Reshak, A. H. and Brik, M. G. and Auluck, S.
(2014)
Dispersion of the linear and nonlinear optical susceptibilities of the CuAl(S1-xSex)(2) mixed chaclcopyrite compounds.
Journal of Applied Physics, 116 (10).
ISSN 0021-8979
Abstract
Based on the electronic band structure, we have calculated the dispersion of the linear and nonlinear optical susceptibilities for the mixed CuAl(S1-xSex)(2) chaclcopyrite compounds with x = 0.0, 0.25, 0.5, 0.75, and 1.0. Calculations are performed within the Perdew-Becke-Ernzerhof general gradient approximation. The investigated compounds possess a direct band gap of about 2.2 eV (CuAlS2), 1.9 eV (CuAl(S0.75Se0.25)(2)), 1.7 eV (CuAl(S0.5Se0.5)(2)), 1.5 eV (CuAl(S0.25Se0.75)(2)), and 1.4 eV (CuAlSe2) which tuned to make them optically active for the optoelectronics and photovoltaic applications. These results confirm that substituting S by Se causes significant band gaps' reduction. The optical function's dispersion epsilon(xx)(2) (omega) and epsilon(zz)(2) (omega)/epsilon(xx)(2) (omega), epsilon(yy)(2) (omega) and epsilon(zz)(2) (omega) was calculated and discussed in detail. To demonstrate the effect of substituting S by Se on the complex second-order nonlinear optical susceptibility tensors, we performed detailed calculations for the complex second-order nonlinear optical susceptibility tensors, which show that the neat parents compounds CuAlS2 and CuAlSe2 exhibit vertical bar chi((2))(123)(-2 omega;omega;omega)vertical bar as the dominant component, while the mixed alloys exhibit vertical bar chi((2))(111)(-2 omega;omega;omega)vertical bar as the dominant component. The features of vertical bar chi((2))(123)(-2 omega omega;omega;omega)vertical bar and vertical bar chi((2))(111)(-2 omega omega;omega;omega)vertical bar spectra were analyzed on the basis of the absorptive part of the corresponding dielectric function epsilon(2) (omega) as a function of both omega/2 and omega.
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