Congruent melting and rapid single-crystal growth of ZnO at 4 GPa

Abstract

Transparent, colorless and contamination-free ZnO single crystals have been grown by rapid crystallization from the melt at ∼4 GPa and ∼1700 K. Recovered crystals exhibit needle-like (along the [0001] direction) morphology and have sizes up to 2 mm in length and 0.2 mm dia. Wurtzite structure (P6₃mc) has been confirmed by single-crystal X-ray diffraction, and lattice parameters (a = 3.2474(5) Å, c = 5.2017(7) Å) are in good agreement with literature data. Photoluminescence measurements revealed an intensive violet line at 398 nm, whose intensity depends non-linearly on the laser excitation power due to collective effects in photoexcited charge carriers or/and an effect of the stimulated emission in the ZnO crystals under study.