Electronic and optical properties of HgIn2S4 thiospinels

Abstract

Photoluminescence ( PL ), transmission ( T ), reflection ( R ), wavelength modulated transmission (Δ T/ Δ λ ) and reflection (Δ R/ Δ λ ) spectra of thiospinel HgIn 2 S 4 crystals were investigated in temperature interval form 10 to 300 K. The band gap 1.64 eV (300 K) and 1.666 eV (10 K) are formed by electron transitions from L to Γ points of Brillouin zone. The edge temperature shift coefficient β (Δ E g / Δ T ) is equal to 4.3 10 ⁻³ eV K ⁻¹ . The direct energy gap in Γ point ( E gdir ) corresponds to 1.748 eV. The top valence bands in k =0 are split by the crystal field on 25 meV. Direct electron transitions a1-a7, observed in energy range 1-6 eV, were interpreted conform the theoretically calculated band structure. The optical functions ( n , k, ϵ 1 and ϵ 2 ) were determined by Kramers-Kronig analysis.