• 한국전기전자재료학회논문지
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• 제22권10호
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• pp.837-843
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• 2009

$TiO_2$(2 wt.%)-doped ZnO(TZO) films with thickness from 100 nm to 500 nm were prepared on polyethylene naphthalate(PEN) substrate under various rf-power range from 40 W to 80 W. Their electrical and optical properties were investigated as a function of rf-power. We think that these properties were closely related with the crystallization and the film density of TZO films. It was also presumed that the vaporization of the water vapor and other adsorbed particles such as an organic solvents can affect the electrical properties of the conventional transparent conductive oxide(TCO) films. On the other hand, since the TZO film deposited on glass substrate at room temperature with rf-power of 80 W shows a very low resistivity of $7.5\times10^{-4}\;\Omega{\cdot}cm$ and a very excellent transmittance over an average 85% in the visible range, that is comparable to that of ITO films. Therefore, we expect that the TZO films can be used as transparent electrode for optoelectronic devices such as touch-panels, flat-panel displays, and thin-film solar cells.

• 한국전기전자재료학회논문지
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• 제30권10호
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• pp.646-650
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• 2017

We have evaluated the ferroelectric and electrical properties of pure $BiFeO_3$ (BFO) and $Bi_{0.9}A_{0.1}Fe_{0.975}V_{0.025}O_{3+{\alpha}}$ (A=Nd, Tb) thin films on $Pt(111)/Ti/SiO_2/Si(100)$ substrates by using a chemical solution deposition method. The remnant polarization ($2P_r$) of the $Bi_{0.9}Tb_{0.1}Fe_{0.975}V_{0.025}O_{3+{\alpha}}$ (BTFVO) thin film was approximately $65{\mu}C/cm^2$, with a maximum applied electric field of 950 kV/cm and a frequency of 10 kHz, where as that of the $Bi_{0.9}Nd_{0.1}Fe_{0.975}V_{0.025}O_{3+{\alpha}}$ (BNFVO) thin film was approximately $37{\mu}C/cm^2$ with a maximum applied electric field of 910 kV/cm. The leakage current density of the co-doped BNFVO thin film was four orders of magnitude lower than that of the pure BFO thin film, at $2.75{\times}10^{-7}A/cm^2$ with an applied electric field of 100 kV/cm. The grain size and uniformity of the co-doped BNFVO and BTFVO thin films were improved, in comparison to the pure BFO thin film, through structural modificationsdue to the co-doping with Nd and Tb.

• 한국재료학회지
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• 제33권6호
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• pp.229-235
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• 2023

An all-perovskite oxide heterostructure composed of SrSnO₃/Nb-doped SrTiO₃ was fabricated using the pulsed laser deposition method. In-plane and out-of-plane structural characterization of the fabricated films were analyzed by x-ray diffraction with θ-2θ scans and φ scans. X-ray photoelectron spectroscopy measurement was performed to check the film's composition. The electrical transport characteristic of the heterostructure was determined by applying a pulsed dc bias across the interface. Unusual transport properties of the interface between the SrSnO₃ and Nb-doped SrTiO₃ were investigated at temperatures from 100 to 300 K. A diodelike rectifying behavior was observed in the temperature-dependent current-voltage (IV) measurements. The forward current showed the typical IV characteristics of p-n junctions or Schottky diodes, and were perfectly fitted using the thermionic emission model. Two regions with different transport mechanism were detected, and the boundary curve was expressed by ln I = -1.28V - 13. Under reverse bias, however, the temperature- dependent IV curves revealed an unusual increase in the reverse-bias current with decreasing temperature, indicating tunneling effects at the interface. The Poole-Frenkel emission was used to explain this electrical transport mechanism under the reverse voltages.

• 한국자기학회지
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• 제15권2호
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• pp.109-112
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• 2005

Electronic and magnetic properties of $Ti_{1-x}M_xO_{2-\delta}$ (M=Co and Fe) thin films grown by sol-gel method have been investigated. Anatase and rutile $Ti_{1-x}Co_xO_{2-\delta}$ films were successfully grown on $Al_2O_3$ (0001) substrates and exhibited p-type electrical conductivity while the undoped films n-type conductivity. Room temperature vibrating sample magnetometry measurements on the anatase and rutile $Ti_{1-x}Co_xO_{2-\delta}$ films with same x ($=4.8 at.{\%}$) showed quite similar magnetic hysteresis curves with the saturation magnetic moment of $\~4 {\mu}_B$ per Co ion despite their differences in structural and electronic properties. Such giant magnetic moment is attributable to the unquenched orbital moment of the $Co^{2+}$ ions substituting the octahedral $Ti^{4+}$ sites. Similar ferromagnetic behavior was observed for $Ti_{1-x}Fe_xO_{2-\delta}$ films that are highly resistive compared to the Co doped samples. Saturation magnetic moment was found to decrease for higher x, i.e., $\~2$ and $\~1.5 {\mu}_B$ per Fe ion for x=2.4 and 5.8 at. $\%$, respectively. Conversion electron $M\ddot{o}ssbauer$ spectroscopy measurements predicted the coexistence of $Fe^{2+}$ and $Fe^{3+}$ ions at the octahedral sites of $Ti_{1-x}Fe_xO_{2-\delta}$.

• Transactions on Electrical and Electronic Materials
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• 제14권5호
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• pp.242-245
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• 2013

Sn-doped $In_2O_3$ (ITO) thin films were prepared by radio frequency magnetron sputtering without intentional substrate heating on bare glass and $TiO_2$-deposited glass substrates to investigate the effect of a $TiO_2$ buffer layer on the electrical and optical properties of ITO films. The thicknesses of $TiO_2$ and ITO films were kept constant at 5 and 100 nm, respectively. As-deposited ITO single layer films show an optical transmittance of 75.9%, while $ITO/TiO_2$ bi-layered films show a lower transmittance of 76.1%. However, as-deposited $ITO/TiO_2$ films show a lower resistivity ($9.87{\times}10^{-4}{\Omega}cm$) than that of ITO single layer films. In addition, the work function of the ITO film is affected by the $TiO_2$ buffer layer, with the $ITO/TiO_2$ films having a higher work-function (5.0 eV) than that of the ITO single layer films. The experimental results indicate that a 5-nm-thick $TiO_2$ buffer layer on the $ITO/TiO_2$ films results in better performance than conventional ITO single layer films.

• 한국전기전자재료학회논문지
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• 제32권3호
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• pp.229-233
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• 2019

Pure $BiFeO_3$ (BFO) and (Eu, V) co-doped $Bi_{0.9}Eu_{0.1}Fe_{0.975}V_{0.025}O_{3+{\delta}}$ (BEFVO) thin films were deposited on $Pt(111)/Ti/SiO_2/Si(100)$ substrates by chemical solution deposition. The effects of co-doping were observed by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM). The electrical properties of the BEFVO thin film were improved as compared to those of the pure BFO thin film. The remnant polarization ($2P_r$) of the BEFVO thin film was approximately $26{\mu}C/cm^2$ at a maximum electric field of 1,190 kV/cm with a frequency of 1 kHz. The leakage current density of the co-doped BEFVO thin film ($4.81{\times}10^{-5}A/cm^2$ at 100 kV/cm) was two orders of magnitude lower than of that of the pure BFO thin film.

• Bulletin of the Korean Chemical Society
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• 제29권5호
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• pp.1038-1042
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• 2008

Mono and multilayer TiO2(Fe, $PEG_{600}$) films were deposited by the dip-coating on $SiO_2$/glass substrate using sol-gel method. In an attempt to improve the antibacterial properties of doped $TiO_2$ films, the influence of the iron oxides and polyethilenglycol ($PEG_{600}$) on the morphological, optical, surface chemical composition and biological properties of nanostructured layers was studied. Complementary measurements were performed including Spectroscopic Ellipsometry (SE), Scanning Electron Microscopy (SEM) coupled with the fractal analysis, X-Ray Photoelectron Spectroscopy (XPS) and antibacterial tests. It was found that different concentrations of Fe and $PEG_{600}$ added to coating solution strongly influence the porosity and morphology at nanometric scale related to fractal behaviour and the elemental and chemical states of the surfaces as well. The thermal treatment under oxidative atmosphere leads to films densification and oxides phase stabilization. The antibacterial activity of coatings against Escherichia Coli bacteria was examined by specific antibacterial tests.

• 한국재료학회지
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• 제20권5호
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• pp.257-261
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• 2010

A non-volatile resistive random access memory (RRAM) device with a Cr-doped $SrZrO_3/SrRuO_3$ bottom electrode heterostructure was fabricated on $SrTiO_3$ substrates using pulsed laser deposition. During the deposition process, the substrate temperature was $650^{\circ}C$ and the variable ambient oxygen pressure had a range of 50-250 mTorr. The sensitive dependences of the film structure on the processing oxygen pressure are important in controlling the bistable resistive switching of the Cr-doped $SrZrO_3$ film. Therefore, oxygen pressure plays a crucial role in determining electrical properties and film growth characteristics such as various microstructural defects and crystallization. Inside, the microstructure and crystallinity of the Cr-doped $SrZrO_3$ film by oxygen pressure were strong effects on the set, reset switching voltage of the Cr-doped $SrZrO_3$. The bistable switching is related to the defects and controls their number and structure. Therefore, the relation of defects generated and resistive switching behavior by oxygen pressure change will be discussed. We found that deposition conditions and ambient oxygen pressure highly affect the switching behavior. It is suggested that the interface between the top electrode and Cr-doped $SrZrO_3$ perovskite plays an important role in the resistive switching behavior. From I-V characteristics, a typical ON state resistance of $100-200\;{\Omega}$ and a typical OFF state resistance of $1-2\;k{\Omega}$, were observed. These transition metal-doped perovskite thin films can be used for memory device applications due to their high ON/OFF ratio, simple device structure, and non-volatility.

• 공업화학
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• 제19권3호
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• pp.270-276
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• 2008

$TiO_2$의 가장 큰 특징은 광촉매적 특성을 들 수 있으나 순수한 $TiO_2$는 자외선 영역에서만 활성을 보이는 단점이 있다. 단점을 보완하고자 본 연구에서는 초고온, 고활성을 이용한 열플라즈마 공정으로 질소가 도핑된 $TiO_2$를 합성하여 $TiO_2$의 광촉매적 특성을 높이고자 하였다. 직류 플라즈마 제트를 이용하여 비금속이온인 질소와 반응 가스인 산소를 $TiCl_4$와 함께 플라즈마 반응기 안에서 반응시켜 질소가 도핑된 $TiO_2$ 나노 분말을 합성하였다. 합성 조건으로 질소의 유량을 변화하였다. 합성 변수에 따른 입자의 상조성, 크기를 분석하였고 아세트알데히드와 곰팡이를 광분해하는 실험을 통해 광촉매 활성을 살펴보았다. 한편 $TiO_2$의 분말 상태와 코팅된 상태의 광촉매 특성을 비교하고자 합성한 분말의 스핀 코팅과 PLD (Pulsed Laser Deposition)을 통해 $TiO_2$를 코팅하였다. 아세트알데히드 분해 실험의 결과 질소가 도핑된 $TiO_2$ 분말의 경우가 순수한 $TiO_2$ 분말에 비해 가시영역에서의 광촉매 활성이 두 배 이상 뛰어난 것을 확인하였으며, 곰팡이 분해 실험 결과 역시 질소가 도핑된 $TiO_2$ 분말에 곰팡이가 분해되는 것을 확인하였다. 분말과 필름을 제조하여 메틸렌블루 광분해 실험한 결과 분말의 경우 100% $TiO_2$입자가 메틸렌블루 분해에 이용되며, 반면 스핀 코팅의 경우 바인더의 함량 때문에 20~30%의 $TiO_2$만이 분해에 이용되기 때문에, 분말의 경우 초기 30 mL 메틸렌블루를 한번에 분해할 수 있었다.

• 열처리공학회지
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• 제36권4호
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• pp.193-197
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• 2023

Transparent and conducting titanium (Ti) doped indium oxide (TIO) thin films were deposited on the poly-imide (PI) substrate with radio frequency magnetron sputtering and then electron irradiation was conducted on the TIO film's surface to investigate the effect electron irradiation on the crystallization and opto-electrical properties of the films. All x-ray diffraction (XRD) pattern showed two diffraction peaks of the In₂O₂ (431) and (444) planes with regardless of the electron beam irradiation energy. In the AFM analysis, the surface roughness of as deposited films was 3.29 nm, while the films electron irradiated at 700 eV, show a lower RMS roughness of 2.62 nm. In this study, the FOM of as deposited TIO films is 6.82 × 10^-3 Ω^-1, while the films electron irradiated at 500 eV show the higher FOM value of 1.0 × 10^-2 Ω^-1. Thus, it is concluded that the post-deposition electron beam irradiation at 500 eV is the one of effective methods of crystallization and enhancement of opto-electrical performance of TIO thin film deposited on the PI substrate.