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FIZIKA A 12 (2003) 2 , 75 - 88
 
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 ¹ 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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