• 통합자연과학논문집
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• 제3권2호
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• pp.117-121
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• 2010

Silicon quantum dots base on photoluminescent porous silicon were prepared from an electrochemical etching of n-type silicon wafer (boron-dopped<100> orientation, resistivity of 1~10 ${\Omega}-cm$) and used as a alcohol sensor. Silicon quantum dots displayed an emission band at the wavelength of 675 nm with an excitation wavelength of 480 nm. Photoluminescence of silicon quantum dots was quenched in the presence of alcohol vapors such as methanol, ethanol, and isopropanol. Quenching efficiencies of 21.5, 32.5, and 45.8% were obtained for isopropanol, ethanol, and methanol, respectively. A linear relationship was obtained between quenching efficiencies and vapor pressure of analytes used. Quenching photoluminescence was recovered upon introducing of fresh air after the detection of alcohol. This provides easy fabrication of alcohol sensor based on porous silicon.

• 한국재료학회지
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• 제20권11호
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• pp.606-610
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• 2010

Films consisting of a silicon quantum dot superlattice were fabricated by alternating deposition of silicon rich silicon nitride and $Si_3N_4$ layers using an rf magnetron co-sputtering system. In order to use the silicon quantum dot super lattice structure for third generation multi junction solar cell applications, it is important to control the dot size. Moreover, silicon quantum dots have to be in a regularly spaced array in the dielectric matrix material for in order to allow for effective carrier transport. In this study, therefore, we fabricated silicon quantum dot superlattice films under various conditions and investigated crystallization behavior of the silicon quantum dot super lattice structure. Fourier transform infrared spectroscopy (FTIR) spectra showed an increased intensity of the $840\;cm^{-1}$ peak with increasing annealing temperature due to the increase in the number of Si-N bonds. A more conspicuous characteristic of this process is the increased intensity of the $1100\;cm^{-1}$ peak. This peak was attributed to annealing induced reordering in the films that led to increased Si-$N_4$ bonding. X-ray photoelectron spectroscopy (XPS) analysis showed that peak position was shifted to higher bonding energy as silicon 2p bonding energy changed. This transition is related to the formation of silicon quantum dots. Transmission electron microscopy (TEM) and electron spin resonance (ESR) analysis also confirmed the formation of silicon quantum dots. This study revealed that post annealing at $1100^{\circ}C$ for at least one hour is necessary to precipitate the silicon quantum dots in the $SiN_x$ matrix.

• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4185-4187
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• 2012

• 통합자연과학논문집
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• 제14권4호
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• pp.147-154
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• 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.

• 한국태양에너지학회 논문집
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• 제39권1호
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• pp.1-9
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• 2019

Light induced degradation is one of the major research challenges of hydrogenated amorphous silicon related thin film silicon solar cells. Amorphous silicon shows creation of metastable defect states, originating from elevated concentration of dangling bonds during light exposure. The metastable defect states work as recombination centers, and mostly affects quality of intrinsic layer in solar cells. In this paper we present results of light induced degradation in thin film silicon solar cells and discussion on physical origin, mechanism and practical solutions of light induced degradation in thin film silicon solar cells. In-situ light-soaking IV measurement techniques are presented. We also present thin film silicon material with silicon nano-quantum dots embedded within amorphous matrix, which shows superior stability during light-soaking. Our results suggest that solar cell using silicon nano-quantum dots in abosrber layer shows superior stability under light soaking, compared to the conventional amorphous silicon solar cell.

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1523-1528
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• 2014

Silicon quantum dots (Si QDs) were synthesized by etching silicon nanopowder with aqueous hydrofluoric acid (HF) and nitric acid ($HNO_3$). Then, the hydride-terminated Si QDs (H-Si QDs) were functionalized by 1- octadecene (ODE). By only controlling the etching time, the maximum luminescence peak of octadecylterminated Si QDs (ODE-Si QDs) was tuned from 404 nm to 507 nm. The average optical gap was increased from 2.60 eV (ODE-Si QDs-5 min) for 5 min of etching to 3.20 eV (ODE-Si QDs-15 min) for 15 min of etching, and to 3.40 eV (ODE-Si QDs-30 min) for 30 min of etching. The electron affinities (EA), ionization potentials (IP), and quasi-particle gap (${\varepsilon}^{qp}_{gap}$) of the Si QDs were determined by cyclic voltammetry (CV). The quasi-particle gaps obtained from the CV were in good agreement with the average optical gap values from UV-vis absorption. In the case of the ODE-Si QDs-30 min sample, the difference between the quasi-particle gap and the average optical gap gives the electron-hole Coulombic interaction energy. The additional electronic levels of the ODE-Si QDs-30 min and ODE-Si QDs-15 min samples determined by the CV results are interpreted to have originated from the Si=O bond terminating Si QD.

• 대한기계학회논문집A
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• 제39권7호
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• pp.653-657
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• 2015

표면확산계수의 활성화를 통한 실리콘-게르마늄(silicon-germanium) 양자점의 성장을 수치해석적으로 구현하였다. 실리콘 기판 위에 증착된 실리콘-게르마늄 박막의 성장을 표현하는 비선형 지배방정식을 유도하였으며, 확산계수를 온도의 함수로 고려하여 표면확산계수의 국소적 향상이 미치는 효과를 살펴보았다. 해석결과는 안정상태의 박막이 섭동될 때에 양자점이 자기조립되는 과정을 보여주며, 박막표면의 국소부위에 선택적으로 구조물이 성장하는 현상을 나타낸다. 본 연구는 바텀업(bottom-up) 방식이 내재적으로 지닌 불규칙성을 해결할 대안을 마련하여 양자기기를 위한 공정개발의 방향을 제시한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2002년도 제22회 학술발표회 초록집
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• pp.41-41
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• 2002

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.221-221
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• 2013

Striving to replace the well known silicon nanocrystals embedded in oxides with solution-processable charge-trapping materials has been debated because of large scale and cost effective demands. Herein, a silicon quantum dot-polystyrene nanocomposite (SiQD-PS NC) was synthesized by postfunctionalization of hydrogen-terminated silicon quantum dots (H-SiQDs) with styrene using a thermally induced surface-initiated polymerization approach. The NC contains two miscible components: PS and SiQD@PS, which respectively are polystyrene and polystyrene chains-capped SiQDs. Spin-coated films of the nanocomposite on various substrate were thermally annealed at different temperatures and subsequently used to construct metal-insulator-semiconductor (MIS) devices and thin film field effect transistors (TFTs) having a structure p-$S^{++}$/$SiO_2$/NC/pentacene/Au source-drain. C-V curves obtained from the MIS devices exhibit a well-defined counterclockwise hysteresis with negative fat band shifts, which was stable over a wide range of curing temperature ($50{\sim}250^{\circ}C$. The positive charge trapping capability of the NC originates from the spherical potential well structure of the SiQD@PS component while the strong chemical bonding between SiQDs and polystyrene chains accounts for the thermal stability of the charge trapping property. The transfer curve of the transistor was controllably shifted to the negative direction by chaining applied gate voltage. Thereby, this newly synthesized and solution processable SiQD-PS nanocomposite is applicable as charge trapping materials for TFT based memory devices.

• 통합자연과학논문집
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• 제8권3호
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• pp.147-152
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• 2015

Photoluminescent porous silicon (PSi) were prepared by an electrochemical etch of n-type silicon under the illumination with a 300 W tungsten filament bulb for the duration of etch. The red photoluminescence emitting at 620 nm with an excitation wavelength of 450 nm is due to the quantum confinement of silicon nanocrystal in porous silicon. As-prepared PSi was sonicated, fractured, and centrifuged in toluene to obtain photoluminescence silicon quantum dots. BET and BHJ methods were employed to study the specific surface area of as-prepared PSi. Optical characterization of red photoluminescent silicon nanocrystal was investigated by UV-vis and fluorescence spectrometer. Also SEM and TEM images of porous silicon and nanoparticles were investigated.