FIZIKA A 12 (2003) 2 , 75 - 88

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STRUCTURE AND OPTICAL PROPERTIES OF THIN POLYCRYSTALLINE
FILMS OF CuGaxIn1-xSe2

B. A. MANSOURa, S. A. ABD EL-HADYb, A. ABDEL-ALLb, I. K. EL ZAWAWIa and H. SHABANa

aSolid State Physics Laboratory, National Research Centre Dokki, Cairo, Egypt
bPhysics Department, Faculty of Science, Helwan University, Cairo, Egypt

Received 4 December 2002;     Accepted 7 April 2003
Online 19 April 2004

Structural and optical properties of CuGaxIn1-xSe2 (0 x 0.75) polycrystalline thin films deposited by vacuum evaporation were studied as a function of composition. The optical absorption spectra of CuGaxIn1-xSe2 thin films (x 0) show four energy gaps (Eg1, Eg2, Eg3 and Eg4) which are attributed to the fundamental edge, band splitting by crystal-field and spin-orbit splitting, and to transitions originating from copper 3d levels, respectively. The primary transition energies exhibit bowing behaviour expressed by the relationship Eg1(x) = 1.011 + 0.448x + 0.186 x2. The second and third transition energies are higher than the primary transition energies by 0.10-0.11 eV and 0.18-0.185 eV, respectively. The effect of thermal treatment on the values of energy gaps is discussed in terms of the structure of the films. The primary transition energies of annealed CuGaxIn1-xSe2 can be fitted by the parabolic form Eg1(x) = 1.04 + 0.46x + 0.22x2.

PACS numbers: 78.66.Jg, 68.60.Dv, 71.20.Nr
UDC 538.958, 538.975

Keywords: polycrystalline thin films, CuGaxIn1-xSe2 (0 x 0.75), optical absorption spectra, energy gaps, thermal treatment, fit to primary transition energies

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