap wurtzite semiconductors GaN, InN and AIN and their solid solutions GaxAl1−xN and InxAl1−xN on the base of existing data on the energy band structure and optical absorption in these materials. We calculated the interband matrix elements for the direct optical transitions between the conductivity band and the valence one using the experimental photon energy dependence of the absorption coefficient near the band edge. In our calculations we assumed that the material parameters of the solid solutions (the interband matrix element, carrier effective masses and so on) could be obtained by a linear interpolation between their values in the alloy components. The temperature dependence of the energy gap was taken in the form proposed by Varshni. The calculations of the radiative recombination rates were performed in the wide range of temperature and alloy compositions.
High-Temperature Switching Characteristics of 6H-SiC Thyristor
Authors: Xie K. , Flemish J. R. , Burke T. , Buchwald W. R. , Zhao J. H. 
Published: April 2011

AbstractA 280 V 6H-SiC thyristor has been fabricated and characterized. The switching characteristics of the SiC thyristor were investigated over a temperature range from 23 °C to 400 °C, with a switched current density of 4900 A/cm2 being observed under pulse bias condition. The thyristor has shown a dV/dt of 400 V/ms. Both the turn-on time and turn-off time increase significantly at 400 °C. The thyristor forward breakover voltage decreases by only 5% when the operating temperature is increased from 23 °C to 400 °C.
Low Temperature Polysilicon Materials and Devices
Authors: Pribat D. , Legagneux P. , Plais F. , Reita C. , Petinot F. , Huet O. 
Published: April 2011

AbstractIn this paper, we essentially discuss the material aspects of low temperature (≤ 600 °C) polysilicon technologies. Emphasis is put on the properties of polysilicon films, depending on the way they are obtained. Solid phase crystallisation as well as pulsed laser crystallisation processes are presented in some detail, together with thin film transistor characteristics. Although not yet stabilised and despite uniformity and reproducibility problems, laser crystallisation will probably end up being the technology of choice for the manufacture of large area electronics products, because it allows the fabrication of devices exhibiting superior properties, with a reduced thermal budget.
Surface Roughness of Silicon-Nitride Gate Insulators Deposited in a 40-MHZ Glow Discharge
Authors: Meiling H. , Grotenhuis E. Ten , Weg W. F. van der , Hautala J. J. , Westendorp J. F. M. 
Published: April 2011

AbstractThe surface morphology of 40-MHz PECVD SiNx films is investigated. We report on the correlation between the deposition conditions, bulk properties, and surface roughness of these TFT insulators. The roughness is measured with atomic-force microscopy, AFM. A link will be presented between the AFM properties and the effects of hydrogen dilution during deposition: gas composition and rf-power-density (P) dependences will be discussed. An increase of the surface roughness to 3.7 nm is observed upon H2 dilution and P increase, ascribed to enhanced ion bombardment of the surface during growth.
A New Electrically Reversible Depassivation/Passivation Mechanism in Polycrystalline Silicon
Authors: Suntharalingam Vyshnavi , Fonash Stephen J. 
Published: April 2011

AbstractAn electrically reversible depassivation/passivation phenomenon, recently found for hydrogen passivated polysilicon [1] is further explored in this report. This reversible effect is seen in both ECR and RE hydrogen passivated n-channel thin film transistors (TFTs) but is not seen in the corresponding hydrogen passivated pchannel TFrs, nor is it seen in either n- or p-channel TETs before hydrogenation. This phenomenon has been observed when room temperature bias stressing TFTs fabricated on solid phase or laser crystallized polysilicon films on quartz substrates [1]. A model involving hydrogen release or capture at defects, positively charged hydrogen motion in device electric fields, and subsequent hydrogen capture at other defects has been proposed. This phenomenon has significant implications for polycrystalline silicon TFT’ design and operation. By extension, it also offers significant insight into the stability problems of hydrogenated amorphous silicon.
Atomic-Ratio effect of transition layer for linear mobility in poly-Si TFTs
Authors: Jung M. Y. , Jung Y. H. , Bae S. S. , Seo S. M. , Moon D. G. , Lee G. H. , Soh H. S. 
Published: April 2011

AbstractPoly-Si TFTs with high field effect mobility are fabricated by using PECVD SiO2layer deposited with a new method: two-step (graded) oxide deposition. To adjust stoichiometry of the poly-Si/oxide interface and the bulk oxide layer, the double layer oxide films were deposited. The oxide films near the interface were deposited with high N2O/SiH4gas ratio to obtain the stoichiometric layer for good matching between poly-Si and SiO2. The remaining bulk oxide films were deposited with low N2O/SiH4gas ratio. The composition of the bulk oxide film was measured by using ESCA and the interface layer was analized with ESR. The poly-Si TFT with the double layer gate oxide resulted to the better performance than conventional TFT wth single layer gate oxde.
Effect of annealing ambient on performance and reliability of low pressure chemical vapor deposited oxides for thin film transistors
Authors: Bhat N. , Wang A. , Saraswat K. C. 
Published: April 2011

AbstractThe performance and reliability of low pressure chemical vapor deposited (LPCVD) oxides subjected to oxidizing, inert and nitriding annealing ambients is characterized both at low temperature (600°C) and high temperature (950°C). The oxidizing ambient results in worse initial interface state density and charge to break down. We attribute this to the interfacial stress developed during the oxidation, due to the volume mismatch between Si and SiO2. The C-V measurements on poly-Si substrate capacitors and the charge pumping measurements on poly-Si thin film transistors (TFTs) indicate lower trap density for inert and nitriding ambients. The TFTs with inert anneal exhibit lower bias temperature instability compared to oxidizing ambient.
Development Of Organic Photoresist For Color Filter Black Matrix
Authors: Kim C. W. , Rho S. G. , Jung D. K. , Jeong E. J. , Kim S. Y. , Yang H. G. 
Published: April 2011

AbstractNormal CrOx/Cr type color filter black matrix requires multi-layer sputtering and photo/etch processes which cause several problems such as particles generation, high production cost, and environmental issues. Various kinds of materials are being reviewed to substitute the existing Cr base materials. Especially carbon based organic type and pigment type photo-sensitive materials are actively under development. Our researches are focused on the characterization of material properties, color filter manufacturing techniques which are optimized for liquid crystal process, and the display quality of newly developed materials. Carbon based organic photoresist has excellent optical, material, and process properties which can be used for TFT-LCD color filter products. 14.2″ VGA panel is fabricated by using this organic black matrix technique. It is expected that this technique will lead the color filter production market.
Nanostructure and Electrical Properties of Anodized Al Gate Insulators for Thin-Film Transistors
Authors: Arai Toshiaki , Hiromasu Yasunobu , Tsuji Satoshi 
Published: April 2011

AbstractA novel anodic oxidation method for aluminum thin-film on the glass substrate is proposed for the fabrication of a gate insulator in thin-film transistor (TFT). A proposed rear-positioned cathode makes for much more smooth surface with an average surface roughness of under 4 nm in comparison with conventional cathode positions. The anodic oxidation conditions were comprehensively investigated. The current density, ethylene glycol concentration, and cathode position were chosen as the elements of anodic oxidation condition matrix, and all these conditions affected the film formation. The surface morphology and nanostructure of the anodized films were characterized with an atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (TEM). Films formed at higher ethylene glycol concentrations of over 50% and higher current densities of over 0.9 mA/cm2 exhibited higher breakdown electric fields of over 7 MV/cm, and lower leakage currents. These films had relatively smooth surfaces and took on the shapes of the underlying aluminum. In contrast, films formed at lower ethylene glycol concentrations of under 50% and lower current densities of under 0.9 mA/cm2 had rough surfaces and microvoids. A high concentration of ethylene glycol increases the cost of mass production, however, the proposed rear-positioned cathode method can be achieved even when the concentration of ethylene glycol is under 50%.
Emission Characteristics of Arrays of Diamondcoated Silicon Tips
Authors: Ohlberg Douglas A.A. , Talin Alec A. , Felter Thomas E. , Givargizov E. I. 
Published: April 2011

ABSTRACTThe electron emission behavior of diamond-coated silicon whisker arrays was examined with a point-probe scanner and compared with the behavior of uncoated silicon whiskers as well as with diamond crystallites on a flat Si surface. Emission in all cases was inhomogeneous, and the emission site density was less than the whisker density. Both the diamond-coated and uncoated whiskers displayed a distribution of turn-on fields which peaked at around 10 V/µ, but the uncoated whiskers were observed to burn out if emission outputs exceeded 0.3 µA.
Phosphor Synthesis Routes and their Effect on the Performance of Garnet Phosphors At Low-Voltages
Authors: Shea L. E. , McKittrick J. , Phillips M. L. F. 
Published: April 2011

ABSTRACTGarnet phosphors have potential for use in field emission displays (FEDs). Greenemitting Gd3Ga5O12:Tb (GGG:Tb) and Y3A15012:Tb (YAG:Tb) are possible alternatives to ZnO:Zn, because of their excellent resistance to burn, low-voltage efficiency, (3.5 Im/W from GGG:Tb at 800 V), and saturation resistance at high power densities. Hydrothermal and combustion synthesis techniques were employed to improve the low-voltage efficiency of YAG:Tb, and Y3Ga5O12:Tb (YGG:Tb). Synthetic technique did not affect low-voltage (100–1000 V) efficiency, but affected the particle size, morphology, and burn resistance. The small particle size phosphors obtained via hydrothermal (<1 µm) and combustion reactions (<1 µm) would benefit projection TV, high-definition TV (HDTV), and heads-up displays (HUDs), where smaller pixel sizes are required for high resolution.
Characterization of Y2SiO5:Ce, YAG:Tb AND YAG:Eu RGB Phosphor Triplet for Field Emission Display Application
Authors: Chakhovskoi A. G , Malinowski M. E , Talin A. A , Felter T. E , Trujillo J. T. , HUNT C. E. , Stewart K. D. 
Published: April 2011

ABSTRACTThe spectral response and outgassing characteristics of the three new, low-voltage phosphors combustion synthesized and electrophoretically deposited for application in field-emission flatpanel displays, are presented. The phosphors, forming a candidate Red-Blue-Green (RGB) triplet are YAG:Eu, YAG:Tb and Y2SiO5:Ce. These cathodoluminescent materials are tested with electron-beam excitation at currents up to 50 x03BC;A within the 200-2000V (eg. "low-voltage") and 3000-8000V (eg. "medium voltage") ranges. The spectral coordinates, as compared with industrially-manufactured P22 phosphors in low voltage operation, are reasonable; however, there is considerable difference in the green coordinates, and the red and green materials show significant satellite intensities. Phosphor outgassing, as a function of time, is measured by a residual gas analyzer at fixed 50 gA beam current in the low-voltage range. We find that after two hours of excitation, levels of outgassed CO, CO2 and H2 stabilize to low values.