Zinc selenide stabilized in a quadrilateral network characterized with optical emissions†

Abstract

A polymorph of K₂Zn₃Se₄ (1) adopting a quadrilateral network induced by the presence of deficient zinc sites is discovered in the ThCr₂Si₂-type lattice. Upon quenching the synthetic reaction at 630 °C, this lattice crystallizes into a higher symmetry and reduced cell in 1·T. DFT calculations explain a coexistence of two pseudo-enantiomeric forms with an equal energy that favors such a flexible network stabilized in 1. With the partial substitution of Zn²⁺ ions by Mg²⁺ ions, one form is then trapped in K₂Mg_0.5Zn_2.5Se₄ (2). For the two ZnSe layered wide bandgap semiconductors, photoluminescence (PL) and X-ray excited optical emission (XEOL) measurements reveal a prominent broad defect emission centered at ∼610 nm relative to the emission position observed in the benchmark ZnSe crystal.