• Title/Summary/Keyword: porous silicon

Search Result 340, Processing Time 0.026 seconds

Fabrication and Characterization of Free-Standing DBR Porous Silicon Film

  • Um, Sungyong;Sohn, Honglae
    • Journal of Integrative Natural Science
    • /
    • v.7 no.1
    • /
    • pp.1-4
    • /
    • 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.

Preparation and Characterization of Porous Polymethylmethacrylate Film Showing Optical Reflectivity

  • Kim, Jihoon
    • Journal of Integrative Natural Science
    • /
    • v.6 no.2
    • /
    • pp.82-86
    • /
    • 2013
  • This paper describes a method for the preparation of porous polymethylmethacrylate showing optical reflectivity from the porous silicon template. A porous polymethylmethacrylate showing optical reflectivity was prepared by replicating porous silicon template which was obtained by applying a computer-generated periodic square current density and resulted in a mirror with high reflectivity in a specific narrow spectral region. A porous polymethylmethacrylate showing an excellent reflectivity was successfully obtained by dissolving the Porous silicon template from the porous polymethylmethacrylate composite film. A porous polymethylmethacrylate exhibited a sharp reflection resonance in the reflectivity spectrum. Surface image of the porous polymethylmethacrylate indicated that the surface of the porous polymethylmethacrylate film had a porous structure. These porous polymethylmethacrylate films in aqueous solutions were stable for several days without any degradation.

Asymmetric Flows for Porous Silicon Electroosmotic Pumps (다공성 실리콘막을 포함한 전기침투 방식 펌프에서의 비대칭적 인 유동)

  • Kim, Dae-Joong;Santiago, Juan G.
    • 한국전산유체공학회:학술대회논문집
    • /
    • 2008.03b
    • /
    • pp.703-704
    • /
    • 2008
  • We fabricated and tested porous silicon-based electroosmotic pumps. Compared to other pumping media, porous silicon is beneficial for obtaining comparable flow rates with much lowered electric potential, while maintaining enough mechanical properties. We fabricated porous silicon with two sided-reactive etching processes. We found higher flow rate per electric potential (consistent with previous studies) and we also found asymmetric flow rates for different pumping directions. We plan to utilize this asymmetry for AC pumping applications.

  • PDF

Formation and humidity-sensing properties of porous silicon oxide films by the electrochemical treatment (전기화학적 처리에 의한 다공질 실리콘 산화막의 형성과 감습 특성)

  • 최복길;민남기;류지호;성영권
    • The Transactions of the Korean Institute of Electrical Engineers
    • /
    • v.45 no.1
    • /
    • pp.93-99
    • /
    • 1996
  • The formation properties and oxidation mechanism of electrochemically oxidized porous silicon(OPS) films have been studied. To examine the humidity-sensitive properties of OPS films, surface-type and bulk-type humidity sensors were fabricated. The oxidized thickness of porous silicon layer(PSL) increases with the charge supplied during electrochemical humidity sensor shows high sensitivity at high relative humidity in low temperature. The sensitivity and linearity can be improved by optimizing a porosity of PSL. (author). refs., figs.

  • PDF

Fabrication and Characterization of Optically Encoded Porous Silicon Smart Particles

  • Sohn, Honglae
    • Journal of Integrative Natural Science
    • /
    • v.7 no.4
    • /
    • pp.221-226
    • /
    • 2014
  • Optically encoded porous silicon smart particles were successfully fabricated from the free-standing porous silicon thin films using ultrasono-method. DBR PSi was prepared by an electrochemical etch of heavily doped $p^{{+}{+}}$-type silicon wafer. DBR PSi was prepared by using a periodic pseudo-square wave current. The surface-modified DBR PSi was prepared by either thermal oxidation or thermal hydrosilylation. Free-standing DBR PSi films were generated by lift-off from the silicon wafer substrate using an electropolishing current. Free-standing DBR PSi films were ultrasonicated to create DBR-structured porous smart particles. Optical characteristics of porous smart particles were measured by FT-IR spectroscopy. The surface morphology of porous smart particles was determined by FE-SEM.

C-V Characteristics of Porous Silicon Alcohol Sensors with the Semi-transparent Electrode (반투명 전극으로 된 다공질 실리콘 알코올 가스 센서의 C-V 특성)

  • 김성진;이상훈
    • Proceedings of the IEEK Conference
    • /
    • 2003.07b
    • /
    • pp.1085-1088
    • /
    • 2003
  • In this work, we fabricated a gas-sensing device based on porous silicon(PS), and its I-V and C-V properties were investigated for sensing alcohol vapor. The structure of the sensor consists of thin Au/Oxidized porous silicon/porous silicon/Silicon/Al, where the silicon substrate is etched anisotropically to be prepared into a membrane shape. As the result, I-V curves showed typical tunneling property, and C-V curves were shaped like those of a MIS (metal-insulator- semiconductor) capacitor, where the capacitance in accumulation was increased with alcohol vapor concentration.

  • PDF

Fabrication and Characterization of DBR Porous Silicon Chip for the Detection of Chemical Nerve Agents

  • Jung, Kyoungsun
    • Journal of Integrative Natural Science
    • /
    • v.3 no.4
    • /
    • pp.237-240
    • /
    • 2010
  • Recently, number of studies for porous silicon have been investigated by many researchers. Multistructured porous silicon (PSi), distributed Bragg reflector (DBR) PSi, has been a topic of interest, because of its unique optical properties. DBR PSi were prepared by an electrochemical etch of $P^{{+}{+}}$-type silicon wafer of resistivity between 0.1 $m{\Omega}cm$ with square wave current density, resulting two different refractive indices. In this work, We have fabricated a simple and portable organic vapor-sensing device based on DBR porous silicon and investigated the optical characteristics of DBR porous silicon. DBR porous silicon have been characterized by FT-IR, Ocean optics 2000 spectrometer. The device used DBR PSi chip has been demonstrated as an excellent gas sensor, showing a great senstivity to a toxic vapor (TEP, DMMP, DEEP) at room temperature.

Fabrication and Characteristics of Porous Silicon (다공성 실리콘의 제조 및 특성에 관한 연구)

  • 이철환;조원일;백지흠;박성용;안춘호;유종훈;조병원;윤경석
    • Journal of the Korean institute of surface engineering
    • /
    • v.28 no.3
    • /
    • pp.182-191
    • /
    • 1995
  • A highly porous silicon layer was fabricated by anodizing single crystalline silicon in a dilute solution of hydrofluoric acid. The color of the porous silicon changed from red and blue to yellow gold during the anodizing process. The current-voltage (I-V) curve of the anodizing process showed a typical Schottky diode rectification form. The cell voltage decreased with the increase of HF concentration in the solution at high current range. However, the voltage was independent on HF concentration in the solution at low current range. The pore size was dependant on anodizing condition (HF concentration, current and anodizing time). The pore size and wall width of porous silicon layer were 4~6 and 1~3 nm, respectively. Surface of the porous silicon was covered with silicon compound ($SiH_x$etc.) according to IR spectrum analysis. The peak wavelength and width of photoluminescence (PL) spectrum of porous silicon were 650~850 nm (1.5~1.9 eV) and 250 nm, respectively. The photoluminescence intensity and peak wavelength, and porosity of porous silicon increased with increasing anodizing current and decreased with increasing HF concentration in the anodizing solution.

  • PDF

The research of anti-reflection coating using porous silicon for crystalline silicon solar cells (다공성 실리콘을 이용한 결정질 실리콘 태양전지 반사방지막에 관한 연구)

  • Lee, Jaedoo;Kim, Minjeong;Lee, Soohong
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2010.06a
    • /
    • pp.90.2-90.2
    • /
    • 2010
  • The crystalline silicon solar cells have been optical losses. but it can be reduced using light trapping by texture structure and anti-reflection coating. The high reflective index of crystalline silicon at solar wavelengths(400nm~1000nm) creates large reflection losses that must be compensated for by applying anti-reflection coating. In this study, the use of porous silicon(PSi) as an active material in a solar cell to take advantage of light trapping and blue-harvesting photoluminescence effect. Porous silicon is form by anodization and can be obtained in an electrolyte with hydrofluoric. We expect our research can results approaching to lower than 10% of several reflectance by porous silicon solar cells.

  • PDF

Hydrosilylation of Photoluminescent Porous Silicon with Aromatic Molecules; Stabilization of Photoluminescence and Anti-photobleaching Properties of Surface-Passivated Luminescent Porous Silicon

  • Sohn, Honglae
    • Journal of Integrative Natural Science
    • /
    • v.14 no.4
    • /
    • pp.147-154
    • /
    • 2021
  • A luminescent porous silicon sensor, whose surface was passivated with organic molecule via hydrosilylation under various conditions, has been researched to measure the photoluminescence (PL) stability of porous silicon (PSi). Photoluminescent PSi were synthesized by an electrochemical etching of n-type silicon wafer under the illumination with a 300 W tungsten filament bulb during the etching process. The PL of PSi displayed at 650 nm, which is due to the quantum confinement of silicon quantum dots in the PSi. To stabilized the photoluminescence of PSi, the hydrosilylation of PSi with silole molecule containg vinyl group was performed. Surface morphologies of fresh PSi and surface-modified PSi were obtained with a cold FE-SEM. Optical characterization of red photoluminescent silicon quantum dots was investigated by UV-vis and fluorescence spectrometer.