npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041


Research Paper

New Physics: Sae Mulli 2006; 53: 240-246

Published online September 1, 2006

Copyright © New Physics: Sae Mulli.

The Optical Properties of a Cubic CdS Epilayer Obtained by Using Spectroscopic Ellipsometry

입방정 CdS 단결정 박막의 타원 분광학적 특성 연구

D. J. KIM1*, T. G. KOO2, Y. D. CHOI3

1Institute of Science and Thecnology, Mokwon University, Daejeon 302-729
2Department of Physics, Chungnam National University, Daejeon 305-764
3Department of Optical & Electronic Physics, Mokwon University, Daejeon 302-729



Cubic CdS epilayers were grown on GaAs(100) substrates by using a hot-wall epitaxy method. The crystal structure of the grown epilayer was confirmed to be a cubic structure by using Xray diffraction, and the optical properties of the layer were studied over a wide photon energy range from 1.0 to 8.5 eV at room temperature by using spectroscopic ellipsometry. The obtained data were analyzed for the critical points of the pseudodielectric function spectra, $<\varepsilon(E)>$ = $<\varepsilon_1(E)>$ + i $<\varepsilon_2(E)>$, such as the $E_0$, $E_1$, $E_2$, $E_0^{\prime}$, $E_1^{\prime}$ structures. Also, the pseudodielectric-function-related optical constants of CdS, such as the refractive index $n(E)$, the extinction coefficient $k(E)$, the reflectivity $R(E)$, and the absorption coefficient $\alpha(E)$, are presented and analyzed. Note that all the structures were observed, for the first time, at 300 K by using ellipsometric measurements.

Keywords: CdS, Spectroscopic ellipsometry, Hot-wall epitaxy, Dielectric functionCdS, Spectroscopic ellipsometry, Hot-wall epitaxy, Dielectric function

열벽 적층 성장법을 이용하여 고품질의 입방정 CdS/GaAs(100) 박막이 성장되었다. 성장된 박막들은 광학적 특성을 알아보기 위하여 분광학적 엘립소미트리 (spectroscopic ellipsometry)를 사용하여 실온에서 1.5 - 8.7 eV 사이 포톤에너지 범위에서 측정되었다. 측정된 데이터들은 유사유전함수 스펙트럼 $<\varepsilon(E)>$ = $<\varepsilon_1(E)>$ + i $<\varepsilon_2(E)>$에 나타난 $E_0$, $E_1$, $E_2$, $E_0^{\prime}$, $E_1^{\prime}$ 와 같은 임계점 구조를 연구하였다. 또한 박막의 복소 유전함수와 밀접한 관계를 가지고 있는 굴절지수 $n(E)$, 소광계수 $k(E)$, 반사계수 $R(E)$ 그리고 흡수계수 $\alpha(E)$와 같은 광학적 특성에 관하여 연구하였다. 특히 분광학적 엘립소미트리를 이용한 이번 연구에서 나타난 모든 임계점 피크들은 300 K에서 처음으로 관측되었다.

Keywords: CdS, 분광학적 엘립소미트리, 열벽 적층 성장법, 유전함수

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