• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.9
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• pp.685-690
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• 2010

ZnO with the wide band gap near 3.37 eV is typically an n-type semiconductor in which deviation from stoichiometry is electrically active. It was known that the films with a resistivity of the order of $10^{-4}{\Omega}cm$ is not easy to obtain. In order to improve electrical characteristic of ZnO, we added 1, 3, 5 wt% Ga element in ZnO. The Ga-doped ZnO (GZO) was grown on a glass substrate by radio frequency (RF) magnetron sputtering at the temperature range from 100 to $500^{\circ}C$. X-ray diffraction (XRD) patterns of GZO films showed preferable crystal orientation of (002) plane. The lowest resistivity of the GZO films was $8.9{\times}10^{-4}{\Omega}cm$. GZO films significantly influenced by the working temperature. The average transmittance of the films was over 80% in the visible ranges.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.11
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• pp.734-739
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• 2017

We prepared $SnS_x$ thin films on both soda-lime glass (SLG) and molybdenum(Mo)/SLG substrates by a two-step process using a Sn precursor followed by sulfur reaction in rapid thermal annealing (RTA) at different sulfurization temperatures ($Ts=200^{\circ}C$, $230^{\circ}C$, $250^{\circ}C$, and $300^{\circ}C$) and annealing times ($t_s=10min$ and 30 min). The single SnS phase was dominant for $200^{\circ}C{\leq}T_s$<$250^{\circ}C$, while an additional phase of $SnS_2$ was appeared at $T_s{\geq}250^{\circ}C$ alongside SnS. The SnS grains in all the samples showed strong growth along the preferred [040] direction. The band-gap energy ($E_g$) of the films was estimated to be 1.24 eV.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.4
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• pp.712-718
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• 2003

The effects of nitrogen ion implantation on vacuum evaporated cadmium sulphide (CdS) thin films were investigated by X-ray diffraction, optical transmittance spectra, and Raman scattering studies. The as-deposited CdS films have a hexagonal structure with preferential (0 0 2) orientation. Formation of Cd metallic clusters was observed in ion implanted films from the XRD patterns. The band gap of N+ implanted films decreased, whereas the optical absorption coefficient values increased with the increase of implantation dose. The Raman peak position appeared at 299 cm-1 and the FWHM increased with the ion dose. A decrease in the area of Raman peak of CdS Al(LO) mode is seen on implantation.

• Journal of IKEEE
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• v.24 no.2
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• pp.435-440
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• 2020

ZnO:Al films with about 500 nm thick were prepared by RF magnetron sputtering. The ZnO:Al films were annealed at 100 ℃, 200 ℃, 300 ℃, and 400 ℃ for 10 h, respectively. The resistivity, carrier concentration, and mobility variation of ZnO:Al films with heat treatments were measured. The causes of the resistivity variation of ZnO:Al films with heat treatments were investigated by utilizing the results of x-ray diffraction and field emission scanning electron microscope. The energy band gap, Urbach energy, and refractive index were obtained from the transmittance of ZnO:Al films. The change in electrical properties of the ZnO:Al film was explained in relation to the optical properties.

• Corrosion Science and Technology
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• v.2 no.4
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• pp.171-177
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• 2003

The electronic properties of the passive film formed on Fe-20Cr ferritic stainless steel in pH 8.5 buffer solution containing 0.05 M EDTA (ethylene diammine tetraacetic acid) were examined by the photocurrent measurements and Mott-Schottky analysis for the film. XPS depth profile for the film demonstrated that Cr content in the outermost layer of the passive film was higher in the solution with EDTA than that in the solution without EDTA, due to selective dissolution of Fe by EDTA. In the solution with EDTA, the passive film showed characteristics of an amorphous or highly disordered n-type semiconductor. The band gap energies of the passive film are estimated to be ~ 3.0 eV, irrespective of film formation potential from 0 to 700 $mV_SCE$ and of presence of EDTA. However, the donor density of the passive film formed in the solution with EDTA is much higher than that formed in the solution without EDTA, due to an increase in oxygen vacancy resulted from the dissolution of Fe-oxide in the outermost layer of the passive film. These results support the proposed model that the passive film formed on Fe-20Cr in pH 8.5 buffer solution mainly consists of Cr-substituted $\gamma$-$Fe_2O_3$.

• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.127-131
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• 2005

We examined the effect of low temperature heat-treatment on the optical properties of the photonic crystals self-assembled using a monodispersed spherical $SiO_2$ nanoparticle. When the heat treatment temperature increased, the reflectance peak, which is induced by the photonic band gap, moved to a shorter wavelength direction, and the peak intensity of Fabry-Perot fringes also increased. The highest reflectance peak intensity was obtained in the sample heat-treated at $250\~300^{\circ}C$. The heat-treatment reduced the average particle size and the quantity of defects, and increased the packing density of the photonic crystal.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.2
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• pp.155-160
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• 2020

Ga₂O₃/n-type 4H-SiC heterojunction diodes were fabricated by RF magnetron sputtering. The optical properties of Ga₂O₃ and electrical properties of diodes were investigated. I-V characteristics were compared with simulation data from the Atlas software. The band gap of Ga₂O₃ was changed from 5.01 eV to 4.88 eV through oxygen annealing. The doping concentration of Ga₂O₃ was extracted from C-V characteristics. The annealed oxygen exhibited twice higher doping concentration. The annealed diodes showed improved turn-on voltage (0.99 V) and lower leakage current (3 pA). Furthermore, the oxygen-annealed diodes exhibited a temperature cross-point when temperature increased, and its ideality factor was lower than that of as-grown diodes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.209-210
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• 2006

We have successfully termed brown colored patterns inside of a transparent borosilicate glass generally known as BK7, laying the focus of near infrared Ti: sapphire femtosecond laser beam in the bulk BK7 glass. It is important to keep the laser power well below the damage threshold of BK7 in forming the color center. Thanks to the low laser power, there was no laser induced mechanical damage such as cracks or threads in the color formed area. From the absorbance spectrum and its gaussian fitting, we found the band gap of BK7, 4.21eV, and three absorption edges.

• Journal of Powder Materials
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• v.23 no.4
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• pp.307-310
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• 2016

$TiOF_2$, which has remarkable electrochemical and optical properties, is used in various applications such as Li-ion batteries, electrochemical displays, and photocatalysts. In addition, it is possible to utilize the template which is allowed to synthesize fluorine doped $TiO_2$ powders with hollow or faceted structures. However, common synthesis methods of $TiOF_2$ powders have some disadvantages such as the use of expensive and harmful precursors and batchtype processes with a limited production scale. In this study, we report a synthetic route for preparing $TiOF_2$ powders by using an inexpensive and harmless precursor and a continuous ultrasonic spray pyrolysis process under a controlled atmosphere to address the aforementioned problems. The synthesized powder has an average size of $1{\mu}m$, a spherical shape, a pure $TiOF_2$ phase, and exhibits a band-gap energy of 3.2 eV.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.48-48
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• 2018

습도는 대기중에 분포되어있는 물 분자의 양으로 사람이 살아가는데 있어 막대한 영향을 주는 환경적 요소중 하나이다. 산업적 가스의 순도에 막대한 영향을 끼치기도 하고, 반도체 산업에서 불량률과도 밀접한 관련이 있다. 또한, 식품학이나 기상학, 농사와도 밀접한 관련이 있어서 습도를 측정하는 것은 중요시 되고 있다. 이를 위해서 많은 물질들이 사용되고, 연구되었다. 산화 구리, 산화 아연, 산화 납 등의 산화금속 물질들이나 전도성 고분자, 실리콘 기반의 물질들이 주로 사용되고 있는데, 그 중 산화 금속이 쉬운 합성 방법과 낮은 단가, 명확한 작동 원리로 인해 널리 사용되고 있다. 산화 아연의 경우 넓은 direct band gap energy와 우수한 내화학성으로 인해 주로 사용되는데 그 중 1차원 물질인 nanowire의 경우 비등성 구조와 높은 비표면적을 갖는 특성으로 인해 산화 아연의 nanowire 구조가 많이 사용된다. 본 연구에서는 열처리 공정을 이용하여 산화아연의 nanowire 구조를 합성하였고, 합성된 nanowire는 양쪽의 미세전극을 직접적으로 연결하여 간편한 방식으로 소형 소자를 만들 수 있다는 장점이 있다. 열처리 공정 이전에 전기도금 방식을 이용하여 아연층을 증착 하였다. 전기도금 조건은 0.1 M의 염화 아연과 1 M의 염화 칼륨으로 구성된 용액에 -1.1 V를 인가하였다. 합성된 아연층은 열처리 공정에 의해 산화아연의 nanowire 구조체로 변환되고, SEM (scanning electron microscope)를 통해 표면 형상을 관찰 하였고, XRD (X-ray diffraction)을 통해 미세구조를 확인하였다. -1 V부터 1 V 범위의 전압을 흘려주어 형성된 소자의 전기적 특성을 확인하였고, 1 V를 인가하였을 때, 습도 변화에 따른 센서 소자의 저항변화를 통해 습도 센서로서의 특성을 확인 하였다.