Interband Absorption Coefficients of the Electronic States Calculated for CdZnS Nanocrystals Grown by Sol-Gel Method

Abstract

<formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm Cd}_{{\rm x}}Zn_{{1-{\rm x}}}{\rm S}$</tex></formula> nanocrystals have been prepared by sol-gel method with different content of Cd, and their optical studies are characterized by taking transmittance spectra experimentally. We have theoretically calculated the eigen energy values of the confined electron in ground and excited states as a function of dot radius of the CdZnS quantum dot with various values of Cd content. The optical band gap investigated by UV transmission spectra is compared with the interband emission energy computed theoretically. We have calculated the oscillator strengths for the transitions and the linear optical absorption coefficients as a function of incident photon energy for <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$1{\rm s}-1{\rm p}$</tex></formula> and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$1{\rm p}-1{\rm d}$</tex></formula> transitions. The main results show that the confined energies and the transition energies between the excited levels are significant for smaller dots. Nonlinearity band gap with the increase in Cd content is observed for smaller dot radius of the CdZnS quantum dot in the strong confinement region, and the magnitude of the absorption spectra increases for the transitions between the higher excited levels.