Young-Tae Kwon

Effects of CdS substrates on the physical properties of polycrystalline CdTe Films

Abstract In this study, CdS thin films were deposited by thermal evaporation, close spaced sublimations, and solution growth methods, respectively, and the effects of the deposition methods on the physical properties of polycrystalline CdS deposited on ITO/glass were investigated. In addition, the effects of variously deposited CdS on the physical properties of thermally evaporated CdTe were also investigated. XRD results showed that CdS thin films deposited by solution growth, thermal evaporation, and close spaced sublimation (CSS) had a hexagonal structure with a random orientation of , (002) and (103) preferred orientation, respectively. All of the CdTe thin films deposited on those CdS substrates had the same cubic zincblende structure, however, they showed a little different crystal orientation relationship depending on the underlying CdS deposition method. Cross-sectional TEM showed that CdTe grain sizes of the furnace annealed CdTe grown on the CSS-CdS was the smallest among the furnace annealed CdTe thin films deposited on the variously prepared CdS substrates.

A Novel Method for Fine Patterning by Piezoelectrically Induced Pressure Adjustment of Inkjet Printing

In this paper, a method is proposed for fine line pattern formation on polyimide films by drop-on-demand inkjet printing without the need to reduce the nozzle size. The rapid change in the shape of a piezoelectric actuator caused by a pressure wave causes the fluid to be ejected as droplets. By shortening the duration of the chamber compression period, smaller droplets can be ejected from the nozzle orifice. The pressure wave is a key factor in determination of the line width. A 20-µm-wide line pattern pulsed at 0.5 µs intervals was successfully fabricated using a Cu complex ion ink and a cartridge with volume of 1 pl. This method is expected to be widely used in various applications that demand high-resolution patterning. The 20-µm line width of the conducting track is a particularly useful size for fabrication of transparent electrodes.

Near-infrared absorbance properties of Cu2−xS/SiO2 nanoparticles and their PDMS-based composites

We synthesized different Cu2−xS nanoparticles (CuS and Cu1.8S NPs) with localized surface plasmon resonance (LSPR) absorbance in the near infrared (NIR) region and applied a silica layer on the surface of Cu2−xS nanoparticles (NPs) to achieve high photo-stability and dispersion stability. These plasmonic Cu2−xS NPs have been much utilized as thermal shielding materials of energy-saving windows, due to shielding the ultraviolet (UV) and NIR regions, and transmitting the visible (Vis) region. However, this application is limited because Cu2−xS NPs show photocatalyst properties that lead to the decomposition of organic matter, and dispersing these NPs into polymer films is difficult. Herein, silica coating successfully suppressed the generation of hydroxyl radicals on the surface of CuS NPs, which caused the photo-degradation of a polydimethylsiloxane (PDMS) polymer. Furthermore, a silica layer with the structure similar to that of PDMS provided the dispersion stability of CuS NPs. The achievement of good photo-stability and dispersion stability in the Cu2−xS NPs was demonstrated by the thermal shielding effect using a simulated experiment. The temperature change of a box shielded with a CuS/SiO2–PDMS film (ΔT = 6.8 °C) was smaller than that when the box was shielded with common glass (ΔT = 12.7 °C) or a CuS–PDMS film (ΔT = 9.2 °C). This research introduces a new and reliable thermal shielding material.