• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.117-117
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• 2012

Si:Ge alloy semiconductor nanocrystals (NCs) offer challenging opportunities for integrated optoelectronics/optoplasmonics, since they potentially allow unprecedentedly strong light-matter interaction in the wavelength range of the optical communication. In this talk, we discuss the recent research efforts of my laboratory to develop optoelectronic components based on individual group IV NCs. We present experimental demonstration of the individual NC optoelectronic devices, including broadband Si:Ge nanowire (NW) photodetectors, intra NW p-n diodes, Ge NC electrooptical modulators and near-field plasmonic NW detectors, where the unique size effects at the nanometer scales commonly manifest themselves. In particular, we demonstrated a scanning photocurrent imaging technique to investigate dynamics of photocarriers in individual Si:Ge NWs, which provides spatially and spectrally resolved local information without ensemble average. Our observations represent inherent size-effects of internal gain in semiconductor NCs, thereby provide a new insight into nano optoplasmonics.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1708-1709
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• 2011

본 논문에서는 Ambipolar 실리콘 나노와이어 FET (SiNW FET)의 빛을 통한 모듈래이션을 분석하였다. Ambipolar SiNW FET를 얻기 위해서는 나노와이어가 저농도로 도핑된 실리콘이어야 한다. 실리콘의 비등방성 습식식각 이후, 산화 공정을 통한 나노와이어 제작을 통해 보론의 확산을 통해 저농도로 도핑된 실리콘 나노와이어를 제작하였다. 빛이 조사될 시에 생기는 Ambipolar SiNW FET의 모듈래이션 특성에 관해 분석하고 간단한 응용 실험을 통하여 검증하였다. 응용 실험 결과 pH 센싱의 감도는 빛을 10000 lux 조사할 경우 8.84 배 증가하였다.

• Advances in nano research
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• v.7 no.2
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• pp.99-108
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• 2019

Higher-order theories are very important to investigate the mechanical properties and behaviors of nanoscale structures. In this study, a free vibration behavior of SiNW resting on elastic foundation is investigated via Eringen's nonlocal elasticity theory. Silicon Nanowire (SiNW) is modeled as simply supported both ends and clamped-free Euler-Bernoulli beam. Pasternak two-parameter elastic foundation model is used as foundation. Finite element formulation is obtained nonlocal Euler-Bernoulli beam theory. First, shape function of the Euler-Bernoulli beam is gained and then Galerkin weighted residual method is applied to the governing equations to obtain the stiffness and mass matrices including the foundation parameters and small scale parameter. Frequency values of SiNW is examined according to foundation and small scale parameters and the results are given by tables and graphs. The effects of small scale parameter, boundary conditions, foundation parameters on frequencies are investigated.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.13-13
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• 2010

The solar energy conversion will take 10 % global energy need by 2033. A thin film type solar cell has been considered as one of the promising candidates for a large area applicable solar cell fabrication at a low cost. The metal-assisted growth of microcrystalline Si (mc-Si) films has been reported for a quality Si film synthesis at a low temperature. It discusses the spontaneous growth of a Si film above a metal-layer for a thin film solar cell. Quite recently, a substantial demand of nanomaterials has been addressed for cost-effective solar cells. The nanostructure provides a large photoactive surface at a fixed volume, which is an advantage in the effective use of solar power. But the promising of nanostructure active solar cell has not been much fulfilled due mainly to the difficulty in architecture of nanostructures. We present here the Si nanowire (SiNW)-embedded Schottky solar cell. Multiple SiNWs were connected to two different metals to form a Schottky or an ohmic contact according to the metal work function values. It discusses the scheme of rectifying contact between metals and SiNWs and the SiNW-embedded Schottky solar cell performances.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.9
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• pp.621-627
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• 2016

In this study, we present a model that can be used to calculate the phonon-surface scattering rate directly from the experimental data on phonon mean free path (MFP) spectra of nanostructures. Using this model and the recently reported length-dependent thermal conductivity measurements on $Si_{0.9}Ge_{0.1}$ nanowires (NWs), we investigate the spectral reduced MFP distribution and the spectral phonon-surface scattering rate in the $Si_{0.9}Ge_{0.1}$ NWs. From the results, it is found that the phonon transport properties with the material and the phonon frequency dependency of the spectral phonon-surface scattering rate per unit length of the NW. The model presented in this study can be used for developing heat transfer analysis models of nanomaterials, and for determining the optimum design for tailoring the heat transfer characteristics of nanomaterials for future applications of phonon nanoengineering.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.1
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• pp.105-108
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• 2011

Newly-developed fabrication of a p-n heterojunction diode constructed with a p-Si nanowire (NW) and an n-ZnO nanoparticle (NP) thin-film by the dielectrophoresis (DEP) technique is demonstrated in this study. With the bias of 20 Vp-p at the input frequency of 1 MHz, the most efficient assembly of the n-ZnO NPs is shown for the fabrication of the p-n heterojunction diode with a p-Si NW. The p-n heterojunction diode fabricated in this study represents current rectifying characteristics with the turn on voltage of 1.1 V. The diode can be applied to the fabrication of optoelectrical devices such as photodetectors, light-emitting diodes (LEDs), or solar cells based on the high conductivity of the NW and the high surface to volume ratio of the NP thin film.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.26.1-26.1
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• 2011

We investigated the atomic layer deposition (ALD) process for nitrogen doped ZnO and the application for n-ZnO : N/p-Si (NW) coaxial hetero-junction photodetectors. ALD ZnO:N was deposited using diethylzinc (DEZ) and diluted $NH_4OH$ at $150^{\circ}C$ of substrate temperature. About 100~300 nm diameter and 5 um length of Si nanowires array were prepared using electroless etching technique in 0.108 g of $AgNO_3$ melted 20 ml HF liquid at $75^{\circ}C$. TEM images showed ZnO were deposited on densely packed SiNW structure achieving extraordinary conformality. When UV (360 nm) light was illuminated on n-ZnO:N/p-SiNW, I-V curve showed about three times larger photocurrent generation than film structure at 10 V reverse bias. Especially, at 660 nm wave length, the coaxial structure has 90.8% of external quantum efficiency (EQE) and 0.573 A/W of responsivity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.77-78
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• 2009

We report numerical simulations to investigate of the dependence of the on/off current ratio and channel charge distributions in silicon nanowire (SiNW) field-effect transistors (FETs) on the channel width and thicknesses. In order to investigate the transport behavior in devices with different channel geometries, we have performed detailed two-dimensional simulations of SiNWFETs and control FETs with a fixed channel length L of 10um, but varying the channel width W from 5nm to 5um, and thickness t from 10nm to 30nm. We have shown that $Q_{ON}/Q_{OFF}$ drastically decreases (from ${\sim}2.9{\times}10^4$ to ${\sim}9.8{\times}10^3$) as the channel thickness increases (from 10nm to 30nm). As a result of the simulation using a quantum model, even higher charge density in the bottom of SiNW channel was observed than that in the bottom of control channel.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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• pp.728-731
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• 2009

We report numerical simulations to investigate of the dependendce of the on/off current ratio and channel charge distributions in silicon nanowire (SiNW) field-effect transistors (FETs) on the channel width and thicknesses. In order to investigate the transport behavior in devices with different channel geometries, we have performed detailed two-dimensional simulations of SiNWFETs and control FETs with a fixed channel length L of $10\;{\mu}m$, but varying the channel width W from 5 nm to $5\;{\mu}m$, and thickness t from 10 nm to 30 nm. We have show that $Q_{ON}/Q_{OFF}$ drastically decreases (from $^{\sim}2.9{\times}10^4$ to $^{\sim}9.8{\times}10^3$) as the channel thickness increases (from 10 nm to 30 nm). As a result of the simulation using a quantum model, even higher charge density in the bottom of SiNW channel was observed then in the bottom of control channel.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.353-353
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• 2012

InAs nanowires (NWs)는 나노소자스케일의 전자소자나 광전자소자를 위한 기본 단위(building block)로 사용될 수 있고, 1차원적 나노구조를 가지면서 나타나는 특별한 전기적, 광학적 특성으로 인해 전계효과 트랜지스터, 레이저, 광발광 다이오드, 가스 검출 센서 등의 많은 응용소자로 활용을 위한 연구가 진행되 있으며 주로 실리콘, 갈륨비소 기판 위에 금속유기기상 증착(MOCVD) 또는 분자선 증착 (MBE)을 이용하여 선택적 수직배열 성장 조절을 위한 연구와 특성 평가 연구가 주로 이뤄지고 있다. 본 연구에서는 InAs NWs를 MBE 장치를 이용하여 Si(111) 기판 위에 Au와 같은 촉매를 사용하지 않고 Si과 InAs의 큰 격자 불일치로 인하여 성장되는 Volmer-weber 성장 모드를 이용 하였다. InAs NW 성장모드는 Si ($5.4309{\AA}$)과 InAs ($6.0584{\AA}$) 사이에 큰 격자상수 차이를 이용하게 되는데 촉매를 사용하여 성장하는 일반적인 이종 화합물 반도체 성장 모드와 달리 액상상태가 존재하지 않고 바로 In과 As이 Si 기판 위를 이동하여 수직방향으로 성장이 이루어지는 vaporsolid(VS) 모드이다. InAs NW V-S 성장 모드는 Si 기판과의 격자 상수차에 의한 스트레스를 이용해야 하므로 Si기판 위에 존재하는 native oxide는 완벽히 제거되어야 한다. InAs NW 최적 성장 조건을 찾기위해 V/III raitio, 성장 온도, 기판표면처리 등의 성장 변수를 변화 시켜가며 실험을 수행하였다. Native oxide를 제거하기 위하여 HF와 buffered oxide etchant (BOE)를 사용하였다. InAs NWs 성장조건은 Indium flux를 고정 시키고 V/III ratio는 50~400까지 변화를 주었다. V/III ratio를 200으로 고정을 시키고 성장온도를 $375{\sim}470^{\circ}C$에서 성장 하였다. 이 때 InAs NWs는 $430^{\circ}C$에서 가장 높은 밀도와 aspect ratio를 얻을 수 있었다. Arsenic flux에 대해서는 많을 수록 좋은 aspect ratio를 얻을 수 있었다. 하지만 InAs 구조의 절대 부피는 거의 같다는 것을 확인 할 수 있었고 이는 온도와 V/III ratio가 Indium adatom의 surface migration length에 대하여 중요한 요소로 작용되는 것을 알 수 있었다.