bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduction of the Optical Absorption of Zinc Germanium Phosphide Via Post-Growth Thermal Anneal
Authors: Ang How-Ghee , Chng Leng-Leng , Lee Yiew-Wang , Flynn Colin J. , Smith Phil C. , Vere Anthony W. 
Published: April 2011

AbstractThis paper describes the reduction of the near-band-edge absorption of zinc germanium phosphide (ZGP) through thermal annealing. The effects of the annealing time, temperature and vapour atmosphere on the reduction of the optical absorption in the near infrared (NIR) region are reported. Results have shown that the optical absorption at 2µm is reduced by at least 50% upon thermal anneal of ZGP. The optimal annealing temperature was 600'C and the optimal annealing time ranged from 200 - 400 h. Annealing in vacuum yielded a larger reduction in the 2-µm optical absorption compared to annealing in the presence of additional zinc and phosphorus vapours. Re-annealing ZGP further reduced the absorption coefficient at 2-µm. However, the percentage decrease in the 2-µm absorption coefficient was much smaller compared to the first thermal anneal.
Correlation Between Surface/Interface States and the Performance of MIS Structures
Authors: Águas Hugo M. B. , Fortunato Elvira M.C. , Cabrita Ana M. , Silva Vitor , Tonello Pedro M.N. , Martins Rodrigo F.P. 
Published: April 2011

ABSTRACTIn order to understand the kinetics of formation of interface/surface states and its correlation on the final device performance, a preliminary study was performed on MIS structures, before and after surface oxidation/passivation, using different oxidation techniques and oxides: thermal (in air), chemical (in H2O2) and oxygen plasma.The devices used in this work are based on a glass/Cr/a-Si:H(n+)/a-Si:H(i)/SiOx/Pd structures, where the amorphous silicon intrinsic layer (i a-Si:H) with a photosensitivity of 107was deposited by a modified plasma enhanced chemical vapour deposition (PECVD) triode system.The electrical properties of a-Si:H MIS structures were investigated by measuring their diode current-voltage characteristics in the dark and under illumination as well as the spectral response, as a function of the various oxidation techniques. Infrared spectroscopy and spectroscopic ellipsometry were used as a complementary tool to characterise the oxidised surface.
Phase Transition in Cr/a-Si:H/V Thin Film Devices
Authors: Hu J. , Snell A.J. , Hajto J. , Rose M.J. , Edmiston W. 
Published: April 2011

ABSTRACTExperimental results on the electronic properties of conditioned Cr/hydrogenated amorphous silicon (a-Si:H)/V thin film devices are presented. The devices under test were electro-formed, and had resistances in the range from several hundred ohms to several kiloohms. The current of conditioned devices varied non-linearly with the bias at low voltages, but exhibited ‘jumps' at a threshold voltage (Vth) (typically 2∼3V ), leading to a resistance change of 1∼3 orders of magnitude. Above Vth the current increased almost linearly with bias, and the carrier transport changed from a semiconducting behaviour into a more conducting (metallic) state. The threshold voltage Vth was found to decrease with increasing temperature and disappear at 340 ∼ 350K, but recovered on reducing the temperature. The transition at Vth has been analysed in terms of electrothermal mechanism. The calculated turnover temperature is about 346K, close to that for the disappearance of Vth. We suggest that the observed transition could involve vanadium oxides such as VO2.
Measurement of Impurity Profiles in Microcrystalline Silicon Solar Cells by SIMS
Authors: Dasgupta Arup , Zastrow Uwe , Lambertz Andreas , Vetterl Oliver , Finger Friedhelm , Beyer Wolfhard , Ray Swati 
Published: April 2011

ABSTRACTThe concentration profiles of B, P, Zn, and O in the active intrinsic (i) νc-Si:H layer and across the interfaces in p-i-n and n-i-p structures have been measured with SIMS. For the ZnO/νc-p/νc-i sequences, an apparent B and O profile extends over several hundred nanometers into the i-layer, and high levels of Zn can be found well above the ZnO substrate layer. These profiles are not affected by annealing at the deposition temperature. Much lower impurity concentrations are measured for n-i-p deposition sequences, or when the p-layer or the i-layer is amorphous. Ruling out diffusion and intermixing processes, evidence for the presence of pinholes in the material is presented, which explain most of the experimental findings.
Open-Circuit Voltage Physics in Amorphous Silicon Solar Cells
Authors: Jiang L. , Lyou J. H. , Rane S. , Schiff E. A. , Wang Q. , Yuan Q. 
Published: April 2011

ABSTRACTWe have performed computer calculations to explore effects of the p/i interface on the open-circuit voltage in a-Si:H based pin solar cells. The principal conclusions are that interface limitation can occur for values of VOC significantly below the built-in potential VBI of a cell, and that the effects can be understood in terms of thermionic emission of electrons from the intrinsic layer into the p-layer. We compare measurements of VOC and electroabsorption estimates of VBI with the model calculations. We conclude that p/i interface limitation is important for current a-Si:H based cells, and that the conduction band offset between the p and i layers is as important as the built-in potential for future improvements to VOC.
Low Temperature Thin-Film Microelectromechanical Devices on Plastic Substrates
Authors: Boucinha M. , Brogueira P. , Chu V. , Alpuim P. , Conde J. P. 
Published: April 2011

ABSTRACTAir-gap micromachined structures such as bridges and cantilevers were fabricated on 50 and 125 µm-thick polyethylene terephthalate (PET) plastic substrates. The maximum processing temperature using PET is limited to 110 °C. Two surface micromachining processes on PET which used two different sacrificial layers - photoresist and Al - were developed. Several materials were used as structural layers in the microstructures including Al, TiW, amorphous silicon (a-Si:H) and a bilayer of a-Si:H and Al. The maximum length of free-standing bridges and cantilevers is discussed as a function of the fabrication process. The bridge structures were actuated electrostatically, in a DC switch setup configuration, and the critical voltage as a function of the length was measured. Mechanical actuation and optical detection were used, in an AC mode, for the measurement of the resonance frequency of bridge structures.
Metastable defects by low-intensity pulsed illumination of hydrogenated amorphous silicon
Authors: Heck Stephan , Branz Howard M. 
Published: April 2011

ABSTRACTIllumination of hydrogenated amorphous silicon (a-Si:H) samples with short (e.g., 40 microsecond) pulses of red light produces a smaller metastable absorption increase in the defect region than continuous illumination of the same intensity for the same integrated exposure time. The defect absorption was measured at 1.3 and 1.4 eV by use of the constant photocurrent method (CPM). This smaller degradation is also observed in the photoconductivity. Careful measurement of the film temperature with several techniques confirm that the film temperature rises by less than 5 °C, under continuous illumination. However, several experiments suggest that the suppressed degradation during pulsed illumination is caused primarily by annealing during the dark time between pulses, even at 15 to 26 °C.
Suppression of Plasma Damage on SnO2 by Means of a Different Surface Chemistry Using Dichlorosilane
Authors: Nakashima T. , Kondo M. , Toyoshima Y. , Matsuda A. 
Published: April 2011

ABSTRACTWe report on that plasma damage on SnO2 can be suppressed by using surface termination by chlorine. It was found that the darkening of SnO2 is decreased and a wider gap p-a-Si material is obtained by using SiH2Cl2 especially at the higher reaction pressure and at the lower substrate temperature. The suppression of darkening of SnO2 and wide optical gap is correlated to chlorine contents in the film. It is demonstrated that SiH2Cl2 is also beneficial for boron-doped material, indicating a suitable material for a window layer of solar cells.
Barrier-Controlled Transport in Doped Microcrystalline Si
Authors: Brehme S. , Kanschat P. , Fuhs W. 
Published: April 2011

ABSTRACTThin μc-Si films doped with P and B are grown on glass at temperatures between 300 °C and 400 °C by electron cyclotron resonance chemical vapor deposition (ECR-CVD). Hall mobilities in the films are found to be temperature-activated with activation energies being correlated to the doping concentrations. The in-grain mobility as determined by an electron spin resonance investigation is much higher than the Hall mobility the values of which are typically near 1 cm2/Vs at 300 K. The experimental results suggest that transport is dominated by potential barriers at the grain boundaries. An extended Seto model is used to probe the interface trap distribution. We obtained the best fitting results by assuming band-tail states decaying exponentially from the respective band edges.
Thermal Oxidation of Si Nanoparticles Grown by Plasma-Enhanced CVD
Authors: Das Debabrata , Farjas Jordi , Costa Josep , Roura Pere , Viera Gregorio , Bertran Enric 
Published: April 2011

ABSTRACTNanoparticles of amorphous silicon were grown by plasma-enhanced CVD. Their high hydrogen content has a great influence on the oxidation kinetics. Oxidation experiments done in a thermo-balance show that during a heating ramp under oxygen the onset of oxidation shifts to higher temperatures when hydrogen content is reduced by annealing. Apparently this higher oxidation rate of the as-grown particles is due to the great density of dangling bonds that are left behind just after the hydrogen is desorpted. This fact is supported by analyzing the oxidation dynamics under isothermal conditions. At lower temperature, when oxidation takes place just after hydrogen desorption, the oxidation transient begins with a finite slope which indicates that oxidation is not diffusion controlled. On the other hand, at higher temperatures, activation energy of the parabolic rate constant indicates that the oxide layer formed is less protective than the oxide layer formed on crystalline silicon.
Microstructure and Electronic Properties of Thin Film Nanoporous Silica as a Function of Processing and Annealing Methods
Authors: Caragianis-Broadbridge Christine , Miecznikowski John R. , Zhu Wenjuan , Luo Zhijiong , Han Jin-ping , Lehman Ann Hein 
Published: April 2011

AbstractAlcogels, aerogel precursors, were prepared by hydrolysis and condensation of the metal alkoxide tetraethylorthosilicate and were catalyzed by both acids and bases, according to a standard reaction. Alcogel solution was spin coated onto p-type silicon wafers and fluid extraction was achieved in an uncontrolled (room temperature, atmospheric pressure) environment. Film porosity was retained through surface modification and/or low vapor pressure solvent techniques. The microstructure and electronic properties of the resulting films were evaluated using non-contact atomic force microscopy (nc-AFM), cross sectional scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Metal insulator semiconductor (MIS) devices were prepared and current-voltage and capacitance-voltage measurements were obtained from these devices. Annealing studies reveal a dramatic temperature dependent effect on both the microstructure and electronic properties of the porous silica films.
Sputter Deposition of GMR Spin Valves
Authors: Zou W. , Zhou X.W. , Quan J.J. , Yang Y.G. , Wadley H.N.G. , Brownell D. , Wang D. , Ghosal S. , Subhas D. , Kosut Robert , Ebert Jon 
Published: April 2011

AbstractRadio frequency (RF) diode sputtering has been used for the growth of giant magnetoresistive (GMR) metal multilayers. Control of the atomic-scale structure of the surfaces and interfaces within these films is critical for GMR applications. A systematic series of experiments have been conducted to evaluate the dependence of the magnetotransport properties upon the growth conditions (i.e. background pressure, input power) for NiFeCo/CoFe/CuAgAu spin valves during RF diode sputter deposition. By using computational fluid dynamics, plasma, molecular dynamics, and various Monte Carlo techniques, a multiscale modeling approach has investigated the atomic assembly events during film growth. Energetic metal atoms and inert gas ion fluxes are shown to have very strong effects upon interfacial structures. The insights gained have led to novel deposition strategy propopositions for interface morphology control.
In Situ Analysis Gaseous Species for CVD Diamond Synthesis and the Possible Reaction Model
Authors: Uede Mayu , Takagi Yoshiki 
Published: April 2011

AbstractFor few years, we had been concentrated of developing completely closed diamond synthesizing system aimed for microgravity experiments. Recently we started the new method with graphite as carbon source. With this method, completely closed system is successfully performed.In-situ gaseous species analyzed with gas chromatographic analysis and possible reaction model will be presented.
Modeling of PVT Growth of Bulk SiC Crystals: General Trends and 2” to 4” Reactor Scaling
Authors: Ramm M.S. , Kulik A.V. , Zhmakin I.A. , Karpov S.Yu. , Bord O.V. , Demina S.E. , Makarov Yu.N. 
Published: April 2011

AbstractWe report on study of a growth system upscaling from 2” to 4” using numerical modeling. The model applied involves heat and mass transfer computations combined with a self-consistent analysis of deposit formation on the reactor walls. General trends in SiC bulk crystal growth originated from upscaling are discussed in detail.
Laser-Induced Liftoff And Laser Patterning Of Large Free-Standing GaN Substrates
Authors: Ambacher O. , Kelly M. K. , Miskys C. R. , Höppel L. , Nebel C. , Stutzmann M. 
Published: April 2011

AbstractFree-standing GaN crystals are produced from 200-300 µn thick GaN films grown on 2 inch sapphire substrates by hydride vapor phase epitaxy. The GaN films are separated from the growth substrate by laser-induced liftoff, using a pulsed laser to thermally decompose a thin layer of GaN close to the film-substrate interface. The free-standing films are polished and used for the homoepitaxial growth of high quality GaN layers by metalorganic chemical vapor deposition. The structural and optical properties of the homoepitaxial films in comparison to layers grown on sapphire are significantly improved, mainly because of lower dislocation density and surface roughness as low as 5×106 cm2 and 0.2 nm, respectively.Laser-induced thermal decomposition is also applied to achieve etching of GaN. At exposures of 500 mJ/cm2 with 355 nm light, etch rates of up to 90 nm for one pulse are obtained. Illumination with an interference grating is used to produce trenches as narrow as 100 nm or sinusoidal surface patterns with a period of 260 nm. Such surface morphologies are very useful for the processing of anti-reflection coatings or distributed Bragg reflectors.
Mechanisms Affecting Emission in Rare-Earth-Activated Phosphors
Authors: Tallant David R. , Seager Carleton H. , Simpson Regina L. 
Published: April 2011

ABSTRACTThe relatively poor efficiency of phosphor materials in cathodoluminescence with low accelerating voltages is a major concern in the design of field emission flat panel displays operated below 5 kV. Our research on rare-earth-activated phosphors indicates that mechanisms involving interactions of excited activators have a significant impact on phosphor efficiency. Persistence measurements in photoluminescence (PL) and cathodoluminescence (CL) show significant deviations from the sequential relaxation model. This model assumes that higher excited manifolds in an activator de-excite primarily by phonon-mediated sequential relaxation to lower energy manifolds in the same activator ion. In addition to sequential relaxation, there appears to be strong coupling between activators, which results in energy transfer interactions. Some of these interactions negatively impact phosphor efficiency by nonradiatively de-exciting activators. Increasing activator concentration enhances these interactions. The net effect is a significant degradation in phosphor efficiency at useful activator concentrations, which is exaggerated when low–energy electron beams are used to excite the emission.
Evaluation of Magnesium Oxide Films by Spectroscopic Ellipsometry
Authors: Kimura Hiroshi 
Published: April 2011

ABSTRACTSpectroscopic ellipsometry was used to evaluate the density and surface roughness of MgO films. The density of a film affects the dispersion of the film's refractive index, and the refractive index can be evaluated by spectroscopic ellipsometry. Among the various fitting models applied to all of the deposited films, the two-layered model gave the best results. For the two-layered model, we found that the thickness of the upper layer was strongly correlated with surface roughness. Thus, spectroscopic ellipsometry can be used to evaluate density and roughness.
Solid Phase Crystallization (SPC) Behavior of Amorphous Si Bilayer Films with Different Concentration of Oxygen: Surface vs. Interface-nucleation
Authors: Ryu Myung-Kwan , Kwon Jang-Yeon , Kim Ki-Bum 
Published: April 2011

ABSTRACTSolid-phase crystallization (SPC) behavior of a-Si film [a-Si(II)] in which oxygen concentration (CO) is higher at the a-Si/SiO2 interface (CO=5×1021/cm3) than at the film surface (CO=3×1020/cm3) has been investigated. The results were also compared with that of a-Si single layer [a- Si(I), 600 Å] with CO=3×1020/cm3. It has been found that the interface-nucleation was suppressed in the a-Si(II) and the surface-nucleation occurred to make a poly-Si/a-Si (300 Å/300Å) bilayer structure. Many equiaxial grains with sizes of 1∼2 [.proportional]m were formed in the surface- nucleated poly-Si layer. Compared with the results of conventional SPC poly-Si (600 Åthick) in which elliptical grains with sizes of 0.5∼1 [.proportional]m were formed by the interface (a-Si/SiO2)- nucleation, we concluded that the poly-Si/a-Si bilayer scheme is a method to improve the microstructure of SPC poly-Si film.
Low Temperature Polycrystalline Si TFTs Fabricated with Directionally Crystallized Si Film
Authors: Jung Y.H. , Yoon J.M. , Yang M.S. , Park W.K. , Soh H.S. , Cho H.S. , Limanov A.B. , Im J.S. 
Published: April 2011

ABSTRACTThe comparison of TFTs fabricated on films processed by conventional excimer laser an- nealing (ELA) and sequential lateral solidification (SLS) demonstrates the dependence of the device characteristics on the microstructure of the device channel region. We report the perform- ance characteristics of non-self-aligned coplanar n- and p-channel low temperature TFTs fabricated on 1000-Å-thick films on Corning 1737 glass substrates that were directionally solidified using SLS. The devices were aligned so that the grain boundaries were parallel to the direction of the source-drain current flow. These results were compared with those obtained from devices fabricated on conventional ELA-processed polycrystalline Si films (with average grain size of ∼3000 Å) with identical methods. The values for channel mobility obtained from the SLS TFTs are ∼370 cm2/Vsec for n-channel and ∼140 cm2/Vsec for p-channel devices, compared to ∼100 and ∼60 respectively for ELA TFTs. Other device characteristics of SLS TFTs were Ion/Ioff > 107 at Vd=0.1V, and subthreshold slopes less than 0.5V/dec. We further discuss the physical implications of the results and present additional details of the devices.
High-Performance Poly-Si TFTs with Multiple Selectively Doped Regions in the Active Layer
Authors: Lee Min-Cheol , Yoo Juhn-Suk , Park Kee-Chan , Jung Sang-Hoon , Han Min-Koo , Kim Hyun-Jae 
Published: April 2011

ABSTRACTWe have proposed and fabricated a new poly-Si TFT that employs selectively doped regions between the source and drain in order to reduce leakage current without the sacrifice of the on current. In the proposed poly-Si TFTs, the selectively doped regions where doping concentration is identical to that of source/drain, reduce the effective channel length during the on state. Under the off state, the selectively doped regions may reduce the lateral electric field induced in the depletion region near drain so that the leakage current reduces considerably. The experimental data of the proposed TFT shows that it has the high on-current, low leakage current and low threshold voltage when compared with conventional TFT. The fabrication steps for the proposed TFT are reduced because ion-implantation for source/drain and selectively doped regions is performed simultaneously prior to an excimer laser irradiation. It should be noted that, in the proposed TFT, only one excimer laser annealing is required while two excimer laser annealing steps are required in conventional TFT.
The Dependence of Poly-Si TFT Characteristics on the Relative Misorientation Between Grain Boundaries and the Active Channel
Authors: Jung Y.H. , Yoon J.M. , Yang M.S. , Park W.K. , Soh H.S. , Cho H.S. , Limanov A.B. , Im J.S. 
Published: April 2011

ABSTRACTWe present device-related experimental results that quantitatively reveal the effect of varying the active channel/grain-boundary misorientation on the resulting TFT characteristics. Specifically, using low-temperature SLS processes, we have fabricated and analyzed n-channel and p-channel devices (40 μm width × 8 μm length) with three different orientations of the channel with respect to the grain boundaries: parallel, 45° inclined, and perpendicular on Corning 1737 glass substrates.The results reveal that the TFTs with the best (worst) characteristics were obtained for the devices with parallel (perpendicular) alignment. In general, for both n- and p-channel devices, the most prominent orientation-dependent effects were observed in the values of the field effect mobilities, which were 340, 227, and 141 cm2/Vsec for n-channel devices and 145, 105, and 80 cm2/Vsec for p-channel devices, in the order of increasing orientation mismatch. In contrast, no notable effect was manifested in the leakage currents, while small effects were seen for the sub-threshold slopes and threshold voltages. The degradation of device performance under hot-carrier stress was found to decrease with increasing orientation mismatch.
Tight Binding Modeling of Properties Related to Field Emission from Nanodiamond Clusters
Authors: Areshkin Denis A. , Shenderova Olga A. , Zhirnov Victor V. , Pal Alexander F. , Hren John J. , Brenner Donald W. 
Published: April 2011

ABSTRACTThe electronic structure of nanodiamond clusters containing between 34 and 913 carbon atoms was calculated using a tight-binding Hamiltonian. All clusters had shapes represented by an octahedron with (111) facets with the top and the bottom vertices truncated to introduce (100) surfaces. The tight-binding Hamiltonian consisted of environment-dependent matrix elements, and C-H parameters fit to reproduce energy states of the cyclic C6 and methane. The calculations predict a density of states similar to bulk diamond for clusters with radii greater than ∼2.5nm, and insignificant differences in the potential distribution between the clusters and bulk diamond for radii greater than ∼1nm. Hydrogen passivated nanodiamond clusters are estimated to have an electron affinity of approximately -1.8 eV.