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Preparation of Pt Films on GaAs by 2-step Electroless Plating
Hungsu Im,Yong Jun Seo,Young Joo Kim,Kai Wang,Sang Sik Byeon,Bon Heun Koo,Ji Ho Chang 한국표면공학회 2009 한국표면공학회지 Vol.42 No.4
Electroless plating is influenced by kinds of parameters including concentrations of electrolyte, plating time, temperature and so on. In this study, the Pt thin films were prepared on GaAs substrate by a 2-step electroless plating depending method. The small Pt catalytic particles by using Pt I bath exhibited islands-morphology dispersed throughout the substrate surface at 65℃, as function as a sensitized thin film, and then a thicker Pt film grew upon the sensitized layer by the second Pt Ⅱ bath. As the growth of Pt film is strongly influenced by the plating time and temperature, the plating time of Pt Ⅱ bath varied from 5 min to 40 min at 60~80℃ after Pt I bath at 60~80℃ for 5 min. It is found that the film grows with the increasing plating time and temperature. The resistivity value of Pt deposited layer was characterized to study the growth mechanism of 2-step plating.
Hydrothermal Reaction for the Preparation of La0.7Ca0.3MnO3 and La0.7Sr0.3MnO3
Sang M. Lee,Hungsu Im,Bon-Heun Koo,Chan-Gyu Lee,Gom-Bai Chon 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6
Fine powders of perovskite structured manganites, La0.7Ca0.3MnO3 and La0.7Sr0.3MnO3, were synthesized by using a hydrothermal reaction, followed by a calcination reaction in some cases. X-ray diffraction (XRD) patterns showed the desired composition without other impurity phases after calcination. Scanning electron microscopy (SEM) showed clean and pure images. The magnetic property measurement was performed in a vibrating sample magnetometer (VSM). The ferromagnetic-paramagnetic transition temperature of La0.7Ca0.3MnO3 was around 240 K and of La0.7Sr0.3MnO3 was around 350 K.hiK
Effect of Lattice Mismatch on the Properties of Self-Assembled InAs/InAlAs/InP Quantum Dots
Bon Heun Koo,Chan Gyu Lee,Gum Bae Chon,Hungsu Im,Takahumi Yao,Takahumi Yao 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.3
We present the results of the formation of InAs quantum dots (QDs) on (100) In1.xAlxAs (In- AlAs)/InP substrates by using relaxed InAlAs buffer layers with different compositions. Variations of the growth-mode-transition thickness, the surface morphology, and the emission-peak positions of InAs QDs as functions of the lattice mismatch between InAs and the InAlAs buffer layer [dotbuffer (DB) mismatch] have been evaluated by using reflection high energy electron diffraction, atomic force microscopy, and photoluminescence (PL), respectively. The growth of InAs QDs on InAlAs/InP strongly depends on the DB mismatch. With increasing DB mismatch, the critical thickness of the InAs QD formation decreases, the average size of the QDs decreases, and the density of the QDs increases under the fixed growth condition. The PL peak positions for the QDs shift to high energy as the DB mismatch increases, corresponding to a decrease in QD size and an increase in the barrier band gap.V