• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.181-181
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• 2016

Hydrogenated microcrystalline silicon (${\mu}c-Si:H$) films have attracted much attention as materials of the bottom-cells in Si thin film tandem photovoltaics due to their low bandgap and excellent stability against light soaking. However, in PECVD, the source gas $SiH_4$ must be highly diluted by $H_2$, which eventually results in low deposition rate. Moreover, it is known that high-rate ${\mu}c-Si:H$ growth is usually accompanied by a large number of dangling-bond (DB) defects in the resulting films, which act as recombination centers for photoexcited carriers, leading to a deterioration in the device performance. During film deposition, Si nanoparticles generated in $SiH_4$ discharges can be incorporated into films, and such incorporation may have effects on film properties depending on the size, structure, and volume fraction of nanoparticles incorporated into films. Here we report experimental results on the effects of nonoparticles incorporation at the different substrate temperature studied using a multi-hollow discharge plasma CVD method in which such incorporation can be significantly suppressed in upstream region by setting the gas flow velocity high enough to drive nanoparticles toward the downstream region. All experiments were performed with the multi-hollow discharge plasma CVD reactor at RT, 100, and $250^{\circ}C$, respectively. The gas flow rate ratio of $SiH_4$ to $H_2$ was 0.997. The total gas pressure P was kept at 2 Torr. The discharge frequency and power were 60 MHz, 180 W, respectively. Crystallinity Xc of resulting films was evaluated using Raman spectra. The defect densities of the films were measured with electron spin resonance (ESR). The defect density of fims deposited in the downstream region (with nonoparticles) is higher defect density than that in the upstream region (without nanoparticles) at low substrate temperature of RT and $100^{\circ}C$. This result indicates that nanoparticle incorporation can change considerably their film properties depending on the substrate temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.320-323
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• 2018

SiGe thin films were deposited by remote plasma enhanced chemical vapor deposition (RPE-CVD) at $400^{\circ}C$ using $SiH_4$ or $SiCl_4$ and $GeCl_4$ as the source of Si and Ge, respectively. The growth rate and the degree of crystallinity of the fabricated films were characterized by scanning electron microscopy and Raman analysis, respectively. The optical and electrical properties of SiGe films fabricated using $SiCl_4$ and $SiH_4$ source were comparatively studied. SiGe films deposited using $SiCl_4$ source showed a lower growth rate and higher crystallinity than those deposited using $SiH_4$ source. Ultraviolet and visible spectroscopy measurement showed that the optical band gap of SiGe is in the range of 0.88~1.22 eV.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.60-67
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• 2017

In this study, we performed surface modification of biodegradable microcrystalline cellulose (MCC) to use as a filler in polyethylene (PE) composite in food packaging application. We modified MCC surface with (3-trimethoxysilylpropyl)diethylenetriamine (TPDT) silane coupling agent, which has one primary amino group and two secondary amino groups per molecule, to introduce amino groups with a carbon dioxide adsorption capability in MCC. Effects of each of the reaction conditions such as amount of TPDT introduced, swelling time, reaction temperature, and reaction time on surface modification degree of MCC were investigated by changing a variety of above reaction conditions. The amount of TPDT grafted on MCC surface and formation of chemical bonds were confirmed by Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and solid state $^{29}Si$ nuclear magnetic resonance (NMR) spectroscopy. We confirmed increase of grafted amount of TPDT on MCC with increasing reaction time, reaction temperature, and amount of introduced TPDT.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.13-13
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• 2010

The solar energy conversion will take 10 % global energy need by 2033. A thin film type solar cell has been considered as one of the promising candidates for a large area applicable solar cell fabrication at a low cost. The metal-assisted growth of microcrystalline Si (mc-Si) films has been reported for a quality Si film synthesis at a low temperature. It discusses the spontaneous growth of a Si film above a metal-layer for a thin film solar cell. Quite recently, a substantial demand of nanomaterials has been addressed for cost-effective solar cells. The nanostructure provides a large photoactive surface at a fixed volume, which is an advantage in the effective use of solar power. But the promising of nanostructure active solar cell has not been much fulfilled due mainly to the difficulty in architecture of nanostructures. We present here the Si nanowire (SiNW)-embedded Schottky solar cell. Multiple SiNWs were connected to two different metals to form a Schottky or an ohmic contact according to the metal work function values. It discusses the scheme of rectifying contact between metals and SiNWs and the SiNW-embedded Schottky solar cell performances.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.130-130
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• 2010

Thin Si films were grown by a plasma-enhanced chemical vapor deposition (PECVD, SNTEK, Korea) system. Two different deposition condition were applied and formed a fully amorphous Si (a-Si) film and a micromorph mixing of microcrystalline Si (mc-Si) and a-Si film. Under one sun illumination, the micromorph device provided the enhanced open circuit voltage and fill factor values. It presents the fabrication of the micromorph Si film and the a-Si film by modulating a deposition condition. The performances of the Si thin film Schottky solar cells are discussed.

• Journal of Information Display
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• v.9 no.2
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• pp.5-8
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• 2008

Bottom gate thin film transistors (TFTs) with microcrystalline and amorphous Si (a-Si) double active layers (DAL) were fabricated. Since the process of DAL TFTs can use that of conventional a-Si TFTs, these DAL TFT process has advantages, such as low cost, large substrate, and mass production capacity. In order to analyze the degradation characteristics in saturation region for driving TFTs of active matrix organic light emitting diode, three different dynamic stresses were applied to DAL TFTs and a-Si TFTs. The threshold voltage shift of DAL TFTs and a-Si TFTs during 10,000 second stress is 0.3V and 2V, respectively. DAL TFTs were more reliable than a-Si TFTs.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.66.1-66.1
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• 2010

Microcrystalline silicon at low temperatures has been developed using plasma enhanced chemical vapor deposition (PECVD). It has been found that energetically positive ion and atomic hydrogen collision on to growing surface have important effects on increasing growth rate, and atomic hydrogen density is necessary for the increasing growth rate correspondingly, while keeping ion bombardment is less level. Since the plasma potential is determined by working pressure, the ion energy can be reduced by increasing the deposition pressure of 700-1200 Pa. Also, correlation of the growth rate and crystallinity with deposition parameters such as working pressure, hydrogen flow rate and input power were investigated. Consequently an efficiency of 7.9% was obtained at a high growth rate of 0.92 nm/s at a high RF power 300W using a plasma-enhanced chemical vapor deposition method (27.12MHz).

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.228-231
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• 2006

This paper briefly introduces silicon based thin film solar cells: amorphous (a-Si:H), microcrystalline ${\mu}c-Si:H$ single junction and $a-Si:H/{\mu}c-Si:H$ tandem solar cells. The major difference of a-Si:H and ${\mu}c-Si:H$ cells comes from electro-optical properties of intrinsic Si-films (active layer) that absorb incident photon and generate electron-hole pairs. The a-Si:H film has energy band-gap (Eg) of 1.7-1.8eV and solar cells incorporating this wide Eg a-Si:H material as active layer commonly give high voltage and low current, when illuminated, compared to ${\mu}c-Si:H$ solar cells that employ low Eg (1.1eV) material. This Eg difference of two materials make possible tandem configuration in order to effectively use incident photon energy. The $a-Si:H/{\mu}c-Si:H$ tandem solar cells, therefore, have a great potential for low cost photovoltaic device by its various advantages such as low material cost by thin-film structure on low cost substrate instead of expensive c-Si wafer and high conversion efficiency by tandem structure. In this paper, the structure, process and operation properties of Si-based thin-film solar cells are discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.322.1-322.1
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• 2014

Many research groups have studied tandem or multi-junction cells to overcome this low efficiency and degradation. In multi-junction cells, band-gap engineering of each absorb layer is needed to absorb the light at various wavelengths efficiently. Various absorption layers can be formed using multi-junctions, such as hydrogenated amorphous silicon carbide (a-SiC:H), amorphous silicon germanium (a-SiGe:H) and microcrystalline silicon (${\mu}c$-Si:H), etc. Among them, ${\mu}c$-Si:H is the bottom absorber material because it has a low band-gap and does not exhibit light-induced degradation like amorphous silicon. Nevertheless, ${\mu}c$-Si:H requires a much thicker material (>2 mm) to absorb sufficient light due to its smaller light absorption coefficient, highlighting the need for a high growth rate for productivity. ${\mu}c$-SiGe:H has a much higher absorption coefficient than ${\mu}c$-Si:H at the low energy wavelength, meaning that the thickness of the absorption layer can be decreased to less than half that of ${\mu}c$-Si:H. ${\mu}c$-SiGe:H films were prepared using 40 MHz very high frequency PECVD method at 1 Torr. SiH4 and GeH4 were used as a reactive gas and H2 was used as a dilution gas. In this study, the ${\mu}c$-SiGe:H layer for triple solar cells applications was performed to optimize the film properties.

• Applied Microscopy
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• v.21 no.2
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• pp.57-66
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• 1991

The main purpose of this paper was to investigate the change of rapidly solidified microstructures and dispersoid behavior according to heat-treatment in the Al-Fe-V-Si-(Mn) alloys. It was found that (111) preferred orientation identified by X-ray diffraction and fine subgrain/large grain were observed in the rapidly solidified Al-Fe-V-Si-(Mn) alloys. Cell boundary of the zone A was composed of the microcrystalline, whereas that of the zone B was amorphous. Decomposition of the Al-Fe-V-Si-(Mn) alloys occurred at about $300^{\circ}C$. These alloys exhibited excellent thermal stability at the elevated temperature. Microstructure of the zone B was more stable than that of the zone A. The spherical dispersoid and 5-fold symmetry phase was also more thermally stable than the amorphous structure of cell boundary.