Synthesis and Characterization of CuIn1−xGaxSe2 Semiconductor Nanocrystals

Abstract

In this paper, the synthesis and characterization of CuIn_1-<i>x</i>Ga<i>_x</i>Se₂ (0 £ <i>x</i> £ 1) nanocrystals are reported with the influences of <i>x</i> value on the structural, morphological, and optical properties of the nanocrystals. The X-ray diffraction (XRD) results showed that the nanocrystals were of chalcopyrite structure with particle size in the range of 11.5-17.4 nm. Their lattice constants decreased with increasing Ga content. Thus, the <i>x</i> value of the CuIn_1-<i>x</i>Ga<i>_x</i>Se₂ nanocrystals was estimated by Vegard's law. Transmission electron microscopy (TEM) analysis revealed that the average particle size of the nanocrystals agreed with the results of XRD. Well-defined lattice fringes were shown in the TEM images. An analysis of the absorption spectra indicated that the band gap energy of these CuIn_1-<i>x</i>Ga<i>_x</i>Se₂ nanocrystals was tuned from 1.11 to 1.72 eV by varying the <i>x</i> value from 0 to 1. The Raman spectra indicated that the A₁ optical vibrational mode of the nanocrystals gradually shifted to higher wavenumber with increasing <i>x</i> value. A simple theoretical equation for the A₁ mode frequency was proposed. The plot of this equation showed the same trend as the experimental data.