bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tailored Laser scanned photodiodes (LSP) for image recognition
Authors: Vieira M. , Fernandes M. , Louro P. , Vygranenko Y. , Schwarz R. , Schubert M. 
Published: April 2011

ABSTRACTA tailored ZnO:Al/a-p-i-n SiC:H/Al configuration for the laser scanned photodiode (LSP) imaging detector is proposed. The LSP utilizes light modulated depletion layers as detector and a laser beam for readout. When highly resistive a-SiC:H doped layers are used its higher optical gap when compared with the active layer are responsible by charge accumulation at the illuminated interfaces which blocks the carrier collection under illumination. Those insulator-like layers act as MIS structures that prevent excess signal charge from blooming to the nearby dark regions avoiding the image smearing.The optical-to-electrical transfer characteristics show reciprocity between light intensity and image signal intensity only limited by the doped layers composition. Data reveal that the sensitivity, the responsivity and the spatial resolution are limited by the cell configuration while the linearity depends on the light source flux used to map the image onto the sensor. By using tailored SiC:H/Si:H/SiC:H p-i-n heterostructures an increase in the image signal optimized to the blue is achieved with a responsivity of 0.2 mW/cm2 and a spatial resolution of 20 µm.
Annealing Kinetics of Amorphous Silicon Alloy Solar Cells Made at Various Deposition Rates
Authors: Yana Baojie , Yanga Jeffrey , Lord Kenneth , Guha Subhendu 
Published: April 2011

ABSTRACTA systematic study has been made of the annealing kinetics of amorphous silicon (a-Si) alloy solar cells. The cells were deposited at various rates using H2 dilution with radio frequency (RF) and modified very high frequency (MVHF) glow discharge. In order to minimize the effect of annealing during light soaking, the solar cells were degraded under 30 suns at room temperature to quickly reach their saturated states. The samples were then annealed at an elevated temperature. The J-V characteristics were recorded as a function of annealing time. The correlation of solar cell performance and defect density in the intrinsic layer was obtained by computer simulation. Finally, the annealing activation energy distribution (Ea) was deduced by fitting the experimental data to a theoretical model. The results show that the RF low rate solar cell with high H2 dilution has the lowest Ea and the narrowest distribution, while the RF cell with no H2 dilution has the highest Ea and the broadest distribution. The MVHF cell made at 8Å/s withhigh H2 dilution shows a lower Ea and a narrower distribution than the RF cell made at 3 Å/s, despite the higher rate. We conclude that different annealing kinetics plays an important role in determining the stabilized performance of a-Si alloy solar cells.
OPTICAL EMISSION SPECTROSCOPY OF GERMANE PLASMA PRODUCED IN AN ECR REACTOR
Authors: deFreese Matt , Dalal Vikram L. , Falter Julie 
Published: April 2011

ABSTRACTPlasma deposition using silane and germane is extensively used for depositing amorphous (Si,Ge) films and devices, and has the potential of also being used for making crystalline films. In this paper, we report results on the electrical and optical characterization of germane plasmas using a Langmuir probe set-up and optical emission spectroscopy. The plasma studied was an electron-cyclotron-resonance plasma. For the first time ever, we have detected the characteristic 246 nm GeH emission peak in the plasma. The GeH emission peak is suppressed significantly when small quantities of hydrogen are added as a diluent gas. We have also studied the effect of adding a voltage bias to the substrate on the plasma properties. We find that adding voltage bias does not simply change the effective ion energy impinging on the substrate, as is usually assumed, but also changes all the plasma properties, including the density of neutral, excited H radicals arriving at the growing surface.
Some Considerations Relating to Growth Chemistry of Amorphous SI and (SI,GE) Films and Devices
Authors: Dalal Vikram L. 
Published: April 2011

ABSTRACTRecent experiments suggest that the chemistry responsible for the growth of amorphous and microcrystalline Si and (Si,Ge) alloys is more complicated than suggested by the standard model of growth. In particular, unexpected phenomena related to the density of ion flux, magnitude of ion energy and the presence of inert gas ions in the discharge suggest that both inert and reactive ion flux profoundly influence the growth of amorphous and microcrystalline films and devices. The influence of the ion flux is particularly important in understanding the growth of high quality a-(Si,Ge):H films. By carefully controlling this flux, we can change significantly the H bonding environment in a-(Si,Ge):H and produce high quality materials and devices. These observations suggest that the standard model of growth, which postulates that the growth is primarily limited by surface diffusion of radicals, and that H is eliminated by spontaneous bond breaking between neighboring Si-H bonds and formation of H2 molecule, does not describe the actual growth chemistry very well. Rather, the growth is limited by both surface diffusion of radicals and more fundamentally, by how rapidly H desorbs from surface and subsurface bonds. Ion induced desorption of excess H is shown to be very important in controlling the growth of both a-Si and a-(Si,Ge):H.
Electrical Properties and Defect States of Laser Crystallized Polycrystalline Silicon Films
Authors: Watanabe Tadashi , Andoh Nobuyuki , Sameshima Toshiyuki 
Published: April 2011

ABSTRACTIn this paper, changes in electrical properties of laser crystallized silicon films doped with 8.5×1017-cm−3-phosphorus atoms as a function of laser shot number are investigated. The samples are treated with plasma hydrogenation for 30 sec at 130 Pa at 250 °C and additional H2O vapor heat treatment at 260 °C for 3 hours with 1.3 MPa. The electrical conductivity at room temperature become about 10−6∼10−-5 S/cm as laser shot number increases from 1 to 100. After hydrogenation and additional H2O vapor heat treatment, electrical conductivity remarkably increases to 100∼101S/cm. At laser irradiation of 20 or 50 shots after both treatments, the density of defect at deep level states and tail states are determined 1.15×1017 cm−3 and 5.7×1017cm−3 using an analysis program. Potential barrier height at grain boundary is 0.048 eV. The effective carrier density and carrier mobility are markedly increased up to1017cm−3 and 209 cm2/Vs by hydrogenation and additional H2O vapor heat treatment.
Hydrogen Concentration Analysis in Pecvd and Rtcvd Silicon Nitride Thin Films and It's Impact on Device Performance
Authors: Wang C. Y. , Lim E. H. , Liu H. , Sudijono J. L. , Ang T. C. , Vassiliev V. Y. , Zheng J. Z. 
Published: April 2011

ABSTRACTIn this paper the impact of the ESL (Etch Stop layer) nitride on the device performance especially the threshold voltage (Vt) has been studied. From SIMS analysis, it is found that different nitride gives different H concentration, [H] in the Gate oxide area, the higher [H] in the nitride film, the higher H in the Gate Oxide area and the lower the threshold voltage. It is also found that using TiSi instead of CoSi can help to stop the H from diffusing into Gate Oxide/channel area, resulting in a smaller threshold voltage drift for the device employed TiSi. Study to control the [H] in the nitride film is also carried out. In this paper, RBS, HFS and FTIR are used to analyze the composition changes of the SiN films prepared using Plasma enhanced Chemical Vapor deposition (PECVD), Rapid Thermal Chemical Vapor Deposition (RTCVD) with different process parameters. Gas flow ratio, RF power and temperature are found to be the key factors that affect the composition and the H concentration in the film. It is found that the nearer the SiN composition to stoichiometric Si3N4, the lower the [H] in SiN film because there is no excess silicon or nitrogen to be bonded with H. However the lowest [H] in the SiN film is limited by temperature. The higher the process temperature the lower the [H] can be obtained in the SiN film and the nearer the composition to stoichiometric Si3N4.
Current Transport Mechanisms in CuIn1−xGaxSe2 and CIS Thin-Film Solar Cells on Flexible Stainless Steel Substrates
Authors: Naik Gaurav A. , Anderson Wayne A. 
Published: April 2011

ABSTRACTCopper indium gallium selenide (CIGS) solar cells on thin film stainless steel substrates were evaluated by current-voltage-temperature (IVT) from 150K-350K to determine current transport mechanisms. Both dark and photo data at reverse and low forward voltages exhibited tunneling-like behavior. At intermediate forward voltages, diffusion or thermionic emission are suggested by an ideality factor close to 1.0. At higher currents and voltages there is a trend towards recombination or space change limited behavior.
Investigation of the Trapping Mechanism for Transient Current-Voltage Behavior In CIGSS-Based Solar Cells
Authors: Johnson Pamela K. , Sites James R. , Tarrant Dale E. 
Published: April 2011

ABSTRACTSome thin-film CIS photovoltaic devices exhibit reversible transient behavior in their electrical properties induced by modestly elevated (70 - 100 °C) temperatures. This paper evaluates changes due to light exposure, thermal exposure, and applied bias in cells fabricated by Siemens Solar Industries (SSI). When a constant bias was maintained across cells subjected to elevated temperatures in the dark, and subsequent moderate- temperature light exposure, there was little reversible transient behavior. When the bias was cycled between zero and open-circuit voltage (VOC), independent of illumination, the fill factor (FF) decreased for zero bias and increased at VOC. Hence, it is the bias rather than photon absorption that drives the transient current-voltage behavior in these cells. Investigations of the relationship between trapping mechanisms and transient behavior using the frequency and temperature dependence of capacitance showed clear cyclic behavior in the trap-response frequency. Trap density profiles were found to be relatively independent of measurement temperature, and the total trap density varied only slightly with the bias cycle.
ERDA analysis of ZnSx(OH)y thin films obtained by chemical bath deposition
Authors: Neve Sven , Bohne Wolfgang , Röhrich Jörg , Scheer Roland 
Published: April 2011

ABSTRACTThin films of Zn-compounds grown in a chemical bath have been studied by Elastic Recoil Detection Analysis (ERDA). The bath contained zinc acetate, thiourea and complexing agents such as ammonia and hydrazine. Large amounts of hydrogen and oxygen are detected within all samples. A strong effect of the pH of the solution is revealed: At high pH (>11.5) mainly ZnS growth takes place, while at lower pH Zn(OH)2 is the dominant product. Hence the pH of the solution can be used to adjust the film stoichiometry. Deposition of Zn-compound films is possible without ammonia in the solution while presence of hydroxide ions and hydrazine species is necessary. It is proposed that film formation takes place via a complex combining hydrazine and hydroxide ligands.
Micron-Resolution Photocurrent of CdTe Solar Cells Using Multiple Wavelengths
Authors: Hiltner Jason F. , Sites James R. 
Published: April 2011

ABSTRACTAn apparatus developed recently at Colorado State University utilizes a diffractionlimited optics system and a high-resolution translation system to measure the laser-induced photocurrent at resolutions of 1 μm and equivalent incident laser intensities of 1 sun (100 mW/cm2). Multiple lasers in the 635-830 nm range can be easily selected by changing the fiberoptic connectors. The spot profile and location are unchanged when different lasers are selected. In addition, a laser temperature tuned through the 825-857 nm range allows measurement of local variations in the quantum efficiency near the CdTe band gap, which track intermixing of CdS/CdTe. This capability extends the previous analysis, which includes the separation of series resistance and shunting effects. The effect of post-deposition processing and elevated temperature stress on local variations in electrical and optical parameters, especially using the near-bandgap wavelengths, are examined using a series of samples fabricated at NREL.
Chemical Vapor Deposition of Titania/Silica and Zirconia Films
Authors: Gladfelter Wayne L. , Smith Ryan C. , Burleson David , Taylor Charles J. , Roberts Jeffrey T. , Campbell Stephen A. , Hoilien Noel , Tiner Mike , Hegde Rama , Hobbs Christopher 
Published: April 2011

ABSTRACTAmorphous thin films of composition TixSi1−xO2 have been grown by low pressure chemical vapor deposition on silicon (100) substrates using Si(OEt)4 and either Ti(OiPr)4 or anhydrous Ti(NO3)4 as the sources of SiO2 and TiO2, respectively. The substrate temperature was varied between 300 and 535°C, and the precursor flow rates ranged from 5 to 100 sccm. Under these conditions growth rates ranging from 0.6 to 90.0 nm/min were observed. Films were amorphous to X-rays as deposited and SEM micrographs showed smooth, featureless film surfaces. Cross-sectional TEM showed no compositional inhomogeneity. RBS revealed that x (from the formula TixSi1−xO2) was dependent upon the choice of TiO2 precursor. For films grown using TTIP-TEOS x could be varied by systematic variation of the flow of N2 through the precursor vessels or the deposition temperature. For the case of TN-TEOS x remained close to 0.5. The results suggested the existence of a specific chemical reaction between TN and TEOS prior to film deposition.The CVD of zirconium dioxide (ZrO2) films from zirconium tetra-tert-butoxide {Zr[OC(CH3)3]4} is also described. The films, which were deposited on Si(100), were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ellipsometry, X-ray diffraction (XRD), and Rutherford backscattering spectroscopy (RBS). Deposition was studied between ∼380 and 825 °C, and at precursor pressures between 4 × 10−5 and 1 × 10−4 Torr. The kinetics for steady-state growth were studied as functions of temperature and precursor pressure. Results were fit to a two-step kinetic model involving reversible precursor adsorption followed by irreversible decomposition to ZrO2.
Transistors Built With ZrO2 And HfO2 Deposited From Nitratos
Authors: Campbell Stephen A. , Hoilien Noel , Ma Tiezhong , Chen Fang , Smith Ryan , Gladfelter Wayne 
Published: April 2011

ABSTRACTThe electrical performance of transistors built using thin films of the column IVB metal oxides ZrO2 and HfO2 deposited from their respective anhydrous metal nitrate precursors is presented. In contrast to earlier work on TiO2, which is thermodynamically unstable on silicon, ZrO2 and HfO2 form well-defined oxynitride interfacial layers and have a good interface with silicon with much less fixed charge. The inversion layer mobility for an HfO2 / SiOxNy / Si stack is comparable to that of a conventional SiOxNy/Si interface.
Comparison of Conductance and Capacitance techniques for Measurement of Interface States in Thin Oxides
Authors: Higman T. K. 
Published: April 2011

ABSTRACTCurrent trends in integrated circuit processing project gate insulators with oxide equivalent thicknesses of 1.5 to 1.0 nm. Gate oxides in this thickness range have oxide capacitances of 1 to 5 μF/cm2. When oxide capacitances are this large, traditional high-frequency capacitance-voltage techniques for measuring interface states can be inaccurate. We show that a combination of high and low frequency capacitance-voltage data, along with frequency dependent conductance methods, produce more accurate results.
Dual Work Function CMOS Gate Technology Based on Metal Interdiffusion
Authors: Polishchuk Igor , Ranade Pushkar , King Tsu-Jae , Hu Chenming 
Published: April 2011

ABSTRACTIn this paper we propose a new metal-gate CMOS technology that uses a combination of two metals to achieve a low threshold voltage for both n- and p-MOSFET's. One of the gate electrodes is formed by metal interdiffusion so that no metal has to be etched away from the gate dielectric surface. Consequently, this process does not compromise the integrity and electrical reliability of the gate dielectric. This new technology is demonstrated for the Ti-Ni metal combination that produces gate electrodes with 3.9 eV and 5.3 eV work functions for n-MOS and p-MOS devices respectively.
Effects of a Ta Interlayer on the Titanium Silicide Reaction: C40 Formation and Higher Scalability of the TiSi2 Process.
Authors: La Via F. , Privitera S. , Mammoliti F. , Grimaldi M.G. 
Published: April 2011

ABSTRACTWhen a Ta layer is deposited at the Si/Ti interface a new phase has been detected, i.e. theTiSi2C40. The C40-C54 transformation kinetics and the film morphology are consistent with an increase of the nucleation density with respect to the C49-C54 transition. The activation energies for the nucleation rate (4.2±0.3 eV) and the growth velocity (4.0±0.4 eV) have been obtained from the in situ sheet resistance and the Transmission Electron Microscopy results. These results show that the process with a Ta layer at the Ti/Si interface has a greater scalability with respect to the standard TiSi2 process.
Increased Thermal Stability of Co-silicide Using Co-Ta Alloy Films
Authors: Kim Min-Joo , Choi Hyo-Jick , Ko Dae-Hong , Ku Ja-Hum , Choi Siyoung , Fujihara Kazuyuki , Kang Ho-Kyu , Lee Hoo-Jeung 
Published: April 2011

ABSTRACTThe silicidation reactions and thermal stability of Co silicide formed from Co-Ta/Si systems have been investigated. In case of Co-Ta alloy process, the formation of low resistive CoSi2phase is delayed to about 660°C, as compared to conventional Co/Si system. Moreover, the presence of Ta in Co-Ta alloy films reduces the silicidation reaction rate, resulting in the strong preferential orientation in CoSi2 films. Upon high temperature post annealing in the furnace, the sheet resistance of Co-silicide formed from Co/Si systems increases significantly, while that of Co-Ta/Si systems maintains low. This is due to the formation of TaSi2 at the grain boundaries and surface of Co-silicide films, which prevents the grain boundary migration thereby slowing the agglomeration. Therefore, from our research, increased thermal stability of Co-silicide films was successfully obtained from Co-Ta alloy process.
Detecting Impurities in the Ultra Thin Silicon Oxide Layer By Hg-Schottky Capacitance–Voltage (CV) Method
Authors: Liu D. , Wang Q. , Paravi H. , Drobny V. , Moquin J. 
Published: April 2011

ABSTRACTDetecting impurities or contaminations in the ultra thin silicon oxide layer is one of the most serious challenges in wafer processing as device is scaled down toward deep sub-micron. These impurities or contaminations will create charge traps in the oxide layer and degrade gate oxide integrity (GOI). The MOS Capacitance-Voltage method which has been used to study the electrical charges in relative thicker oxide layer (> 5 nm) cannot detect, however, these contaminations related charges in the ultra thin silicon oxide layer. In this article, a new method has been developed to determine the electrical charges associated with the contaminations in an ultra thin oxide layer using Hg-Schottky capacitance-voltage method. The oxide layers of 1.2 nm in thickness with and without Cu-contamination have been tested with this new method. The results show that the new method can be used to qualitatively identify the electrical charges trapped in the ultra thin silicon oxide layer and the trapping levels associated with the contamination. The interactions among sub-stochiometric oxide structure and electron traps introduced by the metal impurities have been discussed.
Dislocation Locking by Intrinsic Point Defects in Silicon
Authors: Peidous Igor V. , Loiko Konstantin V. , Simpson Dale A. , La Tony , Frensley William R. 
Published: April 2011

ABSTRACTDislocation pileups with abnormally weak inter-dislocation repulsion have been observed in locally oxidized silicon structures. To verify if this could be attributed to elastic interaction of dislocations with intrinsic point defects, distributions of self-interstitials in dislocation stress fields have been studied using theoretical calculations and computer simulations. According to the obtained results, self-interstitials can form atmospheres about dislocations causing dislocation stress reduction and therefore screening of dislocations from interaction with external stresses. This may represent an additional mechanism of dislocation locking in silicon alternative to oxygen pinning.
Modeling of Dislocations in an Epitaxial Island Structure
Authors: Liu X. H. , Ross F. M. , Schwarz K. W. 
Published: April 2011

ABSTRACTWe present calculations of dislocations in CoSi2 islands grown by reactive epitaxy on a Si(111) substrate. The stress fields due to the lattice mismatch are calculated with standard FEM techniques, and are converted into a structured, multi-level and multi-grid stress table that is imported into the PARANOID code to study the dislocation dynamics. Single and multiple dislocations in the island have been simulated, and the predicted patterns are strikingly similar to those observed experimentally. By looking at the growth behavior of very small loops we also find that dislocation-loop nucleation becomes easier as the islands become larger, and that thick islands are dislocated at smaller sizes than thin ones. These results are also in good agreement with experimental observations. We conclude that current modeling techniques are sufficient to treat this type of problem at a useful level of accuracy.
Blistering on Silicon Surface Caused by Gettering of Hydrogen on Post-Implantation Defects
Authors: Usenko A.Y. , Carr W.N. 
Published: April 2011

ABSTRACTA well-known process for thinning of silicon by slicing submicron-thick crystalline films from substrates uses direct implantation of protons. In this paper we describe a different way of delivering hydrogen to a cleavage plane. In our process a defect-rich buried layer is first formed with ion implantation. Defects in the as-implanted silicon work as traps for hydrogen. Next monatomic hydrogen is delivered to the trap layer by electrolytic charging. To check sliceability, the samples were annealed and blistering was observed. Evidence of blistering is a sign of potential cleavage. The electrolytic charging was performed using a simple two-electrode cell. The front side of the as-implanted silicon wafer was exposed to an electrolyte. The backside of the wafer was contacted with an aluminum layer and connected to a current source. The acidic electrolyte was buffered with ethylene glycol. Buffering was used to suppress bubbling on the wafer surface and to improve the uniformity of charging. To increase charging current the wafer was illuminated with visible light. A graphite rod was used as the positive electrode in the cell. A few Coulombs per square centimeter of the wafer were passed through the cell during the hydrogenation process. The depth of blisters is about 1/2 of projection range of the implanted ions. It means that the hydrogen platelets are formed in the region of maximum of vacancy- enriched post-implantation defects. This process of electrolytic hydrogen charging may be used in future to manufacture silicon-on-insulator wafers with very thin top silicon layer. Thin SOI offers important advantages in the production of substrates for mainstream CMOS integrated circuit manufacturing.