bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantization of crack speeds in dynamic fracture of silicon: Multiparadigm ReaxFF modeling
Authors: Tang Harvey , Rye Janet , Buehler Markus J. , van Duin Adri , Goddard III William A. 
Published: April 2011

AbstractWe report a study of dynamic cracking in a silicon single crystal in which the ReaxFF reactive force field is used for about 3,000 atoms near the crack tip while the other 100,000 atoms of the model system are described with a simple nonreactive force field. The ReaxFF is completely derived from quantum mechanical calculations of simple silicon systems without any empirical parameters. This model has been successfully used to study crack dynamics in silicon, capable of reproducing key experimental results such as orientation dependence of crack dynamics (Buehler et al., Phys. Rev. Lett., 2006). In this article, we focus on crack speeds as a function of loading and crack propagation mechanisms. We find that the steady state crack speed does not increase continuously with applied load, but instead jumps to a finite value immediately after the critical load, followed by a regime of slow increase. Our results quantitatively reproduce experimental observations of crack speeds during fracture in silicon along the (111) planes, confirming the existence of lattice trapping effects. We observe similar effects in the (110) crack direction.
The Influence of Deposition Conditions on the Electronic Properties of a-Si:H Prepared in Expanding Thermal Plasma
Authors: Brinza Monica , Adriaenssens Guy J. 
Published: April 2011

AbstractA number of a-Si:H samples prepared in an expanding thermal plasma under varying conditions were examined by means of time-of-flight transient photocurrent measurements. A high deposition temperature allows high deposition rates while achieving high hole mobility and mobility-lifetime product. Lower hole mobility but higher μτ product result from slower deposition at lower temperature. Electron μτ products are uncharacteristically low for all samples due to pronounced deep trapping. RF biasing of the substrate does not improve the results.
The Influence of the Hot Wire Temperature on the Crystallization of μc-Si:H Films Prepared by Hot Wire-Assisted-ECR-CVD
Authors: Li Ying , Li Zhi zhong , Chen Guang hua , Kumeda Minoru 
Published: April 2011

AbstractWe have constructed a hot wire assisted ECR-CVD system to prepare a-Si:H and μc-Si:H films. The effect of hot wire temperature on crystallization of a-Si:H films is studied in the films prepared by these system. The crystalline fraction and crystalline grain size are analyzed by Raman scattering. The hydrogen content and the bonding scheme of hydrogen were measured by Fourier transform infrared (FTIR) spectroscopy. At low hot wire temperature, about 20 at.% hydrogen is included in the film. With increasing the hot wire temperature, the total content of the hydrogen, SiH2 and SiH decrease and the microcrystalline phase appears. It is found from the ratio of the crystalline TO peak to the total area of the TO peak of the Raman scattering spectra that the volume fraction of the crystalline phase increases with increasing the hot wire temperature. The crystalline peak has a tendency to shift toward the higher wavenumber with increasing the hot wire temperature, suggesting that the grain size increases with increasing the hot wire temperature.
Role of Surface on the Persistent Photoconductivity in Porous Silicon and Boron Doped a-Si:H
Authors: Agarwal S. C. , Kumar Abhishek , Mandal N P 
Published: April 2011

AbstractThe effect of ambient conditions on light soaking (LS) in porous silicon (PS) sample is studied. In vacuum LS on porous silicon increases dark current (DC) while in presence of water vapor it decreases DC. Interestingly, LS gives a higher DC in vacuum as well as in presence of water vapor for boron doped hydrogenated amorphous silicon a-Si:H(B) samples. A thin layer of polystyrene polymer almost eliminates the light induced degradation of porous silicon (PS) layers but can do so only to a smaller extent in a-Si:H(B). This shows that the effect of LS in PS is different than the effect of LS in a-Si:H(B) and that the surface plays a more important role in PS than in a-Si:H.
Blue Light Emission from PECVD Deposited Nanostructured SiC
Authors: Ivashchenko Liudmyla , Vasin Andriy , Ivashchenko Volodymyr , Ushakov Mykola , Rusavsky Andriy 
Published: April 2011

AbstractExperimental data on the room temperature blue light emission from nanocrystalline silicon carbide (nc-SiC) films are presented. The silicon carbide films were deposited on silicon substrates with a plasma enhanced chemical vapor deposition (PECVD) reactor from methyltrichlorosilane at substrate temperature in the range of 200-350°C. The film deposited at 350°C is nanostructured and X-ray diffraction proves the presence of the 3C-SiC crystallites. Infrared absorption spectroscopy in the region of Si-C, C-H, C-O, Si-H and Si-O bonds show the corresponding absorption bands. X-ray photoelectron spectroscopy studies confirm this bond picture. Photoluminescence was measured at 77 and 300 K. The bright blue emission has a double-peak structure at 415 and 437 nm. To clarify the origin of such an emission, tight binding molecular dynamics (TB-MD) simulations of several SiC and Si nanoclusters were carried out. Based on the temperature dependence of the photoluminescence and on the simulation data, a possible model of radiative recombination in nc-SiC films was proposed. According to this model, the emission bands at 415 and 437 nm are assigned to band-to-band and band-to-tail recombination in the nanocrystallite core. The recombination at band tails of the interface and Si-C-O-H amorphous tissue gives rise to a shoulder around 470 nm.
Novel Semiconducting Phase of Amorphous Carbon Nickel Composite Films
Authors: Bhattacharyya Somnath , Henley S. J. , Blanchard N. P. , Silva S. R. P. 
Published: April 2011

AbstractA homogeneously mixed phase of carbon and 10% nickel yielding amorphous carbon-nickel composite (a-C-Ni) films is prepared by an excimer UV pulsed laser ablation. Conductivity study of these films shows a nearly activated conduction. Also a saturation of conductivity below a temperature of 25 K explains the presence of an additional density of states at the Fermi level in these samples. Our experiments demonstrate a very different behaviour of electronic properties of these novel materials compared to undoped diamond-like carbon (DLC) films, which was directly confirmed using valence band spectroscopy.
The Crystallization Mechanism of Poly-Si Thin Film Using High-power Nd:YAG Laser with Gaussian Beam Profile
Authors: Zan Hsiao Wen , Huang Chang Yu , Saito Kazuya , Tamagawa Kouichi , Chen Jack , Wu Tung Jung 
Published: April 2011

AbstractThis paper studies the poly-Si crystallization mechanism under the high power (200 W) Nd:YAG solid state pulsed laser annealing system. It is found that the Gaussian-distributed laser beam profile successfully produce large super lateral growth process window. The devices in the SLG process window exhibit field-effect mobility around 250 cm2/V.s and the threshold voltage lower than 1 V. The influence of a-Si film thickness and the laser scan pitch on the process window is also carefully investigated.
Roughness, impurities and strain in low-temperature epitaxial silicon films grown by tantalum filament hot-wire chemical vapor deposition
Authors: Teplin Charles W. , Page Matthew , Iwaniczko Eugene , Jones Kim M. , Ready Robert M. , To Bobby M. , Moutinho Helio M. , Wang Qi M. , Branz Howard M. 
Published: April 2011

AbstractWe grow epitaxial silicon films onto (100) silicon wafers from pure silane by hot-wire chemical vapor deposition (HWCVD). The films grow epitaxially for a thickness hepi before a Si:H cones nucleate and expand. We study the dependence of hepi on growth rate and the differences between Ta and W filaments. The surface morphology of thin but completely epitaxial films are studied in order to correlate the surface roughness during growth with the eventual epitaxial breakdown thickness. Surface roughness, strain and H at the wafer/film interface are not likely to cause the observed breakdown.
Amorphous Silicon 2-TFT Pixel Circuits on Stainless Steel Foils
Authors: Kattamis Alex Z , Cheng I-Chun , Hong Yongtaek , Wagner Sigurd 
Published: April 2011

AbstractWe have fabricated pixel circuits consisting of two bottom-gate staggered source-drain amorphous silicon thin-film transistors (a-Si:H TFTs) on flexible stainless steel foils. Stainless steel is attractive because it allows for high processing temperatures of >300°C and is a perfect barrier to oxygen and moisture. Our steel foils were 75&#61549;m thick, with a peak-to-peak surface roughness of >1.2&#61549;m. This rough, as-rolled, conductive surface needed a thick planarization and passivation (electrical isolation) layer. The surface was planarized with 1.6&#61549;m of spin-on-glass, which reduced the roughness to ~0.3&#61549;m peak-to-peak. A passivation layer of 0.6&#61549;m of SiNx deposited by plasma-enhanced chemical vapor deposition was used to reduce leakage currents and capacitive coupling to the substrate. The 92&#61549;m × 369&#61549;m voltage-programmed pixel circuits employ a switching (Sw) TFT (W/L=50/5&#61549;m), a driver (Dr) TFT (W/L=200/5&#61549;m), and a 2pF storage capacitor between the gate and source of the Dr TFT. With a supply voltage of VDD=20V and a drive bias of 20V the circuits deliver 26&#61549;A of current. The vertical stripe pixels were integrated into 48 × (4) × 48 arrays and passivated with SiNx. Anode metal of Al-1% Si was also deposited, preparing the displays for subsequent OLED fabrication. Pixel circuits with this performance can drive top-emitting organic light emitting diodes (OLEDs) and therefore can be used in backplanes for flexible, high-resolution, active-matrix OLED displays.
Band Gap Engineering and Electrical Field Tailoring for Voltage Controlled Spectral Sensitivity
Authors: Vieira Manuela , Louro P. , Fantoni A. , Fernandes M. , Lavareda G. , Carvalho C.N. 
Published: April 2011

AbstractStacked ITO/(a-SiC:H)pinpi /(a-Si:H)i'sn/ITO color sensitive detectors are analyzed using the laser scanned photodiode technique. Results show that band gap engineering together with the laser scanned photodiode technique allows a voltage controlled shift of the collection regions, allowing color discrimination at readout voltage that cancels the self-bias effect induced by the steady state illumination, across the back diode. The threshold voltage between green and red discrimination depends on the thickness ratio between a-Si:H (-i')/a-SiCH (-i) layers. As this ratio increases the self-reverse effect due to the front absorption will be balanced by the decrease of the self-forward effect due to the back absorption shifting the threshold voltage to lower reverse bias. The various design parameters and the optical readout process trade-offs are discussed and supported by a 2D numerical simulation. A self-bias model is proposed to explain the voltage controlled spectral sensitivity.
Self-aligned Thin Film Transistor Fabrication with an Ultra Low Temperature Polycrystalline Silicon Process on a Benzocyclobutene Planarized Stainless Steel Foil Substrate
Authors: Moon Jaehyun , Park Dong-Jin , Chung Choong-Heui , Kim Yong-Hae , Yun Sun Jin , Lim Jung Wook , Lee Jin Ho 
Published: April 2011

AbstractCompared to plastic, from the view point of ultra low temperature poly-Si (ULTPS) processes for realizing flexible active matrix organic light emitting diode (AM-OLED) display, SSF offers high thermal resistance and chemical stability, and lithography stability. As SSF is stiffer than plastic film, SSF is expected to reduce stress which originates from difference in coefficient of thermal expansion. However, SSF substrate itself also bears surface roughness problem, which necessitates an appropriate planarization step. Also to fully integrate both the drive circuits and the pixel thin-film transistor(TFT)s in a monolithic complementary metal-oxide-semiconductor (CMOS) technology high mobility is required, calling for poly-Si usage.We will deal with the planarization process, and then address various processing issues. Especially, we will demonstrate our successful SLS of Si on SSF substrates. Finally we show the device performances. All fabrication temperatures were kept below 200 oC to meet a ULTPS process.Due to the rolling process for manufacturing foils, the SSF surface is rough. We have measured average roughness of 500 nm, respectively. With benzocyclobutene (BCB), we have successfully planarized the surface with average roughness was less than 0.5 nm.Our TFT's active layer was obtained by laser crystallizing amorphous Si (a-Si) films. To obtain a high quality gate dielectric film, we formed a SiO2 film using an O2 plasma treatment on the surface of the poly-Si film and then deposited Al2O3 film by plasma enhanced atomic layer deposition. Then gate metal was deposited and patterned. Source and drain regions were p+ doped by ion implantation to form a self-aligned gate structure. We have used SiNx film as interlayer dielectrics.Briefly we discuss a practical approach for realizing SLS on a SiO2 buffer. The Si-on-SiO2 layer stacking is energetically unstable. Should have not controlled the heat during laser crystallization, liquid Si would recede to expose the SiO2 layer. Dewetting is suppressed by adjusting the buffer density, and densifying the a-Si film. To implement the SLS, we have optimally conjugated the densities of the buffer film and the a-Si film to produce Si grains with sizes of ~6 ¥ìm on a BCB planarized SSF.Our p-channel TFT transfer performance exhibits a field effect mobility (¥ì) of 95 cm2/Vs, a threshold voltage (Vt) of -3 V and a sub-threshold swing(S-S) of 0.5 V/dec.. The off-current level is ~ 10 pA at drain voltage (Vd) of -1V and the Ion/Ioff is 106 . Especially our stable Vt consents to the electrical stability for driving displays. This feature might be attributed to the improved interface between the active layer and the gate dielectrics by plasma oxidation.
Application of Thin-Film Amorphous Silicon to Chemical Imaging
Authors: Yoshinobu Tatsuo , Moritz Werner , Finger Friedhelm , Schoening Michael J. 
Published: April 2011

AbstractA thin-film amorphous silicon (a-Si) deposited on a glass substrate was employed as a semiconductor material for the chemical imaging sensor, which can visualize the distribution of ion concentration in a solution. The sensing properties and the spatial resolution of the a-Si sensors were investigated. Nearly-Nernstian pH sensitivities and submicron resolution were demonstrated, which suggests the superior performance of the chemical imaging sensor based on thin-film a-Si.
Performance of Thin-film a-Si:H Microresonators in Dissipative Media
Authors: Adrega Teresa , Prazeres D. M.F. , Chu V. , Conde J.P. 
Published: April 2011

AbstractThe resonance of electrostatically actuated thin-film a-Si:H microbridges immersed in de-ionized water is detected and characterized. When the operating medium changes from vacuum to air, a small decrease of 5% of the resonance frequency occurs and the quality factor decreases from approximately 1000 to 100. The operation of the microresonators in deionized water produces a 60% shift in resonance frequency to lower values and the quality factor decreases to 10. Appropriate actuation conditions at resonance in water are used to avoid electrolysis and electrode field screening. The detection of the resonance frequency of a microbridge operating in solutions with high conductivities, up to 8 mS/cm, and viscosities up to 0.2 Pa.s is demonstrated.
Low Temperature Poly-Si Sputtering Deposition Through Metal-induced Crystallization and its Application
Authors: Guo Hsiu-Wu , Shih Chen-Luen , Ketterl Joe , Dunham Scott 
Published: April 2011

AbstractGrowth of Si thin films via metal-induced crystallization (MIC) has been demonstrated by several research groups. This process lowers the crystallization temperature compared to standard solid phase crystallization (SPC). Ni is the metal that is most often adopted for this purpose. In this work, a 20-50nm Ni layer was deposited by DC magnetron sputtering onto a 500nm SiO2 layer grown on silicon wafers, followed by Si deposition at 500°C without breaking vacuum. X-ray diffraction (XRD) results and cross-sectional transmission electron microscopy (XTEM) confirmed the formation of poly-Si in a columnar structure with grain sizes in the 100-300nm range. XTEM and XPS show that nickel silicide was formed at the Si-Ni interface. We find that doping type and concentration do not have a significant impact on the grain structure. SIMS reveals no significant loss or redistribution in doping concentration during sputtering.
Fabrication of Location-Controlled Silicon Crystal Grains by Combining Excimer Laser Irradiation with Nanometer-sized A-Si
Authors: Tsai Chun-Chien , Chang Ting-Kuo , Chen Hsiu-Hsin , Chen Bo-Ting , Cheng Huang-Chung 
Published: April 2011

AbstractIn this paper, location-controlled Silicon crystal grains are fabricated by a novel excimer laser crystallization method. An array of 1.8-μm-sized disk-liked grains are formed by this method, and the high-performance n-channel LTPS TFTs with field-effect-mobility reaching 308 cm2/Vs can be fabricated owing to the artificially-controlled lateral grain growth. This position-manipulated Silicon grains are essential to high performance and good uniformity thin film transistors.
Thermal and Stress Modeling for the Flash Lamp Crystallization of Amorphous Silicon Films
Authors: Smith Mark , McMahon Richard A. , Seffen Keith A. , Panknin Dieter , Voelskow Matthias , Skorupa Wolgang 
Published: April 2011

AbstractThin poly-crystalline silicon films are attractive for the fabrication of active matrix liquid crystal displays. We investigate the use of flash lamp annealing to crystallize amorphous silicon layers on glass substrates as a low cost manufacturing route. In this process amorphous silicon (a-Si) can be crystallized by solid phase crystallization (SPC) or in the super lateral growth (SLG) regime. We present a thermal model incorporating the phase transitions during annealing; providing a valuable tool for optimizing the process conditions. Another consideration is the evolution of stress resulting from the transient thermal loading of the substrate material. Results are presented for various substrate geometries and important scalability issues are addressed.
P Channel Mosfet Devices in Nanocrystalline Silicon
Authors: Panda Durga , Noack Max , Dalal Vikram 
Published: April 2011

AbstractWe report on the growth and properties of p-channel nanocrystalline Si thin film transistor (TFT) devices. In contrast to previous work, the devices are fabricated in n-body nanocrystalline Si. The doping of the n-body is systematically changed by doping with ppm levels of phosphorous. The threshold voltage was found to change systematically as phosphorus content increased. The TFT devices are of the bottom-gate type, grown on oxidized Si wafers. Source and drain contacts were provided by using either plasma grown p type nanocrystalline layers, or by the simple process of Al diffusion. A top layer of plasma-deposited silicon dioxide was found to decrease the off current significantly. High on-off current ratios exceeding 106 were obtained. Hole mobilities in the devices were consistently good, with the best mobility being in the range of ~1.3 cm2/V-s.
Boron Doped Polycrystalline Silicon Produced By Step-by-Step XeCl Excimer Laser Crystallization
Authors: Saleh Rosari , Nickel Norbert H 
Published: April 2011

AbstractA series of boron doped polycrystalline silicon were produced using step-by-step laser crystallization process from amorphous silicon. The influence of doping concentrations on laser- induced dehydrogenation and crystallization of amorphous silicon and on hydrogen bonding have been investigated employing Raman spectroscopy and hydrogen effusion measurements. From hydrogen effusion spectra the hydrogen chemical potential is determined as a function of hydrogen concentration, which can be related to the hydrogen density-of-states distribution. The results from hydrogen effusion are consistent with the results obtained from Raman spectroscopy.
Temperature Dependence of Dark Current-Voltage Characteristics of Hydrogenated Amorphous and Nanocrystalline Silicon Based Solar Cells
Authors: Yan Baojie , Yang Jeffrey , Guha Subhendu 
Published: April 2011

AbstractSystematic measurements of dark current density versus voltage (J-V) characteristics were carried out on a-Si:H, a-SiGe:H, and nc-Si:H solar cells at different temperatures from 23°C to 150°C. In a first order approximation, the dark J-V characteristics follow the standard diode characteristic formula for most high quality solar cells. The temperature dependence of the reverse saturation current can be used for deducing the intrinsic layer bandgap for the three types of solar cells. From a detailed analysis using the derivative of the measured dark J-V characteristics, we obtain different features in the plot of ideality factor versus bias voltage for the three types of solar cells. We also deduce the distribution of density of states using a recently proposed procedure [1]. In general, a peak near the middle of the bandgap appears for the three types of solar cells; below the middle of the bandgap, there is an exponential-like broad distribution of gap states. However, the calculated gap state distribution shows a temperature dependence, which may be caused by the simplification of the calculation procedure.
Enhanced Antimony Activation for Ultra-Shallow Junctions in Strained Silicon
Authors: Bennett Nick , Smith A. J. , Beer C. S. , O'Reilly L. , Colombeau B. , Dilliway G. D. , Harper R. , McNally P. J. , Gwilliam R. , Cowern N. E. B. , Sealy B. J. 
Published: April 2011

AbstractSheet resistance (Rs) reductions are presented for antimony and arsenic doped layers produced in strained Si. Results re-emphasise the Rs reduction for As comes purely as a result of mobility improvement whereas for Sb, a superior lowering is observed from improvements in both mobility and activation. For the first time, strain is shown to enhance the activation of dopant atoms whilst Sb is seen to create stable ultra-shallow junctions. Our results propose Sb as a viable alternative to As for the creation of highly activated, low resistance ultra-shallow junctions for use with strain-engineered CMOS devices.
Integration of Solid Phase Epitaxial Re-Growth, Flash and Sub-Melt Laser Annealing for S/D Junctions in CMOS Digital Technology
Authors: Severi Simone , Augendre Emmanuel , De Meyer Kristin 
Published: April 2011

AbstractSeveral aspects of the integration of diffusion-less junctions in a NMOS and PMOS conventional flows are evaluated. Processes as Solid Phase Epitaxial Regrowth (SPER) or advanced annealing techniques, as flash or laser, demonstrates benefits not only on the 1D junction profiles but also on the transistor characteristics. An optimization of the implants and of the annealing conditions lead to improved or equivalent transistors performance and short channel effects control compared to the conventional spike RTA process. A significant gain in the overlap capacitance could allow for reduced CV/I. Furthermore the junction leakage can be lowered down to the values reached with the conventional spike RTA process.