• Electrical & Electronic Materials
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• v.10 no.9
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• pp.930-937
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• 1997

Polycrystalline CdTe thin films have been studied for photovoltaic application because of their high absorption coefficient and optimal band energy(1.45 eV) for solar energy conversion. In this study CdTe thin films were deposited on CdS(chemical bath deposition)/ITO(indium tin oxide) substrate by rf-magnetron sputtering under various conditions. Structural optical and electrical properties are investigated with XRD UV-Visible spectrophotometer SEM and solar simulator respectively. The fabricated CdTe/CdS solar cell exhibited open circuit voltage( $V_{oc}$ ) of 610 mV short circuit current density( $J_{sc}$ ) of 17.2 mA/c $m^2$and conversion efficiency of about 5% at optimal sputtering conditions.

• Journal of the Korean Vacuum Society
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• v.17 no.5
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• pp.455-460
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• 2008

In recent years, there has been highly interestedin pulsed laser deposition (PLD) method for fabrication of the organic thin films, as an alternative to conventional fabrication method such as vacuum evaporation and spin coating techniques. In this study, organic thin films of $Alq_3$ (aluminato-tris-8-hydroxyquinolate) and TPD for organic light emitting diodes (OLED) were deposited by PLD using KrF excimer ($\lambda$=278 nm) laser in nitrogen atmosphere. Deposited films were evaluated by photoluminescence(PL), Fourier-transform Infrared Spectroscopy (FT-IR) to study the effect of the laser and $N_2$ atmosphere parameters on the structural and optical properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.393-394
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• 2008

$TiO_2$ is a wide band-gap semiconductor (3.4 eV) and can only absorb about 5% of sun light in the ultraviolet light region, which largely limits its practical applications because of the lower utility of sun light and quantum yield. In order to move the absorption edge of $TiO_2$ films to visible spectrum range, we have made the impurity level within a band-gap of $TiO_2$ thin film by introduction of oxygen vacancy. Oxygen-defected $TiO_2$ thin film have prepared by reactive sputtering with the partial pressure of Ar:$O_2$=10:90~99.33:0.66 ratio. As a result, we could have the impurity level of about 2.75 eV on condition that oxygen partial pressure is below 7%.

• Carbon letters
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• v.18
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• pp.30-36
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• 2016

Well-dispersed Ag₃VO₄ nanoparticles @polyacrylonitrile (PAN) nanofibers were synthesized by an easily controlled, template-free method as a photo-catalyst for the degradation of methylene blue. Their structural, optical, and photocatalytic properties have been studied by X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy equipped with rapid energy dispersive analysis of X-ray, photoluminescence, and ultraviolet-visible spectroscopy. The characterization procedures revealed that the obtained material is PAN nanofibers decorated by Ag₃VO₄ nanoparticles. Photocatalytic degradation of methylene blue investigated in an aqueous solution under irradiation showed 99% degradation of the dye within 75 min. Finally, the antibacterial performance of Ag₃VO₄ nanoparticles @PAN composite nanofibers was experimentally verified by the destruction of Escherichia coli. These results suggest that the developed inexpensive and functional nanomaterials can serve as a non-precious catalyst for environmental applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.398-399
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• 2006

$TiO_2$ is a wide band-gap semiconductor (3.4 eV) and can only absorb about 5% of sun light. in the ultraviolet light region, which largely limits its practical applications because of the lower utility of sun light and quantum yield. In order to move the absorption edge of $TiO_2$ films to visible spectrum range, we have made the impurity level within a band-gap of $TiO_2$ thin film by introduction of oxygen vacancy. Oxygen-defected $TiO_2$ thin film have prepared by reactive sputtering with the partial pressure of Ar:$O_2$=10:90~99.33:0.66 ratio. As a result, we could have the impurity level of about 2.75 eV on condition that oxygen partial pressure is below 7%.

• Korean Journal of Materials Research
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• v.30 no.5
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• pp.239-245
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• 2020

Synthesizing one-dimensional nanostructures of oxide semiconductors is a promising approach to fabricate highefficiency photoelectrodes for hydrogen production from photoelectrochemical (PEC) water splitting. In this work, vertically aligned zinc oxide (ZnO) nanorod arrays are successfully synthesized on fluorine-doped-tin-oxide (FTO) coated glass substrate via seed-mediated hydrothermal synthesis method with the use of a ZnO nanoparticle seed layer, which is formed by thermally oxidizing a sputtered Zn metal thin film. The structural, optical and PEC properties of the ZnO nanorod arrays synthesized at varying levels of Zn sputtering power are examined to reveal that the optimum ZnO nanorod array can be obtained at a sputtering power of 20 W. The photocurrent density and the optimal photocurrent conversion efficiency obtained for the optimum ZnO nanorod array photoanode are 0.13 mA/㎠ and 0.49 %, respectively, at a potential of 0.85 V vs. RHE. These results provide a promising avenue to fabricating earth-abundant ZnO-based photoanodes for PEC water oxidation using facile hydrothermal synthesis.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.152-153
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• 2006

The new approach to buffer layer design for CIGS solar cells that permitted to reduce the buffer absorption losses in the short wavelength range and to overcome the disadvantages inherent to Cd-free CIGS solar cells was proposed. A chemical bath deposition method has been used to produce a high duality buffer layer that comprises thin film of CdS and Zn-based film. The double layer was grown on either ITO or CIGS substrates and its morphological, structural and optical properties were characterized. The Zn-based film was described as the ternary compound $ZnS_x(OH)_y$. The composition of the $ZnS_x(OH)_y$ layer was not uniform throughout its thickness. $ZnS_x(OH)_y$/CdS/substrate region was a highly intermixed region with gradually changing composition. The short wavelength cut-off of double layer was shifted to shorter wavelength (400nm) compared to that (520 nm) for the standard CdS by optimization of the double buffer design. The results show the way to improve the light energy collection efficiency of the nearly cadmium-free CIGS-based solar cells.

• Korean Journal of Crystallography
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• v.2 no.2
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• pp.1-6
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• 1991

ZnO thin films were deposited on p-Si(100) and Coming glass 7059 by f magnetron sputtering mothod. The effect of deposition parameters on the electrical, structural and optical properties were investigated. Highly c-axis oriented ZnO thin films were deposited at high rf power. Standard deviation(σ) of X-ray rocking curve of peak at 26θ=34,4˚ ranged from 6.8˚ to 7.2˚, depending on the deposition condition. ZnO thin films deposited on glass substrate eihibited 80% transmittance in the visible range, regardless of the deposition parameters. Resistivity of ZnO thin films was significantly affected by f power and Ar pressure, and ranged widely from 3×102 to 2×109 Ω.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.645-649
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• 2009

We investigated the effects of a high density $O_2$ plasma treatment on the structural and electrical properties of Ga-, B- codoped ZnO (GZOB) films. The GZOB films were deposited on polymer substrate without substrate heating by DC magnetron sputtering. Prior to the GZOB film growth, we treated a polymer substrate with highly dense inductively coupled oxygen plasma. The optical transmittance of the GZOB film, about 80 %, was maintained regardless of the plasma pre-treatment. The resistivity of the GZOB film on PC substrate decreased from 9.08 ${\times}$ $10^{-3}$ ${\Omega}-cm$ without an $O_2$ plasma pre-treatment to 2.12 ${\times}$ $10^{-3}$ ${\Omega}-cm$ with an $O_2$ plasma pre-treatment. And PES substrate decreased from 1.14 ${\times}$ $10^{-2}$ ${\Omega}-cm$ without an $O_2$ plasma pre-treatment to 6.13 ${\times}$ $10^{-3}$ ${\Omega}-cm$ with an $O_2$ plasma pre-treatment.

• Applied Science and Convergence Technology
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• v.23 no.6
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• pp.376-386
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• 2014

Zinc oxysulfide nanocrystals (ZnOS NCs) were synthesized by forming ZnS phase on a ZnO matrix. ZnO nanocrystals (NCs) with a diameter of 10 nm were synthesized by forced hydrolysis in an organic solvent. As-synthesized ZnO NCs aggregated with each other due to the high surface energy. As acetic acid (AA) was added into the milky suspension of the aggregated ZnO NCs, transparent solution of well dispersed ZnO NCs formed. Finally ZnOS NCs were formed by adding thioacetic acid (TAA) to the transparent solution. The effect of recrystallization on the structural, optical and electrical properties of the ZnOS NCs were studied. The results of UV-vis absorption confirmed the band gap tunability caused by increasing the curing temperature of ZnOS thin films. This may have originated from the larger effective size due to the recrystallization of zinc sulfide (ZnS). From XRD result we identified that ZnOS thin films have a zinc blende crystal structure of ZnS without wurtzite ZnO structure. This is probably due to the small amount of ZnO phases. These assertions were verified through EDS of FE-SEM, XPS and EDS mapping of HR-TEM results; we clearly proved that ZnOS were comprised of ZnS and ZnO phases.