• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.02a
• /
• pp.51-54
• /
• 2003

We investigated the quench characteristics of thin film type SFCLs with shunt layers of various thickness. The SFCLs ware based on 2 inch diameter YBa$_2$Cu$_3$O$_{7}$ thin films coated in-situ with a gold shunt layer. The shunt layer thickness was varied by Ar ion milling. The limiters were tested with simulated fault currents at various source voltages. The thinner the shunt layer was, the slower was the rise of SFCL temperatures. This means SFCLs of thinner shunt layers had higher voltage ratings. The voltage rating was approximately inversely proportional to the square root of the shunt layer thickness. This result could be understood through the concept of heat balance.e.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.02a
• /
• pp.242-245
• /
• 2003

We investigated the quench characteristics of thin film type SFCLs with shunt layers of various thickness. The SFCLs ware based on 2 inch diameter YBa$_2$Cu$_3$3O$_{7}$ thin films coated in-situ with a gold shunt layer. The shunt layer thickness was varied by Ar ion milling. The limiters were tested with simulated fault currents at various source voltages. The thinner the shunt layer was, the slower was the rise of SFCL temperatures. This means SFCLs of thinner shunt layers had higher voltage ratings. The voltage rating was approximately inversely proportional to the square root of the shunt layer thickness. This result could be understood through the concept of heat balance.e.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.304-305
• /
• 2013

We report a positive exchange bias (HE) in thinmultilayered filmscontaining nano-oxide layer. The positive HE, obtained for our system results from an antiferromagnetic coupling between the ferromagnetic (FM) CoFe and the antiferromagnetic (AFM) CoO layers, which spontaneously form on top of the nano-oxide layer (NOL). The shift in the hysteresis loop along the direction of thecooling field and the change in the sign of exchange bias are evidence of antiferromagnetic interfacial exchange coupling between the CoO and CoFe layers. Our calculation indicates that uncompensated oxygen moments in the NOL results in antiferromagnetic interfacial exchange coupling between the CoO and CoFe layers. One of the interesting features observed with our system is that it displays the positive HE even above the bulk Neel temperature (TN) of CoO. Although the positive HEsystem has a different AFM/FM interfacial spin structure compare to that of the negative HE one, the results of the angular dependence measurements show that the magnetization reversal mechanism can be considered within the framework of the coherent rotation model.

• Korean Journal of Optics and Photonics
• /
• v.26 no.5
• /
• pp.275-282
• /
• 2015

The effective reflection coefficients for light obliquely incident upon a substrate coated with uniaxially anisotropic films and with isotropic films are derived. Multiple reflections inside anisotropic films, as well as those inside isotropic films, are properly treated. These expressions, together with the related ellipsometric expressions, can be used to find the nonuniform distribution of an uniaxially anisotropic film perpendicular to the film's surface, by approximating it as consisting of uniaxially anisotropic uniform layers and applying the conventional modeling technique for spectroscopic ellipsometry.

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

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.171-171
• /
• 2012

We have studied the effects of plasma treatments on CdS buffer layers in CIGS thin film solar cells. The CdS layers were deposited on CIGS films by chemical bath deposition (CBD) method. The RF plasma treatments of the CdS thin films were performed with Ar, $O_2 and $N_2 gases, respectively. After plasma treatments, the solar cells with Al:ZnO/i-ZnO/CdS/CIGS structures were fabricated. The surface properties of the CdS/CIGS thin films after plasma treatments were investigated with SEM, EDX and AFM measurements. The electrical properties of manufactured solar cell were discussed with the results of current-voltage measurements. The plasma treatments have a strong influence on the open circuit voltage (VOC) and the fill factor of the solar cells. Finally, a correlation between the surface properties of CdS layer and the efficiencies of the CIGS thin film solar cells is discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.25 no.7
• /
• pp.491-495
• /
• 2012

The effects of various buffer layers on the $In_2O_3$ transparent conducting films grown on glass substrates by radio-frequency reactive magnetron sputtering were investigated. The $In_2O_3$ thin films were deposited at $400^{\circ}C$ of growth temperature and 100% of oxygen flow rate. The optical, electrical, and structural and morphological properties of the $In_2O_3$ thin films subjected to buffer layers were examined by using ultraviolet-visible spectrophotometer, Hall-effect measurements, and X-ray diffractometer, respectively. The properties of $In_2O_3$ thin films showed different results, depending on the type of buffer layer. As for the $In_2O_3$ thin film deposited on ZnO buffer layer, the average transmittance was 89% and the electrical resistivity was $7.4{\times}10^{-3}\;{\Omega}cm$. The experimental results provide a way for growing the transparent conducting film with the optimum condition by using an appropriate buffer layer.

• Journal of the Korean institute of surface engineering
• /
• v.25 no.3
• /
• pp.107-116
• /
• 1992

The optimum thickness of Pd-Ni plated layers used as an electrical contact film was investigated by evaluating mechanical, thermal and environmental characteristics. The variations of morphologies and chemical compositions were studied by using SEM, EDS and ESCA. As a result of wear test, the wear resistance behavior of the gold plated layers was not changed with the sliding velocity changes. The palladium-nickel plated layer showed better wear resistance than the gold plated layer at low sliding velocity, but it showed poor wear resistance at high sliding velocity. Under the thermal condition of $400^{\circ}C$ in air, the gold thickness of $2\mu\textrm{m}$ without underplate on phosphorous bronze formed copper oxide on the surface layer by rapid diffusion of copper whereas the gold thickness of $0.8\mu\textrm{m}$ deposited on nickel and palladium-nickel underplate was stable at $400^{\circ}C$. Under the sulfur dioxide environments, the gold thickness of $0.3\mu\textrm{m}$ deposited on the nickel thickness of$ 3\mu\textrm{m}$ and the palladium-nickel thickness of $2\mu\textrm{m}$ underplate was more corrosion-resistant than the gold thickness of $2\mu\textrm{m}$ without underplate on phosphorous bronze. Under the nitric acid vapor environment, corrosion resistance of the gold film was superior to an equivalent thickness of the palladium-nickel film.

• Journal of Adhesion and Interface
• /
• v.8 no.1
• /
• pp.15-27
• /
• 2007

Polyimide (PI) surface modification was carried out by ion-beam treatment and silane-imidazole coupling agent to improve the adhesion between polyimide film and copper. Silane-imidazole coupling agent contains imidazole functional groups for the formation of a complex with copper metal through a coordination bonding and methoxy silane groups for the formation of siloxane polymers. The PI film surface was first treated by argon (Ar)/oxygen ($O_2$) ion-beam, followed by dipping it into a modified silane-imidazole coupling agent solution. The results of X-ray photoelectron spectroscopy (XPS) spectra revealed that the $Ar/O_2$ plasma treatment formed oxygen functional groups such as hydroxyl and carbonyl groups on the polyimide film surface and confirmed that the PI surface was modified by a coupling reaction with imidazole-silane coupling agent. Adhesion between copper and the treated PI film by ion-beam and coupling agent was superior to that with untreated PI film. In addition, adhesion of PI film treated by an $Ar/O_2$ plasma to copper was better than that of PI film treated by a coupling agent. The peeled-off layers from the copper-PI film joint were completely different in chemical composition each other. The layer of PI film side showed similar C1s, N1s, O1s spectra to the original Upilex-S and no Si and Cu atoms appeared. On the other hand the layer of copper side showed different C1s and N1s spectra from the original PI film and many Si and Cu atoms appeared. This indicates that the failure occurs at an interface between the imidazole-silane and PI film layers rather than within the PI layers.

• Current Photovoltaic Research
• /
• v.2 no.3
• /
• pp.95-102
• /
• 2014

Light trapping techniques can change the propagation direction of incident light and keep the light longer in the absorption layers of solar cells to enhance the power conversion efficiency. In thin film silicon (Si) solar cells, the thickness of absorption layer is generally not enough to absorb entire available photons because of short carrier life time, and light induced degradation effect, which can be compensated by the light trapping techniques. These techniques have been adopted as textured transparent conduction oxide (TCO) layers randomly or periodically textured, intermediate reflection layers of tandem and triple junction, and glass substrates etched by various patterning methods. We reviewed the light trapping techniques for thin film Si solar cells and mainly focused on the commercially available techniques applicable to textured TCO on patterned glass substrates. We described the characterization methods representing the light trapping effects, texturing of TCO and showed the results of multi-scale textured TCO on etched glass substrates. These methods can be used tandem and triple thin film Si solar cells to enhance photo-current and power conversion efficiency of long term stability.