Effects of Chamber Pressures on the Passivation Layer of Hydrogenated Nano-Crystalline Silicon Mixed-Phase Thin Film by Using Microwave Annealing

This paper proposes the effects of chamber pressures on the passivation layer of hydrogenated nano-crystalline silicon (nc-Si:H) mixed-phase thin film using microwave annealing (MWA) to achieve a high-quality thin film. The use of 40.68 MHz very-high-frequency plasma-enhanced chemical vapor deposition (VHFPECVD) deposited the nc-Si:H mixed-phase thin film on the top and bottom of the n-type crystalline silicon substrate. The chamber pressures (0.2, 0.4, 0.6, and 0.8 Torr) of the VHFPECVD were critical factors in controlling the carrier lifetime of the symmetric structure. By using the VHFPECVD to deposit the nc-Si:H and using the MWA to enhance the quality of the symmetric structure, the deposited nc-Si:H’s properties of a crystalline volume fraction of 29.6%, an optical bandgap of 1.744 eV, and a carrier lifetime of 2942.36 μs were well achieved, and could be valuable in thin-film solar-cell applications.

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Nano-Crystalline Si Based Alloy (nc-SiXY) with Band Gap of 1.5 eV as the Solar Cell Absorber Layer Fabricated by VHF-PECVD Technique

MRS Proceedings ◽

10.1557/opl.2012.932 ◽

2012 ◽

Vol 1426 ◽

pp. 87-92

Author(s):

Feng Zhu ◽

Jian Hu ◽

Ilvydas Matulionis ◽

Josh Gallon ◽

Arun Madan

Keyword(s):

Volume Fraction ◽

Crystalline Silicon ◽

Chemical Vapor ◽

Optical Bandgap ◽

Absorber Layer ◽

Crystalline Volume Fraction ◽

Very High Frequency ◽

Nano Crystalline ◽

Silicon Based ◽

Gas Ratio

ABSTRACTWe describe the properties of nano-crystalline silicon based alloy (nc-SiXY) prepared by a very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique with silane (SiH4) and XY gas mixtures and diluted in hydrogen (H2) at low deposition temperature. Varying the gas ratio among SiH4, H2 and XY gasses could alter the optical bandgap and structure. The nc-Si films with high crystalline volume fraction were first prepared, and then the XY gasses were added in order to tune the microstructure and opto-electronic properties of this nano-crystalline silicon based alloy. We have characterized the materials using UV-VIS-NIR, Raman, Constant Photocurrent Method (CPM), dark- and photo-conductivity. As XY gas flows were increased, the optical bandgap of nc-SiXY films increased, while its crystalline volume fraction and conductivity decreased. With proper control of the silane concentration, XY/SiH4 gas ratio, and deposition pressure, we have fabricated the nc-SiXY film with optical bangap of about 1.5eV. Applying this material as the absorber layer in p-i-n devices with configuration of textured ZnO/nc-p+/nc-SiXY/a-n+/Ag, the efficiency is 7.25% (Voc=0.616V, Jsc=17.69mA/cm2, FF= 0.666) with thickness of ∼0.8μm.

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The effect of post-hydrogen annealing and multilayer channel structure on nano-crystalline silicon thin film transistor performance

Journal of Physics D Applied Physics ◽

10.1088/0022-3727/43/19/195102 ◽

2010 ◽

Vol 43 (19) ◽

pp. 195102 ◽

Cited By ~ 3

Author(s):

Cheng-I Lin ◽

Yean-Kuen Fang ◽

Feng-Renn Juang ◽

Yen-Ting Chiang ◽

Pao-Tung Chen ◽

...

Keyword(s):

Thin Film ◽

Crystalline Silicon ◽

Thin Film Transistor ◽

Channel Structure ◽

Silicon Thin Film ◽

Hydrogen Annealing ◽

Nano Crystalline

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Atomistic Character of Nanocrystalline and Mixed Phase Silicon

MRS Proceedings ◽

10.1557/proc-762-a11.4 ◽

2003 ◽

Vol 762 ◽

Cited By ~ 3

Author(s):

R. Biswas ◽

B. C. Pan

Keyword(s):

Crystalline Silicon ◽

Electronic Band Structure ◽

Nanocrystalline Silicon ◽

Distribution Functions ◽

Mixed Phase ◽

Electronic Band ◽

Nano Crystalline ◽

Excess Density ◽

Heterogeneous Phase ◽

The Stability

AbstractMaterials grown close to the phase boundary of amorphous and microcrystalline growth have the best electronic properties for solar cells. Systematic molecular dynamics methods have generated such nano-crystalline silicon, consisting of a mixed phase of nano-crystallites in an amorphous matrix, using an embedding method. An excess density of H resides on the surface of the nanocrystallites. The structure of this heterogeneous phase will be characterized by atomic distribution functions and structure factors. The electronic band structure of smaller models of nanocrystalline silicon reveals no midgap states and is similar to a-Si:H. There is a highly strained region surrounding the crystallites. The presence of localized strain region may increase the stability of the material.

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Microcrystalline and Nanocrystalline Silicon: Simulation of Material Properties

MRS Proceedings ◽

10.1557/proc-862-a24.3 ◽

2005 ◽

Vol 862 ◽

Cited By ~ 2

Author(s):

R. Biswas ◽

B. C. Pan ◽

V. Selvaraj

Keyword(s):

Silicon Nanowires ◽

Amorphous Matrix ◽

Volume Fraction ◽

Crystalline Silicon ◽

Amorphous Region ◽

Nanocrystalline Silicon ◽

Nano Crystalline ◽

Crystalline Core ◽

Silicon Structures ◽

Dynamics Simulations

AbstractWe have simulated nano-crystalline silicon and microcrystalline silicon structures with varying crystallite volume fractions, using molecular dynamics simulations. The crystallite regions reside in an amorphous matrix. We find the amorphous matrix is better ordered in nanocrystalline-Si than in the homogenous amorphous silicon networks, consistent with the observed higher stability of H-diluted films. There is a critical size above which the crystallites are stable and may grow. Sub-nm size crystallites in the protocrystalline phase are found to reduce the strain of the amorphous matrix. We simulated micro-crystalline silicon with a substantial crystallite volume fraction. Microcrystalline structures exhibit a crystalline core surrounded by an amorphous shell with similarities to silicon nanowires. We find a relatively uniform H distribution in the amorphous region and a crystal-amorphous phase boundary that is not welldefined.

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Determination of the minority carrier lifetime in crystalline silicon thin-film material

Progress in Photovoltaics Research and Applications ◽

10.1002/pip.2242 ◽

2012 ◽

Vol 22 (2) ◽

pp. 180-188 ◽

Cited By ~ 2

Author(s):

Dominic Walter ◽

Philipp Rosenits ◽

Bastian Berger ◽

Stefan Reber ◽

Wilhelm Warta

Keyword(s):

Thin Film ◽

Carrier Lifetime ◽

Minority Carrier ◽

Crystalline Silicon ◽

Minority Carrier Lifetime ◽

Film Material ◽

Silicon Thin Film ◽

Thin Film Material

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Nano-Crystalline Silicon-Based Bottom Gate Thin-Film Transistor Grown by LTPECVD With Hydrogen-Free He Diluted ${\hbox{SiH}} _{4}$

Journal of Display Technology ◽

10.1109/jdt.2013.2241015 ◽

2013 ◽

Vol 9 (7) ◽

pp. 536-544 ◽

Cited By ~ 10

Author(s):

Chih-Hsien Cheng ◽

Po-Sheng Wang ◽

Chih-I Wu ◽

Gong-Ru Lin

Keyword(s):

Thin Film ◽

Crystalline Silicon ◽

Thin Film Transistor ◽

Nano Crystalline ◽

Silicon Based ◽

Bottom Gate

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Comparative Study of MVHF and RF Deposited Large Area Multi-junction Solar Cells Incorporating Hydrogenated Nano-Crystalline Silicon

MRS Proceedings ◽

10.1557/proc-1153-a22-02 ◽

2009 ◽

Vol 1153 ◽

Author(s):

Xixiang Xu ◽

Yang Li ◽

Scott Ehlert ◽

Tining Su ◽

Dave Beglau ◽

...

Keyword(s):

Solar Cells ◽

Crystalline Silicon ◽

Steel Substrate ◽

Process Conditions ◽

Large Area ◽

Very High Frequency ◽

Cell Efficiency ◽

Cell Structures ◽

Nano Crystalline ◽

Double Junction

AbstractWe report our investigations of large area multi-junction solar cells based on hydrogenated nano-crystalline silicon (nc-Si:H). We compared results from cells deposited by RF (13.56 MHz) at lower deposition rate (˜3 Å/s) and by Modified Very High Frequency (MVHF) at higher rate (≥ 10 Å/s). With optimized process conditions and cell structures, we have obtained ˜12% initial small active-area (˜0.25 cm2) efficiency for both RF and MVHF cells and 10˜11% large aperture-area (˜400 cm2) encapsulated MVHF cell efficiency for both a-Si:H/nc-Si:H double-junction and a-Si:H/nc-Si:H/nc-Si:H triple-junction structures on Ag/ZnO coated stainless steel substrate.

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Poly and Nano-crystalline High Electron Mobility Thin Film Transistors on Plastic Substrates for Large Area Applications

MRS Proceedings ◽

10.1557/proc-1030-g07-07 ◽

2007 ◽

Vol 1030 ◽

Author(s):

Sara Paydavosi ◽

Amir-Hossein Tamaddon ◽

Shams Mohajerzadeh ◽

Michael D Robertson

Keyword(s):

Thin Film ◽

Electron Mobility ◽

Thin Film Transistors ◽

Crystalline Silicon ◽

Silicon Film ◽

Chemical Vapor ◽

Rf Plasma ◽

High Electron ◽

Large Area ◽

Nano Crystalline

AbstractThin-film transistors (TFT) of poly and nano crystalline silicon have been made at temperature as low as 170°C on flexible PET (polyethylene terephthalate) substrates.The crystallization of the silicon film has been achieved using external mechanical stress assisted by a plasma hydrogenation technique. The formation of TFT is possible by means of a lateral crystallization of amorphous silicon under the channel region. High mobility TFTs with an electron mobility of 25cm2/Vs and an on/off ratio of 2000 have been obtained. Scanning electron microscopy, X-ray diffraction analysis and optical microscopy have been used to examine the crystallinity of the layer. In addition we report the deposition of high quality low-temperature silicon-oxide layers on PET substrates using an RF-plasma enhanced chemical vapor deposition unit with direct introduction of oxygen gas into the chamber and its reaction with Silane. Infrared spectroscopy was used to examine the quality of the oxide layer.

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