Highly ordered mesoporous CdxZn1−xSe ternary compound semiconductors with controlled band gap energies

Abstract

Highly ordered mesoporous compound semiconductors (Cd_xZn_1−xSe) with crystalline frameworks were successfully synthesized via a nano-replication method from a mesoporous silica template (bicontinuous 3D cubic Ia3d mesostructure, KIT-6). Simple impregnation with various molar compositions of the precursors within mesopores of the silica template, reduction at 500 °C under hydrogen atmospheres and subsequent removal of the silica template using NaOH solution resulted in the mesoporous Cd_xZn_1−xSe ternary compound semiconductor. The mesoporous Cd_xZn_1−xSe materials with high surface areas (90–120 m² g⁻¹) were investigated by X-ray diffraction, N₂ adsorption–desorption, electron microscopy, and UV-visible spectroscopy. The unique optical properties and band gap profiles of the template-free Cd_xZn_1−xSe materials were controlled chemically by different Cd/Zn molar compositions, and also physically by the framework thickness. Diffuse reflectance UV-visible studies indicate that the band gap energies (E_g) of the mesoporous Cd_xZn_1−xSe materials widened as the amount of Cd decreased. Decreasing the framework thickness also results in the band gap widening of the mesoporous Cd_0.5Zn_0.5Se materials due to the nano-size effect.