• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.6
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• pp.633-639
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• 1992

The physical and electrical properties of TiN/TiSiS12T contact barrier were studied. The TiN/TiSiS12T system was formed by rapid thermal anneal in NS12T ambient after the Ti film was deposited on silicon substrate. The Ti film reacts with NS12T gas to make a TiN layer at the surface and reacts with silicon to make a TiSiS12T layer at the interface respectively. It was found that the formation of TiN/TiSiS12T system depends on RTA temperature. In this experiment, competitive reaction for TiN/TiSiS12T system occured above $600^{\circ}C$. Ti-rich TiNS1xT layer and Ti-rich TiSiS1xT layer were formed at $600^{\circ}C$. stable structure TiN layer and TiSiS1xT layer which has CS149T phase and CS154T phase were formed at $700^{\circ}C$. Both stable TiN layer and CS154T phase TiSiS12T layer were formed at 80$0^{\circ}C$. The thickness of TiN/TiSiS12T system was increased as the thickness of deposited Ti film increased.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.8
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• pp.869-874
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• 1992

The physical and electrical properties of TiN/TiSiS12T bilayer were studied. The TiN/TiSiS12T bilayer was formed by rapid thermal anneal in NHS13T ambient after the Ti film was deposited on silicon substrate. The Ti film reacts with NHS13T gas to make a TiN layer at the surface and reacts with silicon to make a TiSiS12T layer at the interface respectively. It was found that the formation of TiN/TiSiS12T bilayer depends on RTA temperature. In this experiment, competitive reaction for TiN/TiSiS12T bilayer occured above $600^{\circ}C$. Ti-rich TiNS1xT layer and Ti-rich TiSiS1xT layer and Ti-rich TiSiS1xT layer were formed at $600^{\circ}C$. stable structure TiN layer TiSiS12T layer which has CS149T phase and CS154T phase were formed at $700^{\circ}C$. Both stable TiN layer and CS154T phase TiSiS12T layer were formed at 80$0^{\circ}C$. The thickness of TiN/TiSiS12T bilayer was increased as the thickness of deposited Ti film increased.

• Journal of the Korean Ceramic Society
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• v.45 no.9
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• pp.549-555
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• 2008

The thermal barrier coating must withstand erosion when subjected to flowing gas and should also maintain good stability and mechanical properties while it must also protect the turbine component from high temperature, hot corrosion, creep, and oxidation during operation. In this study we investigated the influence of subsurface layer, $Al_2O_3$ or NiCrCoAIY bond coat layer, on the indentation damage behavior of YSZ thermal barrier coating layers deposited by electron beam physical vapor deposition (EB-PVD). The bond coat is deposited using different process such as air plasma spray (APS) or spray of high velocity oxygen fuel (HVOF) and the thickness is varied. Hertzian indentation technique is used to induce micro damages on the coated layer. The stress-strain behaviors are characterized by results of the indentation tests.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.462-462
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• 2014

The effect of rear passivation for passivated emitter and rear cell (PERC) using ozone and H2O oxidant of atomic layer deposited (ALD) Al2O3 was studied by post-annealing in N2 and forming gas ambients. Rear surface of PERC solar cell was passivated by Al2O3 grown by ALD with ozone and H2O oxidant. Al2O3 grown by ALD with ozone oxidant has been known to have many advantages, such as lower interface defects, low leakage current density. Its passivation quality is better than Al2O3 with H2O. Al2O3 layer with 10 nm and 20 nm thickness was grown at $150^{\circ}C$ with ozone oxidant and at $250^{\circ}C$ with H2O oxidant. And then each samples were post-annealled at $450^{\circ}C$ in N2 ambients and at $850^{\circ}C$ in forming gas ambients. The passivation quality was investigated by measuring the minority carrier lifetime respectively. We examined atomic layer deposited Al2O3 such as growth rate, film density, thickness, negative fixed charge density at AlOx/Si interface, and reflectance. The influences of process temperature and heat treatment were investigated using Sinton (WCT-120) by Quasi-Steady State Photoconductance (QSSPC) mode. Ozone-based ALD Al2O3 film shows the best carrier lifetime at lower deposition temperature than H2O-based ALD.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.235-240
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• 2010

We investigated the carbon monoxide (CO) gas-sensing properties of nanostructured Al-doped zinc oxide thin films deposited on self-assembled Au nanodots (ZnO/Au thin films). The Al-doped ZnO thin film was deposited onto the structure by rf sputtering, resulting in a gas-sensing element comprising a ZnO-based active layer with an embedded Pt/Ti electrode covered by the self-assembled Au nanodots. Prior to the growth of the active ZnO layer, the Au nanodots were formed via annealing a thin Au layer with a thickness of 2 nm at a moderate temperature of $500^{\circ}C$. It was found that the ZnO/Au nanostructured thin film gas sensors showed a high maximum sensitivity to CO gas at $250^{\circ}C$ and a low CO detection limit of 5 ppm in dry air. Furthermore, the ZnO/Au thin film CO gas sensors exhibited fast response and recovery behaviors. The observed excellent CO gas-sensing properties of the nanostructured ZnO/Au thin films can be ascribed to the Au nanodots, acting as both a nucleation layer for the formation of the ZnO nanostructure and a catalyst in the CO surface reaction. These results suggest that the ZnO thin films deposited on self-assembled Au nanodots are promising for practical high-performance CO gas sensors.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.127-127
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• 2011

We investigate the transparent TFTs using a transparent ZnSnO3 (ZTO)/Ag/ZTO multilayer electrode as S/D electrodes with low resistivity of $3.24{\times}10^{-5}$ ohm-cm, and high transparency of 86.29% in ZTO based TFTs. The Transparent TFTs (TTFTs) are prepared on glass substrate coated 100 nm of ITO thin film. On atomic layer deposited $Al_2\;O_3$, 50 nm ZTO layer is deposited by RF magnetron sputtering through a shadow mask for channel layer using ZTO target with 1 : 1 molar ratio of ZnO : $SnO_2$. The power of 100W, the working pressure of 2mTorr, and the gas flow of Ar 20 sccm during the ZTO deposition. After channel layer deposition, a ZTO (35 nm)/Ag (12 nm)/ZTO(35 nm) multilayer is deposited by DC/RF magnetron sputtering to form transparent S/D electrodes which are patterned through the shadow mask. Devices are annealed in air at 300$^{\circ}C$ for 30 min following ZTO deposition. Using UV/Visible spectrometer, the optical transmittances of the TTFT using ZTO/Ag/ ZTO multilayer electrodes are compared with TFT using Mo electrode. The structural properties of ZTO based TTFT with ZTO/Ag/ZTO multilayer electrodes are analyzed by high resolution transmission electron microscopy (HREM) and X-ray photoelectron spectroscopy (XPS). The transfer and output characterization of ZTO TTFTs are examined by a customized probe station with HP4145B system in are.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.10
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• pp.652-657
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• 2015

We have investigated the properties of Al-doped ZnO (AZO) thin films as functions of atomic layer deposition (ALD) oxidants. AZO transparent conducting oxides (TCOs) layer was deposited by ALD with adding trimethylaluminum (TMA) and diethylzinc (DEZn). AZO films were deposited at low temperature with $H_2O$ and $O_3$ as oxidants. Electrical, optical and structural properties of AZO thin films were investigated by 4-point probe, Hall effect measurement, UV-VIS, and AFM. Microstructure and atomic bonding states were investigated by HRXRD and XPS. The resistivity of AZO films grown using $H_2O$ was lower than the films grown using $H_2O$ and $O_3$, by approximately two orders of magnitude. The differences in oxygen vacancy peak intensity of AZO films were correlated to the optical and electrical properties.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.77.2-77.2
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• 2013

In this talk, I will briefly review recent results of my group related to application of atomic layer deposition (ALD) for fabricating environmental catalysts and organic solar cells. ALD was used for preparing thin films of TiO2 and NiO on mesporous silica with a mean pore size of 15 nm. Upon depositing TiO2 thin films of TiO2 using ALD, the mesoporous structure of the silica substrate was preserved to some extent. We show that efficiency for removing toluene by adsorption and catalytic oxidation is dependent of mean thickness of TiO2 deposited on silica, i.e., fine tuning of the thickness of thin film using ALD can be beneficial for preparing high-performing adsorbents and oxidation catalysts of volatile organic compound. NiO/silica system prepared by ALD was used for catalysts of chemical conversion of CO2. Here, NiO nanoparticles are well dispersed on silica and confiend in the pore, showing high catalytic activity and stability at 800oC for CO2 reforming of methane reaction. We also used ALD for surface modulation of buffer layers of organic solar cell. TiO2 and ZnO thin films were deposited on wet-chemically prepared ZnO ripple structures, and thin films with mean thickness of ~2 nm showed highest power conversion efficiency of organic solar cell. Moreover, performance of ALD-prepared organic solar cells were shown to be more stable than those without ALD. Thin films of oxides deposited on ZnO ripple buffer layer could heal defect sites of ZnO, which can act as recombination center of electrons and holes.

• Journal of Sensor Science and Technology
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• v.15 no.2
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• pp.84-89
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• 2006

Highly concentrated p-type ZnO thin films can be obtained by doping of N, P and As elements. In this study, undoped ZnO buffer layers were prepared on a (0001) sapphire substrate by a ultra high vaccum pulsed laser deposition(UHV-PLD) method. ZnO buffer layers were deposited with various deposition temperature($400{\sim}700^{\circ}C$) at 350 mtorr of oxygen working pressure. Arsenic doped(1 wt%) ZnO thin films were deposited on the ZnO buffer layers by UHV-PLD. Crystallinity of the samples were evaluated by X-ray diffractometer and scanning electron microscopy. Optical, electrical properties of the ZnO thin films were estimated by photoluminescence(PL) and Hall measurements. The optimal condition of the undoped ZnO buffer layer for the deposition of As-doped ZnO thin films was at $600^{\circ}C$ of deposition temperature.

• Transactions on Electrical and Electronic Materials
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• v.13 no.4
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• pp.208-211
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• 2012

In the present study, a ZnO thin film, as a buffer layer of ITO (indium tin oxide) film was deposited on glass substrates by RF magnetron sputtering at low temperature of $150^{\circ}C$. In order to estimate the optical characteristics and compare with the experimental results in Glass/ZnO(100 nm)/ITO(35 nm) multilayered film, the simulation program, EMP (Essential Macleod Program) was adopted. The sheet resistance and optical transmittance of the films were measured using the four-point probe method and spectrophotometer, respectively. From X-ray diffraction patterns, all the films deposited at $150^{\circ}C$ demonstrated only the amorphous phase. Optical transmittance was the highest at a ZnO thickness of 100 nm. The ITO(35 nm)/ZnO(100 nm) film exhibits an optical transmittance of >92% at 550 nm. The multilayered film showed an electrical sheet resistance of 407 ${\Omega}/sq.$, which is significantly better than that of a single-layer ITO film without a ZnO buffer layer (815 ${\Omega}/sq.$).