• Title/Summary/Keyword: porous silicon

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Detection of Nitroaromatic Compounds with Functionalized Porous Silicon Using Quenching Photoluminescence

  • Cho, Sungdong
    • Journal of Integrative Natural Science
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    • v.3 no.4
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    • pp.202-205
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    • 2010
  • Nanocrystalline porous silicon surfaces have been used to detect nitroaromatic compounds in vapor phase. The mode of photoluminescence is emphasized as a sensing attitude or detection technique. Quenching of photoluminescence from nanocrystalline porous surfaces as a transduction mode is measured upon the exposure of nitroaromatic compounds. Reversible detection mode for nitroaromatics is, too, observed. To verify the detection afore-mentioned, photoluminescent freshly prepared porous silicons are functionalized with different groups. The mechanism of quenching of photoluminescence is attributed to the electron transfer behaviors of quantum-sized nano-crystallites in the porous silicon matrix to the analytes(nitroaromatics). An attempt has been done to prove that the surface-derivatized photoluminescent porous silicone surfaces can act as versatile substrates for sensing behaviors due to having a large surface area and highly sensitive transduction mode.

Fabrication of Optically Images Using Nanostructured Photoluminescenct Porous Silicon (나노 구조를 갖는 다공성 실리콘의 광 발광성을 이용한 광학이미지 칩의 제작)

  • Jung, Daehyuk
    • Journal of Integrative Natural Science
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    • v.2 no.3
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    • pp.202-206
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    • 2009
  • Optical images based on the porous silicon exhibiting photoluminescence have been prepared from an electrochemical etching of n-type silicon wafer (boron-doped,<100> orientation, resistivity $1{\sim}10{\Omega}-cm$) by using a beam projector. The images remained in the substrate displayed an optical images correlating to the optical pattern and could be useful for optical data storage. This provides the ability to fabricate complex optical encoding in the surface of silicon.

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Enhancement of Analyte Ionization in Desoprtion/Ionization on Porous Silicon (DIOS)-Mass Spectrometry(MS)

  • Lee Chang-Soo;Kim Eun-Mi;Lee Sang-Ho;KIm Min-Soo;Kim Yong-Kweon;Kim Byug-Gee
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.10 no.3
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    • pp.212-217
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    • 2005
  • Desorption/ionization on silicon mass spectrometry (DIOS-MS) is a relatively new laser desorption/ionization technique for mass spectrometry without employing an organic matrix. This present study was carried to survey the experimental factors to improve the efficiency of DIOS-MS through electrochemical etching condition in structure and morphological properties of the porous silicon. The porous structure of silicon structure and its properties are crucial for the better performance of DIOS-MS and they can be controlled by the suitable selection of electrochemical conditions. The fabrication of porous silicon and ion signals on DIOS-MS were examined as a function of silicon orientation, etching time, etchant, current flux, irradiation, pore size, and pore depth. We have also examined the effect of pre- and post-etching conditions for their effect on DIOS-MS. Finally, we could optimize the electrochemical conditions for the efficient performance of DIOS-MS in the analysis of small molecule such as amino acid, drug and peptides without any unknown noise or fragmentation.

The sensing characteristics of MOPS structure based on porous silicon for ethanol gas (다공질규소를 이용한 MOPS 구조의 에탄올 감지 특성)

  • Sohn, Sihn-Young;Kim, Han-Jung;Lee, Ki-Won;Kim, Young-You
    • Journal of Sensor Science and Technology
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    • v.15 no.6
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    • pp.457-461
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    • 2006
  • To use the porous silicon as gas sensors, we made the MOPS structure from the porous silicon with Al evaporation and investigated the sensing characteristic of ethanol. When the MOPS structure is in contact with ethanol gas, the maximum peak of PL changes and it return to original intensity without contact. The MOPS structure had response time 0.78s and recovery time 4.13s when it is in contact with ethanol, which satisfied the required sensor standards. Further complimentary researches, however, are required to investigate the contact mechanism between MOPS structure and ethanol and to solve the surface contamination problem.

Improvement of Sensitivity in Porous Silicon Alcohol Gas Sensors by UV Light (자외선조사에 의한 다공질 실리콘 알코올 센서의 감도 개선)

  • Kim, Seong-Jin;Choe, Bok-Gil
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.9
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    • pp.676-680
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    • 1999
  • To do breath alcohol measurement, a sensor is necessary that it can detect low alcohol gas concentration of 0.01% at least. In this work, a capacitance-type alcohol gas sensor using porous silicon layer is developed to measure low alcohol gas concentration. The sensor using porous silicon layer has some sensitivity at room temperature by very large effective surface area, but there is still much room for improvement. In this experiment, we measured the capacitance of the sensor under 254 nm UV light on the porous silicon layer, in which alcohol solution was kept in a flask at 25, 35, and $45^{\circ}C$ by a heater. As the result, the improvement of sensitivity by illuminating UV light was observed. The increasing rate of the capacitance was shown to be double more than those measured under UV-off state. It is supposed that UV light activates response of the oriental and interfacial polarizations which have slow relaxation time for AC field.

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Fabrication and Mechanical Properties of Porous Silicon Carbide Ceramics from Silicon and Carbon Mixture (실리콘과 카본을 이용한 다공질 탄화규소의 제조와 기계적 특성)

  • Kim, Jong-Chan;Lee, Eun Ju;Kim, Deug-Joong
    • Journal of the Korean Ceramic Society
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    • v.50 no.6
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    • pp.429-433
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    • 2013
  • Silicon, carbon, and B4C powders were used as raw materials for the fabrication of porous SiC. ${\beta}$-SiC was synthesized at $1500^{\circ}C$ in an Ar atmosphere from a silicon and carbon mixture. The synthesized powders were pressed into disk shapes and then heated at $2100^{\circ}C$. ${\beta}$-SiC particles transformed to ${\alpha}$-SiC at over $1900^{\circ}C$, and rapid grain growth of ${\alpha}$-SiC subsequently occurred and a porous structure with elongated plate-type grains was formed. The mechanism of this rapid grain growth is thought to be an evaporation-condensation reaction. The mechanical properties of the fabricated porous SiC were investigated and discussed.

Investigation of the Changes of Fabry-Perot Fringe Patterns in Porous Silicon During Etching Process

  • Jang, Seunghyun
    • Journal of Integrative Natural Science
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    • v.5 no.1
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    • pp.13-17
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    • 2012
  • Changes of Fabry-Perot fringe patterns in porous silicon during etching process has been investigated. Four porous silicon samples were prepared with four different etch currents: (a) 10 $mA/cm^2$, (b) 30 $mA/cm^2$, (c) 50 $mA/cm^2$, (d) 100 $mA/cm^2$, respectively. Optical characterization of Fabry-Perot fringe pattern on porous silicon was achieved by Ocean optics 2000 spectrometer. The change of Fabry-Perot fringes was monitored and measured during the etching process. Fabry-Perot fringes pattern start to form after couple of minutes. As the etching time increased, more reflection peaks were observed. Its full width at half maximum (FWHM) decreased rapidly when the etching time increased.

Enhancement of Thermal Stability in Photoluminescence by Carbonization of Porous silicon (다공성실리콘의 탄화를 이용한 PL의 열적안정성 증진)

  • 최두진;서영제;전희준;박홍이;이덕희
    • Journal of the Korean Ceramic Society
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    • v.34 no.5
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    • pp.467-472
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    • 1997
  • Porous silicon was prepared by an anodic etching. The pore size was about 10 nm at an etching time of 20 sec and a current density of 20 mA/$\textrm{cm}^2$. The porous layer was composed of an micro-porous layer (0.6 ${\mu}{\textrm}{m}$) and a macro-porous layer (10 ${\mu}{\textrm}{m}$). Room temperature PL with maximum peak 6700$\AA$ appeared. The peak disappeared by an oxidation reaction when the porous silicon was heated to 100~20$0^{\circ}C$ in atmosphere. In order to avoid the oxidation a heat treatment was done in H2 atmosphere. The micro-pore and Si column, which formed quantum well, were collapsed by the high temperature. The PL maximum peak of heated sample was gradually red-shifted and showed about 300$\AA$ red-shift at 50$0^{\circ}C$. The intensity of PL was maintained to high temperatures in lower pressures. The porous Si was carbonized in C2H2+H2 gas in order to increase thermal stability. The carbonization of the porous Si prevented red-shift of the maximum PL peak caused by sintering effect at high temperatures, and the carbonized porous Si showed Pl signal at higher temperatures by above 20$0^{\circ}C$ than the sample in H2 atmosphere.

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A Study on Characteristics of Light Emitting Diode with Porous Silicon (다공성 실리콘을 이용한 LED의 발광 특성에 관한 연구)

  • Lee Sung-Hoon;Lee Chi-Woo
    • Journal of the Korean Electrochemical Society
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    • v.3 no.1
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    • pp.39-43
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    • 2000
  • The light emitting diode (LED) was fabricated from n-type porous silicon. We investigated both the current-voltage characteristics of the LED with various electrode materials and changes of electroluminescence with applied current density. Also we probed changes in electroluminescence as a function of operation time at a given current. In order to Improve the contact area between the electrode material and porous silicon layer, we deposited indium on porous silicon layer by electroplating and investigated the electric characteristics of the LED and changes of electroluminescence.

Detection of Nitroaromatic Compounds Based on Silicon Nanoparticles (실리콘 나노 입자를 이용한 니트로방향족 화합물의 탐지)

  • Song, Jinwoo
    • Journal of Integrative Natural Science
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    • v.2 no.1
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    • pp.37-40
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    • 2009
  • Synthesis and characterization of alkyl-capped nanocrystalline silicon (R-n-Si) have been achieved from the reaction of silicontetrachloride with magnesiumsilicide. Surface of silicon nanocrystal has been derivatized with various alkyl groups (R=methyl, n-butyl, etc.). Silicon nanoparticles have been also obtained by the sonication of luminescent porous silicon. Former exhibits an emission band at 360 nm, but latter exhibits an emission band at 680 nm. In this study very sensitive detection of TNT (2,4,6-trinitrotoluene), DNT (2,4-dinitrotoluene), NB (nitrobenzene), and PA (picric acid) has been achieved in gas phase with porous silicon using photoluminescence quenching of the silicon crystallites as a transduction mode. Porous silicon are electrochemically etched from crystalline silicon wafers in an aqueous solution of hydrofluoric acid. We have characterized these silicon nanoparticles by Luminescence Spectrometer (LS 55).

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