• Title/Summary/Keyword: porous n-Si

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Enhanced Photoelectrochemical Behavior of Gold-coated Porous n-Si Electrochemically Modified with Polyaniline

  • Park, Soo-Jin;Chae, Won-Seok;Kim, Kang-Jin
    • Analytical Science and Technology
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    • v.8 no.4
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    • pp.637-642
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    • 1995
  • The presence of a porous Si layer(PSL) formed on the surface of crystalline silicon by electrochemical etclling in HF solution is found to enhance the stability of n-Si photoanodes, but porous n-Si thus formed is still liable to corrode upon exposure to excitation light. To improve the stability of the porous n-Si electrodes and to reduce the photo-induced corrosion, we have examined the PEC behavior of porous n-Si modified with polyaniline(PANI) and 3 nm thick layer of Au. Comparisons were made between Au/PSL and PANl/Au/PSL photoelectrodes.

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Effects of In-situ doping Concentration on the Characteristics of Porous 3C-SiC Thin Films (In-situ 도핑량이 다공성 3C-SiC 박막의 특성에 미치는 영향)

  • Kim, Kang-San;Chung, Gwiy-Sang
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.6
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    • pp.487-490
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    • 2010
  • This paper describes the elecrtical and optical characteristics of $N_2$ doped porous 3C-SiC films. Polycrystalline 3C-SiC thin films are anodized by $HF+C_2H_5OH$ solution with UV-LED exposure. The growth of in-situ doped 3C-SiC thin films on p-type Si (100) wafers is carried out by using APCVD (atmospheric pressure chemical vapor deposition) with a single-precursor of HMDS (hexamethyildisilane: $Si_2(CH_3)_6)$. 0 ~ 40 sccm $N_2$ was used for doping. After the growth of doped 3C-SiC, porous 3C-SiC is formed by anodization with $7.1\;mA/cm^2$ current density for anodization time of 60 sec. The average pore diameter is about 30 nm, and etched area is increased with $N_2$ doping rate. These results are attributed to the decrease of crystallinity by $N_2$ doping. Mobility is dramatically decreased in porous 3C-SiC. The band gaps of polycrystalline 3C-SiC films and doped porous 3C-SiC are 2.5 eV and 2.7 eV, respectively.

Microstructures Of Continuously Porous SiC-Si3N4 Composites Fabricated Using Waste SiC Sludge (폐 SiC 슬러지를 이용하여 제조한 연속다공질 SiC-Si3N4 복합체의 미세조직)

  • Gain Asit Kumar;Lee Hee-Jung;Jang Hee-Dong;Lee Byong-Taek
    • Korean Journal of Materials Research
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    • v.15 no.3
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    • pp.177-182
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    • 2005
  • Large amounts of the waste SiC sludge containing small amounts of Si and organic lubricant were produced during the wire cutting process of the single silicon crystal ingots. The waste SiC sludge was purified by the washing process and the purified SiC powders were used to fabricate continuously porous $SiC-Si_3N_4$ composites using a fibrous monolithic process, in which carbon, $6wt\%\;Y_2O_3-2\;wt\%\;A1_2O_3$ and ethylene vinyl acetate were added as a pore-forming agent, sintering additives, and binder, respectively. In the burning-out process, carbon was fully removed and continuously porous $SiC-Si_3N_4$ composites were successfully fabricated. The green bodies containing SiC, Si particles and sintering additives were nitrided at $1410^{\circ}C$ in a flowing $N_2+10\%\;H_2$ gas mixture. Continuously porous composites were combined with SiC, ${\alpha}Si_3N_4,\;\beta-Si_3N_4$ and a few $\%$ of Fe phases. The pore size of the 2nd and the 3rd passed $SiC-Si_3N_4$ composites was $260\;{\mu}m$ and $35\;{\mu}m$ in diameter, respectively.

Thermal and Mechanical Properties of a N2 Doped Porous 3C-SiC Thin Film (질소가 도핑된 다공질 3C-SiC 박막의 열적, 기계적 특성)

  • Kim, Kang-San;Chung, Gwiy-Sang
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.8
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    • pp.651-654
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    • 2010
  • This paper describes the thermal and mechanical properties of doped thin film 3C-SiC and porous 3C-SiC. In this work, the in-situ doped thin film 3C-SiC was deposited by using atmospheric pressure chemical vapor deposition (APCVD) method at $120^{\circ}C$ using single-precursor hexamethyildisilane: $Si_2(CH_3)_6$ (HMDS) as Si and C precursors. 0~40 sccm $N_2$ gas was used as doping source. After growing of doped thin film 3C-SiC, porous structure was achieved by anodization process with 380 nm UV-LED. Anodization time and current density were fixed at 60 sec and 7.1 mA/$cm^2$, respectively. The thermal and mechanical properties of the $N_2$ doped porous 3C-SiC was measured by temperature coefficient of resistance (TCR) and nano-indentation, respectively. In the case of 0 sccm, the variations of TCR of thin film and porous 3C-SiC are similar, but TCR conversely changed with increase of $N_2$ flow rate. Maximum young's modulus and hardness of porous 3C-SiC films were measured to be 276 GPa and 32 Gpa at 0 sccm $N_2$, respectively.

Oxidation Mechanism of $Si_3N_4$ ($Si_3N_4$의 산화반응 기구)

  • 이홍림;최태운;김종우
    • Journal of the Korean Ceramic Society
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    • v.17 no.4
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    • pp.197-202
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    • 1980
  • The oxidation mechanism of the not sintered pellets and sintered bodies of $Si_3N_4$ was investigated. in air over the temperature range of 800~130$0^{\circ}C$. The $\beta$-cristobalite was instantaneously formed and covered the particles of powder packed in the not sintered and weakly sintered porous $Si_3N_4$ bodies by molecular diffusion of oxygen through the porous Si3N4 bodies and an immediate oxidation. The diffusion of oxygen ion through the formed $\beta$-cristobalite surface layer is assumed to control the further oxidation of the $Si_3N_4$ particles of the porous $Si_3N_4$ bodies. The diffusion coefficients and activation energies of oxygen ion through the $\beta$-cristobalite layer were obtained by the use of a derived equation.

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Microstructure Control and Mechanical Properties of Continuously Porous SiC-Si3N4 Composites (연속다공질 SiC-Si3N4 복합체의 미세구조 및 기계적 특성)

  • Paul Rajat Kanti;Gain Asit Kumar;Lee Hee-Jung;Jang Hee-Dong;Lee Byong-Taek
    • Korean Journal of Materials Research
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    • v.16 no.3
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    • pp.188-192
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    • 2006
  • The microstructures and mechanical properties of continuously porous $SiC-Si_3N_4$composites fabricated by multi-pass extrusion were investigated at different Si levels added. Si-powder with different weight percentages (0%, 5%, 10%, 15%, 20%) was added to the SiC powder to make the raw mixture powders, with $6wt%Y_2O_3-2wt%Al_2O_3$ as sintering additives, carbon ($10-15{\mu}m$) as a pore-forming agent, ethylene vinyl acetate as a binder and stearic acid ($CH_3(CH_2)_{16}COOH$) as a lubricant. In the continuously porous $SiC-Si_3N_4$ composites, $Si_3N_4$ whiskers like the hairs of nostrils were frequently observed on the wall of the pores. In this study, the morphology of the $Si_3N_4$ whiskers was investigated with the silicon addition content. In the composites containing of 10 wt% Si, a large number of $Si_3N_4$ whiskers was found at the continuous pore regions. In the sample to which 15 wt% Si powder was added, maximum values of about 101 MPa bending strength and 57.5% relative density were obtained.

Electrical and optical characteristics of porous 3C-SiC thin films with dopants (도핑량에 따른 다공성 3C-SiC 박막의 전기 및 광학적 특성)

  • Kim, Kan-San;Chung, Gwiy-Sang
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2010.06a
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    • pp.27-27
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    • 2010
  • This paper describes the electrical and optical characteristics of $N_2$ doped porous 3C-SiC films. Average pore diameter is about 30 nm and etched area was increased with $N_2$ doping rate. The mobility was dramatically decreased in porous 3C-SiC. The band gaps of polycrystalline 3C-SiC films and doped porous 3C-SiC were 2.5 eV and 2.7 eV, respectively.

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Microstructure Control of Porous In-situ Synthesized $Si_2N_2O-Si_3N_4$ Ceramics

  • Paul, Rajat Kanti;Lee, Chi-Woo;Kim, Hai-Doo;Lee, Byong-Taek
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.325-326
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    • 2006
  • Using $6wt%Y_2O_3-2wt%Al_2O_3$ as sintering additives and Si as a raw powder, the continuously porous in-situ $Si_2N_2O-Si_3N_4$ bodies were fabricated by multi-pass extrusion process and their microstructures were investigated depending on the addition of carbon (0-9wt%) in the mixture powder. The introduction of $Si_2N_2O$ fibers observed in the unidirectional continuous pores as well as in the pore-frame regions of the nitrided bodies can be an effective method in increasing the filtration efficiency. In the case of no carbon addition, the network type $Si_2N_2O$ fibers with high aspect ratio appeared in the continuous pores with diameters of 150-200 nm. However, in the case of 9wt% C addition, the fibers were found without any network type and had diameters of 200-250 nm.

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Optical Properties of Porous-Si Layers on Si-substrate and its Application of Polarization Devices (Porous Si layer의 광학특성과 편광소자에의 응용)

  • Koo, K.W.;Hwang, J.H.;Shiraishi, K.;Matsumura, K.
    • Proceedings of the KIEE Conference
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    • 1999.07e
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    • pp.2453-2455
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    • 1999
  • We propose that we use a porous-Si for a new spatial walk-off polarizing material with a large split angle. The beam-split an91e f is determined by the filling factor g(or porosity p) of the columnar dielectric substance and the slant angle $\theta$. Theoretically, by the assuming that $n_2$=3.5, and $n_1$=1 one can predict that a large split angle, up to $27^{\circ}$, is possible if one can construct such films with $Si.^{[3]}$ To accomplish this, we use porous-Si. As a result of theoretical simulation, the best structural parameters for attaining the maximum split angle $\phi$=$27.5^{\circ}$ are $\theta$=$58.7^{\circ}$ and p=57.6%.

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Effect of Si/Si3N4 Ratio on the Microstructure and Properties of Porous Silicon Nitrilde Prepared by SHS Methode (규소/질화규소 비가 자전연소합성공정을 이용한 다공질 질화규소 세라믹스의 미세구조와 특성에 미치는 영향)

  • Kim, Dong-Baek;Park, Dong-Soo;Hahn, Byung-Dong;Jung, Yeon-Gil
    • Journal of the Korean Ceramic Society
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    • v.44 no.6 s.301
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    • pp.338-342
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    • 2007
  • Porous silicon nitride ceramics were prepared by SHS (Self-Propagating High Temperature Synthesis) from silicon powder, silicon nitride powder and pore-forming precursor. The microstructure, porosity and the flexural strength of the porous silicon nitride ceramics were varied according to the Si/Si3N4 ratio, size and amount of the pore-forming precursors. Some sample exhibited as high flexural strength as $162{\pm}24\;MPa$. The high strength is considered to result from the fine pore size and the strong bonding amoung the silicon nitride particles.