SO₄ in Cadmium Chalcogenides: CdSe versus CdTe

Abstract

A study combining infrared (IR) absorption spectroscopy and first‐principles theory is presented for a sulfur–oxygen complex in CdSe characterized by IR absorption lines located at 1094, 1107, and 1126 cm−1 (10 K). The properties of the center are compared to a similar species occurring in CdTe that gives rise to two absorption lines at 1097 and 1108 cm−1 (10 K). Temperature‐ and polarization‐sensitive measurements performed on 18O‐enriched samples reveal that for both materials the IR absorption lines are due to split stretch vibrations of a distorted sulfate () tetrahedron, whereby the local point group of the complex is reduced to and in hexagonal CdSe and cubic CdTe, respectively. Measurements on the vibrational spectrum of the sulfate species in the spectral range of symmetric stretch (), bend (), and combination modes () are presented. The cation vacancy is discussed as a likely site occupied by in CdSe.