bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two-Dimensional Amorphous Silicon Color Sensor Array
Authors: Lemmi F. , Mulato M. , Ho J. , Lau R. , Lu J. P. , Street R. A. 
Published: April 2011

ABSTRACTThis paper reports on the first full realization and characterization of a two-dimensional array of amorphous silicon (a-Si:H) color sensors, addressed by integrated amorphous silicon-based thin-film transistors (TFTs). The array includes 512 × 512 pixels with 75-µm pitch, or about 340 dpi. Each pixel features a color sensor realized by a p-i-n-i-p stack of doped and undoped a-Si:H layers, and the TFT. The color sensors are made of two back-to-back p-i-n diodes, which selectively sense the illumination according to the polarity of the applied bias voltage. The sensor layers are grown on top of the TFTs to improve the array fill factor. The p-in-i-p sensor stack is mesa-isolated into single sensors to reduce cross-talk.Images are acquired using two bias voltages and yield the red and blue/green components of the original with a good color separation. A color image is reconstructed using the information from the two images acquired. Aside from a color bias, which is expected for a two-color reconstruction, the imaging system works well. In particular, the array shows very low leakage currents, which enable a very large dynamic range and sensitivity. In the response of the array to a light pulse, the bottom thick diode ensures a fast drop in the signal after the flash, while the top thin diode exhibits some residual image lag.
The Determination of Optoelectronic Properties of Microcrystalline andAmorphous Silicon Films
Authors: Kunst Marinus , Aichberger Susanne von , Thom Wilhelm , Wünsch Frank 
Published: April 2011

ABSTRACTThe study and characterization of the (opto)electronic properties of a-Si:H and µSi filmsby contactless transient photoconductivity measurements is presented. The importance ofminority carrier trapping is shown for the example of a-Si:H films prepared with different dopinglevels. It is shown that the microwave mobility determined by these measurements is a versatiletool for the characterization of the films. Examples are given by the study of µ Si filmsproduced by laser crystallization of a-Si:H films and the optimization of the substratetemperature for the Hot Wire deposition of µ Si films.
Integrated Optical and Electrical Modeling of a-Si:H Based Solar Cells
Authors: Zeman Miro , Swaaij René A.C.M.M. van , Heuvel Joost J.G. van den , Metselaar Wim 
Published: April 2011

ABSTRACTNew features of the ASA software package are described that allow the analyses of the performance of hydrogenated amorphous silicon (a-Si:H) based solar cells with rough interfaces and buffer and graded layers. Using the updated version of ASA improved understanding of i) the effect of the front and back contact roughness on the external quantum efficiency and the absorption of light in the individual layers of a-Si:H solar cells and ii) the role of band gap grading of the intrinsic a-SiGe:H layer in a solar cell is obtained. The simulated results using the ASA package agree well with measured data on solar cells and are used to give insight into the behavior of the internal parameters of the solar cells.
Evidence for Long-range Hydrogen Motion in a-Si:H under Room-temperature Illumination Using Raman Scattering of Amorphous Tungsten Oxide Overlayer
Authors: Cheong Hyeonsik M. , Lee Se-Hee , Nelson Brent , Mascarenhas Angelo , Deb Sayten K. 
Published: April 2011

ABSTRACTWe demonstrate that one can detect minuscule amounts of hydrogen diffusion out of a-Si:H under illumination at room temperature, by monitoring the changes in the Raman spectrum of amorphous tungsten oxide as a function of illumination. The Staebler-Wronski effect, the light-induce creation of metastable defects in hydrogenated amorphous silicon (a-Si:H), has been one of the major problems that has limited the performance of such devices as solar cells. Recently, Branz suggested the hydrogen collision model that can explain many aspects of the Staebler-Wronski effect. One of the main predictions of this model is that the photogenerated mobile hydrogen atoms can move a long distance at room temperature. However, light-induced hydrogen motion in a-Si:H has not been experimentally observed at room temperature. We utilized the high sensitivity of the Raman spectrum of electrochromic a-WO3 to hydrogen insertion to probe the long-range motion of hydrogen at room temperature. We deposited a thin (200 nm) layer of a-WO3 on top of a-Si:H, and under illumination, a change in the Raman spectrum was detected. By comparing the Raman signal changes with those for control experiments where hydrogen is electrochemically inserted into a-WO3, we can estimate semiquantitatively the amount of hydrogen that diffuses out of the a-Si:H layer.
Formation of Polycrystalline Silicon Films Using Electrical-Current-Induced Joule Heating
Authors: Andoh Nobuyuki , Takahashi Hiroyuki , Sameshima Toshiyuki 
Published: April 2011

ABSTRACTElectrical current induced joule heating method was applied to crystallization of 50 nm-thick amorphous silicon films formed on glass substrates. Voltages were applied to silicon films connected with a capacitance in parallel. Irradiation with 5 ns-pulsed-laser melted films partially and caused electrical current induced joule heating because of reduction of electrical resistance. Lateral grain growth with 12.6 µm was realized using the tapered-shaped-electrodes to apply voltages to silicon films with a capacitance of 0.33 µF. For 2.6×1017cm−3phosphorus-doped films, analysis of temperature change in the electrical conductivity gave that defect states at grain boundaries was low of ∼1017cm−3.
Photoluminescence Characterisation of Ion Implanted CdTe
Authors: Halliday D. P. , Potter M. D. G. , Boyle D. S. , Durose K. 
Published: April 2011

ABSTRACTWe have ion implanted a series of dopants into single crystal CdTe. The influence of the impurities on the CdTe has been studied by low temperature photoluminescence spectroscopy. The impurities studied are: O, Cl, Cu, S, Na and Sb, and were selected because of their potential importance in thin film CdTe/CdS photovoltaic devices. Each impurity was implanted to give a smooth gaussian distribution in the first few microns of material with a doping density of 1×1015cm−3. Low temperature photoluminescence spectra were recorded from each sample and compared with an undoped sample. The PL features observed in each sample are discussed and the data is compared to an earlier photoluminescence study of thin film CdTe/CdS photovoltaic device structures.
Flexible and monolithically integrated CIGS-Modules
Authors: Kessler F. , Herz K. , Powalla M. , Hartmann M. , Schmidt M. , Jasenek A. , Schock H. W. 
Published: April 2011

ABSTRACTMonolithically integrated Cu(In,Ga)Se2-mini-modules (CIGS) have been fabricated on polymer as well as on metal foils. Preferred foils with view on costs and physical properties were ferritic steel, titanium, Fe/Ni-alloys (e.g. Kovar®) and polyimide as the only appropriate low temperature candidate. The metal substrates were isolated by multiple layers of SiOx and Al2O3 which served both as diffusion barrier against substrate elements and dielectric barrier. Small area cell efficiencies of 13.8% on ferritic steel foils and 10.6% on polymer foils (both without antireflective coating) were obtained. First monolithically integrated submodules of up to 10×10cm2 substrate area were fabricated both on ferritic steel and polyimide substrates. Different patterning methods have been applied and matched to the respective substrate materials.
A Detailed Study of Cu(In,Ga)Se2 Thin Films by Electron-Beam-Induced-Current and Cathodoluminescence
Authors: Romero M.J. , Hasoon F.S. , Al-Jassim M.M. , Garcia R. , Noufi R. 
Published: April 2011

ABSTRACTCu(In,Ga)Se2 (CIGS) thin films were deposited using the three-stage process. At the third stage, an amount of Indium was added to the CIGS that is greater than the standard used in processing high-efficient CIGS solar cells. The effects of Indium excess and substrate temperature were then investigated by electron-beam-induced-current (EBIC) and cathodoluminescence (CL). The addition of more indium compared to the standard noticeably affects the ZnO/CdS/CIGS heterojunction. On the other hand, the substrate temperature primarily affects the luminescence behavior of these films. It is suggested than In enrichment and Na incorporation play a main role in the electronic properties of the film. From these results, the efficiencies obtained for this set of CIGS cells are finally understood.
Fabrication of CuInSe2 Solar Cells by the Evaporation of Binary Selenide Compounds
Authors: Lee Doo Youl , Yun Jae Ho , Ahn Byung Tae , Yoon Kyung Hoon , Song Jinsoo 
Published: April 2011

ABSTRACTCuInSe2 films were prepared by the three-stage process using the evaporation of In2Se3, Cu2Se and Se. In the third stage, the depth of Cu-poor surface region was precisely adjusted by the control of the evaporation rate of In2Se3 and Se. The interface between Cu-poor surface region and stoichiometric CuInSe2 film was characterized using AES, microEDAX, and RBS. The 9.59% efficiency was achieved in the 0.16 cm2 area cell. The efficiency is the same level of the CIS cell prepared using the element coevaporation, opening up the application of binary compounds for highly efficient Cu(In,Ga)Se2 cells.
Annealing time and collection efficiency in electrodeposited CdS/CdTe solar cells
Authors: Agostinelli G. , Dunlop E.D. , Ebner B. , Gibson N. 
Published: April 2011

ABSTRACTThis paper presents a detailed analysis of the spatially resolved evolution of External Quantum Efficiency of electrodeposited CdS/CdTe solar cells as a function of the duration of the post-deposition annealing process which promotes n to p-type conversion of electrodeposited CdTe. Strips of 30×4 cm were cut from deposited plates at various stages of the fabrication process and processed into cells. Annealing treatments were carried out on these strips at 400°C for times ranging from 1 to 120 minutes. 130 spectral response curves (in the range of 300 to 900 nm) have been measured to trace temporal evolution and spatial non-uniformity of the materials and extrapolate parameters such as effective diffusion lengths, evolution of the collection profiles, and junction depth. Correlation between these parameters suggests that recrystallisation does not take place uniformly but progresses through the film. The analysis of structural vs. optical parameters along the cells provides evidence for spatial non-uniformities of the state of crystallisation of as-deposited and annealed material. Poor performance has been observed near the edges of the cells where material is resistant to recrystallisation.
Materials and Physical Properties of Novel High-k and Medium-k Gate Dielectrics
Authors: Liu Ran , Zollner Stefan , Fejes Peter , Gregory Rich , Lu Shifeng , Reid Kim , Gilmer David , Nguyen Bich-Yen , Yu Zhiyi , Droopad Ravi 
Published: April 2011

ABSTRACTRapid shrinking in device dimensions calls for replacement of SiO2 by new gate insulators in future generations of MOSFETs. Among many desirable properties, potential candidates must have a higher dielectric constant, low leakage current, and thermal stability against reaction or diffusion to ensure sharp interfaces with both the substrate Si and the gate metal (or poly-Si). Extensive characterization of such materials in thin-film form is crucial not only for selection of the alternative gate dielectrics and processes, but also for development of appropriate metrology of the high-k films on Si. This paper will report recent results on structural and compositional properties of thin film SrTiO3 and transition metal oxides (ZrO2and HfO2).
Plastic Deformation of Thin Metal Foils without Dislocations and Formation of Point Defects and Point Defect Clusters
Authors: Kiritani Michio , Yasunaga Kazufumi , Matsukawa Yoshitaka , Komatsu Masao 
Published: April 2011

ABSTRACTEvidence for plastic deformation of crystalline metal thin foils without dislocations is presented. Direct observation during deformation under an electron microscope confirmed the absence of the operation of dislocations even for heavy deformation. In fcc metals including aluminum, deformation leads to the formation of an anomalously high density of vacancy clusters, in the form of stacking fault tetrahedra. The dependency of vacancy cluster formation on temperature and deformation speed indicates that the clusters are formed by the aggregation of deformation-induced vacancies. Conditions required for the absence of the dislocation mechanism are explained, and a new atomistic model for plastic deformation of crystalline metals is proposed.
Structure and mechanical behavior relationship in nano-scaled multilayered materials
Authors: Sergueeva A. , Mara N. , Mukherjee A.K. 
Published: April 2011

ABSTRACTMultilayered foils with 10%Cu/90%Ni and different bi-layer thickness (100-1000 nm) have been fabricated by electrodeposition. TEM and x-ray diffraction analysis indicate discrete layer formation and a (100) textured structure. The maximum tensile strength (590 MPa) is obtained for foils with the smallest layer thickness. Preliminary results on high temperature deformation show a strong dependence of strength and plasticity on layer thickness.
Molecular dynamics simulations of wafer bonding
Authors: Scheerschmidt Kurt 
Published: April 2011

ABSTRACTMolecular dynamics simulations using empirical potentials have been employed to describe atomic interactions at interfaces created by the macroscopic wafer bonding process. Investigating perfect or distorted surfaces of different semiconductor materials as well as of silica enables one to study the elementary processes and the resulting defects at the interfaces, and to characterize the ability of the potentials used. Twist rotation due to misalignment and bonding over steps influence strongly the bondability of larger areas. Empirical potentials developed by the bond order tight-binding approximation include ∏-bonds and yield enhanced interface structures, energies, and transferability to new materials systems.
Electrical characterisation of UHV-bonded silicon interfaces
Authors: Reznicek A. , Senz S. , Breitenstein O. , Scholz R. , Gösele U. 
Published: April 2011

ABSTRACTDirect wafer bonding can be used to mechanically and electrically connect semiconductors. In our experiments two 100 mm diameter (100) Si wafers (n-doping: 1014 cm−3) are first cleaned by standard chemical cleaning (RCA 1, 2). The surface is terminated by hydrogen after a HF dipping. The wafers are prebonded in air to protect the surface. After introduction into the ultra high vacuum (UHV) system the wafers are separated again. The hydrogen termination is released in a heating chamber. RHEED confirmed a surface reconstruction. The wafers are then cooled down to room temperature and bonded in UHV. The bonding energy is very close to the bulk bonding energy.Measurements of whole n-n wafers showed a linear relationship of voltage and current at a low current density of 0.05 A/cm2. The current flow is inhomogeneous, which is visible in IR- thermography images. Above 0.1 V the current density first saturates, but increases super- linearly for higher voltages. The electrical properties of a grain boundary can be modeled by a double Schottky barrier. The barrier height decreases with increasing applied voltage. C-V measurements show a strong dependence of capacitance on frequency, temperature and applied voltage.The capacitance increases with higher temperature and lower frequency. The interface state density can be estimated from the low temperature and high frequency capacitance limit as Dit = 1·1011 cm−2 eV−1 assuming a constant density of states.We can conclude that in order to avoid the undesirable effect of the potential barrier and trap states at the bonding interface a high doping near the interface is required for the application of wafer bonding to devices with a high current density across the bonded interface.
Field Emission Characteristic of Silicon Cathodes Coated with GaN Nanoparticles
Authors: Hajra M. , Chubun N.N. , Chakhovskoi A.G. , Hunt C.E. , Liu K. , Murali A. , Risbud S H. , Tyler T. , Zhirnov V. 
Published: April 2011

AbstractArrays of p-type silicon micro-emitters have been formed using a subtractive tip fabrication technique. Following fabrication, the emitter surface was coated with GaN nanoparticles and nanocrystalline diamond by a dielectrophoresis deposition technique. The emitters were evaluated and compared before and after the surface treatment using I-V measurements in the diode configuration. The phosphor screen, used as the anode, was spaced nominally about 70 µm from the cathode. The field emission characteristics were measured in a high vacuum chamber at a pressure range between 10−5and 10−8Torr. The results suggest that the emitters benefit from coating the surface with nanocrystalline diamond in terms of reduction in the turn on voltage, GaN coating increase the turn on voltage. Both diamond and GaN improved the emission uniformity in the region of the low voltage operation.
Performances Presented by Large Area ZnO Thin Films Deposited by Spray Pyrolysis
Authors: Nunes Patrícia , Marques Antonio , Fortunato Elvira , Martins Rodrigo 
Published: April 2011

AbstractIn this work we present the results of a study on the uniformity of ZnO thin films produced by spray pyrolysis. The properties of the thin films depend essentially on the carrier gas pressure and gas flow used. The best films for optoelectronic applications were obtained with a carrier gas pressure of 2 bar and solution flow of 37 ml/min. The velocity of the nozzle affects essentially the uniformity of the ZnO thin films. However this important characteristic of the large area thin films is independent of the nature (doped and undoped) of the thin film and exhibits a high dependence on the variation of the temperature along the substrate.
Charge Carrier Transport in a-Si:H/a-SiC:H Heterojunction with Blocking Layer
Authors: Vygranenko Yu. , Fernandes M. , Louro P. , Mačarico A. , Vieira M. 
Published: April 2011

AbstractThis paper presents a one-dimensional numerical simulation of the charge carrier transport and photogeneration within a p-i-n (a-Si:H) homojunction and a p(a-SiC:H)/i (a-Si:H)/n (a-SiC:H) heterojunction with weakly-doped n-layers. A good matching between the simulated J-V characteristics and the corresponding experimental curves has been achieved for both configurations. By analysing the simulated band diagrams, electric fielddistributions, the electron and hole current densities, and the free carrier population profiles we conclude that in short-circuit mode the carrier transport is different in the homojunction and heterojunction due to band offsets.
Silicon Field Emitter Arrays Integrated with MOSFET Devices
Authors: Hong Ching-yin , Akinwande Akintunde I. 
Published: April 2011

AbstractWe report a metal oxide semiconductor field effect transistor (MOSFET) controlled field emission array (FEA) device. The device uses a lateral double diffused MOSFET (LD-MOSFET) to control electron supply to the surface. The FEAs were fabricated using isotropic etch of silicon, oxidation sharpening and chemical mechanical polishing. The LD-MOSFETs have a threshold voltage of 0.48V while the FEAs have a turn-on voltage of 28V. Analysis using the FN formulation indicates that a silicon tip radius of 11 nm would fit the FEA IV data. The tip radius from the electrical data is very close to the average tip radius of 10 nm obtained from transmission electron microscope (TEM) analysis. The IV characterization of the MOSFET/FEA demonstrated control of electron emission by the MOSFET gate voltage.
Grain Quality Enhancement of Nickel-Crystallized Polysilicon Film in Quantum-Wire-Like Structures
Authors: Wang Hongmei , Jagar Singh , Zhan N. , Cheng C. F. , Poon M. C. , Chan Mansun 
Published: April 2011

AbstractMethods for forming high quality re-crystallizing polysilicon films are being actively studied due to their ability to provide significant improvement to polysilicon Thin-Film-Transistors (TFT). Recently, a simple Metal-Induced-Lateral-Crystallization (MILC) method with nickel, together with high temperature annealing, can result in single crystal like polysilicon film [1]. TFTs fabricated on this so-called Large-grain Silicon-On-Insulator (LPSOI) can achieve SOI MOSFET performance especially for making small dimension devices. This paper reports that the polysilicon grain quality can be further enhanced by crystallizing the polysilicon film into the shape of long-wire.The crystallization procedure started with a regular Nickel-Induced-Lateral-Crystallization (NILC) process at 560 °C as described in [1]. The film was then etched into narrow wires, which were parallel to the direction of nickel propagation. The NILC second anneal at 900 °C was then performed on these silicon wire. Through surface energy anisotropy stimulated grain expansion in the NILC high-temperature second annealing, enhanced grain quality beyond that on planar polysilicon film.Transistor fabricated on these wire is similar to gate-all-around structure as that of FinFET [2]. Much better scalability to the deep submicron region was observed for these wire transistors than regular planar TFTs formed on the same NILC film. Experimental results showed that a wide transistor formed by the parallel combination of the quantum wire transistors much higher current drive than a TFT on the same NILC film with equivalent width.
A Model for Heterogeneous Nucleation and Growth of Silicon Nanoparticles on Silicon Dioxide from Disilane
Authors: Leach William T. , Zhu Jian-Hong , Ekerdt John G. , Mashiro Supika , Sakai Junro , Kawshima Takayuki 
Published: April 2011

AbstractA model is presented that describes silicon nanoparticle deposition in terms of disilane decomposition on silicon dioxide, adatom diffusion, nucleation, nanoparticle growth and coalescence. Total nanoparticle densities are output as a function of time, and segregation of nanoparticles into subsets with common size allows size distributions to be reported for all times during the simulation. Model parameters are fit to low pressure chemical vapor deposition data with disilane pressures ranging from 5×10−4 to 5×10−3 Torr and surface temperatures from 510 to 570 °C. Simulations are used to explain how growth pressure and surface temperature influence incubation time, nanoparticle density and size distribution.
Size Effects Determined from Tensile Tests of Perforated MEMS Scale Specimens
Authors: Chasiotis Ioannis , Knauss Wolfgang G. 
Published: April 2011

AbstractA systematic study of small-scale size effects has been conducted on elliptically perforated specimens with minimum radius of curvature of 1 micron. This study aimed at assessing the dependence of failure stress at the tip of a notch on varying: (a) stress concentration for constant radius of curvature, (b) radius of curvature of micro-notches relative to the material grain size and constant stress concentration. The experiments demonstrate a strong influence of notch radius on the failure strength of MEMS scale specimens, while the effect of the stress concentration factor is of rather secondary importance. The local failure strength at the tip of a notch increases when the radius of curvature becomes smaller, which is in accordance with the probabilistic nature of failure. When the notch radius becomes as small as 1 micron (only three times larger than the grain size) then a strong size effect is observed. This effect becomes moderate for larger radii of curvature, up to 8 microns (25 times the grain size), when the failure stress at the notch tip almost reaches the tensile strength recorded for 50 micron wide samples.