• Korean Journal of Materials Research
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• v.13 no.2
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• pp.69-73
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• 2003

In this work, $IrO_2$thin films as bottom electrode of ferroelectric capacitors were deposited and characterized. The $IrO_2$films deposited in the conditions of 25, 40 and 50% oxygen ambient by sputtering method were annealed at 600, 700 and $800^{\circ}C$, respectively. It was found that the crystallinity and the surface morphology of $IrO_2$films affected the surface properties and electrical properties of SBT thin films prepared by the MOD method. With increasing temperature, the crystallinity and the roughness of $IrO_2$films were also increasing. This increasing of roughness degraded the surface properties and electrical properties of SBT films. We found an optimum condition of $IrO_2$films as bottom electrode for ferroelectric capacitor at 50% oxygen ambient and $600^{\circ}C$ annealing temperature. Electrical characterizations were performed by using$ IrO_2$bottom electrodes grown at an optimum conditions. The remanent polarization ($P_{r}$) of the Pt/SBT/$IrO_2$/$SiO_2$/Si structure was 2.75 $\mu$C/$\textrm{cm}^2$ at an applied voltage of 3 V. The leakage current density was $1.06${\times}$10^{-3}$ A/$\textrm{cm}^2$ at an applied voltage of 3 V.

• Current Photovoltaic Research
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• v.6 no.1
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• pp.21-26
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• 2018

Beside several advantages, the PV power generation as a clean energy source, is still below the supply level due to high power generation cost. Therefore, the interest in fabricating low-cost thin film solar cells is increasing continuously. $Cu_2O$, a low cost photovoltaic material, has a wide direct band gap of ~2.1 eV has along with the high theoretical energy conversion efficiency of about 20%. On the other hand, it has other benefits such as earth-abundance, low cost, non-toxic, high carrier mobility ($100cm^2/Vs$). In spite of these various advantages, the efficiency of $Cu_2O$ based solar cells is still significantly lower than the theoretical limit as reported in several literatures. One of the reasons behind the low efficiency of $Cu_2O$ solar cells can be the formation of CuO layer due to atmospheric surface oxidation of $Cu_2O$ absorber layer. In this work, atomic layer deposition method was used to remove the CuO layer that formed on $Cu_2O$ surface. First, $Cu_2O$ absorber layer was deposited by electrodeposition. On top of it buffer (ZnO) and TCO (AZO) layers were deposited by atomic layer deposition and rf-magnetron sputtering respectively. We fabricated the cells with a change in the deposition temperature of buffer layer ranging between $80^{\circ}C$ to $140^{\circ}C$. Finally, we compared the performance of fabricated solar cells, and studied the influence of buffer layer deposition temperature on $Cu_2O$ based solar cells by J-V and XPS measurements.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.1
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• pp.31-36
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• 2011

$TiO_2$ films were deposited on a glass substrate with RF magnetron sputtering and then surface of $TiO_2$ films were electron beam irradiated in a vacuum condition to investigate the effect of electron bombardment on the thin film crystallization, surface roughness and gas sensitivity for hydrogen. $TiO_2$ films that electron beam irradiated at 450eV were amorphous phase, while the films irradiated at 900 eV show the anatase (101) diffraction peak in XRD pattern. AFM measurements show that the roughness is depend on the electron irradiation energy. As increase the hydrogen gas concentration and operation temperature, the gas sensitivity of $TiO_2$ and $TiO_2$/ZnO films is increased proportionally and $TiO_2$ films that electron beam irradiated at 900 eV show the higher sensitivity than the films were irradiated at 450eV. From the XRD pattern and AFM observation, it is supposed that the crystallization and rough surface promote the hydrogen gas sensitivity of $TiO_2$ films.

• Journal of Sensor Science and Technology
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• v.8 no.2
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• pp.189-194
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• 1999

The heat treatment effects of the undoped ZnO and Al doped ZnO(AZO) transparent conductive films prepared by rf magnetron sputtering were investigated. The variations of the electrical and optical properties with heat treatment temperature and ambient were studied. The resistivity of the un doped ZnO films heat treated in air and $H_z$ plasma for 1 hour increased rapidly above $200^{\circ}C$ and $300^{\circ}C$, respectively. And that of the ZnO:Al films heat treated in air also increased rapidly above $300^{\circ}C$. On the other hand that of the ZnO:Al films heat treated in $H_z$ plasma was constant regardless of heat treatment temperature. The optical transmittance above 550nm is about 90% for all thin films regardless of impurity doping, the heat treatment temperature and ambient.

• Journal of Sensor Science and Technology
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• v.6 no.6
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• pp.491-499
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• 1997

We fabricated the ceramic PLT tablet which was composed of 5, 10 and 15 mol% lanthanum concentration and thin film PLT to develope pyroelectric materials, and investigated their characteristics. Using TG/DTA, we determined calcination and sintering temperature to sinter the PLT completely and to prevent volatilization of the Pb components. The calcination and sintering temperature were $850^{\circ}C$, $1150^{\circ}C$ respectively, and there was a lot of mass loss at higher sintering temperature. By measuring temperature-dielectric constant characteristics of ceramic tablet we investigated dielectric constant characteristics depends on La concentration. The Curie point of PLT with 5, 10 and 15 mol% lanthanum concentration were $330^{\circ}C$, $269^{\circ}C$ and $210^{\circ}C$ respectively. Using PLT ceramic tablet we observed IR detection characteristics, and then deposited PLT thin film by rf magnetron sputtering. We verified that PLT thin film fabricated with completely sintered PLT target had the same structure to target by investigating lattice constant and optical transparency.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.35-50
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• 2012

$900^{\circ}C$이상 초고온 He-gas 분위기 또는 용융불화염 (molten salts, FLINAK) 환경에서 사용될 VHTR(Very High Temperature Reactor)의 IHX(Intermediate heat exchanger)용 열수송 구조재료로 가장 가능성이 높은 합금인 Inconel 617 및 Hastelloy X 상에 습식화학적, 물리적기상합성법(Vacuum arc-plasma과 RF magnetron sputtering) 및 pack cementation에 의한 표면개질 및 마이크로 초내열(refractory ceramics) 코팅층(TiN, TiCN, TiAlN, $Al_2O_3$, $TiO_2$)을 형성시켰다. 고온 장기사용 시 문제가 될 수 있는 고온에서의 조직변화, 미세구조와 상(phase)형성, 고온 부식 및 그에 따른 마모(wear resistance) 손상 등 이들 소재의 내열, 내식 및 내마모 물성을 개선하는 연구를 수행하였다. TiAlN 박막의 경우 공기분위기에서 N이 분해되나 치밀한 산화물($TiO_2/Al_2O_3$ layer)을 형성하여 내식성 있는 보호피막을 형성함으로 기판과의 열팽창 계수로 인한 박리가 발생하지 않아 보호피막으로 적합하였다. Pack cementation법에 의한 aluminiding(Al-Ni합금)도 He 및 공기분위기에서 고온물성의 저하를 가져오는 $Cr_2O_3$의 생성을 충분히 억제하고 있었으며 He 및 air 분위기에서 사용이 가능한 박막으로 여겨진다. 내열 및 내식성에 대한 실험을 종합한 결과, 공기분위기에서 사용할 수 없는 박막은 He-gas 및 FLINAK(LiF-NaF-KF) 용융염 분위기에서도 사용할 수 없었으며, He-gas, FLINAK 및 air 분위기에서 모두 사용이 가능한 박막으로는 Inconel 617에서는 $(TiO_2-)Al_2O_3$, TiAlN 및 Al-Ni이었고 Hastelloy에서는 Al-Ni 및 $Al_2O_3$가 가장 적당하였다.

• Journal of the Korean institute of surface engineering
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• v.53 no.3
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• pp.104-108
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• 2020

ZnO single layer films (100 nm thick) and Au intermediated ZnO films (ZnO/Au/ZnO; ZAZ) were deposited on the glass substrate by RF and DC magnetron sputtering at room temperature and then the influence of the Au interlayer on the electrical and optical properties of the films were investigated. ZnO thin films show the visible transmittance of 90.3 % and sheet resistance of 63.2×10⁸ Ω/□. In ZAZ films, as Au interlayer thickness increased from 6 to 10 nm, the sheet resistance decreased from 58.3×10⁸ to 48.6 Ω/□, and the visible transmittance decreased from 84.2 to 73.9 %. From the observed results, it can be concluded that the intermediate Au thin film enhances the opto-electrical performance of ZnO films without intentional substrate heating.

• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.258-261
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• 2000

Highly (h00)-oriented (Ba, Sr)TiO$_3$(BST) thin films were grown by pulsed laser deposition on the perovskite LaNiO$_3$(LNO) metallic oxide layer as a bottom electrode. The LNO films were deposited on SiO$_2$/Si substrates by rf-magnetron sputtering method. The crystalline phases of the BST film were characterized by x-ray $\theta$-2$\theta$, $\omega$-rocking curve and $\psi$-scan diffraction measurements. The surface microsturcture observed by scanning electron microscopy was very dense and smooth. The low-frequency dielectric responses of the BST films grown at various substrate temperatures were measured as a function of frequency in the frequency range from 0.1 Hz to 10 MHz. The BST films have the dielectric constant of 265 at 1 kHz and showed multiple dielectric relaxation at the low frequency region. The origin of these low-frequency dielectric relaxation are attributed to the ionized space charge carriers such as the oxygen vacancies and defects in BST film, the interfacial polarization in the grain boundary region and the electrode polarization. We studied also on the capacitance-voltage characteristics of BST films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.163-166
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• 2002

We investigated structural and electrical properties of Metal-Oxide-Semiconductor(MOS) structure using Hafnium $oxide(HfO_{2})$ as high-k gate dielectric material. $HfO_{2}$ films are ultrathin gate dielectric material witch have a thickness less than 2.0nm， so it is spotlighted to be substituted $SiO_{2}$ as gate dielectric material. In this paper We have grown $HfO_{2}$ films with pt electrode on P-type Silicon substrate by RF magnetron sputtering system using $HfO_{2}$ target and oserved the property of semiconductor-oxide interface. Using pt electrode, it is necessary to be annealed at ${300^{\circ}C}$. This process is to increase an adhesion ratio between $HfO_{2}$ films with pt electrode. In film deposition process, the deposition time of $HfO_{2}$ films is an important parameter. Structura1 properties are invetigated by AES depth profile, and electrical properties by Capacitance-Voltage characteristic. Interface trap density are measured to observe the interface between $HfO_{2}$ with Si using High-frequency(1MHz) C-V and Quasi - static C-V characteristic.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1424-1426
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• 1997

저전압 구동이 가능한 교류구동형 박막전기발광소자를 구현하기 위해 높은 유전상수를 가지며 특히 광학적 굴절률이 발광박막과 유사하여 광학적 특성 개선에도 효과적인 것으로 알려져 있는 $Ta_2O_5$를 제조하였다. $Ta_2O_5$박막은 rf-magnetron sputtering방법으로 형성하였으며 기판온도, working pressure, 박막의 두께에 따른 전기적인 특성을 조사하였다. 10mTorr에서 제조된 $Ta_2O_5$박막은 $22{\sim}26$의 비유전율을 보였고, 유전손실은 $0.007{\sim}0.03(1kHz{\sim}10kHz)$의 값을 보였다. $100^{\circ}C$에서 제조된 박막의 전하저장용량은 $7.9{\mu}C/cm^2$이었다. 제조된 박막의 항복전압은 인가 전압의 극성에 의존하며, 전류특성은 기판온도와 200nm와 300nm의 두께에서는 $V^{1.95}{\sim}V^{2.35}$에 비례하는 space charge limited current특성을 보였고, 400nm에서는 Poole Frenkel특성을 보였다. 이상의 결과로 TFEL소자에 응용에 적합한 $Ta_2O_3$ 박막은 $200^{\circ}C$에서 증착되고 200nm와 300nm인 것으로 나타났으며, 제조된 MIS구조(ITO-$Ta_2O_5$-ZnS-Al)의 ACTFEL소자에서의 전도전하는 각각 $13uC/cm^2$, $8.3uC/cm^2$로 조사되었다.