Myoung Seok Kwon

Transparent conducting Ga‐doped ZnO thin film for flat‐panel displays with a sol‐gel spin coating

Abstract A novel non‐alkoxide sol‐gel process for synthesizing Ga‐doped ZnO thin film on glass was derived for possible use as a transparent electrode in flat‐panel displays, using zinc acetate dehydrate as the starting material. The structural and electrical properties of thin films have been characterized as functions of Ga addition and post‐heat‐treatments. Their carrier density, Hall mobility, and optical transmittance were measured and discussed herein to explain the characteristics of the sol‐gel‐derived Ga‐doped ZnO thin film on glass.

White Organic Light-Emitting Devices Fabricated Utilizing a Down-Conversion CaAl12O19 : Mn Phosphor Layer

White organic light-emitting devices (OLEDs) were fabricated utilizing a CaAl 12 O 19 :Mn phosphor layer. X-ray diffraction patterns for CaAl 12 O 19 :Mn phosphors showed that Mn ions in the CaAl 12 O 19 :Mn phosphors were completely substituted into Ga ions. Field-emission-scanning electron microscopy images showed that the sizes of the CaAl 12 O 19 :Mn phosphor crystals were approximately between 0.1 and 3 μm. Although a broad band approximately between 250 and 550 nm of an excitation spectrum for CaAl 12 O 19 :Mn appeared, peaks were observed at 639, 654, and 665 nm of the fluorescence emission spectrum. The color coordinates of the electroluminescence spectra for white OLEDs with phosphor thicknesses of 0.25 and 0.35 mm shifted to the white emission side because the generated blue light from the blue OLEDs combined with the red light converted by the CaAl 12 O 19 :Mn phosphor down-conversion layer. The color conversion efficiency of white OLEDs was significantly affected by the excitation source and the thickness of the phosphor layer.

Al‐doped ZnO via sol‐gel spin‐coating as a transparent conducting thin film

Abstract A simple nonalkoxide sol‐gel route for depositing an Al‐doped ZnO thin film on a glass substrate was derived in this study. The initial Al dopant concentration in the sol‐gel preparation varied and ranged from 0 to 5%. The sol‐gel‐derived thin films showed c‐plane preferred crystallization of their hexagonal phase, with nanosized grain structures. First and second post‐heat‐treatments were carried out to improve the films electrical resistivity. The carrier density and the Hall mobility were measured and discussed to explain the electrical resistivity. The optical transmittance within the visible range showed compatible properties, which indicates the possible use of Al‐doped ZnO as a transparent electrode in flat panel displays.

Coexistence of a phase separation and an ordered structure in CdxZn1−xTe epilayers grown on GaAs(001) substrates

The coexistence of a phase separation and an ordered structure in CdxZn1−xTe epilayers grown on GaAs(001) substrates by using molecular beam epitaxy was investigated. The results of selected-area electron diffraction pattern and transmission electron microscopy measurements showed that ordered structures, such as CuPt-type and CuAu-I-type ordered structures, together with a spinodal-like phase separation were formed in the CdxZn1−xTe∕GaAs heteroepitaxial layers. The coexistence of the phase separation and the ordered structures is discussed.