• The Korean Journal of Ceramics
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• v.2 no.3
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• pp.162-166
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• 1996

The effects of NiO addition on the microstructure and microwave dielectric properties of ($Zr_{08}Sn_{02}$)$TiO_4$ (ZST) were investigated. With the NiO addition, a higher density of ZST ceramics than 95% of the theoretical values has been obtained in the sintering temperature range of 1400 to 150$0^{\circ}C$. Energy dispersive X-ray spectrometry (EDS) analysis of sintered specimen shows the presence of second phase at grain boundaries, which is considered to be $NiTiO_3$. Dielectric constant of the specimen is found to increase linearly with density. Q-values and TC$_r$ decrease with increasing NiO content. The variation of dielectric properties with NiO content is discussed in terms of the second phase. The ZST ceramics with 0.25 wt% NiO showed ${\varepsilon}_{\gamma}$=38, Q=7000 at GHz and TC$\gamma$=-0.5 ppm/$^{\circ}C$, comparable with the values obtained by the previous investigations.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.231-231
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• 2011

본 연구에서는 co-sputtering 시스템을 이용하여 아나타세 TiO2의 도핑 농도 변화에 따른 다성분계 TiO2-ITO (TITO) 박막의 전기적, 광학적, 구조적 특성 변화 및 급속 열처리(RTA) 공정에 따른 전기적, 광학적 특성 변화를 분석하였다. 실험을 위해 아나타세 TiO2 타겟과 ITO 타겟(10 wt% $SnO_2$ doped $In_2O_3$)이 tilted cathode에 장착되었으며, ITO 타겟의 인가전류를 120 W로 고정한 채 아나타세 TiO2 타겟의 인가전류를 증가시킴으로써 도핑 농도를 변화하였다. 제작된 TITO 투명 전극의 전기적, 광학적, 구조적 특성 평가를 위해 four-point probe measurement, Hall effect measurement, UV/Vis. spectrometry, scanning electron microscopy (SEM) 이용하여 각각의 특성을 분석하였다. 상온에서 제작된 TITO의 경우 최적화된 $TiO_2$ 인가전류 100W에서 460.8 ohm/sq. 의 전기적 특성과 가시광선 영역 400~550 nm에서 85% 이상의 광학적 투과율을 확보할 수 있었다. 뿐만 아니라 상온에서 최적화된 TITO 투명 전극의 급속 열처리 시 600$^{\circ}C$ 급속 열처리 조건에서 매우 낮은 25.94 ohm/sq.면저항, $5.1{\times}10^{-4}$ ohm-cm 비저항과 81% 투과율을 확보할 수 있었다. 아나타세 $TiO_2$가 도핑된 TITO 투명 전극의 급속 열처리 공정에도 불구하고 매우 평탄한 표면을 나타냄을 SEM 이미지를 통하여 확인할 수 있었다. 이러한 TITO 투명 전극의 우수한 전기적, 광학적, 구조적 특성은 indium saving 투명 전극으로써 고가 ITO 박막의 대치가능성을 나타낸다.

• Journal of Sensor Science and Technology
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• v.21 no.6
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• pp.395-401
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• 2012

The bond strength of three types of $TiO_2$ coatings onto fluorine-doped $SnO_2$ (FTO) glass was investigated with the aid of a tape test according to ASTM D 3359-95. Transmittance was then measured using an UV-vis spectrophotometer in the wavelength range of 300 nm to 800 nm to evaluate the extent of adhesion of $TiO_2$ nanorods/nanoparticles on FTO glass. A sharp interface between the coating layer and the substrate was observed for single $TiO_2$ coating ($TiO_2$ nanorods/FTO glass), which may be detrimental to the bonding strength. In multicoating sample ($TiO_2$ nanorod/$TiO_2$ nanoparticle/$TiO_2$ nanoparticle/FTO glass), the tape test was not performed due to severe peeling-off prior to the test. On the other hand, the dual coating sample ($TiO_2$ nanorod/$TiO_2$ nanoparticle/FTO glass) showed minimum variation of transmittance (4%) after the test, suggesting that the topcoat adheres well with the FTO substrate due to the presence of the $TiO_2$ nanoparticle buffer layer. The use of a $TiO_2$ nanorod electrode layer with good adhesion may be attributed to the excellent dye sensitized solar cell performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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• pp.766-771
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• 2009

Lead-free $0.94(Na_{0.5}K_{0.5})NbO_3$-0.06Ba$(Ti_{0.9}Sn_{0.1})O_3$ [0.94NKN-0.06BTS] ceramics doped with 1 mol% $MnO_2$ were synthesized by a conventional solid state method. The phase transitional behavior and piezoelectric properties of the ceramics sintered at various temperatures were investigated. The 0.94NKN-0.06BTS ceramics sintered at $1050^{\circ}C$, having morphotropic phase boundary of orthorhombic and tetragonal phases, exhibited a microstructure with abnormal grain growth. A diffused phase transition behavior for all the specimens was verified as high degree of diffuseness (${\gamma}$) values from 1.45 to 1.79. A high piezoelectric constant of $d_{33}=256$ pC/N and a satisfactory electromechanical coupling factor of $k_p=42%$ were obtained for the relatively dense 0.94NKN-0.06BTS ceramics sintered at $1050^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.329-331
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• 2003

In this paper, $0.10Pb(Sb_{1/2}Sn_{1/2})O_3-0.25PbTiO_3-0.65PbZrO_3$ ceramics were fabricated by the mixed-oxide method. The sintering temperature and time were $1230^{\circ}C$ and 2(hr), respectively. The structural, dielectric and pyroelectric properties with addition of $Y_2O_3$ were studied. The crystal structure of a specimen was rhombohedral. As a result of SEM, the average grain size were decreased with increasing the contents of $Y_2O_3$. Relative dielectric constant and dielectric loss of the specimen doped with 0.2wt% $Y_2O_3$ were 597 and 0.022, respectively. Remanent polarization and coercive field of the specimen doped with 0.4wt% $Y_2O_3$ were $8.5[{\mu}C/cm^2]$ and 10.2[kV/cm], respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.296-299
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• 2003

In this paper, $0.10Pb(Sb_{1/2}Sn_{1/2})O_3-0.25PbTiO_3-0.65PbZrO_3$ ceramics were fabricated by the mixed-oxide method. The sintering temperature and time were $1230^{\circ}C$ and 2[hr], respectively. The structural, dielectric and piezoelectric properties with addition of NiO were studied. The crystal structure of a specimen was rhombohedral. As a result of SEM, the average grain size were decreased with increasing the contents of NiO. But the grains of the specimens doped with 0.4wt% NiO were increased, due to deposits of excess NiO at grain boundaries in the liquid phase. Relative dielectric constant and dielectric loss of the specimen doped with 0.1wt% NiO were 701 and 0.026, respectively.

• Journal of the Korean Ceramic Society
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• v.48 no.1
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• pp.94-98
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• 2011

A Sn-doped $In_2O_3$ (ITO) nanowire photoelectrode was produced using a simple metal evaporation method at low synthesis temperature (< $540^{\circ}C$). The nanowire electrodes have large surface area compared with that of flat ITO thin film, and show low electrical resistivity of $5.6{\times}10^{-3}{\Omega}cm$ at room temperature. In order to apply ITO nanowires to the photoelectrodes of dye-sensitized solar cell (DSSC), those surfaces were modified by $TiO_2$ nanoparticles using a chemical bath deposition (CBD) method. The conversion efficiency of the fabricated $TiO_2$/ITO nanostructure-based DSSC was obtained at 1.4%, which was increased value by a factor of 6 than one without ITO nanowires photoelectrode. This result is attributed to the large surface area and superior electrical property of the ITO nanowires photoelectrode, as well as the structural advantages, including short diffusion length of photo-induced electrons, of the fabricated $TiO_2$/ITO nanostructure-based DSSC.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.33.1-33.1
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• 2009

Lead-free (1-x)$(Na_{0.5}K_{0.5})NbO_3$-xBa($Ti_{0.9}Sn_{0.1})O_3$ [NKN-BTS-100x] ceramics doped with 1 mol% $MnO_2$ have been prepared by the conventional solid state method and their structural and piezoelectric properties were investigated. The NKN-BTS-100x ceramics exhibited a dense and homogeneous microstructure when they were sintered at $1030-1150^{\circ}C$. Grain growth was observed for the specimen sintered at relatively low temperature of $1050^{\circ}C$. A tetragonal/orthorhombic morphotropic phase boundary (MPB) in the perovskite structure was also appeared for the NKN-BTS-100x ceramics (0.04$1050^{\circ}C$. The enhanced piezoelectric properties in the NKN-BTS ceramics with a MPB composition were obtained. Especially, for the NKN-BTS-6 ceramics, a high dielectric constant (${\varepsilon}^T_3/\varepsilon_0=1,400$), piezoelectric constant ($d_{33}=237$) and electromechanical coupling factor ($k_p=0.42$) were obtained.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.453.1-453.1
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• 2014

Fluorine-doped tin oxide (FTO), which is commonly used in dye-sensitized solar cells (DSSCs), is a promising material of transparent conducting oxides (TCOs) because of advantages such as high chemical stability, high resistance, high optical transparency (>80% at 550nm), and low electrical resistivity (${\sim}10-4{\Omega}{\cdot}cm$). Especially, dye-sensitized solar cells (DSSCs) have been actively studied since Gratzel's research group required FTO substrate as a charge collector. When FTO substrates are used in DSSCs, photo-injected electrons may experience recombination at interface between dye-bonded semiconductor oxides ($TiO_2$) on FTO substrate and the electrolyte. To solve these problems, one is that because recombination at FTO substrate cannot be neglected, thin $TiO_2$ layer on FTO substrate as a blocking layer was introduced. The other is to control the morphology of surface on FTO substrate to reduce a loss of electrons. The structural, electrical, and optical characteristics of morphology controlled-FTO thin films as TCO materials were analyzed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Hall Effect Measurement, and UV spectrophotometer. The performance of DSSCs fabricated with morphology controlled FTO substrates was performed using Power Conversion Efficiency (PCE). We will discuss these results in detail in Conference.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.21-25
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• 2017

In this study, we have fabricated Schottky barrier diodes (SBD) on single-crystal ${\beta}-Ga_2O_3$ semiconductor that has received much attention for use in next-generation power devices. The SBD had a Pt/Ti/Au Schottky contact on a $2{\mu}m$ Sn-doped low concentration N-type epitaxial layer. The fabricated device exhibited a breakdown voltage of > 180 V, a specific on-resistance of $1.26m{\Omega}{\cdot}cm^2$, and forward current densities of $77A/cm^2$ at 1 V and $473A/cm^2$ at 1.5 V, which proved the potential for use in power device fabrication.