• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.291.2-291.2
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• 2014

ZnO 박막(thin film)은 씨앗층(seed layer)의 종류, 두께, 증착 조건 등에 따라 그 특성이 달라지는 것으로 알려져 있다. 이에 본 연구에서는 씨앗층의 종류에 따른 박막의 특성변화를 알아 보기 위해, 졸겔 스핀코팅(sol-gel spin-coating) 방법으로 4가지 종류의 씨앗층(Al-ZnO, Co-ZnO, Cu-ZnO, In-ZnO) 위에 ZnO 박막을 성장 한 후 성장된 ZnO 박막의 구조적, 광학적 특성을 field emission scanning electron microscope, X-ray diffractometer, UV-visible spectrometer를 통해 조사하였다. ZnO 박막의 표면구조는 씨앗층의 종류에 따라 변하였으며, 씨앗층 위에 성장된 ZnO 박막들의 c축 배향성과 결정성이 씨앗층 없이 성장된 ZnO 박막보다 더 우수하게 나타났다. 투과도(transmittance) 측정값을 통해 계산된 광학적 밴드갭(optical bandgap)과 Urbach 에너지는 씨앗층에 따라 다른 값을 나타내었다. 광학적 밴드갭은 Al-ZnO 씨앗층 위에 성장된 ZnO 박막에서 가장 크게 나타났으며, Urbach 에너지는 Co-ZnO 씨앗층 위에 성장된 ZnO 박막에서 가장 낮았다. 따라서 ZnO박막 성장 시 용도에 맞게 적절한 씨앗층을 사용하는 것은 소자의 성능을 향상시키는데 매우 중요한 역할을 할 수 있다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.74-75
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• 2005

ZnO epilayer were synthesized by the pulesd laser deposition(PLD) process on $Al_2O_3$ substrate after irradiating the surface of the ZnO sintered pellet by the ArF(193 nm) excimer laser. The epilayers of ZnO were achieved on sapphire ($Al_2O_3$) substrate at a temperature of $400^{\circ}C$. The crystalline structure of epilayer was investigated by the photoluminescence. The carrier density and mobility of ZnO epilayer measured with Hall effect by van der Pauw method are $8.27{\times}10^{16}cm^{-3}$ and $299cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the ZnO obtained from the absorption spectra was well described by the Varshni's relation, $E_g$(T) = 3.3973 eV - ($2.69{\times}10^{-4}$ eV/K)$T_2$/(T + 463 K). The crystal field and the spin-orbit splitting energies for the valence band of the ZnO have been estimated to be 0.0041 eV and 0.0399 eV at 10 K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the $\triangle$so definitely exists in the $\ulcorner_6$ states of the valence band of the ZnO. The three photocurrent peaks observed at 10K are ascribed to the $A_1-$, $B_1-$, and $C_1$-exciton peaks for n = 1.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.292-292
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• 2012

현재 투명전극은 주로 ITO를 사용하고 있으며, ITO는 인듐산화물(In2O3)과 주석산화물(SnO2)이 9대 1의 비율로 혼합된 화합물로 인듐이 주성분이다. 따라서 ITO 사용량의 증가는 인듐의 수요 증가를 이끌어 2003년 이후 인듐 잉곳의 가격이 급등하였다. LCD에 응용되는 금속재료의 가격추이를 비교해보면, 인듐이 가장 큰 변화를 보이고 있으며, 2005년 인듐 가격은 2002년 대비 1,000% 이상 상승하였다가 2007년 이후 500%p 하락하여 2008년 2월 22일 기준으로 톤당 49만 달러에 거래되고 있다. 같은 기간 동안 알루미늄의 가격은 76.6% 상승하였으며 구리는 394%, 주석은 331% 상승하였다. 이러한 인듐의 가격 상승폭은 동일한 기간 동안 다른 금속 재료와 비해 매우 크며, 단위 질량당 가격도 20배 이상 높은 수준이다. ITO의 주성분인 인듐의 이러한 가격의 급등 및 향후 인듐의 Shortage 예상으로 인해 ITO 대체재 확보의 필요성이 증가되고 있다. 태양광 발전산업에서 현재 주류인 결정질 실리콘 태양전지의 변환효율은 꾸준히 향상되고 있으나, 태양전지의 가격이 매년 서서히 하강되고 있는 실정에서 결정질 실리콘 가격의 상승 등으로 고부가 가치 산업유지에 어려움이 있으며, 생산 원가를 낮출 수 있는 태양전지 제조기술로는 2세대 태양전지로 불리는 박막형이 현재의 대안으로 자리매김하고 있으며, 박막태양전지 산업분야가 현재의 정부정책 지원 없이 자생력을 갖추고 또한 시장 경쟁력을 확보하기 위해서는 박막태양전지 개발과 더불어 저가의 재료개발도 시급한 상황이다. 본 연구에서는 In-line magnetron sputtering system을 사용하여 소다라임 유리기판 위에 박막태양전지용 투명전도성 ZnO(Al) 박막을 제작하였고, 특히 이 박막은 n-형 반도체 특성을 가져야하기 때문에 홀이동도와 개리어농도의 상관관계 및 박막의 두께, 광투과율 특성, 온도 의존성을 조사하였고, 이를 논하고자 한다. (본 연구는 중소기업청의 기술혁신개발사업 연구지원금으로 이루어졌음).

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.283-283
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• 2011

The n-doping effect by doping metal carbonate into an electron-injecting organic layer can improve the device performance by the balanced carrier injection because an electron ohmic contact between cathode and an electron-transporting layer, for example, a high current density, a high efficiency, a high luminance, and a low power consumption. In the study, first, we investigated an electron-ohmic property of electron-only device, which has a ITO/$Rb_2CO_3$-doped $C_{60}$/Al structure. Second, we examined the I-V-L characteristics of all-ohmic OLEDs, which are glass/ITO/$MoO_x$-doped NPB (25%, 5 nm)/NPB (63 nm)/$Alq_3$ (32 nm)/$Rb_2CO_3$-doped $C_{60}$(y%, 10 nm)/Al. The $MoO_x$doped NPB and $Rb_2CO_3$-doped fullerene layer were used as the hole-ohmic contact and electron-ohmic contact layer in all-ohmic OLEDs, respectively, Third, the electronic structure of the $Rb_2CO_3$-doped $C_{60}$-doped interfaces were investigated by analyzing photoemission properties, such as x-ray photoemission spectroscopy (XPS), Ultraviolet Photoemission spectroscopy (UPS), and Near-edge x-ray absorption fine structure (NEXAFS) spectroscopy, as a doping concentration at the interfaces of $Rb_2CO_3$-doped fullerene are changed. Finally, the correlation between the device performance in all ohmic devices and the interfacial property of the $Rb_2CO_3$-doped $C_{60}$ thin film was discussed with an energy band diagram.

• Journal of Sensor Science and Technology
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• v.14 no.3
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• pp.160-168
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• 2005

ZnO epilayer were synthesized by the pulesd laser deposition(PLD) process on $Al_{2}O_{3}$ substrate after irradiating the surface of the ZnO sintered pellet by the ArF(193 nm) excimer laser. The epilayers of ZnO were achieved on sapphire ($Al_{2}O_{3}$) substrate at a temperature of $400^{\circ}C$. The crystalline structure of epilayer was investigated by the photoluminescence. The carrier density and mobility of ZnO epilayer measured with Hall effect by van der Pauw method are $8.27{\times}1016cm^{-3}$ and $299cm^{2}/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the ZnO obtained from the absorption spectra was well described by the Varshni's relation, $E_{g}(T)$=3.3973 eV-($2.69{\times}10^{-4}$ eV/K)$T^{2}$/(T+463K). The crystal field and the spin-orbit splitting energies for the valence band of the ZnO have been estimated to be 0.0041 eV and 0.0399 eV at 10 K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_{6}$ states of the valence band of the ZnO. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1}-$, $B_{1}-$, and $C_{1}-$exciton peaks for n = 1.

• Membrane Journal
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• v.9 no.2
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• pp.97-106
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• 1999

A and 2SM-5 type zeoli tic crystal films were synthesized on porous supports from the reaction mixture of 1.9 ${SiO}_2$1.5 $Na_20-Al_2O_3-40$ $H_20$ and $Si0_2$-0.l3 $Na_2O$-52 $H_20$-O.l2 TPAOH composition, respectively. The zeolite films were characterized by XRD and SEM. The 2SM -5 crystals grown on the porous matrix were very closely bound together. It was so difficult to obtain the perfectly intergrown crystals in the case of A-type zeolite and this crystal was transformed into P-type zeolite membrane with a prolonged reaction time. The densely intergrown A type zeolite crystal membrane could be also synthesized by the hydrothermal treatment at 100$^{\cirt}C$ after pressing the reaction mixture without addition of water. The pervaporation performance of the synthesized porous inorganic membranes was investigated for alcohol and water mixtures. A-type zeolite membrane crystallized as a thin film showed the selective \'Jermeability of water from the mixtures through the molecular sieving activity of micropores.

• Transactions on Electrical and Electronic Materials
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• v.10 no.3
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• pp.93-96
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• 2009

The Al-doped ZnO (AZO) films were deposited on a glass substrate by RF magnetron sputtering in pure Ar and $Ar+H_2$ gas ambient at temperature of $100^{\circ}C$ and annealed in hydrogen ambient at the temperature range from 100 to 300 $^{\circ}C$, respectively. It was found that either the addition of hydrogen to the sputtering gas or the annealing treatment effectively reduced the resistivity of the AZO films. When the AZO films were annealed at the temperature of 300 $^{\circ}C$ for lhr in a hydrogen atmosphere, the resistivity decreased from $2.60{\times}10^{-3}\;{\Omega}cm$ to $8.42{\times}l0^{-4}\;{\Omega}cm$ for the film deposited in pure Ar gas ambient. Under the same annealing conditions of temperature and hydrogen ambient, the resistivity of AZO films deposited in the $Ar+H_2$ gas mixture decreased from $8.22{\times}l0^{-4}\;{\Omega}cm$ to $4.25{\times}l0^{-4}\;{\Omega}cm$. The lowest resistivity of $4.25{\times}l0^{-4}\;{\Omega}cm$ was obtained by adding hydrogen gas to the deposition and annealing process. X-ray diffraction (XRD) pattern of all films showed preferable growth orientation of (002) plane. The average transmittance is above 85 % and in the range of 400-1000 nm for all films.

• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.141-147
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• 2010

In this study, high-k oxide films like $Al_2O_3$, $TiO_2$, $HfO_2$ were deposited on Si, $SiO_2$/Si, GaAs wafers, and then the thermal conductivity was measured by using thermo-reflectance method which utilizes the reflectance variation of the film surface produced by the periodic temperature variation. The result shows that high-k oxide films with 50 nm thickness have high thermal conductivity of 0.80~1.29 W/(mK). Therefore, effectively dissipate the heat generated in the electric circuit such as CMOS memory device, and the heat transfer changes according to the micro grain size.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.11
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• pp.1311-1316
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• 2014

To be used in a transmitter of a satellite transponder of this paper, X band 25W power amplifier module, a part constituting of high-power amplifier is transmitted to the equipment for transmitting to geostationary communications satellites(36,000Km distance). PAM consisted a total of four power amplifier module has a high output characteristic of the high-output amplifier is used in the ground station. Used in conjunction with the structured type power amplifier module is composed of Serial Combining Structure. This PAM(Power Amplifier Module) configured by combining the circuit with the power amplifier, 10 MMIC chips and the Al2O3 thin film substrate using a Hybrid Technique of power amplifier module, was implemented at X band PAM(Power Amplifier Module) of 25W grade.

• Journal of the Korean institute of surface engineering
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• v.43 no.3
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• pp.148-153
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• 2010

Transparent conducting films having a hybrid structure of GZO/Metal/GZO were prepared on glass substrates by sequential deposition using DC magnetron sputtering. Silver, copper, aluminum and zinc thin films were used as the intermediate metal layers in the hybrid structure. The electrical and optical properties of hybrid transparent conducting films were investigated with varying the thickness of metal layer or GZO layers. With increasing the metal thickness, hybrid films showed a noticeable improvement of the electrical conductivity, which is mainly dependent on the electrical property of the metal layer. GZO(40 nm)/Ag(10 nm)/GZO(40 nm) film exhibits a resistivity of $5.2{\times}10^{-5}{\Omega}{\cdot}cm$ with an optical transmittance of 82.8%. For the films with Zn interlayer, only marginal reduction in the resistivity was observed. Furthermore, unlike other metals, hybrid films with Zn interlayer showed a decrease in the resistivity with increasing the GZO thickness. The optimal thickness of GZO layer for anti-reflection effect at a given thickness of metal (10 nm) was found to be critically dependent on the refractive index of the metal. In addition, x-ray diffraction analysis showed that the insertion of Ag layer resulted in the improvement of crystallinity of GZO films, which is beneficial for the electrical and optical properties of hybrid-type transparent conducting films.