The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform

H Wagner - One of the best experts on this subject based on the ideXlab platform.

  • Large Grain Size and High Deposition Rate for Microcrystalline Silicon Prepared by VHF-GD
    MRS Proceedings, 2011
    Co-Authors: P Hapke, M Luysberg, Friedhelm Finger, Reinhard Carius, H Wagner
    Abstract:

    The growth mechanism and material properties of -type µc-Si:H prepared with Plasma enhanced chemical vapour deposition in the very high Frequency range is investigated. By increasing the Plasma Excitation Frequency the grain size, deposition rate and Hall mobility can be simultaneously increased without having to adjust other deposition parameters in particular the temperature. This effect is explained by an enhanced selective etching of amorphous tissue and grain boundary regions together with a sufficient supply of growth species at high Frequency Plasmas.

  • Preparation of Microcrystalline Silicon with the Layer-by-Layer Technique at Various Plasma Excitation Frequencies
    MRS Proceedings, 2011
    Co-Authors: P Hapke, Friedhelm Finger, Reinhard Carius, Andreas Lambertz, O. Vetterl, H Wagner
    Abstract:

    AbstractFor application as nucleation layer in thin film devices, microcrystalline silicon was deposited with the layer-by-layer technique using Plasma Excitation frequencies between 27 and 95 MHz, various hydrogen treatment times and various film thicknesses per layer. An optimum phase transformation is found at an intermediate Plasma Excitation Frequency, i.e. at this Frequency the shortest hydrogen annealing time is necessary for an effective amorphous-to-crystalline phase transformation.

  • new materials and deposition techniques for highly efficient silicon thin film solar cells
    Solar Energy Materials and Solar Cells, 2002
    Co-Authors: B Rech, F Finger, T. Repmann, O Kluth, T Roschek, J Springer, J Muller, Helmut Stiebig, H Wagner
    Abstract:

    This paper reviews recent efforts to provide the scientific and technological basis for cost-effective and highly efficient thin film solar modules based on amorphous (a-Si:H) and microcrystalline (pc-Si:H) silicon. Textured ZnO:Al films prepared by sputtering and wet chemical etching were applied to design optimised light-trapping schemes. Necessary prerequisite was the detailed knowledge of the relationship between film growth, structural properties and surface morphology obtained after etching. High rate deposition using Plasma enhanced chemical vapour deposition at 13.56 MHz Plasma Excitation Frequency was developed for pc-Si:H solar cells yielding efficiencies of 8.1% and 7.5% at deposition rates of 5 and 9 Angstrom/s, respectively. These pc-Si: H solar cells were successfully up-scaled to a substrate area of 30 x 30 cm(2) and applied in a-Si:H/muc-Si:H tandem cells showing initial test cell efficiencies up to 11.9%. (C) 2002 Elsevier Science B.V. All rights reserved.

  • Growth of microcrystalline silicon using the layer-by-layer technique at various Plasma Excitation frequencies
    Journal of Non-crystalline Solids, 1998
    Co-Authors: O. Vetterl, P Hapke, M Luysberg, Friedhelm Finger, Lothar Houben, H Wagner
    Abstract:

    Abstract Microcrystalline silicon (μc-Si:H) was deposited with the layer-by-layer technique at various Plasma Excitation frequencies. For hydrogen treatment times (tH) less than a critical time (tC), the films are amorphous and the thickness decreases linearly with tH. For tH larger than tC microcrystalline growth was observed, while the thickness remained constant. The range of tH for microcrystalline growth and constant film thickness increased with the Plasma Excitation Frequency. Transmission electron microscopy of films with comparable thickness show that the Excitation Frequency affects the structure of the layer-by-layer films. For low frequencies, amorphous growth is observed; for intermediate and high frequencies, the structure is crystalline with variations in density and crystallite sizes.

  • Structural investigation and growth of 〈n〉-type microcrystalline silicon prepared at different Plasma Excitation frequencies
    Journal of Non-crystalline Solids, 1996
    Co-Authors: P Hapke, M Luysberg, R Carius, Friedhelm Finger, Marian Tzolov, H Wagner
    Abstract:

    Phosphorus doped microcrystalline silicon films prepared with very high Frequency Plasma enhanced chemical vapor deposition are characterized with respect to their structural properties in order to get information on the growth processes of this material. As deposition parameter the Plasma Excitation Frequency is varied from 27 to 116 MHz. The experimental results suggest that the growth of microcrystalline silicon is induced by the chemical equilibrium of deposition and etching, where the etching is predominantly given by the erosion of the amorphous phase.

F Finger - One of the best experts on this subject based on the ideXlab platform.

  • new materials and deposition techniques for highly efficient silicon thin film solar cells
    Solar Energy Materials and Solar Cells, 2002
    Co-Authors: B Rech, F Finger, T. Repmann, O Kluth, T Roschek, J Springer, J Muller, Helmut Stiebig, H Wagner
    Abstract:

    This paper reviews recent efforts to provide the scientific and technological basis for cost-effective and highly efficient thin film solar modules based on amorphous (a-Si:H) and microcrystalline (pc-Si:H) silicon. Textured ZnO:Al films prepared by sputtering and wet chemical etching were applied to design optimised light-trapping schemes. Necessary prerequisite was the detailed knowledge of the relationship between film growth, structural properties and surface morphology obtained after etching. High rate deposition using Plasma enhanced chemical vapour deposition at 13.56 MHz Plasma Excitation Frequency was developed for pc-Si:H solar cells yielding efficiencies of 8.1% and 7.5% at deposition rates of 5 and 9 Angstrom/s, respectively. These pc-Si: H solar cells were successfully up-scaled to a substrate area of 30 x 30 cm(2) and applied in a-Si:H/muc-Si:H tandem cells showing initial test cell efficiencies up to 11.9%. (C) 2002 Elsevier Science B.V. All rights reserved.

  • structure and growth of hydrogenated microcrystalline silicon investigation by transmission electron microscopy and raman spectroscopy of films grown at different Plasma Excitation frequencies
    Philosophical Magazine, 1997
    Co-Authors: M Luysberg, P Hapke, R Carius, F Finger
    Abstract:

    Abstract Microcrystalline silicon prepared by Plasma-enhanced chemical vapour deposition consists of variable volume fractions of amorphous phase, grain boundaries, cavities and crystalline grains. In this paper the structural properties, which strongly depend on the growth conditions, were investigated in detail by transmission electron microscopy and by Raman spectroscopy. A columnar structure parallel to the growth direction is observed for all conditions investigated. By increasing the Plasma Excitation Frequency the crystalline volume fraction and the grain sizes are enhanced. Simultaneously an increase in the growth rate can be achieved, which is accompanied by an increasing etch rate of amorphous material. In addition, spherical voids were found predominantly in samples prepared at a low Plasma Excitation Frequency. The growth of a porous initial layer containing a high density of ‘crack-line’ voids is observed when high Plasma Excitation frequencies are applied. These results suggest that the micr...

  • improvement of grain size and deposition rate of microcrystalline silicon by use of very high Frequency glow discharge
    Applied Physics Letters, 1994
    Co-Authors: F Finger, P Hapke, M Luysberg, R Carius, H Wagner, M Scheib
    Abstract:

    The influence of the Plasma Excitation Frequency on the growth conditions and the material properties of microcrystalline silicon prepared by Plasma enhanced chemical vapor deposition at low deposition temperature is investigated. It is found that an increase of the Plasma Excitation Frequency leads to a simultaneous increase of the growth rate, the grain size, and the Hall mobility of microcrystalline silicon. This is attributed to an effective selective etching of disordered material creating more space to develop crystalline grains, while also more species for faster growth of the crystallites are available.

  • influences of a high Excitation Frequency 70 mhz in the glow discharge technique on the process Plasma and the properties of hydrogenated amorphous silicon
    Journal of Applied Physics, 1992
    Co-Authors: F Finger, Arvind Shah, U Kroll, V Viret, W Beyer, X M Tang, J Weber, A A Howling, Christoph Hollenstein
    Abstract:

    Hydrogenated amorphous silicon has been prepared at a Plasma Excitation Frequency in the very‐high‐Frequency band at 70 MHz with the glow discharge technique at substrate temperatures between 280 and 50 °C. The structural properties have been studied using hydrogen evolution, elastic recoil detection analysis, and infrared spectroscopy. The films were further characterized by dark and photoconductivity and by photothermal deflection spectroscopy. With respect to films prepared at the conventional Frequency of 13.56 MHz considerable differences concerning the electronic and structural properties are observed as the substrate temperature is decreased from 280 to 50 °C. Down to a substrate temperature of 150 °C the electronic film properties change only a little and the total hydrogen content cH and the degree of microstructure that can be directly correlated to cH increase only moderately. Below 150 °C the electronic properties deteriorate in the usual manner but still the total hydrogen content does not ex...

Friedhelm Finger - One of the best experts on this subject based on the ideXlab platform.

  • Large Grain Size and High Deposition Rate for Microcrystalline Silicon Prepared by VHF-GD
    MRS Proceedings, 2011
    Co-Authors: P Hapke, M Luysberg, Friedhelm Finger, Reinhard Carius, H Wagner
    Abstract:

    The growth mechanism and material properties of -type µc-Si:H prepared with Plasma enhanced chemical vapour deposition in the very high Frequency range is investigated. By increasing the Plasma Excitation Frequency the grain size, deposition rate and Hall mobility can be simultaneously increased without having to adjust other deposition parameters in particular the temperature. This effect is explained by an enhanced selective etching of amorphous tissue and grain boundary regions together with a sufficient supply of growth species at high Frequency Plasmas.

  • Preparation and Characterization of Highly Conductive (100 S/cm) Phosphorus Doped νc-Si:H Films Deposited Using the VHF-GD Technique
    MRS Proceedings, 2011
    Co-Authors: K. Prasad, H. Curtins, Arvind Shah, Friedhelm Finger, J. Bauman
    Abstract:

    We report on the preparation and characterization of phosphorus doped gc-Si:H films produced by the very high Frequency glow discharge (VHF-GD) at a Plasma Excitation Frequency of 70 MHz. We present a systematic study of the deposition parameters i.e. hydrogen dilution of silane, VHF power density, gas phase doping ratio and deposition temperature and their influences on the electrical and structural properties of the material. In contrast to 13.56 MHz GD the VHF Plasma conditions favour microcrystalline formation at low power densities; the resulting conductivities are significantly higher than those obtained at 13.56 MHz.

  • Preparation of Microcrystalline Silicon with the Layer-by-Layer Technique at Various Plasma Excitation Frequencies
    MRS Proceedings, 2011
    Co-Authors: P Hapke, Friedhelm Finger, Reinhard Carius, Andreas Lambertz, O. Vetterl, H Wagner
    Abstract:

    AbstractFor application as nucleation layer in thin film devices, microcrystalline silicon was deposited with the layer-by-layer technique using Plasma Excitation frequencies between 27 and 95 MHz, various hydrogen treatment times and various film thicknesses per layer. An optimum phase transformation is found at an intermediate Plasma Excitation Frequency, i.e. at this Frequency the shortest hydrogen annealing time is necessary for an effective amorphous-to-crystalline phase transformation.

  • Growth and Structure of Microcrystalline Silicon Prepared with Glow Discharge at Various Plasma Excitation Frequencies
    MRS Proceedings, 2011
    Co-Authors: Friedhelm Finger, P Hapke, M Luysberg, R Carius, Lothar Houben, Marian Tzolov
    Abstract:

    Microcrystalline silicon was prepared with glow discharge deposition from silane/hydrogen mixtures at Plasma Excitation frequencies in the range 13.56 MHz - 116 MHz. The influence of the Plasma Excitation Frequency on the growth and the structural properties of the material is investigated. At high Excitation frequencies, higher growth and etching rates, larger grain sizes with less disorder within the grains, higher crystalline volume fractions, a reduced amorphous but more porous interface layer on glass and quartz substrates, and faster nucleation on amorphous silicon substrates are obtained. The results are discussed within a schematical growth model.

  • Role of SiH 2 in 1 H Nmr of μc-Si:H Deposited with Different Plasma Excitation Frequencies and Silane Concentrations
    MRS Proceedings, 2011
    Co-Authors: Parameswar Hari, P. C. Taylor, Friedhelm Finger
    Abstract:

    Previous l H NMR and IR studies of six samples of μc-Si:H prepared under Plasma Excitation frequencies ranging from 13 MHz to 95 MHz and silane concentrations ranging from 3% to 8% revealed three important results: (1) for a fixed Plasma Excitation Frequency (95 MHz) the hydrogen content increases with silane concentration; (2) for fixed silane concentration the hydrogen content is roughly constant over a wide range of Plasma Excitation frequencies; and (3) the 1 H NMR free induction decay exhibits beat frequencies which correspond to the calculated frequencies due to SiH 2 in microcrystalline silicon. In this study we investigate the role of SiH 2 in the μc-Si:H structure using 1 H NMR measurements. We studied two samples prepared at two different Plasma Excitation frequencies (13 MHz and 95 MHz). The l U NMR lineshapes of these samples were measured at 300 K and 77 K. The motionally narrowed component of the 1 H NMR is not as rapid at room temperature as that observed previously, but the linewidth of this component increases significantly at 77 K. Because of this difference between our results and those reported previously, it is possible that H 2 molecules are not responsible for the motional narrowing in our samples. We present plausible arguments for the hindered motion of SiH 2 groups in our μc-Si:H samples.

P Hapke - One of the best experts on this subject based on the ideXlab platform.

  • Large Grain Size and High Deposition Rate for Microcrystalline Silicon Prepared by VHF-GD
    MRS Proceedings, 2011
    Co-Authors: P Hapke, M Luysberg, Friedhelm Finger, Reinhard Carius, H Wagner
    Abstract:

    The growth mechanism and material properties of -type µc-Si:H prepared with Plasma enhanced chemical vapour deposition in the very high Frequency range is investigated. By increasing the Plasma Excitation Frequency the grain size, deposition rate and Hall mobility can be simultaneously increased without having to adjust other deposition parameters in particular the temperature. This effect is explained by an enhanced selective etching of amorphous tissue and grain boundary regions together with a sufficient supply of growth species at high Frequency Plasmas.

  • Preparation of Microcrystalline Silicon with the Layer-by-Layer Technique at Various Plasma Excitation Frequencies
    MRS Proceedings, 2011
    Co-Authors: P Hapke, Friedhelm Finger, Reinhard Carius, Andreas Lambertz, O. Vetterl, H Wagner
    Abstract:

    AbstractFor application as nucleation layer in thin film devices, microcrystalline silicon was deposited with the layer-by-layer technique using Plasma Excitation frequencies between 27 and 95 MHz, various hydrogen treatment times and various film thicknesses per layer. An optimum phase transformation is found at an intermediate Plasma Excitation Frequency, i.e. at this Frequency the shortest hydrogen annealing time is necessary for an effective amorphous-to-crystalline phase transformation.

  • Growth and Structure of Microcrystalline Silicon Prepared with Glow Discharge at Various Plasma Excitation Frequencies
    MRS Proceedings, 2011
    Co-Authors: Friedhelm Finger, P Hapke, M Luysberg, R Carius, Lothar Houben, Marian Tzolov
    Abstract:

    Microcrystalline silicon was prepared with glow discharge deposition from silane/hydrogen mixtures at Plasma Excitation frequencies in the range 13.56 MHz - 116 MHz. The influence of the Plasma Excitation Frequency on the growth and the structural properties of the material is investigated. At high Excitation frequencies, higher growth and etching rates, larger grain sizes with less disorder within the grains, higher crystalline volume fractions, a reduced amorphous but more porous interface layer on glass and quartz substrates, and faster nucleation on amorphous silicon substrates are obtained. The results are discussed within a schematical growth model.

  • High deposition rates for microcrystalline silicon with low temperature Plasma enhanced chemical vapor deposition processes
    Journal of Non-crystalline Solids, 1998
    Co-Authors: P Hapke, Friedhelm Finger
    Abstract:

    Intrinsic microcrystalline silicon (μc-Si:H) was prepared with Plasma enhanced chemical vapor deposition (PECVD) from silane/hydrogen mixtures at 200°C with the aim to increase the deposition rate. Using a Plasma Excitation Frequency of 95 MHz we obtain an increase of the deposition rate by a factor of 25 from that of our standard PECVD process at 13.56 MHz. This increase is obtained by the combination of a higher Plasma Excitation Frequency, an increased silane concentration (SC) and larger discharge powers. Material prepared under these conditions at a deposition rate of 0.46 nm s−1 maintains crystallinity and electronic properties with dark conductivities, σD≈10−7 S cm−1, and spin densities in the range of 1016 cm−3.

  • Growth of microcrystalline silicon using the layer-by-layer technique at various Plasma Excitation frequencies
    Journal of Non-crystalline Solids, 1998
    Co-Authors: O. Vetterl, P Hapke, M Luysberg, Friedhelm Finger, Lothar Houben, H Wagner
    Abstract:

    Abstract Microcrystalline silicon (μc-Si:H) was deposited with the layer-by-layer technique at various Plasma Excitation frequencies. For hydrogen treatment times (tH) less than a critical time (tC), the films are amorphous and the thickness decreases linearly with tH. For tH larger than tC microcrystalline growth was observed, while the thickness remained constant. The range of tH for microcrystalline growth and constant film thickness increased with the Plasma Excitation Frequency. Transmission electron microscopy of films with comparable thickness show that the Excitation Frequency affects the structure of the layer-by-layer films. For low frequencies, amorphous growth is observed; for intermediate and high frequencies, the structure is crystalline with variations in density and crystallite sizes.

Sumita Mukhopadhyay - One of the best experts on this subject based on the ideXlab platform.

  • Structural characteristics of RF- and VHF-deposited nanocrystalline silicon films for solar cell application
    Philosophical Magazine, 2020
    Co-Authors: Sumita Mukhopadhyay
    Abstract:

    Nanocrystalline silicon films have been deposited using RF and VHF (54.24 MHz) Plasma-enhanced chemical vapor deposition (PECVD) methods. The effects of Plasma Excitation Frequency, Plasma power density, chamber pressure, hydrogen dilution of silane and total gas flow-rates on the structural properties of nanosilicon films have been investigated. For all films prepared under different conditions, grain size varied in the range 5–14.4 nm and crystalline volume fraction varied in the range 21–86%. Films with low microstructure factor have been developed successfully using a 54.24-MHz Plasma Excitation Frequency at high total gas flow-rate and optimum power–pressure. Single junction cells have been fabricated using the nanocrystalline silicon films with different crystallinity.

  • Influence of Excitation Frequency and electrode separation on the growth of microcrystalline silicon films and their application in single junction microcrystalline solar cell
    Journal of Materials Science: Materials in Electronics, 2017
    Co-Authors: Sourav Mandal, Sumita Mukhopadhyay, Sukanta Dhar, Sukanta Bose, Jayasree Roy Sharma, Chandan Banerjee, A.k. Barua
    Abstract:

    In this paper we present the role of Plasma Excitation Frequency and electsrode separation on the growth of microcrystalline silicon thin films at two different hydrogen dilutions of silane and different power densities. We optimized the process conditions to develop device quality microcrystalline material. Optoelectronic and structural properties of the developed material have been correlated with the solar cell properties. Growth rate ~7 A/s has been achieved using Plasma Excitation Frequency of 27.12 MHz at 15 mm electrode separation. We have noticed the positive effects after reducing the electrode separation in higher Frequency (27.12 MHz). Optimized microcrystalline film of activation energy 0.55 eV and grain size of 14.61 nm has been developed and is applied to fabricate single junction microcrystalline solar cell. Solar cell with initial cell efficiency of 7.75% with short circuit current density of 24.98 mA/cm2 and open circuit voltage of 0.47 V and fill factor of 0.66 has been achieved.

  • Fabrication of low defect density nanocrystalline silicon absorber layer and its application in thin-film solar cell
    Thin Solid Films, 2008
    Co-Authors: Amartya Chowdhury, Sumita Mukhopadhyay
    Abstract:

    Effect of Plasma Excitation Frequency and total gas flow rate on the structural properties as well as defect density of nanocrystalline silicon films have been investigated using Raman analysis, Fourier transform infrared spectroscopy, electron spin resonance. It has been found that defect density and microstructural defect in the films are low (1) at higher Plasma Excitation Frequency of 54.24 MHz and (2) at higher total gas flow rate. Defect density and microstructural defect increase as crystallinity of the films increases. Performance of solar cells, prepared with different absorber layers confirm the fact that fill factor and short circuit current increases as defect density decreases.

  • Effect of gas flow rates on PECVD-deposited nanocrystalline silicon thin film and solar cell properties
    Solar Energy Materials and Solar Cells, 2008
    Co-Authors: Amartya Chowdhury, Sumita Mukhopadhyay
    Abstract:

    Abstract Nanocrystalline silicon films have been deposited at a Plasma Excitation Frequency of 54.24 MHz by varying the flow rates of SiH 4 +H 2 mixture in the reaction chamber. It has been found that with increase in gas flow rate from 100 to 300 sccm the defect density, microstructural defect fraction and the crystalline volume fraction in the film decrease. Films deposited at optimum total gas flow rate of 200 sccm with comparable crystalline volume fraction have shown better structural and optoelectronic properties compared to the films deposited at 100 sccm total gas flow rate for application in solar cell. Solar cells have been fabricated using these layers as absorber layers and the maximum cell efficiency obtained is 6.2% (AM1.5, 28 °C) at 200 sccm total gas flow rate. It has been found that material prepared using higher total gas flow rate of 200 sccm together with higher hydrogen dilution is better suited for solar cell application.

  • structural and transport properties of nanocrystalline silicon thin films prepared at 54 24 mhz Plasma Excitation Frequency
    Journal of Crystal Growth, 2007
    Co-Authors: Amartya Chowdhury, Sumita Mukhopadhyay
    Abstract:

    Abstract The effects of power density and chamber pressure on the nanocrystalline silicon thin films have been studied in high-pressure–high-power regime by Plasma-enhanced chemical vapour deposition process at a Plasma Excitation Frequency of 54.24 MHz. For all the films prepared at high hydrogen dilution, grain sizes lie in the range 6–14.4 nm. Maximum crystalline volume fraction of 84.9% is obtained for films deposited at a power density of 0.7 W/cm 2 . Crystallinity decreases with increase in chamber pressure. Long grains are observed using the high-resolution transmission electron micrograph when films are deposited at high power density. High diffusion length of 610 nm is obtained for films deposited in the transition region of amorphous to nanocrystalline phase.