bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of a-Si-H Solar Cells at Higher Growth Rates
Authors: Ganguly G. , Lin G. , Chen L.F. , He M. , Wood G. , Carlson D. , Arya R. 
Published: April 2011

AbstractWe have studied the effects of external growth parameters during the deposition of the i-layers of a-Si p-i-n solar cells using dc plasma decomposition of silane-hydrogen mixtures at growth rates of up to 3A/s. The loss of initial performance with increasing growth rate is mainly due to a loss of short-circuit current. The relative degradation of efficiency upon extended light soaking also increases with growth rate, and is mainly due to a decrease in the fill factor. Systematic comparisons of the performance and its degradation with changes in growth conditions reveal that these two components of the total degradation have distinct origins.
Preparation of Triple-Junction A-Si:H NIP Based Solar Cells at Deposition Rates of 10 Å/s using a Very High Frequency Technique
Authors: Jones S.J. , Deng X. , Liu T. , Izu M. 
Published: April 2011

AbstractIn an effort to find an alternative deposition method to the standard low deposition rate 13.56 M-z PECVD technique, the feasibility of using a 70 MiHz rf plasma frequency to prepare a-Si:H based i-layer materials at high rates for nip based triple-junction solar cells has been tested. As a prelude to multi-junction cell fabrication, the deposition conditions used to make single-junction a-Si:H and a-SiGe:H cells using this Very High Frequency (VHF) method have been varied to optimize the material quality and the cell efficiencies. It was found that the efficiencies and the light stability for both a-Si:H and a-SiGe:H single-junction cells remain relatively constant as the i-layer deposition rate is varied from 1 to 10 Å/s. Also these stable efficiencies are similar to those for cells made at low deposition rates (1 Å/s) using the standard 13.56 MHz PECVD technique and the same deposition equipment. Using the knowledge obtained in the fabrication of the single-junction devices, a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cells have been fabricated with all of the i-layers prepared using the VHF technique and deposition rates near 10 Å/s. Thin doped layers for these devices were prepared using the standard 13.56 MIHz rf frequency and deposition rates near 1 Å/s. Pre-light soaked efficiencies of greater than 10% have been obtained for these cells prepared at the high rates. In addition, after 600 hrs. of light soaking under white light conditions, the cell efficiencies degraded by only 10-13%, values similar to the degree of degradation for high efficiency triple-junction cells made by the standard 13.56 MiHz method using i-layer deposition rates near 1 Å/s. Thus, use of this VHF method in the production of large area a-Si:H based multi-junction solar modules will allow for higher i-layer deposition rates, higher module throughput and reduced module cost.
Low-Temperature Preparation of Poly-Si Thin-Films Having Giant Grains
Authors: Yeh Wen-Chang , Matsumura Masakiyo 
Published: April 2011

AbstractA low heat-capacitance substrate has been introduced to lateral grain-growth for Si thin-films. Grains as large as 13μm could be fabricated by irradiation of a single shot of an excimer-laser light pulse with intensity gradient. The film has an orientation in the (110) direction, different from (111) for the conventional excimer-laser-annealed film, and is applicable to a seed layer for solid-phase epitaxial-growth aiming at solar cell application.
Development of Ultra-Clean Plasma Deposition Process
Authors: Kamei Toshihiro , Matsuda Akihisa 
Published: April 2011

AbstractWe have developed a new type of ultra-high vacuum plasma-enhanced chemical vapor deposition (UHV/PECVD) system. According to high sensitivity secondary ion mass spectrometry, device quality hydrogenated amorphous silicon (a-Si:H) films deposited at 250°C at a deposition rate of 1 Å/s contains 1015 cm-3 of O, 1015 cm-3 of C, and 1014 cm-3 of N impurities, while low defect hydrogenated microcrystalline silicon (μc-Si:H) films deposited at 200°C at a very low rate of 0.1 Å/s include 1016 cm-3 of O, 1015 cm-3 of C and 1016 cm-3 of N. These are the lowest concentrations of atmospheric contaminants for these kinds of materials observed so far. The essential features of the present UHV/PECVD system are an extremely low outgassing rate of 8×10-9 Torr·s, extremely low partial pressure of contaminant gas species <10-12 Torn, and purification of feed gas SiH4 at “point of use”. These efforts are quite important not only for clarifying the microscopic mechanism of photo-induced degradation in a-Si:H, but also for enlarging the crystalline grain size in μc-Si:H. μc-Si:H with a grain size of ≍1000 Å as determined by Scherrer's formula can be obtained at the higher rate of 1.5 Å/s by utilizing a VHF (Very High Frequency) plasma. The specific origins of impurities in the films are also discussed.
Lateral Solid Phase Crystallization of Amorphous Silicon Under High Pressure
Authors: Lee Seung-Mahn , Singh Rajiv K. 
Published: April 2011

AbstractWe have investigated a novel surface-seeded crystallization technique at low processing temperatures (≤ 550°C) and high pressures (10MPa~25MPa) using polished polycrystalline diamond seeds. By controlling the high pressure, the nucleation and growth of silicon can be controlled to obtain improved quality silicon films on amorphous substrates at low temperatures. Depending on the annealing temperature and applied pressure, the orientation of crystallized silicon thin films varies as seen by x-ray diffraction and transmission electron microscopy results. In addition, crystallization of amorphous silicon thin films has effect on their roughness.
Spectroscopic Investigations of Crystallinity and Electronic-Structural Transitions Due to Solid Phase Crystallization of Amorphous Si1-xGex
Authors: Yamaguchi S. , Sugh N. , Nakagawa K. , Miyao M. 
Published: April 2011

AbstractSolid phase crystallization of Si1-xGex, have been investigated by means of change in crystallinity and crystallization temperature using the ellipsometric spectroscopy (2-5 eV). Dispersion analysis on the spectra revealed that the Si1-xGex alloys show both abrupt increase and rapid saturation of the crystallinities according to the structural transitions. The saturated values of crystallinities did not reach those of single crystals in all samples and rapidly decreased with increase of Ge concentration. Ion-implanted amorphous SilxGe, exhibited much lower activation energies of re-crystallization than those of the deposited amorphous samples. Furthermore, their crystallization temperature were strongly depend on the species of implanted ions such as As+ and BF2+. It was found that the crystallization velocity of the As+-implanted Si1-xGex was estimated as 4 times faster than that of the BF2+-implanted Si1-xGex. Itinerant property of Ge in Si may give rise to the decrease of the crystallinities as well as the decrease of the activation energy of solid phase crystallization which may be strongly affected by the catalytic effects of the implanted impurities.
Comparative Study of Hydrogen Diffusion in Hot-Wire and Glow-Discharge-Deposited a-Si:H
Authors: Shinar J. , Shinar R. , Junge K. E. , Iwaniczko E. , Mahan A. H. , Crandall R. S. , Branz H. M. 
Published: April 2011

AbstractLong-range atomic H motion in hot-wire deposited (HW) a-Si:H is compared directly to that in glow-discharge deposited (GD) a-Si:H by monitoring the deuterium secondary ion mass spectrometry (DSLMS) profiles in [GD a-Si:H]/[GD a-Si:(H,D)]/[HW a-Si:H] multilayers vs annealing temperature and time. While the profiles in the GD layer are in excellent agreement with complementary error-function behavior and previous studies, the profiles in the HW layer suggest that the multiple-trapping motion of the H and D atoms is much slower, possibly due to an interface layer of defects. However, an exponential “tail” of D atoms extends deep into the HW layer, probably due to a long diffusion length of mobile D atoms, consistent with the established release times of H and D from the GD layer and H loss typical during growth of HW films. The results are also discussed in terms of the H exchange model and compared to previous NMIR studies of HW a-Si:H, which suggest that most of the hydrogen in the HW layer is concentrated in H-rich clusters dispersed in a network of very low H content.
The Formation and Behavior of Particles in Silane Discharges
Authors: Gallagher Alan 
Published: April 2011

AbstractParticle growth in silane RF discharges, and the incorporation of particles into hydrogenated-amorphous-silicon (a-Si:H) devices is described. These particles have a structure similar to a-Si:H, but their incorporation into the device is believed to yield harmful voids and interfaces. Measurements of particle density and growth in a silane RF plasma, for particle diameters of 8-50 nm, are described. This particle growth rate is very rapid, and decreases in density during the growth indicate a major flux of these size particles to the substrate. Particle densities are a very strong function of pressure, film growth rate and electrode gap, increasing orders of magnitude for small increases in each parameter. A full plasma- chemistry model for particle growth from SiHm radicals and ions has been developed, and is outlined. It yields particle densities and growth rates, as a function of plasma parameters, which are in qualitative agreement with the data. It also indicates that, in addition to the diameter >2 nm particles that have been observed in films, a very large flux of SixH,, molecular radicals with × >1 also incorporate into the film. It appears that these large radicals yield more than 1% of the film for typical device-deposition conditions, so this may have a serious effect on device properties.
Structural Origin of Bulk Molecular Hydrogen in Hydrogenated Amorphous Silicon
Authors: Liu Xiao , Pohl R.O. , Crandall R.S. 
Published: April 2011

AbstractThe elastic anomaly observed previously at the triple point of bulk molecular hydrogen in hydrogenated amorphous silicon films prepared by hot-wire chemical-vapor deposition has also been observed in deuterated films at the triple point of D2. The origin of this anomaly has now been traced to bubbles formed at the crystalline-amorphous interface. An upper limit of the pressure in these bubbles at their formation temperature, 440°C, has been estimated to be 11 MPa, and is suggested to be a measure of the bonding strength between film and substrate at that temperature. Bubble formation after heat treatment at 400°C has also been observed in films prepared by plasma-enhanced chemical-vapor deposition. The internal friction anomalies resemble those observed previously in cold-worked hydrogenated iron where they have been interpreted through plastic deformation of solid hydrogen in voids.
Effects of Chlorine on Dopant Activation in a-Si:H
Authors: Payne Adam M. , Wagner Sigurd 
Published: April 2011

AbstractThe incorporation of chlorine has a significant effect on the dark conductivity of doped and undoped hydrogenated amorphous silicon (a-Si:H). The dark conductivity of a-Si:H films deposited from dichlorosilane (SiCl2H2) and SiH4, and doped with diborane, increases by as much as a factor of 100 over the usual a-Si:H,B films deposited without SiCl2H2. The effect is observed at gas phase concentrations of diborane ranging from 0.006% to 0.5%, and for both DC and RF plasma depositions, although it is more noticeable for the DC discharge. An increase in dark conductivity is also observed in B doped a-Si,C:H films deposited with dichlorosilane, albeit coupled with a change in the Tauc gap. Chlorine reduces the conductivity of undoped and phosphorus doped a-Si:H films. Undoped a-Si:H films deposited from SiCl2H2 and SiH4 have a dark conductivity of ~1. 10-12 S.cm-1, which is an order of magnitude lower than films deposited from pure SiH4. We discuss several alternatives for the mechanism of chlorine enhanced or reduced dopant activation. We have made solar cells using chlorinated p-type a-SiC:H films as the p-layers.
Microcrystalline Silicon - Relation of Transport Properties and Microstructure
Authors: Kočka J. , Fejfar A. , Vorlíček V. , Stuchlíková H. , Stuchlík J. 
Published: April 2011

AbstractUnderstanding of transport in hydrogenated microcrystalline silicon (μc-Si:H) is difficult due to its complicated microstructure (grains, grain boundaries, amorphous tissue). μc-Si:H layers often exhibit preferential orientation leading to transport anisotropy. Furthermore, specific μc-Si:H growth features lead to the thickness dependence of the structure and properties.μc-Si:H incubation layer was studied by AFM with conductive cantilever measuring simultaneously morphology and local conductivity maps with submicron resolution. Clear identification of Si crystallites (with size of few tens of nanometers) is demonstrated. The crystalline fraction at the surface may be easily evaluated.For the charge collection in solar cells we need to study transport perpendicular to the substrate. Measurement of frequency spectra of A.C. conductivity is introduced as a new tool which can exclude the influence of contact barriers in sandwich geometry and can be used for finding the “true” conductivity perpendicular to the substrate. Using this technique transport anisotropy in some μc-Si:H samples was clearly demonstrated.Finally, it is shown how the transport properties change with growing μc-Si:H thickness and how these changes correlate with the structure observed by AFM.
Stress in Hydrogenated Microcrystalline Silicon Thin Films
Authors: Peiró D. , Voz C. , Bertomeu J. , Andreu J. , Martínez E. , Esteve J. 
Published: April 2011

AbstractHydrogenated microcrystalline silicon films have been obtained by hot-wire chemical vapor deposition (HWCVD) in a silane and hydrogen mixture at low pressure (<5 × 10-2 mbar). The structure of the samples and the residual stress were characterised by X- ray diffraction (XRD). Raman spectroscopy was used to estimate the volume fraction of the crystalline phase, which is in the range of 86 % to 98%. The stress values range between 150 and -140 MPa. The mechanical properties were studied by nanoindentation. Unlike monocrystalline wafers, there is no evidence of abrupt changes in the force-penetration plot, which have been attributed to a pressure-induced phase transition. The hardness was 12.5 GPa for the best samples, which is close to that obtained for silicon wafers.
Long-Term Stability of Microcrystalline Silicon P-I-N Solar Cells Exposed to Sun Light
Authors: Sanguino P. , Koynov S. , Schwarzl R. , Fernandes M. , Vieira M. , Manso R. , Joyce A. , Collares-Pereira M. 
Published: April 2011

AbstractThe performance of an entirely microcrystalline p-i-n solar cell was monitored during a long-term outdoor test in Lisbon starting in September 1998. A small decrease of the short circuit current was observed after 5 months of operation. The open-circuit voltage remained stable around 400 mV. From the analysis of the I-V characteristic in dark and under illumination we could identify the weak points of the test structure, like large series resistance, high recombination rate, and intensity-dependent collection efficiency.
Structure Sensitive Hydrogenation Effects in Polysilicon High Voltage thin Film Transistors
Authors: Clough F.J. , Xu Y.Z. , Narayanan E.M. Sankara , Cross R. 
Published: April 2011

AbstractHydrogen passivation of grain boundary and in-grain defects is a key process step in the fabrication of high quality poly-Si TFTs. The sensitivity of the hydrogenation process to device geometry is therefore an important consideration. The effects of rf-plasma hydrogenation on the operating performance of a range of self-aligned and offset drain (Loff = 5 to 40 μm) poly-Si TFT configurations is reported. The hydrogenation of offset drain structures results in a predictable increase in the pre-threshold slope and a reduction in the device threshold voltage. However, extended hydrogenation (up to 12 h) can result in a significant reduction in the device drive current (by up to 2 orders). A similar effect is observed in metal field plate HVTFTs in which some portion of the offset region is un-modulated by the additional electrode. The on state conduction in the offset region is examined as a function of hydrogenation time, temperature and planar electric field. The increase in the on resistance is attributed to a reduction in the poly-Si defect density, which moderates carrier transport through the offset region.
Rugged a-Si:H TFTs on Plastic Substrates
Authors: Gleskovas H. , Wagner S. , Suo Z. 
Published: April 2011

AbstractMuch of the mechanical strain in semiconductor devices can be relieved when they are made on compliant substrates. We demonstrate this strain relief with amorphous silicon thin-film transistors (a-Si:H TFTs) made on 25-μm thick polyimide foil, which can be bent to radii of curvature R down to 0.5 mm without substantial change in electrical characteristics. At R= 0.5 mm the channel area of the TFTs is strained by ~ 1%. The reduction in bending radius, from R ≠ 2 mm on steel foil of the same thickness, agrees with the theoretical prediction that changing from a stiff to a compliant substrate can reduce the bending strain in the device plane by a factor of up to 5.
CAT-CVD Process and its Application to Preparation of Si-Based Thin Films
Authors: Matsumura Hideki , Masuda Atsushi , Izumi Akira 
Published: April 2011

AbstractThis is to review the present understanding on Cat-CVD (catalytic chemical vapor deposition) or hot wire CVD. Firstly, the deposition mechanism in Cat-CVD process is briefly mentioned along with key issues such as the effect of heat radiation and a method to avoid contamination from the catalyzer. Secondly, the properties of Cat-CVD Si-based thin films such as amorphous silicon (a-Si), polycrystalline silicon (poly-Si) and silicon nitride (SiNx) films are demonstrated, and finally, the feasibility of such films for industrial application is discussed.
The Recrystallization Depth Control of the Excimer-Laser-Recrystallized Poly-Crystalline Silicon Film
Authors: Park Kee-Chan , Choi Kwon-Young , Jeon Jae-Hong , Lee Min-Cheol , Han Min-Koo 
Published: April 2011

AbstractA novel method to control the recrystallization depth of amorphous silicon (a-Si) film during the excimer laser annealing (ELA) is proposed in order to preserve a-Si that is useful for fabrication of poly-Si TFT with a-Si offset in the channel. A XeCl excimer laser beam is irradiated on a triple film structure of a-Si thin native silicon oxide (~20Å)/thick a-Si layer. Only the upper a-Si film is recrystallized by the laser beam irradiation, whereas the lower thick a-Si film remains amorphous because the thin native silicon oxide layer stops the grain growth of the poly-crystalline silicon (poly-Si). So that the thin oxide film sharply divides the upper poly-Si from the lower a-Si.
Novel Amorphous Silicon Solar Cell using a Manufacturing Procedure with a Temporary Superstrate
Authors: Schropp R.E.I. , Werf C.H.M. Van Der , Zeman M. , Sanden M.C.M. Van de , Spee C.I.M.A. , Middelman E. , Jonge-Meschaninova L.V. de , Peters P.M.G.M. , Zijden A.A.M. Van der , Besselink M.M. , Severens R.J. , Winkeler J. , Jongerden G.J. 
Published: April 2011

AbstractWe developed a novel temporary-superstrate concept for SnO2/p-i-n amorphous silicon solar cells. This concept combines roll-to-roll manufacturability, the utilization of light scattering, the conductive properties of SnO2:F, and the possibility of monolithic series connection. To this purpose, the deposition of high quality textured SnO2:F layers on aluminum foil has been developed using APCVD. Layers have been obtained with a transmission of 80 % and a sheet resistance of 12 Ω/□. After definition of the entire p-i-n cell structure including the back contact, the cell is laminated with a permanent carrier foil. By removing the aluminum foil, light can enter the cell through the textured TCO layer. A wide variety of transparent encapsulants can be used to finalize the (flexible or preshaped) product. Preliminary cells made according to this scheme have an efficiency of 6 %.
Effect of Interface Roughness on Light Scattering and Optical Properties of a-Si:H Solar Cells
Authors: Zeman M. , Swaau R.A.C.M.M. Van , Zuiddam M. , Metselaar J.W. , Schropp R.E.I. 
Published: April 2011

AbstractThe effect of interface roughness on the optical properties of amorphous silicon (a-Si:H) solar cells was investigated using rms roughness measurements and computer modeling. We deposited four single junction a-Si:H solar cells on Asahi U type substrate each with a different intrinsic layer thickness. The roughness of the substrate and of the subsequent interfaces of the cells was measured by Atomic Force Microscopy. The relations between the computer input parameters, which describe the diffuse part of reflected and transmitted light at a rough interface, and the rms roughness of the interfaces in a-Si:H solar cell are presented. After obtaining a good matching between the simulated and measured external quantum efficiencies (QE) of the four cells, we investigated the effect of interface roughness on the absorption in all individual layers of the a-Si:H solar cell using the determined scattering parameters.The rms roughness of the Asahi U-type substrate surface is determined to be 40 nm. Deposition of a 9 nm thick p-type a-SiC:H layer on the substrate has not changed the surface roughness. Due to a high refractive index of n-type a-Si:H the back contact interface acts as a nearly perfect diffuser for the reflected light when the rms roughness of the interface is higher than 25 nm. The rms roughness of the back interface of the four cells is found to be dependent on the intrinsic layer thickness and is larger than 25 nm.
Material Requirements for Buffer Layers Used to Obtain Solar Cells with High Open Circuit Voltages
Authors: Roedern Bolko Von , Bauer Gottfried H. 
Published: April 2011

AbstractThis paper discusses material requirements for junction layers needed to obtain solar cells with highest possible open-circuit voltages (VOC). In a typical a-Si:H-based “p/i/n” solar cell, this includes the transparent conductive oxide (TCO) contact layer, the p-layer, a “buffer layer” inserted at the p/i interface, and the surface portion of the intrinsic layer. In HIT-cells, the i-layer between (n-type) c-Si and (p-type) a-Si:H may be regarded as the buffer. Our suggestion to obtain high values of VOC relies on using materials with high lifetimes and low carrier mobilities that are capable of reducing surface or junction recombination by reducing the flow of carriers into this loss-pathway. We provide a general calculation that supports these approaches and can explain why these schemes are beneficial for all solar cells.
Simulation of Hydrogenated Amorphous Silicon Germanium Alloys for Bandgap Grading
Authors: Schroten E. , Zeman M. , Swaaij R. A. C. M. M. van , Vosteen L. L. A. , Metselaar J. W. 
Published: April 2011

AbstractComputer simulations are reported of hydrogenated amorphous silicon germanium (a-SiGe:H) layers that make up the graded part of the intrinsic layer near the interfaces of a-SiGe:H solar cells. Therefore the graded part is approached with a ‘staircase’ bandgap profile, consisting of three layers within which the material properties are constant. Calibrated model parameters are obtained by matching simulation results of material properties of intrinsic a-SiGe:H single layers to measurements. Using the obtained model parameter sets subsequent simulations of p-i-n devices with intrinsic material similar to the single layers are matched to measured current-voltage characteristics. The changes in parameter values are evaluated as a function of optical gap.