• Title/Summary/Keyword: porous silicon

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Characterization of Microstructure on Porous Silicon Carbide Prepared by Polymer Replica Template Method (고분자 복제 템플릿 방법을 이용하여 제조된 다공성 탄화규소의 미세구조 특성)

  • Lee, Yoon Joo;Kim, Soo Ryong;Kim, Young Hee;Shin, Dong Geun;Won, Ji Yeon;Kwon, Woo Teck
    • Journal of the Korean Ceramic Society
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    • v.51 no.6
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    • pp.539-543
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    • 2014
  • Foam type porous silicon carbide ceramics were fabricated by a polymer replica method using polyurethane foam, carbon black, phenol resin, and silicon powder as raw materials. The influence of the C/Si mole ratio of the ceramic slurry and heat treatment temperature on the porous silicon carbide microstructure was investigated. To characterize the microstructure of porous silicon carbide ceramics, BET, bulk density, X-ray Powder Diffraction (XRD), and Scanning Electron Microscope (SEM) analyses were employed. The results revealed that the surface area of the porous silicon carbide ceramics decreases with increased heat treatment temperature and carbon content at the $2^{nd}$ heat treatment stage. The addition of carbon to the ceramic slurry, which was composed of phenol resin and silicon powder, enhanced the direct carbonization reaction of silicon. This is ascribed to a consequent decrease of the wetting angles of carbon to silicon with increasing heat treatment temperature.

Investigation of the crystalline silicon solar cells with porous silicon layer (다공성 실리콘 막을 적용한 결정질 실리콘 태양전지 특성 연구)

  • Lee, Eun-Joo;Lee, Il-Hyung;Lee, Soo-Hong
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.06a
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    • pp.295-298
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    • 2007
  • Reduction of optical losses in crystalline silicon solar cells by surface modification is one of the most important issues of silicon photovoltaics. Porous Si layers on the front surface of textured Si substrates have been investigated with the aim of improving the optical losses of the solar cells, because an anti-reflection coating(ARC) and a surface passivation can be obtained simultaneously in one process. We have demonstrated the feasibility of a very efficient porous Si ARC layer, prepared by a simple, cost effective, electrochemical etching method. Silicon p-type CZ (100) oriented wafers were textured by anisotropic etching in sodium carbonate solution. Then, the porous Si layers were formed by electrochemical etching in HF solutions. After that, the properties of porous Si in terms of morphology, structure and reflectance are summarized. The structure of porous Si layers was investigated with SEM. The formation of a nanoporous Si layer about 100nm thick on the textured silicon wafer result in a reflectance lower than 5% in the wavelength region from 500 to 900nm. Such a surface modification allows improving the Si solar cell characteristics. An efficiency of 13.4% is achieved on a monocrystalline silicon solar cell using the electrochemical technique.

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Nano-porous Silicon Microcavity Sensors for Determination of Organic Fuel Mixtures

  • Pham, Van Hoi;Bui, Huy;Hoang, Le Ha;Nguyen, Thuy Van;Nguyen, The Anh;Pham, Thanh Son;Ngo, Quang Minh
    • Journal of the Optical Society of Korea
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    • v.17 no.5
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    • pp.423-427
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    • 2013
  • We present the preparation and characteristics of liquid-phase sensors based on nano-porous silicon multilayer structures for determination of organic content in gasoline. The principle of the sensor is a determination of the cavity-resonant wavelength shift caused by refractive index change of the nano-porous silicon multilayer cavity due to the interaction with liquids. We use the transfer matrix method (TMM) for the design and prediction of characteristics of microcavity sensors based on nano-porous silicon multilayer structures. The preparation process of the nano-porous silicon microcavity is based on electrochemical etching of single-crystal silicon substrates, which can exactly control the porosity and thickness of the porous silicon layers. The basic characteristics of sensors obtained by experimental measurements of the different liquids with known refractive indices are in good agreement with simulation calculations. The reversibility of liquid-phase sensors is confirmed by fast complete evaporation of organic solvents using a low vacuum pump. The nano-porous silicon microcavity sensors can be used to determine different kinds of organic fuel mixtures such as bio-fuel (E5), A92 added ethanol and methanol of different concentrations up to 15%.

Chemical and Physical Properties of Porous Silicon

  • Jang, Seunghyun
    • Journal of Integrative Natural Science
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    • v.4 no.1
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    • pp.1-6
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    • 2011
  • The properties of porous silicon, such as substrate properties, porosity, thickness, refractive index, surface area, and optical properties of porous silicon were reviewed. Some properties, such as porosity, refractive index, thickness, pore diameter, multi-structures, and optical properties, are strongly dependent on the anodization process parameters. These parameters include HF concentration, current density, anodization time, and silicon wafer type and resistivity.

Development of Capacitance-type Humidity Sensors Using Porous Silicon Layer (다공질 실리콘층을 이용한 정전용량형 습도센서의 개발)

  • Kim, Seong-Jeen;Lee, Ju-Hyuk;Yoon, Yeo-Kyung;Choi, Bok-Gil
    • Proceedings of the KIEE Conference
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    • 1998.11c
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    • pp.1014-1016
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    • 1998
  • A capacitance-type humidity sensor using porous silicon layer is developed. The unique property of this sensor is a structure which has electrodes on the surface of the wafer like a general IC device. To do this. the sensor was fabricated using process such as localized formation of porous silicon, oxidation of porous silicon layer, and etching of oxidized porous silicon layer. The measurement of humidity-sensing ability was done for two type of sensors using porous silicon layer formed in 25 and 35% HF solutions, respectively. As the result, the former sensors showed larger value and variation of capacitance for the relative humidity.

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Characterization and Surface-Derivatization of Porous Silicon

  • Lee, Bo-Yeon;Hwang, Min-Woo;Cho, Hyun;Kim, Hee-Chol;Jang, Seunghyun
    • Journal of Integrative Natural Science
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    • v.4 no.3
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    • pp.182-186
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    • 2011
  • Chemical modification of porous silicon surface has been investigated to have different physical surface properties. Porous silicon modified with dodecyl functionality exhibits hydrophobic feature, however the oxidation of porous silicon to modify with hydroxyl group displays hydrophilic properties. Surface characterization for both dodecyl and hydroxyl derivatized porous silicon was investigated by FT-IR spectroscopy. To determine the surface coverage, the amine functionalized surface was reduced by dithiothreitol (DTT) and the released 2-thiopyridone was quantified by UV/vis spectroscopy.

Fabrication of Porous Silicon Using Electrochemical Etching (전기화학적 식각을 이용한 다공성 실리콘 제조)

  • Jin, Dong-Woo;No, Sang-Soo;Kim, Gue-Hyun;Chung, Gwiy-Sang
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.04b
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    • pp.121-124
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    • 2004
  • The research on the porous silicon having low wafer stress during the oxidation process in IPOS(Isolation by Porous Oxidized Silicon) were carried out. Fine pores with less than 100A of diameter were found in the porous silicon which from p-type Si by electrochemical etching. In this study, it is possible to make the porous silicon with 59% of porosity.

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Detection of Voletile Organic Compounds by Using DBR Porous Silicon (DBR 다공성 실리콘을 이용한 휘발성 유기화합물의 감지)

  • Park, Cheol Young
    • Journal of Integrative Natural Science
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    • v.2 no.4
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    • pp.275-279
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    • 2009
  • Recently, number of studies for porous silicon (PSi) have been investigated by many researchers. Multistructured porous silicon such as a distributed Bragg reflector (DBR) PSi, has been a topic of interest, because of its unique optical properties. DBR PSi were prepared by using an electrochemical etch of $P{^+}{^+}$-type silicon wafer with resistivity between 0.1 and $10m{\Omega}cm$. The electrochemical etch with square wave current density results in two different refractive indices in the porous layer. In this work, DBR porous silicon chips for a simple and portable organic vapor-sensing device have fabricated. The optical characteristics of DBR PSi have been investigated. DBR porous silicon have been characterized by FT-IR and Ocean optics 2000 spectrometer. The device used DBR PSi chip has been demonstrated as an excellent gas sensor, showing a great senstivity to organic vapor at room temperature.

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Second Harmonic Generation on the Surface of Porous Silicon Superlattice (초격자 다공질규소 표면에서 제 2고조파 발생)

  • Cho, Chang-Ho;Park, Jong-Dae
    • The Journal of Natural Sciences
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    • v.12 no.1
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    • pp.31-39
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    • 2002
  • Second harmonic generation was measured in porous silicon superlattices surface which were made by changing and anodization current density and the anodization time periodically in the process of obtaining porous silicon. The technique of second harmonic generation is used as a probe to the surface of porous silicon superlattice by using Nd:YAG laser. We have investigated the surface structure and nonlinear-optics properties of porous silicon superlattice.

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Investigation of the surface structure improvement to reduce the optical losses of crystalline silicon solar cells (결정질 실리콘 태양전지의 광학적 손실 감소를 위한 표면구조 개선에 관한 연구)

  • Lee Eun-Joo;Lee Soo-Hong
    • New & Renewable Energy
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    • v.2 no.2 s.6
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    • pp.4-8
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    • 2006
  • Reduction of optical losses in crystalline silicon solar cells by surface modification is one of the most important issues of silicon photovoltaics. Porous Si layers on the front surface of textured Si substrates have been investigated with the aim of improving the optical losses of the solar cells, because an anti-reflection coating and a surface passivation can be obtained simultaneously in one process. We have demonstrated the feasibility of a very efficient porous Si AR layer, prepared by a simple, cost effective, electrochemical etching method. Silicon p-type CZ (100) oriented wafers were textured by anisotropic etching in sodium carbonate solution. Then, the porous Si layer were formed by electrochemical etching in HF solutions. After that, the properties of porous Si in terms of morphology, structure and reflectance are summarized. The surface morphology of porous Si layers were investigated using SEM. The formation of a porous Si layer about $0.1{\mu}m$ thick on the textured silicon wafer result in an effective reflectance coefficient Reff lower than 5% in the wavelength region from 400 to 1000nm. Such a surface modification allows improving the Si solar cell characteristics.

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