• Title, Summary, Keyword: Porous Silicon

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Preparation and Optical Characterization of DBR/Host Dual Porous Silicon Containing DBR and Host Structures (DBR 다공성 실리콘과 Host 다공성 실리콘으로 이루어진 이중 다공성 실리콘의 제조와 광학적 특성)

  • Choi, Tae-Eun;Yang, Jinseok;Um, Sungyong;Jin, Sunghoon;Cho, Bomin;Cho, Sungdong;Sohn, Honglae
    • Journal of the Chosun Natural Science
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    • v.3 no.2
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    • pp.78-83
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    • 2010
  • DBR/Host dual porous silicons containing DBR and host structure were prepared and their optical properties were characterized using Ocean Optics spectrometer. In this dual porous silicon, single porous silicon layer was used as host layer for possible biomolecule and drug materials and DBR porous silicon layer was used for signal transduction due to the recognition of molecules. Optical reflection spectrum of dual porous silicon displayed only DBR reflection but Fabry-Perot fringe pattern. DBR reflection band of dual porous silicon shifted to the shorter wavelength as the etching time of host layer increased. Cross-sectional FE-SEM image of dual porous silicon displayed a thickness of about 20 micrometer for DBR porous silicon layer. Developed etching technology could be useful to prepare DBR porous silicon which exhibited specific reflection resonance at the required wavelength and to provide an label-free biosensors and drug delivery materials.

Well Defined One-Dimensional Photonic Crystal Templated by Rugate Porous Silicon

  • Lee, Sung Gi
    • Journal of the Chosun Natural Science
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    • v.6 no.3
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    • pp.183-186
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    • 2013
  • Well defined 1-dimentional (1-D) photonic crystals of polystyrene replicas have been successfully obtained by removing the porous silicon from the free-standing rugate porous silicon/phenylmethylpolysiloxane composite film. Rugate porous silicon was prepared by an electrochemical etching of silicon wafer in HF/ethanol mixture solution. Exfoliated rugate porous silicon was obtained by an electropolishing condition. A composite of rugate porous silicon/phenylmethylpolysiloxane composite film was prepared by casting a toluene solution of phenylmethylpolysiloxane onto the top of rugate porous silicon film. After the removal of the template by chemical dissolution, the phenylmethylpolysiloxane castings replicate the photonic features and the nanostructure of the master. The photonic phenylmethylpolysiloxane replicas are robust and flexible in ambient condition and exhibit an excellent reflectivity in their reflective spectra. The photonic band gaps of replicas are narrower than that of typical semiconductor quantum dots.

Reflectance spectrum properties of DBR and microcavity porous silicon (Distributed Bragg Reflector, Microcavity 구조를 갖는 다공질규소의 반사율 스펙트럼)

  • Kim, Young-You;Kim, Han-Jung
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.19 no.6
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    • pp.293-297
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    • 2009
  • In this paper, we made three kinds of porous silicon samples (single layer, distributed Bragg reflector, and microcavity) by electrochemical etching p-type silicon substrate. And then, we investigated their reflectance spectrum properties. We found that the number of fringe patterns and the maximum reflectivity of porous silicon multilayer increased compared with a porous silicon sinlge layer. In addition, we can observe that the DBR (distributed Bragg reflector) porous silicon has a full-width at half-maximum about 33 nm which is narrower than the porous silicon single layer and porous silicon microcavity.

Simply Modified Biosensor for the Detection of Human IgG Based on Protein AModified Porous Silicon Interferometer

  • Park, Jae-Hyun;Koh, Young-Dae;Ko, Young-Chun;Sohn, Hong-Lae
    • Bulletin of the Korean Chemical Society
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    • v.30 no.7
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    • pp.1593-1597
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    • 2009
  • A biosensor has been developed based on induced wavelength shifts in the Fabry-Perot fringes in the visible reflection spectrum of appropriately derivatized thin films of porous silicon semiconductors. Porous silicon (PSi) was generated by an electrochemical etching of silicon wafer using two electrode configurations in aqueous ethanolic HF solution. Porous silicon displayed Fabry-Perot fringe patterns whose reflection maxima varied spatially across the porous silicon. The sensor system studied consisted of a mono layer of porous silicon modified with Protein A. The system was probed with various fragments of an aqueous Human Immunoglobin G (Ig G) analyte. The sensor operated by measurement of the Fabry-Perot fringes in the white light reflection spectrum from the porous silicon layer. Molecular binding was detected as a shift in wavelength of these fringes.

Detection of Organic Vapors Using Change of Fabry-Perot Fringe Pattern of Surface Functionalized Porous Silicon (표면 기능성을 가진 다공성 실리콘의 Fabry-Perot fringe pattern의 변화를 이용한 유기 화합물의 감지)

  • Hwang, Minwoo;Cho, Sungdong
    • Journal of the Chosun Natural Science
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    • v.3 no.3
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    • pp.168-173
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    • 2010
  • Novel porous silicon chip exhibiting dual optical properties, both Frbry-Perot fringe (optical reflectivity) and photoluminescence had been developed and used as chemical sensors. Porous silicon samples were prepared by an electrochemical etch of p-type sillicon wafer (boron-doped, <100> orientation, resistivity 1 - 10 ${\Omega}$). The ething solution was prepared by adding an equal volume of pure ethanol to an aqueous solution of HF (48% by weight). The porous silicon was illuminated with a 300 W tungsten lamp for the duration of etch. Ething was carried out as a two-electrode Kithley 2420 preocedure at an anodic current. The surface of porous silicon was characterized by FT-IR instrument. The porosity of samples was about 80%. Three different types of porous silicon, fresh porous silicon (Si-H termianated), oxidized porous silicon (Si-OH terminated), and surface-derivatized porous silicon (Si-R terminated), were prepared by the thermal oxidation and hydrosilylation. Then the samples were exposed to the wapor of various organics vapors. such as chloroform, hexane, methanol, benzene, isopropanol, and toluene. Both reflectivity and photoluminescence were simultaneously measured under the exposure of organic wapors.

Analysis on Oxidation of Porous Silica Obtained from Thermal Oxidation of Porous Silicon (다공성 실리콘의 산화로부터 얻은 다공성 실리카의 산화에 대한 분석)

  • Koh, Young-Dae
    • Journal of the Chosun Natural Science
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    • v.3 no.3
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    • pp.153-156
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    • 2010
  • Oxidation behaviors of porous silicon were investigated by the measurement of area of $SiO_2$ vibrational peaks in FT-IR spectra during thermal oxidation of porous silicon at corresponding temperatures. Visible photoluminescent porous silicon samples were obtained from an electrochemical etch of n-type silicon of resistivity between 1-10 ${\Omega}/cm$. The etching solution was prepared by adding an equal volume of pure ethanol to an aqueous solution of HF. The porous silicon was illuminated with a 300 W tungsten lamp for the duration of etch. Etching was carried out as a two-electrode galvanostatic procedure at applied current density of 200 $mA/cm^2$ for 5 min. The porosity of samples prepared was about 80%. After formation of porous silicon, the samples were thermally oxidized at $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$, and $400^{\circ}C$, respectively. The growth rate of $SiO_2$ layer of porous silicon was investigated by using FT-IR spectroscopy. The effect of oxidation of porous silicon was presented.

Variation of the Nanostructural and Optical Features of Porous Silicon with pH Conditions (pH 조건에 따른 기공성 실리콘의 나노구조 및 광학적 특성의 변화)

  • Kim, Hyo-Han;Cho, Nam-Hee
    • Journal of the Korean Ceramic Society
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    • v.50 no.4
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    • pp.294-300
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    • 2013
  • The effect of chemical treatments of porous silicon in organic solvents on its nanostructural and optical features was investigated. When the porous Si was dipped in the organic solvent with various PH values, the morphological, chemical, and structural properties of the porous silicon was sensitively affected by the chemical conditions of the solvents. The size of silicon nanocrystallites in the porous silicon decreased from 5.4 to 3.1 nm with increasing pH values from 1 to 14. After the samples were dipped in the organic solvents, the Si-O-H bonding intensity was increased while that of Si-H bonding decreased. Photoluminescence peaks shifted to a shorter wavelength region in the range of 583 to 735 nm as the pH value increased. PL intensity was affected by the size as well as the volume fraction of the nanocrystalline silicon in the porous silicon.

A Novel Ultraviolet Sensor using Photoluminescent Porous Silicon (광 루미네슨스 다공질 실리콘을 이용한 새로운 자외선 센서)

  • Min, Nam-Gi;Go, Ju-Yeol;Gang, Cheol-Gu
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.50 no.9
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    • pp.444-449
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    • 2001
  • In this paper, a novel ultraviolet sensor is presented based on a photoluminescent porous silicon. Porous silicon layer was formed by chemical etching of surface of pn junction in a $HF(48%)-HNO_3(60%)-H_20$ solution. Incident ultraviolet(UV) light is converted to visible light by photoluminescent porous silicon layer, and then this visible light generates electron-hole pairs in the pn junction, which produces a photocurrent flow through the device. In order to maximize detection efficiency, the peak sensitivity wavelength of the pn junction diode was matched with the peak wavelength of Photoluminescence from porous silicon layer. The porous silicon ultraviolet sensor showed a large output current as UV intensity increases and but very low sensitivity to visible light. The detection sensitivity of porous silicon sensor was calculated as 2.91mA/mW. These results are expected to open up a possibility that the present porous silicon sensor can be used for detecting UV light in a visible background, compared to silicon UV detectors which have an undesirable response to visible light.

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Photoluminescence of Porous Silicon According to Various Etching Times and Various Applied Current Densities (식각시간 및 식각전류에 따른 다공성 실리콘의 발광 특성에 대한 조사)

  • Han, Jungmin
    • Journal of the Chosun Natural Science
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    • v.3 no.3
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    • pp.148-152
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    • 2010
  • Photoluminescence properties and surface morphologies of porous silicon etched with various applied current densities at fixed etching times. FE-SEM image of porous silicon surface indicated that the porous silicon prepared at currents below 200 mA exhibited very bright red photoluminescence properties. As the applied current densities increased, the photoluminescence efficiencies of porous silicon prepared at applied current densities above 300 mA decreased, and displayed the cracked surface on porous silicon. This cracked surface start to collapsed to give cracked domains.

Fabrication and Characterization of Free-Standing DBR Porous Silicon Film

  • Um, Sungyong;Sohn, Honglae
    • Journal of the Chosun Natural Science
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    • v.7 no.1
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    • pp.1-4
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    • 2014
  • Distributed Bragg reflector porous silicon of different characteristics were formed to determine their optical constants in the visible wavelength range using a periodic square wave current between low and high current densities. The surface and cross-sectional SEM images of distributed Bragg reflector porous silicon were obtained using a cold field emission scanning electron microscope. The surface image of distributed Bragg reflector porous silicon indicates that the distributions of pores are even. The cross-sectional image illustrates that the multilayer of distributed Bragg reflector porous silicon exhibits a depth of few microns and applying of square current density during the etching process results two distinct refractive indices in the contrast. Distributed Bragg reflector porous silicon exhibited a porosity depth profile that related directly to the current-time profile used in etch. Its free-standing film was obtained by applying an electro-polishing current.