bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zoom in on Life: Using Biological Processes to Teach the Public about Nanotechnology
Authors: Wade Maya , Tinker Beth , Greenberg Andrew , Redwing Ronald Dean 
Published: April 2011

AbstractThrough a partnership between the NSF-funded Material Research Science and Engineering Center, Center for Nanoscale Science, at Penn State University and Philadelphia's science museum The Franklin Institute the "Nano-Bio: Zoom in on Life!" program has been produced and distributed to 20 science and children museums in the United States and one science museum in Canada. Distributed shows include the materials needed to perform the demonstration, supplies for a year and additional information including educational materials and a training video. This cart based program includes interactive demonstrations that highlight processes in the human body that occur at the nanoscale and how scientists are exploring natural processes to develop new nanotechnology and nanomaterials. This show is the second in a series of collaborations to create programs for the informal science education world. A development team including Penn State University faculty, postdoctoral fellows, graduate students and Franklin Institute staff worked over two years to develop the show. Instrumental in the development were graduate students who were part of a jointly run Penn State-Franklin Institute NSF-funded Internships in Public Science Education (IPSE) program. These science education graduate students helped create, test, and enhance the demonstrations for the Zoom in on Life program.
Electronic Characterization and Light-Induced Degradation in nc-Si:H Solar Cells
Authors: Hugger P. G. , Datta Shouvik , Erslev P. T. , Yue Guozhen , Ganguly Gautam , Yan Baojie , Yang Jeffrey , Guha Subhendu , Cohen J. D. 
Published: April 2011

AbstractThe electronic properties of working nanocrystalline silicon (nc-Si:H) solar cell devices with conversion efficiencies up to 8.6% were studied using junction capacitance methods. The set of devices examined were deposited on both specular stainless steel substrates and Ag/ZnO textured back reflectors. These devices included nc-Si:H grown under constant H2 dilution, and also with profiled H2 dilution to control the crystallite sizes and volume fraction. Transient photocapacitance and transient photocurrent spectroscopies were used to obtain sub-band-gap optical spectra. A comparison of these two kinds of spectra also allowed us to deduce the minority carrier collection fractions as a function of temperature and light-induced degradation. Light-soaking was found to cause a distinct decrease in minority carrier collection, as well as a consistent decrease in defects responding to drive-level capacitance profiling. A tentative microscopic model is proposed that accounts for these degradation effects in nc-Si:H.
Surface Roughening Transition in Si1-xGex:H Thin Films
Authors: Podraza Nikolas J. , Wronski Christopher R. , Horn Mark W. , Collins Robert W. 
Published: April 2011

AbstractIn this study, the amorphous-phase roughening transition thickness has been determined as a function of process variables in plasma-enhanced chemical vapor deposition (PECVD) of hydrogenated amorphous silicon-germanium alloys (a Si1-xGex:H). Among the process variables include the H2-dilution gas flow ratio, the alloying flow ratio, the electrode configuration (anode vs. cathode), and the He-dilution ratio. One clear feature of this study is a maximum in the amorphous roughening transition thickness (and hence surface stability) at a H2-dilution ratio just below the transition from amorphous to mixed-phase (amorphous+microcrystalline) (a+μc) growth. A second feature for high Ge content films is a significant increase in the roughening transition thickness for cathode PECVD (with a self-bias of ~ −20 V) relative to anode PECVD. Additional features of interest involve suppression of the mixed-phase transition to (a+μc) for (i) alloying with Ge, (ii) cathodic substrate biasing, and (iii) diluting the gas with He. The close correlation of high surface stability with enhanced short-range order and overall electronic performance has led to a simple model for the transition in terms of a competition between roughening due to the atomic size and smoothening due to precursor surface diffusion. It is proposed that diffusing precursors are immobilized by surface defects (or by other diffusing precursors), and the pre-existing (or resulting) defects are ultimately incorporated in the bulk.
Research on Amorphous Silicon Thin-Film Structure and Growth Processes Using Nonlinear Dynamics Methods
Authors: Bodyagin Nikolay Viktorovich , Vikhrov Sergey Pavlovich , Larina Tatiana Gennadievna , Mursalov Stanislav Mursalovich 
Published: April 2011

AbstractThere proved a possibility of applying the self-organization theory to the growth of noncrystalline thin-films and to the detection of ordering in their structure. Methods of analyzing the dynamics of complex systems are modified so as to investigate the structure of noncrystalline thin films. There offered new principles of the construction of material growth control systems.
Grain Nucleation and Grain Growth During Crystallization of HWCVD a-Si:H Films
Authors: Ahrenkiel S. P. , Roy B. , Mahan A. H. , Ginley D. S. 
Published: April 2011

AbstractHydrogenated amorphous silicon (a-Si:H) films of high and low hydrogen content were deposited directly on molybdenum, carbon-coated TEM grids by hot-wire chemical vapor deposition. The material was annealed at 600°C and 630°C for variable times to achieve various degrees of crystallinity. The films thickness of 100-nm allowed characterization by TEM without additional thinning. The grain growth in such thin films is nearly two-dimensional, allowing clear identification of crystalline and amorphous regions. Thus, the crystalline volume fraction can be tracked by simple image-processing methods. The evolution of crystallization by grain nucleation and growth for these films is accurately described by classical phase-change kinetics. Analysis of the randomly distributed grains at early stages of crystallization also provides the average areal grain number density and grain size. From the image analysis, we determine the grain nucleation rate and the grain growth velocity. The final grain size is then estimated by extrapolation to the fully crystallized state, assuming the kinetic parameters remain constant after the onset of crystallization.
The Influence of Thermophoresis Effects During Deposition of Hydrogenated Amorphous Silicon Thin Films with Nanocrystalline Silicon Inclusions
Authors: Blackwell C. , Anderson C. , Deneen J. , Carter C. B. , Kortshagen U. , Kakalios J. 
Published: April 2011

AbstractSilicon cluster formation is known to occur within silane plasmas when a capacitively-coupled deposition reactor is operated at high gas chamber pressures. These clusters are sensitive to the thermophoretic forces that will, depending on the sign of the thermal gradient, direct them toward or away from the silicon film's growing surface. We have developed a dual-chamber deposition system that produces nanocrystalline silicon particles (roughly 3-5 nm in diameter) in a flow-through reactor, and injects these particles into a separate capacitively-coupled plasma chamber where the amorphous film is produced. The structural, optical and electronic properties of these mixed-phase materials are investigated as a function of the controllable thermal gradient applied across the silane plasma during deposition.
Influence of Annealing on Crystallinity and Conductivity of p-type Nanocrystalline Si films
Authors: Panda Durga P. , Dalal Vikram 
Published: April 2011

AbstractNanocrystalline p-type Si:H layers are important for photovoltaic and MOSFET devices. A high conductivity in these layers leads to better voltages in PV devices and to lower series resistance in both PV and MOSFET devices. The lower resistance results in higher channel mobility in MOSFET devices and higher fill factors in PV devices. In this work, we discuss the improvement in conductivity and crystallinity of p-type nanocrystalline Si:H layers by the use of post-deposition annealing. The p layers were deposited at ~ 180&#61616;C from mixtures of silane, hydrogen, helium and diborane using ECR plasma deposition techniques. It was found that addition of He to H at first improved both the conductivity and crystallinity, but too much He led to an amorphous phase and lower conductivity. The as-grown films were measured for their crystallinity using both Raman spectroscopy and x-ray diffraction. The conductivity and activation energies were also measured. The films were then successively annealed at temperatures of 250, 300, 350 and 400&#61616;C. The crystallinity and grain size were found to increase as the annealing temperature increased. The greatest relative increase was during the initial annealing stages. The conductivity of the films increased significantly as a consequence of the annealing. Conductivities as large as 20 S/cm were obtained in very thin films (~50-150 nm). The corresponding activation energies were in the range of 0.03 eV. When these annealed layers were used for MOSFET and PV devices, there was an appreciable increase in performance characteristics.
The Concentration of (SiH2)n Sites in Low and High Defect Density a-Si:H
Authors: Bobela David C. , Su T. , Taylor P. C. , Madan A. , Ganguly G. 
Published: April 2011

AbstractThe concentration of polysilane chains (SiH2)n, where n≥1, is estimated for higher quality hydrogenated amorphous silicon (a-Si:H) by pulsed proton nuclear magnetic resonance techniques (1H NMR). Our measurements indicate the minimum hydrogen content of approximately 10% of the total hydrogen is in the (SiH2)n configuration. Similar measurements in a high defect density sample (1017 silicon dangling bond defects cm-3) show that (SiH2)n sites account for ~ 15% of the total hydrogen. While the (SiH2)n infrared absorption (IR) modes are observed in the highly defective sample, no such modes are seen in the higher quality material. The results indicate that a significant amount of the total hydrogen content exists as (SiH2)n regardless of film quality.
Enlargement of Grain Size and Location Control of Grain in Excimer-laser Crystallization of Si Film
Authors: Yeh Wenchang , Ke Dunyuan , Zhuang Chunjun 
Published: April 2011

AbstractA technique for enlargement of grain size were shown and a technique for location controlled super lateral growth (SLG) grain in excimer laser annealing (ELA) were proposed and realized. In the technique for grain size enlargement, the grain size was enlarged to 10£gm that is more than 10 times larger than that in conventional method(~0.8£gm). The proposed sample structure was Si film/light absorptive film/Glass structure with applying the laser light from the back side of glass substrate. Time resolved(~1ns) optical measurement (TROM) revealed that the melt duration of Si film was increased to 800ns that is also 10 times longer than that in conventional method. As for the grain location control technique, a new method contains pre seeding process and post growth process were proposed and realized. In the pre seeding process, micro light beam(£g-light beam) was exposed to Si film to form a grain within the crystallized spot. £g-light beam was formed by micro-lens-array(MLA). After post growth process, single grain array with the diameters of 6£gm was formed in a period of 10£gm.
Periodic Alignment of Silicon Dot Fabricated by Linearly Polarized Nd:YAG Pulse Laser
Authors: Nishioka Kensuke , Horita Susumu 
Published: April 2011

AbstractPeriodically aligned submicron Si dots were fabricated by only irradiating linearly polarized Nd:YAG pulse laser to the amorphous silicon (a-Si) thin film deposited on silicon dioxide (SiO2) film. Interference between the incident beam and the scattered surface wave leads to the spatial periodicity of beam energy density distribution on the surface of the irradiated samples. The a-Si thin film was melted by laser beam, and then, the molten thin Si film was split and condensed due to its surface tensile according to the periodic energy density distribution. The polycrystalline Si (poly-Si) fine lines were formed periodically. After the first irradiation, the sample was rotated by 90o, and the laser beam was irradiated. The periodic energy density distribution was generated on the Si fine lines. Then, the lines were split off and condensed according to the periodic energy density distribution, and the periodically aligned submicron Si dots were fabricated on the SiO2 film.
Physics of Solid-Phase Epitaxy of Hydrogenated Amorphous Silicon for Thin Film Si Photovoltaics
Authors: Stradins Paul , Yan Yanfa , Reedy Robert , Young David L. , Teplin Charles W , Iwaniczko Eugene , Xu Yueqin , Jones Kim , Teeter Glenn , Mahan A. Harv , Branz Howard M. , Wang Qi 
Published: April 2011

AbstractSolid state crystallization of hydrogenated amorphous silicon (a-Si:H) prepared by hot-wire CVD is studied in solid phase epitaxy mode. By using a novel optical method combined with cross-sectional TEM and SIMS, a reduction of epitaxial growth speed is observed with increase in a-Si:H film thickness. Namely, in films thinner that 0.5 micron, solid phase epitaxy velocity depends linearly on film thickness. As the film thickness increases beyond 1 micron, the average velocity of solid phase epitaxy decreases considerably with respect to that in thinner films. In this regime, its velocity becomes also time-dependent: initial slow propagation of crystallization front gets considerably accelerated after the front has traveled above 400nm. SIMS thickness profiles of hydrogen shows considerably more residual hydrogen in thicker films after the start of solid phase epitaxy. In addition, prolonged pre-dehydrogenation at lower temperatures results in the increase in the average epitaxy speed in thicker films. These phenomena are likely related to delayed hydrogen outdiffusion in thicker films, which also leads to time-dependent speed of the solid-phase epitaxy front. We conclude that excess residual hydrogen reduces the rate of solid-phase crystalline growth.
Hot-wire CVD a-Si:H TFT on Plastic Substrates
Authors: Taghibakhsh Farhad , Karim K.S. 
Published: April 2011

AbstractFabrication of hot-wire chemical vapor deposition (HWCVD) of amorphous silicon (a-Si) thin film transistors (TFT) on thin polyamide sheets is reported. A single graphite filament at 1500 °C was used for HWCVD and device quality amorphous silicon films were deposited with no thermal damage to plastic substrate. Top-gate staggered thin film transistors (TFTs) were fabricated at 150°C using hot-wire deposited a-Si channel, Plasma enhanced chemical vapor deposition (PECVD) silicon nitride gate dielectric, and microcrystalline n+ drain/source contacts. Low leakage current of 5×10-13 A, high switching current ratio of 1.3×107, and small sub threshold swing of 0.3 V/dec was obtained for TFTs with aspect ratio of 1300μm/100μm. The field effect mobility was extracted to be 0.34 cm2/V.s.
Mechanisms for Defect Creation and Removal in Hydrogenated and Deuterated Amorphous Silicon Studied using Thin Film Transistors
Authors: Flewitt Andew , Lin Shufan , Milne William I , Wehrspohn Ralf B , Powell Martin J 
Published: April 2011

AbstractIt has been widely observed that thin film transistors (TFTs) incorporating an hydrogenated amorphous silicon (a-Si:H) channel exhibit a progressive shift in their threshold voltage with time upon application of a gate bias. This is attributed to the creation of metastable defects in the a-Si:H which can be removed by annealing the device at elevated temperatures with no bias applied to the gate, causing the threshold voltage to return to its original value. In this work, the defect creation and removal process has been investigated using both fully hydrogenated and fully deuterated amorphous silicon (a-Si:D) TFTs. In both cases, material was deposited by rf plasma enhanced chemical vapour deposition over a range of gas pressures to cover the a-g transition. The variation in threshold voltage as a function of gate bias stressing time, and annealing time with no gate bias, was measured. Using the thermalisation energy concept, it has been possible to quantitatively determine the distribution of energies required for defect creation and removal as well as the associated attempt-to-escape frequencies. The defect creation and removal process in a-Si:H is then discussed in the light of these results.
Analytical Studies of the Capping Layer Effect on Aluminum Induced Crystallization of Amorphous Silicon
Authors: Abu-Safe Husam , Sajjadul-Islam Abul-Khair M. , Naseem Hameed A. , Brown William D. 
Published: April 2011

AbstractThe effect of capping layer on metal induced crystallization of amorphous silicon was studied. Three sets of samples were prepared in this study. All samples had the basic layer structure of amorphous silicon layer deposited on a glass substrate. This was followed by a thin aluminum layer deposition. The second and third sets, however, had a third layer of amorphous silicon with thicknesses of 20 and 50 nm, respectively. These layers were deposited on top of the aluminum. The samples were annealed at 400°C for 15, 30 and 45 minutes. The crystallization fraction in the resultant films was analyzed using X-Ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, and atomic force microscopy. It was observed that the capping layer reduces nodule formation improving the smoothness of the crystallized polysilicon films.
Fabrication of Crystallized Si Film Deposited on a Polycrystalline YSZ Film/Glass Substrate at 500°C
Authors: Horita Susumu , Kanazawa Keisuke , Nishioka Kensuke , Higashimine Koichi , Koyano Mikio 
Published: April 2011

AbstractWe used a polycrystalline YSZ film deposited on the quartz substrate as a seed layer to enhance crystallization of the Si film deposited on it. The YSZ film was deposited by reactive sputtering at less than 50°C and the preferential orientation was (111). The 60-nm-thick Si film was deposited by e-beam evaporation method on the substrate with and without the YSZ film. It was found that the crystallization of the Si film deposited on the YSZ film occurs but not without the YSZ film at the temperature of 515°C. The SEM image of the Secco-etched Si film showed that the crystallized Si film consisted of ~50-nm-size grains and, from the TEM image, it is supposed that the Si grains are grown directly from the YSZ film.
Improvement of Threshold Voltage Degradation Characteristics of a-Si:H TFT by Pre-Electrical Bias-Aging for Amoled Display
Authors: Lee Jae-Hoon , Park Sang-Geun , Shin Kwang-Sub , Han Min-Koo , Goh Joon-Chul , Huh Jong-Moo , Choi Joonhoo , Chung Kyuha 
Published: April 2011

AbstractWe propose a pre-electrical bias aging to reduce threshold voltage (Vth) shift of hydrogenated- amorphous silicon thin-film transistor (a-Si:H TFT) for AMOLED display. The quantity of Vth shift in the sample subjected to a bias-aging is reduced due to the reduction of created dangling bond density, compared with a sample without a bias-aging. When an identical stress duration of 50,000 sec is applied to a-Si:H TFT with or without a pre-electrical bias-aging, the created dangling bond density (ΔNDB) after a pre-electrical bias-aging is decreased from 1.38 × 1011/cm2 to 0.685 × 1011/cm2. Our experimental results indicate that after the pre-electrical bias aging, a newly created dangling bond during an electrical stress is decreased because a weak bond density and hydrogen diffusion may be decreased.
Silicon Etching Study in a RT-CVD Reactor with the HCl/H2 Gas Mixture
Authors: Loubet Nicolas , Talbot Alexandre , Dutartre Didier 
Published: April 2011

AbstractA promising candidate to etch silicon totally selective against the dielectrics is here studied. This paper reports a detailed study of the silicon chemical vapor etch with HCl/H2 mixtures. Kinetics measurements on (001)-oriented wafers permitted us to extract apparent activation energies varying from 95.2kcal/mol and 73.9kcal/mol, depending on the HCl dilution in the chamber. On the other hand, etch rates measurements as a function of the HCl partial pressure are found to follow a sub-linear behavior indicating complex mechanisms occurring with the use of the HCl/H2 gas mix. In a second part, thanks to SEM cross-section observations, morphological analysis permitted us to point out that the {311} facet behave differently as compared to the {111} and {100} planes. To conclude, we extracted rugosity data after HCl treatment from AFM measurements and all these results permitted us to validate the potential industrialization of this etching process for the formation of localized cavities or junctions on patterned wafers.
17.8%-efficient Amorphous Silicon Heterojunction Solar Cells on p-type Silicon Wafers
Authors: Wang Qi , Page Matt P. , Iwancizko Eugene , Xu Yueqin , Yan Yanfa , Roybal Lorenzo , Levi Dean , Bauer Russell , Branz Howard M. , Wang Qi 
Published: April 2011

AbstractWe have achieved an independently-confirmed 17.8% conversion efficiency in a 1-cm2, p-type, float-zone silicon (FZ-Si) based heterojunction solar cell. Both the front emitter and back contact are hydrogenated amorphous silicon (a-Si:H) deposited by hot-wire chemical vapor deposition (HWCVD). This is the highest reported efficiency for a HWCVD silicon heterojunction (SHJ) solar cell. Two main improvements lead to our most recent increases in efficiency: 1) the use of textured Si wafers, and 2) the application of a-Si:H heterojunctions on both sides of the cell. Despite the use of textured c-Si to increase the short-circuit current, we were able to maintain the same 0.65 V open-circuit voltage as on flat c-Si. This is achieved by coating a-Si:H conformally on the c-Si surfaces, including covering the tips of the anisotropically-etched pyramids. A brief atomic H treatment before emitter deposition is not necessary on the textured wafers, though it was helpful in the flat wafers. It is essential to high efficiency SHJ solar cells that the emitter grows abruptly as amorphous silicon, instead of as microcrystalline or epitaxial Si. The contact on each side of the cell comprises a thin (< 5 nm) low substrate temperature (~100°C) intrinsic a-Si:H layer, followed by a doped layer. Our intrinsic layers are deposited at 0.3-1.2 nm/s. The doped emitter and back-contact layers were deposited at a higher temperature (>200°C) and grown from PH3/SiH4/H2 and B2H6/SiH4/H2 doping gas mixtures, respectively. This combination of low (intrinsic) and high (doped layer) growth temperatures was optimized by lifetime and surface recombination velocity measurements. Our rapid efficiency advance suggests that HWCVD may have advantages over plasma-enhanced (PE) CVD in fabrication of high-efficiency heterojunction c-Si cells; there is no need for process optimization to avoid plasma damage to the delicate, high-quality, Si wafers.
The Carbon Co-implant with Spike RTA Solution for Boron Extension
Authors: Pawlak Bartek , Augendre Emmanuel , Severi Simone , Eyben Pierre , Janssens Tom , Falepin Annelies , Absil Philippe , Vandervorst Wilfried , Felch Susan , Collart Erik , Schreutelkamp Robert , Cowern Nick 
Published: April 2011

AbstractWe present B junction extensions that are extremely abrupt and shallow manufactured by amorphization, C co-implantation and conventional rapid thermal annealing (RTA). Resulting junctions have abruptnesses of 2 nm/dec better than as-implanted profiles. The most shallow B junction that has been manufactured is 15 nm deep and Rs = 626 Ω/sq. Successful implementation of these junctions is straightforward for P-MOS 30 nm gate length devices.