Optical Absorption and Raman Scattering Measurements in CuAlSe2 at High Pressure

Abstract

AbstractThe ternary compound CuAlSe2 is a direct energy gap semiconductor (Eg = 2.6 eV at 300 K) crystallizing in the tetragonal chalcopyrite structure. In this work the optical absorption edge and the Raman active modes of CuAlSe2 were measured as a function of pressure up to 30 GPa. The measurements were performed in a membrane diamond‐anvil cell at ambient temperature using neon gas as pressure transmitting medium. The direct energy gap (Γ → Γ) increases linearly with pressure at the rate of 4.7 × 10−2 eV GPa−1. At 6.7 GPa the character of the fundamental gap changes to pseudodirect (Γ → Γ). This gap decreases with pressure at a rate of −2.9 × 10−2 eV GPa−1. The effect of pressure on the phonon frequencies is discussed in terms of the Grüneisen parameters. A first‐order structural phase transition was observed at 12 GPa in the upstroke and at 2 GPa in the downstroke.