• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.275-278
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• 2017

Heterogeneous semiconductor composites have been widely used to establish high-performance microelectronic or optoelectronic devices. During a deposition of silicon atoms on silicon/germanium compound surfaces, germanium (Ge) atoms are segregated from the substrate to the surface and are mixed in incoming a silicon layer. To suppress Ge segregation to obtain the interface sharpness between silicon layers and silicon/germanium composite layers, approaches have used silicon hydride gas species. The hydrogen atoms can play a role of inhibitors of silicon/germanium exchange. However, there are few kinetic models to explain the hydrogen effects. We propose using segregation probability which is affected by hydrogen atoms covering substrate surfaces. We derived the model to predict the segregation probability as well as the profile of Ge fraction through layers by using chemical reactions during silicon deposition.

• Transactions on Electrical and Electronic Materials
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• v.12 no.4
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• pp.140-143
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• 2011

The growth and characterization of $In_{0.5}Ga_{0.5}As/In_{0.5}Al_{0.5}As$ narrow-gap inverted high electron mobility transistor structures, developed as a candidate material for spin-injection devices, are presented in this study. We have grown samples possessing surface $In_{0.5}Ga_{0.5}As$ channels of different thicknesses (30 nm and 60 nm) both with and without a thin 3 nm $In_{0.5}Ga_{0.5}As$ cap layer by using molecular beam epitaxy. We then investigated the in-plane transport properties as well as the Rashba spin-orbit coupling constant of the two-dimensional electron gas confined at the heterojunction interface.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1213-1218
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• 2004

Film growth rate of InP and GaAs using TMI, TMG, TBA and TBP is numerically predicted and compared to the experimental results. Obtained results show that the film growth rate is very sensitive to the thermal condition in the reactor. To obtain exact thermal boundary conditions at the reactor walls, we analyzed the gas flow and heat transfer in the reactor including outer tube as well as the inner reactor parts using a full three-dimensional model. The results indicate that the exact thermal boundary conditions are important to get precise film growth rate prediction.

• Journal of Magnetics
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• v.7 no.1
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• pp.4-8
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• 2002

The magnetoresistance (MR) and the magnetization reversal of a lateral spin-injection device based on a spin-polarized field effect transistor (spin FET) have been investigated. The device consists of a two-dimensional electron gas (2DEG) system in an InAs single quantum well (SQW) and two ferromagnetic $(Ni_{80}Fe_{20})$ contacts: all injector (source) and a detector (drain). Spin-polarized electrons are injected from the first contact and, after propagating through the InAs SQW are collected by the second contact. By engineering the shape of the permalloy contacts, we were able to observe distinct switching fields $(H_c)$ from the injector and the collector by using scanning Kerr microscopy and MR measurements. Magneto-optic Kerr effect (MOKE) hysteresis loops demonstrate that there is a range of magnetic field (20~60 Oe), at room temperature, over which the magnetization in one contact is aligned antiparallel to that in the other. The MOKE results are consistent with the variation of the magnetoresistance in the spin-injection device.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.52.1-52.1
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• 2009

Cupric oxide (CuO) is a p-type semiconductor with band gap of ~1.7 eV and reported to be suitable for catalysis, lithium-copper oxide electrochemical cells, and gas sensors applications. The nanoparticles, plates and nanowires of CuO were found sensing to NO2, H2S and CO. In this work, we report about the comparison about hydrogen sensing of nano thin film and nanowires structured CuO deposited on single-walled carbon nanotubes (SWNTs). The thin film and nanowires are synthesized by deposition of Cu on different substrate followed by oxidation process. Nano thin films of CuO are deposited on thermally oxidized silicon substrate, whereas nanowires are synthesized by using a porous thin film of SWNTs as substrate. The hydrogen sensing properties of synthesized materials are investigated. The results showed that nanowires cupric oxide deposited on SWNTs showed higher sensitivity to hydrogen than those of nano thin film CuO did.

• Proceedings of the KIEE Conference
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• summer
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• pp.1205-1207
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• 2004

AC plasma power supply is used to control a ozone generator and a air pollution gas. AC plasma power supply is composed of power semiconductor switch devices and control board adapted SHE(Selected Harmonic Elimination) PWM method. AC plasma power supply with sinusoidal VVVF(variable voltage and variable frequency) is realized. Its output voltage range is from 0 [V] to 20[kV] and output frequency range is from 8[kHz] to 20[kHz]. Using proposed system, AC high voltage and high frequency discharge is tested in the DBD(dieletric barrier discharge) reactor, and the space distribution of a its non-thermal plasma is observed. In spite of the increasement of voltage and frequency, the proposed system have a stable operation characteristics. It is verified by the experimental results.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2079-2081
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• 2003

현재 산업화 사회가 가속됨에 따라 인체에 유해한 물질들이 발생한다. 그 중에서 VOC(Volatile Organic Component)는 인체에 치명적인 해를 일으키는 물질이다. 본 논문은 MOS(Metal Oxide Semiconductor) 센서를 이용하여 인체에 치명적인 유해 물질인 VOC를 측정하였다. 현재 VOC의 측정은 GC(Gas Chromatograph)를 이용하는데 이는 측정 시간이 길며 숙련된 측정자에 의해서만 측정이 가능하고 그 분석이 가능하다. 그러나 MOS 센서를 이용하면 숙련되지 않은 측정자도 측정이 가능하며 인공신경망을 이용하여 그 분석을 함으로서 누구나 쉽게 분석이 가능하고 실시간으로 측정이 가능하다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.11
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• pp.1143-1148
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• 2004

In this study, photoresist stripping in semiconductor or LCD (liquid crystal display) fabrication processes using DIO, was investigated. In order to obtain the high PR stripping efficiency of DIO. we have developed new ozone-generating system with high ozone concentration and ozone-resolving system with high contact ratio. In this study, we obtained ozone gas concentrations of 11 % by new ozone-generating system, ozone-resolving efficiency of 99.5 % and maximum solubility of 130 ppm in deionized water. We applied the newly designed equipments to photoresist stripping processes and obtained similar results to SPM(sulfuric-peroxide mixture) process characteristics.

• Journal of the Korean Vacuum Society
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• v.8 no.3A
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• pp.218-223
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• 1999

We investigated the interfacial reactions between the $Y_2O_3$ film deposited by ICB processing and p-type (100) Si substrates upon annealing treatments in $O_2$ and Ar gas ambients. we also investigated the evolution of surface morphology of ICB deposited $Y_2O_3$ films upon annealing treatments. We observed that the root-mean-square(RMS) value of surface roughness measured by AFM increased with annealing time at $800^{\circ}C$ in $O_2$ ambient, while the change of surface roughness was not observed in Ar ambient. We also found the growth of $SiO_2$ layer and the formation of yttium silicate layer. From the capacitance values $(C_{acc})$ measured by C-V measurements, the relative didldctric constant of $Y_2O_3$ film in metal-insulator-semiconductor(MIS) structure was estimated to be about 9.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.189.1-189.1
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• 2013

Titanium dioxide (TiO2) is a wide bandgap semiconductor possessing photochemical stability and thus widely used for photocatalysis. However, enhancing photocatalytic efficiency is still a challenging issue. In general, the efficiency is affected by physio-chemical properties such as crystalline phase, crystallinity, exposed crystal facets, crystallite size, porosity, and surface/bulk defects. Here we propose an alternative approach to enhance the efficiency by studying interfaces between thin TiO2 layers to be stacked; that is, the interfacial phenomena influencing on the formation of porous structures, controlling crystallite sizes and crystallinity. To do so, multi-layered TiO2 thin films were fabricated by using a sol-gel method. Specifically, a single TiO2 thin layer with a thickness range of 20~40 nm was deposited on a silicon wafer and annealed at $600^{\circ}C$. The processing step was repeated up to 6 times. The resulting structures were characterized by conventional electron microscopes, and followed by carrying out photocatalytic performances. The multi-layered TiO2 thin films with enhancing photocatalytic efficiency can be readily applied for bio- and gas sensing devices.