• Journal of Korean Vacuum Science & Technology
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• v.2 no.2
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• pp.107-117
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• 1998

Epitaxial undoped and Sb-doped si films have been grown on Si(001) substrates at temperatures T between 80 and 750$^{\circ}C$ using energetic Si in ultra-high-vacuum Kr+-ion-beam sputter deposition(IBSD). Critical epitaxial thicknesses te, The average thickness of epitaxial layers, in undoped films were found to range from 8nm at Ts=80$^{\circ}C$ to > 1.2 ${\mu}$m at Ts=300$^{\circ}C$ while Sb incorporation probabilities $\sigma$sb varied from unity at Ts 550$^{\circ}C$ to 0.1 at 750$^{\circ}C$. These te and $\sigma$Sb values are approximately one and one-to-three orders of magnitude, respectively, higher than reported results achieved with molecular-beam epitaxy. Plan-view and cross-sectional transmission electron microscopy, high-resolution x-ray diffraction, channeling and axial angular-yield profiles by Rutherford back scattering spectroscopy for epitaxial Si1-x Gex(001) alloy films (0.15$\leq$x$\leq$0.30) demonstrated that the films are of extremely high crystalline quality. critical layer thicknesses hc the film thickness where strain relaxation starts, I these alloys wre found to increase rapidly with decreasing growth temperature. For Si0.70 Ge0.30, hc ranged from 35nm at Ts=550$^{\circ}C$ to 650nm at 350$^{\circ}C$ compared to an equilibrium value of 8nm.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.5
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• pp.1-6
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• 2000

We prepared organic light-emitting-diodes (LEDs) with a squarylium(Sq)-doped aluminum quinoline(Alq3) emission layer by the vapor deposition method. We discussed their electro-luminescence(EL) and electrical properties. The EL from Sq had a peak wavelength of 670nm and a half-width of 30nm. Only the EL from So(purely red) could be observed at the doping concentration of over 15mol%, but the luminance were low (0.21cd/$m^2$, 0.1cd/$m^2$) and EL efficiency was under the $10^{-2}$W. Although Sq molecules seemed to act as trap site in Alq3 molecules, they acted as carrier drafts site at doping concentration of over 5mol%.

• Journal of Radiation Protection and Research
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• v.30 no.2
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• pp.77-84
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• 2005

The authors submit the data concerning the methods of obtaining semiconductor scintillators on the basis of the zinc chalcogenide crystal doped with impurities (Te, Cd, O, $Me^{III}-metals$ Al, In, etc.). Characteristics of such crystals and mechanisms for the semiconductor scintillator luminescence are described as well. The scintillator luminescence spectra maximums are located within the range 450-640nm, which depends on the method of preparing the scintillator. The luminescence decay time ranges within $0.5-10{\mu}s\;and\;30-150{\mu}s$. The afterglow level is less than 0.01% after $10-20{\mu}s$, and the radiation stability is ${\geq}5{\cdot}10^8$ rad. Thermostability of the output characteristics of new semiconductor scintillators on the basis of zinc selenide is prescribed by thermodynamic stability of the principal associative radiative recombination centers that come into existence due to the crystal lattice inherent imperfections. Certain application fields of the new scintillators are examined taking into account their particular qualities.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.48-49
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• 2006

Highly conductive and transparent films of Ga-doped ZnO have been prepared by pulsed laser deposition using a ZnO target with 3 wt% ${Ga_2}{O_3}$ dopant. Films with the resistivity as low as $3.3{\times}10^{-4}{\Omega}cm$ and the transmittance above 80 % at the wavelength of 400 to 800 nm can be fabricated on glass substrate at room temperature. It is shown that a stable resistivity for the use in oxidation ambient at high temperature can be obtained for the films. Heat treatments were performed to examine the thermal stability of ZnO and GZO films at ptemperature range from $100^{\circ}C$ to $400^{\circ}C$ in $O_2$ ambient for 30 minutes. The resistivity of ZnO film annealed at $400^{\circ}C$ increased by two orders of magnitude, in case of GZO film was relatively stable up to at $400^{\circ}C$. For practical applications at high temperatures the thermal stability of resistivity of GZO thin films might become an advantage for transparent electrodes.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.1
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• pp.6-10
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• 2009

In this paper, a selective area growth (SAG) of a GaN/AlGaN double heterostructure (DH) has been performed on r-plane sapphire substrate by using the mixed-source hydride vapor phase epitaxy (HVPE) with multi-sliding boat system. The SAG-GaN/AlGaN DH consists of GaN buffer layer, Te-doped AlGaN n-cladding layer, GaN active layer, Mg-doped AlGaN p-cladding layer, and Mg-doped GaN p-capping layer. The electroluminescence (EL) characteristics show an emission peak of wavelength, 439 nm with a full width at half maximum (FWHM) of approximately 0.64 eV at 20 mA. The I-V measurements show that the turn-on voltage of the SAG-GaN/AlGaN DH is 3.4 V at room temperature. We found that the mixed-source HVPE method with a multi-sliding boat system was one of promising growth methods for III-Nitride LEDs.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.1
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• pp.9-15
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• 2002

In this thesis, blue emission organic light emitting devices were fabricated by using vacuum deposition method. Two types of device were employed to realize blue emission. Type I had an emitting layer containing TPB-doped $Alq_3$ and type II had an emitting layer containing DPA-doped $Alq_3$. The variable dopant concentration was 0.5 ~2 wt%. The electrical and optical characteristics of these devices have been investigated. The more dopant concentration increased, the nearer the blue coordinate. Type I than type II had a lower turn on voltage and driving voltage. The emission luminescence of type II was brighter than that of type I. When we applied 15V to type II with DPA(2wt%)-doped $Alq_3$, we have achived the emission luminescence of 1282cd/$m^2$, the emission wavelength of 476nm and the blue emission CIE coordination of (0.1273, 0.0672)

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.434-436
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• 2013

Ga-doped ZnO (GZO) was substitutes of the SnO2:F films on soda lime glass substrate in the photovoltaic devices such as CIGS, CdTe and DSSC due to good properties and low cost. However, it was reported that the electrical resistivity of GZO is unstable above $300^{\circ}C$ in air atmosphere. To improve thermal stability of GZO thin films at high temperature above $300^{\circ}C$ an $TiO_2$ thin film was deposited on the top of GZO thin films as a barrier layer by Pulsed Laser Deposition (PLD) method. $TiO_2$ thin films were deposited at various thicknesses from 25 nm to 100 nm. Subsequently, these films were annealed at temperature of $300^{\circ}C$, $400^{\circ}C$, $500^{\circ}C$ in air atmosphere for 20 min. The XRD measurement results showed all the films had a preferentially oriented ( 0 0 2 ) peak, and the intensity of ( 0 0 2 ) peak nearly did not change both GZO (300 nm) single layer and $TiO_2$ (50 nm)/GZO (300 nm) double layer. The resistivity of GZO (300 nm) single layer increased from $7.6{\times}10^{-4}{\Omega}m$ (RT) to $7.7{\times}10^{-2}{\Omega}m$ ($500^{\circ}C$). However, in the case of the $TiO_2$ (50 nm)/GZO (300 nm) double layer, resistivity showed small change from $7.9{\times}10^{-4}{\Omega}m$ (RT) to $5.2{\times}10^{-3}{\Omega}m$ ($500^{\circ}C$). Meanwhile, the average transmittance of all the films exceeded 80% in the visible spectrum, which suggests that these films will be suitable for photovoltaic devices.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1249-1251
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• 1998

We have studied the properties of $GaAs_{0.35}P_{0.65}$ epitaxial films on the GaP according to doping of $NH_3$ gas using VPE method by CVD. The efficiency of $GaAs_{0.35}P_{0.65}$ epitaxial films found to be greatly enhanced by the according of nitrogen doping. The diodes were fabricated by means of Zn diffusion into vapor grown $GaAs_{0.35}P_{0.65}$ epitaxial films doped with N and Te. The effects of nitrogen doping on carrier density of epitaxial films, PL wavelength and the power out, forward voltage of diodes are discussed. In the end, The effect of electrical and optical properties is influenced by the deep level and deep level density of nitrogen doping.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.253-253
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• 2016

최근 세계적으로 대체 에너지는 중요한 이슈가 되고 있으며 그 중 열전 재료는 유망한 에너지 기술로서 주목 받고 있다. 특히 고 직접화 전자 소자의 발열 문제를 해결하기 위해, 소형화와 정밀 온도 제어가 가능한 박막형 열전 소자에 연구가 주목 받고 있다. 박막형 열전소자 중 산화물 반도체계에 대한 연구가 활발히 진행되고 있으며, 이러한 산화물 반도체계 중 In2O3는 BiTe, PbTe 등의 기존의 재료에 비해 독성이 낮을 뿐만 아니라 내 산화성 및 고온에서 열적 안정성이 우수하여 고온에서 적용 불가능한 금속계 열전 재료의 한계를 극복 할 수 있다는 장점을 가진다. 우수한 성능 가장 낮은 캐리어 밀도를 가지기 때문에 의 열전 재료는 높은 전기 전도도 및 제백 계수 그리고 낮은 열전도도 특성을 가져야만 한다. IZO:Sn(Zn 10 wt.%, Sn 800 ppm) 박막의 경우, 높은 전기 전도성을 가지면서 비정질 구조를 가진다. 이와 같이 비정질 구조를 가지는 박막 열전 재료는 격자에 의한 열 전도도가 낮기 때문에 결정질 구조에 비해 전체 열 전도도 값이 낮을 것으로 기대된다. 따라서 높은 전기 전도도를 가지면서 동시에 낮은 열 전도도를 가지게 되어 우수한 열전 특성을 가질 것이라 예상된다. 이러한 특성을 바탕으로 본 연구에서는 비정질 구조를 갖는 Zn와 미량의 Sn을 동시에 첨가한 In2O3박막의 전기적 특성및 열전 특성을 관찰하고자 한다. 본 연구에서는 magnetron sputtering법으로 IZO:Sn(Zn 10 wt.%, Sn 800 ppm) 타깃을 이용하여 기판 가열없이 DC Power 70 W, 작업 압력 0.7 Pa으로 SiO2 기판 위에 $400{\pm}20nm$ 두께의 박막을 증착하였다. 이러한 공정으로 만들어진 박막은 대기 중 후 열처리를 각각의 200, 300, 400, 500, $600^{\circ}C$ 온도에서 진행하였다. 박막의 미세 구조는 XRD를 통해 관찰하였다. 그리고 박막의 전기적 특성은 Hall effect measurement을 통해 측정하였고, 열전 특성은 Seebeck 상수의 측정을 통하여 평가하였다. XRD 확인 결과 RT에서 증착한 박막과 후 열처리 200, 300, 400, $500^{\circ}C$ 결과 비정질 구조를 보였고, 후열처리 $600^{\circ}C$에서는 결정의 회절 피크를 보였다. 전기적 특성의 경우, 후 열처리 온도가 증가함에 따라 전기 전도도는 감소한다. 이는 공기중의 산소가 박막에 침투하여 oxygen vacancy를 막아 캐리어 밀도가 감소한것에 기인 된 것으로 판단된다. 열전 특성의 경우 제백상수는 후 열처리 $600^{\circ}C$에서 가장 높은 제백상수를 나타낸다. 제백 상수는 수식에 따라 캐리어 밀도의 -2/3승에 비례하게 된다. 수식에 따라 후 열처리 $600^{\circ}C$에서 가장 낮은 캐리어 밀도를 가지기 때문에 가장 높은 제백 상수를 가지게 된다. 열전 성능 척도인 Power factor는 제백 상수의 제곱과 전기전도도의 곱으로 나타내는데, 후 열처리 $200^{\circ}C$에서 가장 높은 Power factor를 보인다. 이는 캐리어 밀도 감소에 따라 전기 전도도는 감소하였지만 이로 인해 제백상수는 증가하였고, 또한 캐리어 밀도 감소에 따라 이온화 불순물 산란의 감소에 의해 이동도의 증가에 의한 것으로 판단된다. 박막의 경우 기판의 영향으로 인해 열 전도도 측정이 어려워 열전 성능 지수(ZT)를 계산을 할 수 없지만, 마그네트론 스퍼터링법으로 증착한 IZO:Sn 박막은 비정질 구조를 가지므로 격자진동에 의한 열 전도도가 낮아 전체 열 전도도가 결정질에 비해 낮을 것이며 이는 높은 열전 성능 지수를 가질 것으로 예상된다.

• Nuclear Engineering and Technology
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• v.33 no.3
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• pp.307-314
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• 2001

The changes of weight gain, structure, morphology and uranium oxidation states in l0wt% G $d_2$ $O_3$-doped U $O_2$ during the oxidation below 475$^{\circ}C$ and heat treatment at 130$0^{\circ}C$ in air were investigated using TGA, XRD, SEM, EPMA and XPS. The room temperature ( $U_{0.86}$G $d_{0.14}$) $O_2$Cubic Phase Converted to highly distorted ( $U_{0.86}$G $d_{0.14}$)$_3$ $O_{8}$ -type sing1e Phase by oxidation at 475 $^{\circ}C$ in air. This oxidized phase was reduced by annealing at 130$0^{\circ}C$ in air. The room temperature XRD pattern of the 130$0^{\circ}C$ annealed powder revealed that ( $U_{0.86}$G $d_{0.14}$)$_3$ $O_{8}$ -type single phase was separated into Gd-depleted $U_3$ $O_{8}$ and Gd-enriched ( $U_{0.7}$G $d_{0.3}$) $O_2$$_{+x}$ type cubic phase. The reduction and phase separation by the high temperature annealing of kinetically metastable and highly deformed ( $U_{0.86}$G $d_{0.14}$)$_3$ $O_{8}$ -type phase are interpreted in terms of cation size difference between G $d^3$$^{+}$ and U according to the oxidation state of U.U.U.U.U.te of U.U.U.U.U.