bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Characterization of Wurtzitic Gan Single Crystals in Nano and Micro Scale
Authors: Yu San , Li Hongdong , Yang Haibin , Li Dongmei , Sun Haiping , Zou Guangtian 
Published: April 2011

AbstractGallium nitride and its alloys are the most promising materials for short wave light emitters. If high quality GaN single crystals can be prepared, the GaN base light emitters should be fabricated directly on the lattice-matched GaN substrate.In this work, GaN crystals in nano and micro scale with definite faces have been prepared by dc arc discharge using gallium and N2+NH3 as starting materials. Transmission electron microscope, selected area diffraction, x-ray microanalysis of energy dispersive spectroscopy, and x-ray diffraction investigation of the as grown GaN crystals show that the well faceted crystals are single crystalline GaN in wurtzite structure having lattice constants a0=3.18Å and c0=5.18Å. The crystal size of stoichoimetric GaN in wurtzite structure depends on the partial pressure of nitrogen in the plasma. The maximum crystal size in this work is about several micrometers.
Growth and Characterization of Polycrystalline Diamond Thin Films on Porous Silicon by Hot Filament Chemical Vapor Deposition
Authors: Mirzakuchaki S. , Charlson E. J. , Charlson E. M. , Stacy T. , Shahedipour F. , White H. W. 
Published: April 2011

AbstractHot filament chemical vapor deposition (HFCVD) was utilized to grow high quality diamond film on porous silicon (PS) substrates to a thickness of 5–6 μm. Boron-doped silicon substrates of <100> orientation and resistivity of 5–15 ohm-cm were anodized by the electrochemical process to form PS. A slurry of diamond paste (1/4 micron average grain size) was rubbed on the samples for a few seconds before introduction into the chamber. Diamond film growth on the PS has the advantages of shorter incubation time and higher nucleation density as evident from scanning electron microscopy (SEM). The results of X-ray diffraction confirm the growth of predominatly (111) oriented high quality diamond film. Electrical properties were also studied by sputtering circular gold contacts on top of diamond film and measuring current-voltage (I-V) characteristics.
Reconstruction of Nonpolar Gan Surfaces
Authors: Elsner J. , Haugk M. , Frauenheim Th. 
Published: April 2011

AbstractA density-functional theory based nonorthogonal tight-binding scheme is used to investigate the nonpolar surfaces of GaN in the wurtzite and zinc-blende phases. In III-V semiconductors the nonpolar surfaces mainly reconstruct by a bond-length conserving rotation of the surface atoms. In contrast to that for all nonpolar GaN surfaces this bond-length is shortened by ≈3 − 4%. We furthermore find the rotation angle to be significantly smaller than could be expected from results for GaAs and GaP.
A New, Nearly Single-Domain Surface Structure of Homoepitaxial Diamondr (001) Films
Authors: Kuang Yalei , Lee Naesung , Badzian Andrzej , Badzian Teresa , Tsong Tien T. 
Published: April 2011

AbstractBoron-doped homoepitaxial diamond films were grown on natural diamond (001) substrates using microwave-assisted plasma chemical vapor deposition techniques. The surface structures were investigated using scanning tunneling microscopy (STM). This showed a dimertype 2×1 reconstruction structure with single-layer steps where dimer rows on the upper terrace are normal to or parallel to the step edges. We found that dimer rows parallel to the step edges are much longer than those normal to the step edges. The nearly single-domain surface structure observed by STM is in agreement with the low-energy electron diffraction (LEED) patterns from these surfaces. The high atomic resolution STM image showed that the local 1×1 configurations exist.
Theory of Defects, Doping, Surfaces and Interfaces in Wide Gap Nitrides
Authors: Bernholc J. , Boguslawski P. , Briggs E. L. , Nardelli M. Buongiorno , Chen B. , Rapcewicz K. , Zhang Z. 
Published: April 2011

AbstractThe results of extensive theoretical studies of group IV impurities and surface and interface properties of nitrides are presented and compared with available experimental data. Among the impurities, we have considered substitutional C, Si, and Ge. CN is a very shallow acceptor, and thus a promising p-type dopant. Both Si and Ge are excellent donors in GaN. However, in AlGaN alloys the DX configurations are stable for a sufficiently high Al content, which quenches the doping efficiency. At high concentrations, it is energetically favorable for group IV impurities to form nearest-neighbor Xcation-XN pairs. Turning to surfaces, AIN is known to exhibit NEA. We find that the NEA property depends sensitively on surface reconstruction and termination. At interfaces, the strain effects on the band offsets range from 20% to 40%, depending on the substrate. The AIN/GaN/InN interfaces are all of type I, while the A10.5Ga0.5 N/A1N zinc-blende (001) interface may be of type II. Further, the calculated bulk polarizations in wurtzite AIN and GaN are -1.2 and -0.45 μC/cm2, respectively, and the interface contribution to the polarization in the GaN/AlN wurtzite multi-quantum-well is small.
Effect of Si Doping on The Structure of Gan
Authors: Liliental-Weber Zuzanna , Ruvimov S. , Suski T. , Ager J. W. , Swider W. , Chen Y. , Kisielowski Ch. , Washburn J. , Akasaki I. , Amano H. , Kuo C. , Imler W. 
Published: April 2011

AbstractThe influence of Si doping on the structure of GaN grown by metal-organic chemicalvapor deposition (MOCVD) has been studied using transmission electron microscopy (TEM), x-ray diffraction and Raman spectroscopy. Undoped and low Si doped samples were compared with samples of increased dopant concentration. In addition, defect reduction due to different buffer layers (AIN and GaN) is discussed. Silicon doping improves surface morphology and influences threading dislocation arrangement. High doping leads to a more random distribution of dislocations. Based on this study it appears (for the same dopant concentration) that an AIN buffer layer can significantly reduce the number of threading dislocations, leaving the samples more strained. However, no significant reduction of threading dislocations could be observed in the samples with GaN buffer layer. These samples are the least strained.
OBIC Measurements on 6H-SiC Schottky Diodes
Authors: Rottner K. , Schöner A. , Frischholz M. , Helbig R. 
Published: April 2011

AbstractThe OBIC (Optical Beam Induced Current) technique is a powerful method to investigate the electric field distribution of p-n junctions in SiC. In a previous work we found strong indications for the presence of a high density of negative surface charge in n-type SiC. In order to study samples of both conductivity types under similar conditions we prepared Schottky contacts on ntype and p-type 6H-SiC CVD epitaxial layers.OBIC measurements show an extension of the depletion region of several hundreds of microns from the edge of the contact on n- and p-type samples, thus interconnecting diodes on an area up to several mm2. Our results imply that there is no fixed surface charge but a high density of both acceptor- and donorlike surface states leading to a dependence of the net surface charge on the Fermi energy, in which case the sign of the surface charge reverses from negative on ntype material to positive on p-type 6H-SiC.
Deep Level Defects in Mg-Doped GaN
Authors: Yi Gyu-Chul , Wessels Bruce W. 
Published: April 2011

AbstractDeep level defects in Mg compensated GaN grown by metal-organic vapor phase epitaxy were investigated using photocapacitance spectroscopy measurements on Schottky barrier diodes. Addition of magnesium resulted in the formation of a series of deep centers with optical threshold energies of 1.0, 1.2, 1.8, and 3.1 eV. Upon annealing the epitaxial GCN in nitrogen at 850°C the ind-gap levels disappeared and only the trapping level at 3.1 eV remained. The mid-gap levels are ascribed to Mg dopant complexes which may in part be responsible for low doping efficiency of Mg in the as-grown, doped GaN. The deep level at 3.1 eV commonly observed from all Mgdoped GaN most likely involves the Mg acceptor. The photo-excited state of the 3.1 eV level had relaxation times of the order of 103 sec at 295 K.
Dlts and CV Analysis of Doped and N-Implanted GaN
Authors: Haase D. , Schmid M. , Dörnen A. , Härle V. , Bolay H. , Scholz F. , Burkard M. , Schweizer H. 
Published: April 2011

AbstractWe studied by deep level transient spectroscopy (DLTS) and capacitance-voltage (CV) measurements the effects of doping (Zn, S), nitrogen implantation and annealing of n-type GaN grown on sapphire by MOVPE. The DLTS spectra of the as grown samples show two defect levels which are assumed to be identical with recently reported levels [10, 11]. In N-implanted GaN a third level is introduced which is not detectable in our as grown samples. This levels concentration follows the increasing N-implantation density. The depth profiles of its concentration correlate with the distribution of implantation defects expected from Monte-Carlo simulation. After annealing at 900°C for 60s the additional defect level vanishes. The DLTS spectrum then resembles those of annealed as grown samples. The n-type carrier concentration (CV measurements) increases in samples with low N-implantation dose. This implantation effect can be removed also with the RTA step. The increasing carrier concentration provides evidence that the N vacancy is a donor in GaN. For Zn and S doped GaN deep defect levels has been found, which are reported here.
Extrapolation of critical thickness of GaN thin films from lattice constant data using synchrotron X-ray
Authors: Kim Chinkyo , Robinson I. K. , Myoung Jaemin , Shim Kyuhwan , Kim Kyekyoon , Yoo Myung-Cheol 
Published: April 2011

AbstractIn some materials, Van der Merwe's equilibrium theory of strain relief is believed to explain the sudden transition from pseudomorphic growth of a thin film to a progressively relaxed state. We show, for the first time for GaN, how an accurate estimate of the critical thickness of a thin film can be extrapolated from suitable measurements of lattice constants as a function of film thickness using synchrotron X-ray. We do this both for an elementary elastic energy function, in which the interactions between the dislocations are ignored, and for a more realistic energy estimate due to Kasper. The method is found to work quantitatively for thin films of GaN on AIN. The critical thickness is determined to be 29 ± 4 Å.
Ex Situ and In Situ Methods for Complete Oxygen and Non-Carbidic Carbon Removal from (0001)SI 6H-SiC Surfaces
Authors: King Sean W. , Benjamin Mark C. , Kern Richard S. , Nemanich Robert J. , Davis Robert F. 
Published: April 2011

AbstractComparisons between the wetting characteristics of (0001)si 6H-SiC and (111) Si surfaces in various acids and bases were made. It was found that 10:1 HF dipped Si (111) surfaces were hydrophobic where as the (0001)si 6H-SiC surfaces were hydrophilic. (0001)si 6H-SiC surfaces capped with a 20Å Si layer, however, were hydrophobic after HF dipping and exhibited outgassing levels on annealing which were several orders of magnitude lower than SiC wafers dipped in HF without the capping layer. Annealing the Si capped (0001)si 6H-SiC surfaces in UHV at 1100°C for 5 min. was found to be sufficient to thermally desorb the Si capping layer and produce a (3×3) Si rich, oxygen free (0001)si 6H-SiC surface.
Electrical Characterization of Magnesium-Doped Gallium Nitride Grown by Metalorganic Vapor Phase Epitaxy
Authors: Huang J. W. , Lu H. , Cederberg J. G. , Bhat I. , Kuech T. F. 
Published: April 2011

AbstractWe have applied frequency-dependent capacitance measurements and admittance spectroscopy on metalorganic vapor phase epitaxy GaN:Mg to study the electronic states associated with Mg doping. Samples with different Mg doping levels were grown and annealed in nitrogen. Lateral dot-and-ring Schottky diodes using Au/Ti were fabricated. After a 800 °C anneal, frequency-dependent measurements show that the capacitance is reduced at a higher frequency, most likely due to the inability of a deep center to maintain an equilibrium ionization state under a high frequency modulation. The net ionized acceptor concentrations was found to be greater at a higher Mg doping level. Admittance spectroscopy, in which the conductance is monitored as a function of temperature, verifies the existence of at least one impurity-related acceptor level with an activation energy of ∼ 140 meV. A reduction in the annealing temperature was found to lead to a lower net ionized acceptor concentration, as well as a higher activation energy.
Impurity Conduction in n-Type 4H-SIC
Authors: Evwaraye A. O. , Smith S. R. , Mitchel W. C. , Roth M. D. 
Published: April 2011

AbstractImpurity conduction (or hopping conduction) has been observed in the more heavily n-type 4H-SiC samples by both temperature dependent resistivity measurements and thermal admittance spectroscopy. The measured activation energies ɛ 3 for hopping were 4–5 meV and 2.3–3.0 meV respectively. No evidence of hopping conduction was seen by either method in the sample where ND-NA < 1018 cm-3. The thermal admittance spectrum of the lightly n-type sample showed the two nitrogen levels at 53 and 100 meV.
Raman Spectroscopy Investigation of (SiC)1-x (Ain)x, Layers Formed by Ion Implantation in 6H-SiC
Authors: Zahn D. R. T. , Werninghaus T. , Thümer M. , Pezoldt J. , Heera V. 
Published: April 2011

Abstract6H silicon carbide (SiC) substrates were implanted with nitrogen and aluminum at different doses and annealed in the temperature range from 1300°C-1700°C. Micro-Raman Spectroscopy (μ-RS) measurements were performed in two sample geometries (conventional plane-view and cross-sectional). Changes of the polytype from 6H- to a cubic (SiC)1-xAIN)x, and influences in the 6H-SiC wafer up to depths of 2μm were detected. The results obtained by crosssectional μ-RS are discussed in comparison to other results from Reflection High Electron Energy Diffraction (RHEED), Rutherford Backscattering (RBS), Auger Electron Spectroscopy (AES), Transmission Electron Microscopy (TEM), and Positron Annihilation Spectroscopy (PAS) measurements.
Low Energy Ion Doping Technology for Poly-Si TFTs
Authors: Mimura A. , Nagai M. , Shinagawa Y. 
Published: April 2011

AbstractIon doping technology using a bucket-type ion source to fabricate low temperature poly-Si TFTs is presented. Low energy and high ion density conditions are applied to realize the short doping time and resist mask doping for large area glass substrates. A novel CMOS doping technology with one resist mask process is proposed using compensation and inversion of the shollow doped layer. In combination with excimer laser crystallization and activation below 450°C, high performance CMOS TFTs are produced.
Electrical Performance Of an N-Channel TFT Fabricated on a Quartz Substrate by ZMR
Authors: Leeo Si-Woo , Joo Seung-Ki , Lee Byung-Il , Lim In-Gon 
Published: April 2011

AbstractSingle crystalline silicon thin films were formed on a transparent quartz substrate by zone melting recrystallization for the application of flat panel display. The recrystallized film shows a perfect (100) texture and the main defects are subgrainboundaries. High residual tensile stress, which can cause the film cracking, can be successfully eliminated by post-annealing. The nchannel thin film transistors fabricated on a recrystallized film showed excellent device characteristics: carrier mobility ˜ 420cm2/Vsec, subthreshold slope ˜ 100mV/dec and off-state leakage current < 0.2pA.
Ecr Plasma Oxidation of Amorphous Silicon for Improvement of The Interface State in a Poly Silicon Thin Film Transistor
Authors: Ihn Tae-Hyung , Lee Seok-Woon , Lee Byung-Il , Jeon Yoo-Chan , Joo Seung-Ki 
Published: April 2011

AbstractA new oxidation process of the poly Silicon thin films has been demonstrated, where the amorphous silicon thin film was oxidized by ECR plasma at room temperature and then crystallized at 600°C for 30hrs(pre-oxidation). For comparison, amorphous silicon thin film was oxidized after crystallization(post-oxidation). The interface roughness turned out to be only 3Å in case of the pre-oxidation process, while the post-oxidation showed about 8Å of the interface roughness. The pre-oxidized TFT showed the constant mobility at high gate voltages, the post-oxidized TFT showed serious degradation of the mobility at high gate voltages.
Device Characteristics of a Poly-Silicon Thin Film Transistor Fabricated by Milc at Low Temperature
Authors: Lee Seok-Woon , Lee Byung-IL , Ihn Tae-Hyung , Kim Tae-Kyung , Kang Young-Tae , Joo Seung-Ki 
Published: April 2011

AbstractHigh performance poly-Si thin film transistors were fabricated by using a new crystallization method, Metal-Induced Lateral Crystallization (MILC). The process temperature was kept below 500°C throughout the fabrication. After the gate definition, thin nickel films were deposited on top of the TFT's without an additional mask, and with a one-step annealing at 500°C, the activation of the dopants in source/drain/gate a-Si films was achieved simultaneously with the crystallization of the a-Si films in the channel area. Even without a post-hydrogenation passivation, mobilities of the MILC TFT's were measured to be as high as 120cm2/Vs and 90cm2/Vs for n-channel and p-channel, respectively. These values are much higher than those of the poly-Si TFT's fabricated by conventional solid-phase crystallization at around 6001C.
Effects of Germanium on Grain size and surface roughness of the solid phase crystallized polycrystalline Si1−xGex films
Authors: Kim Jin-Won , Ryu Myung-Kwan , Kim Tae-Hoon , Kim Ki-Bum , Kim Sang-Joo 
Published: April 2011

AbstractSi1−xGex (x≤0.5) films were deposited by using Si2H4 and GeH4 source gases in a low pressure chemical vapor deposition (LPCVD). The deposition temperature was varied from 375 °C for Si0.5Ge0.5 to 450 °C for Si film in order to deposit amorphous Si1−xGex films and the deposition pressure was about 1 Torr. The grain size of polycrystalline Si1−xGex films made by solid phase crystallization (SPC) decreases with germanium content in the films, and the activation energy obtained from the dependence of grain size on annealing temperature was 0.4 eV for Si and 0.45 eV for Si0 69Ge0.31. From obtaining a similar activation energy irrespective of Ge content in the film, the decrease of grain size with germanium content is attributed to the difference of the asdeposited film conditions. The surface roughness of Si1−xGex films investigated by atomic force microscope (AFM) increases with germanium content in the film before and after SPC. For instance, the root-mean square (rms) values of the surface roughness of the as-deposited Si and Si0.5Ge0.5 films were 2.3 and 17 Å, while those values were increased to 2.6 and 41 Å, respectively, after SPC. In order to reduce the surface roughness of Si0.5Ge0.5 film, we have deposited a thin Si capping layer on top of the Si1−xGex layer and identified that this capping layer effectively reduces the increase of surface roughness after SPC.
Low Resistivity Transparent Indium Tin Oxide (Ito) Films Sputtered At Room Temperature With H2O Addition
Authors: Onisawa Ken-Ichi , Nishimura Etsuko , Ando Masahiko , Satou Takeshi , Takabatake* Masaru , Minemura Tetsuroh 
Published: April 2011

AbstractA new kind of amorphous indium tin oxide (ITO) film with good pattern delineation properties and mass production capability, as well as low resistivity and high transparency has been developed. The film was prepared by a cluster-type DC magnetron sputtering apparatus at room temperature with H2O addition to the argon sputtering gas. The amorphous ITO film quality was improved by effective termination of oxygen vacancies with -OH species generated by enhanced decomposition from the added H2O in the plasma.
Atomic Hydrogen Effects on the Optical and Electrical Properties of Transparent Conducting Oxides For a-Si:H TFT-LCDs
Authors: Lan Je-Hsiung , Kanicki Jerzy 
Published: April 2011

AbstractThe effects of the atomic hydrogen treatment (H-treatment) of indium-tin oxide (ITO) and aluminum-doped zinc oxide (AZO) films have been investigated. The atomic hydrogen was generated by hot-wire chemical vapor deposition (HW-CVD) technique. Experimental results have shown that AZO films are chemically very stable under the H-treatment; almost no variation in the optical transmittance and electrical resistivity was observed. On the contrary, ITO films, either prepared by sputtering with ex-situ or in-situ thermal-annealing, have shown severe optical and electrical degradation and surface whitening after the H-treatment. SEM studies of the H-treated ITO surfaces have revealed that the surface whitening was due to the increase in surface roughness and the formation of granule-like metallic balls. Auger electron spectroscopy has indicated that the balls were mainly composed of indium atoms and the areas between balls were rich in oxygen atoms. These results were confirmed by X-ray diffraction and X-ray photoelectron spectroscopy measurements done on ITO before and after the H-treatment. Finally, we have demonstrated that a-SiO, deposited by PECVD will completely suppress the chemical reaction between ITO surfaces and atomic hydrogen generated by HW-CVD technique.
Electron Emission From Diamond and Carbon Nitride Grown by Hot Filament Cvd or Helical Resonator Pecvd
Authors: Chi Eung Joon , Shim Jae Yeob , Rho Soon Joon , Baik Hong Koo 
Published: April 2011

AbstractTo improve silicon field emitters, diamond and carbon nitride coatings were applied by hot filament CVD and helical resonator CVD, respectively. Helical resonator CVD was first proposed as a new method to grow carbon nitride on silicon tips without damage. Diamond and carbon nitride coatings lowered turn-on voltage and increased emission current. Microstructural and electronic investigations of carbon nitride film were performed. The negative electron affinity of carbon nitride is suggested for enhancing emission current.
Degradation Mechanisms and Vacuum Requirements for Fed Phosphors
Authors: Holloway Paul H. , Sebastian Joe , Trottier Troy , Jones Sean , Swart Hendrik , Petersen Ronald O. 
Published: April 2011

ABSTRACTDegradation of phosphors in field emission displays (FED's) is described and related to electron beam stimulated surface reactions between ZnS and residual gas in the vacuum system. The requirements for producing and maintaining vacuums in FED packages is reviewed and limitations associated with the size of the FED's are discussed. It is concluded that vacuum production and maintenance is critical to the performance of FED's, and this is not a simple task.
Cross-Sectional Observations of Molecular Orientation in LCDs using a UV Curable Liquid Crystal
Authors: Masuda Shin , Nose Toshiaki , Sato Susumu 
Published: April 2011

AbstractCross-sectional observations of the molecular orientation in typical display modes are demonstrated. ECB (Electrically Controlled Birefringence), Bend and TN (Twisted Nematic) cells are fabricated using a UV curable liquid crystal material. LC cells are photo-polymerized with applying appropriate AC voltages and cut into slices to obtain the cross-sectional images. As a result, frozen molecular orientation states in a cross section of the LC cell are successfully visualized clearly using a polarizing microscope.
Spatially Resolved Characterization of the Electroclinic Effect in Chiral Smectic a Liquid Crystals
Authors: Lindle J. R. , Flom S. R. , Bartoli F. J. , Harter A. T. , Geer R. E. , Ratna B. R. , Shashidhar R. 
Published: April 2011

AbstractThe electro-optical properties of an electroclinic liquid crystal have been investigated using a spatially resolved technique which measures the birefringence, optical tilt angle and extinction within adjacent stripe domains. A comparison of these results with the data obtained from standard optical and X-ray measurements suggests the presence of substripes or an angular distribution of molecular directors within the stripe domains.