• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.5
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• pp.201-205
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• 2003

We synthesized dendrimers containing light switchable units, azobenzene group. And the dendrimer containing 48 pyridinepropanol functional end group, which could form a complex structure with metal ions was synthesized. To apply to the molecular level devices or data storage system using Langmuir-Blodgett(LB) film, we firstly investigated the monolayer behavior using the surface pressure-area($\pi$-A) isotherms at air-water interface. And then the surface pressure shift of monolayer by light irradiation was also measured to the dendrimer with azobezene group. As a result, the monolayer of dendrimer with azobenzene group showed the reversible photo-switching behavior by the isomerization of azobenzene group in their periphery. The samples for electrical measurement were fabricated to two types which were pure dendrimer with pyridinepropanol group and its complexes with $Pt^4+$ ions by LB method. We have studied the electrical properties of the ultra thin dendrimer LB films investigated by the current-voltage(I-V) characteristics of Metal/Dendrimer LB films/Metal(MIM) structure. And we have investigated different results in the surface activity at the air-water interface as well as the electrical properties for the monolayers of pure dendrimer with pyridinevopanol group and its complex with $Pt^4+$ ions. In conclusion, it is demonstrated that the metal ion around dendrimer with pyri야nepropanol group can contribute to make formation of network structure among dendrimers and it result from the change of electrical properties. This results suggest that the dendrimers with azobenzene group and pvridinedropanol group can be applied to high efficient nano-device of molecular level.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.5
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• pp.201-201
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• 2003

We synthesized dendrimers containing light switchable units, azobenzene group. And the dendrimer containing 48 pyridinepropanol functional end group, which could form a complex structure with metal ions was synthesized. To apply to the molecular level devices or data storage system using Langmuir-Blodgett(LB) film, we firstly investigated the monolayer behavior using the surface pressure-area($\pi$-A) isotherms at air-water interface. And then the surface pressure shift of monolayer by light irradiation was also measured to the dendrimer with azobezene group. As a result, the monolayer of dendrimer with azobenzene group showed the reversible photo-switching behavior by the isomerization of azobenzene group in their periphery. The samples for electrical measurement were fabricated to two types which were pure dendrimer with pyridinepropanol group and its complexes with $Pt^4+$ ions by LB method. We have studied the electrical properties of the ultra thin dendrimer LB films investigated by the current-voltage(I-V) characteristics of Metal/Dendrimer LB films/Metal(MIM) structure. And we have investigated different results in the surface activity at the air-water interface as well as the electrical properties for the monolayers of pure dendrimer with pyridinevopanol group and its complex with $Pt^4+$ ions. In conclusion, it is demonstrated that the metal ion around dendrimer with pyri야nepropanol group can contribute to make formation of network structure among dendrimers and it result from the change of electrical properties. This results suggest that the dendrimers with azobenzene group and pvridinedropanol group can be applied to high efficient nano-device of molecular level.

• Journal of the Korean Magnetics Society
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• v.25 no.2
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• pp.43-46
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• 2015

$Si(100){\backslash}200nm$ $SiO_2{\backslash}5nm$ $Ta{\backslash}5nm$ $MgO{\backslash}35nm$ $Fe_3O_4$ multi-layers were prepared by using RF-sputtering and ultra-high vacuum molecular beam epitaxy (UHV-MBE) techniques. After post-annealing the multi-layers at $500^{\circ}C$ for 1 hour under the high vacuum of ${\sim}1{\times}10^{-6}Torr$, we observed ferromagnetic properties at room temperature as well as the Verwey transition which is the typical features of magnetite crystals formed. We have carried out a comparative study of the effect of Ta buffered layer on the crystallinity and magnetic properties of $Fe_3O_4$ thin films prepared under different growth and annealing conditions.

• Journal of Sensor Science and Technology
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• v.13 no.2
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• pp.128-132
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• 2004

Short wave infrared (SWIR) photovoltaic devices have been fabricated from metal organic vapour phase epitaxy (MOVPE) grown n- on p- HgCdTe films on GaAs substrates. The MOVPE grown films were processed into mesa type discrete devices with wet chemical etching employed for meas delineation and ZnS surface passivatlon. ZnS was thermally evaporated from effusion cell in an ultra high vacuum (UHV) chamber. The main features of the ZnS deposited from effusion cell in UHV chamber are low fixed surface charge density, and small hysteresis. It was found that a negative flat band voltage with -0.6 V has been obtained for Metal Insulator Semiconductor (MIS) capacitor which was evaporated at $910^{\circ}C$ for 90 min. Current-Voltage (I-V) and temperature dependence of the I-V characteristics were measured in the temperature range 80 - 300 K. The Zero bias dynamic resistance-area product ($R_{0}A$) was about $7500{\Omega}-cm^{2}$ at room temperature. The physical mechanisms that dominate dark current properties in the HgCdTe photodiodes are examined by the dependence of the $R_{0}A$ product upon reciprocal temperature. From theoretical considerations and known current expressions for thermal and tunnelling process, the device is shown to be diffusion limited up to 180 K and g-r limited at temperature below this.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.3
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• pp.431-437
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• 1998

In this paper, we have investigated the electrical properties of ultra-thin nitrided oxide(NO) and re-oxidized nitrided oxide(ONO) films that are considered to be promising candidates for replacing conventional silicon dioxide film in ULSI level integration. Especially, we have studied a variation of I-V characteristics, gate voltage shift, and time-dependent dielectric breakdown(TDDB) of thin layer NO and ONO film depending on nitridation and reoxidation time, respectively, and measured a variation of leakage current and charge-to-breakdown(Q$\_bd$) of optimized NO and ONO film depending on ambient temperature, and then compared with the properties of conventional SIO$\_2$. From the results, we find that these NO and ONO thin films are strongly influenced by process time and the optimized ONO film shows superior dielectric characteristics, and (Q$\_bd$) performance over the NO film and SIO$\_2$, while maintaining a similar electric field dependence compared with NO layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.341-341
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• 2016

The discovery of light emission in nanostructured silicon has opened up new avenues of research in nano-silicon based devices. One such pathway is the application of silicon quantum dots in advanced photovoltaic and light emitting devices. Recently, there is increasing interest on the silicon quantum dots (c-Si QDs) films embedded in amorphous hydrogenated silicon-nitride dielectric matrix (a-SiNx: H), which are familiar as c-Si/a-SiNx:H QDs thin films. However, due to the limitation of the requirement of a very high deposition temperature along with post annealing and a low growth rate, extensive research are being undertaken to elevate these issues, for the point of view of applications, using plasma assisted deposition methods by using different plasma concepts. This work addresses about rapid growth and single step development of c-Si/a-SiNx:H QDs thin films deposited by RF (13.56 MHz) and ultra-high frequency (UHF ~ 320 MHz) low-pressure plasma processing of a mixture of silane (SiH4) and ammonia (NH3) gases diluted in hydrogen (H2) at a low growth temperature ($230^{\circ}C$). In the films the c-Si QDs of varying size, with an overall crystallinity of 60-80 %, are embedded in an a-SiNx: H matrix. The important result includes the formation of the tunable QD size of ~ 5-20 nm, having a thermodynamically favorable <220> crystallographic orientation, along with distinct signatures of the growth of ${\alpha}$-Si3N4 and ${\beta}$-Si3N4 components. Also, the roles of different plasma characteristics on the film properties are investigated using various plasma diagnostics and film analysis tools.

• Journal of the Korean Chemical Society
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• v.41 no.5
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• pp.223-233
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• 1997

Ultra-thin $TiO_2$ films are grown on the Mo(100) surface using evaporated Ti metal under ambient $O_2$ pressure. The thickness of the $TiO_2$ film is controlled by the dosing rate of Ti metal over Mo(100) which is determined from the Auger signal changes with dosing time. 30 ML, 5 ML, and 1.6 ML thick films are prepared and used to determine the growth mechanism, the chemical composition, and the surface structure of the films. The growth mechanism of the $TiO_2$ film on Mo(100) is observed to follow the layer-by-layer growth mechanism. The chemical composition of the film is found to be that of bulk $TiO_2$. The surface plane of the film is (001), which facets irreversibly at 1200 K. The LEED pattern obtained from the film can be explained with the faceted surface with {011} planes reconstructed to $(2\sqrt2{\times}\sqrt2)R45^{\circ}$ with respect to the $TiO_2$ (001) surface. The film is somewhat thermally unstable when annealed to 1300 K. The film sputtered with $Ar^+$ ion is also studied by XPS.

• Journal of Electrochemical Science and Technology
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• v.10 no.4
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• pp.424-432
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• 2019

Planar BiVO₄ and 3 wt% Mo-doped BiVO₄ (abbreviated as Mo:BiVO₄) film were prepared by the facile spin-coating method on fluorine doped SnO₂(FTO) substrate in the same precursor solution including the Mo precursor in Mo:BiVO₄ film. After annealing at a high temperature of 450℃ for 30 min to improve crystallinity, the films exhibited the monoclinic crystalline phase and nanoporous architecture. Both films showed no remarkably discrepancy in crystalline or morphological properties. To investigate the effect of surface passivation exploring the Al₂O₃ layer, the ultra-thin Al₂O₃ layer with a thickness of approximately 2 nm was deposited on BiVO₄ film using the atomic layer deposition (ALD) method. No distinct morphological modification was observed for all prepared BiVO₄ and Mo:BiVO₄ films. Only slightly reduced nanopores were observed. Although both samples showed some reduction of light absorption in the visible wavelength after coating of Al₂O₃ layer, the Al₂O₃ coated BiVO₄ (Al₂O₃/BiVO₄) film exhibited enhanced photoelectrochemical performance in 0.5 M Na₂SO₄ solution (pH 6.5), having higher photocurrent density (0.91 mA/㎠ at 1.23 V vs. reversible hydrogen electrode (RHE), briefly abbreviated as V_RHE) than BiVO₄ film (0.12 mA/㎠ at 1.23 V_RHE). Moreover, Al₂O₃ coating on the Mo:BiVO₄ film exhibited more enhanced photocurrent density (1.5 mA/㎠ at 1.23 V_RHE) than the Mo:BiVO₄ film (0.86 mA/㎠ at 1.23 V_RHE). To examine the reasons, capacitance measurement and Mott-Schottky analysis were conducted, revealing that the significant degradation of capacitance value was observed in both BiVO₄ film and Al₂O₃/Mo:BiVO₄ film, probably due to degraded capacitance by surface passivation. Furthermore, the flat-band potential (V_FB) was negatively shifted to about 200 mV while the electronic conductivities were enhanced by Al₂O₃ coating in both samples, contributing to the advancement of PEC performance by ultra-thin Al₂O₃ layer.

• Journal of the Korean Magnetics Society
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• v.20 no.6
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• pp.212-215
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• 2010

Spin polarized tunneling studies were carried out with Al-Ga bilayer as a spin detector, by Meservey-Tedrow technique. The superconductor (SC)/Insulator (I)/Ferromagnet (FM) tunnel junctions were provided by ultra high vacuum molecular beam epitaxy (UHV-MBE) technique. The analysis of interfacial properties in the Al-Ga bilayer was also carried out by Auger electron spectroscopy. It was observed that the superconducting transition temperature and energy gap were raised in comparison with that of bulk Ga and pure ultrathin Al films. Current studies clearly show how one can modify the material properties at the interface just with a few monolayers.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.31-35
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• 2016

This paper demonstrates the successful application of yttria-stabilized zirconia thin films deposited by atomic layer deposition to the anode-side interlayer for cerium oxide electrolyte based solid oxide fuel cell. At the operating temperature over $500^{\circ}C$, the electrical conductivity of cerium oxide electrolyte is known to dramatically increase and, therefore, the open circuit voltage of the cell decreases leading to the decrease of the performance. Ultra-thin (60 nm) atomic layer deposited yttria-stabilized zirconia thin film in this study conformally coated the anode-side surface of the cerium oxide electrolyte and efficiently blocked the electrical conduction through the electrolyte. Accordingly, the open circuit voltage increased by up to 20%, and the maximum power density increased by 52% at $500^{\circ}C$