Substrate-Induced Anisotropic Growth of CuAlO Platelets in a Liquid-Solid Reaction.

This study reports a simplified method to grow CuAlO crystals of submillimeter sizes with a highly anisotropic shape of a platelet. The solid-state reaction of forming CuAlO at ca. 1373 K in the first stage of the conventional flux method is no longer required. The CuAlO platelets nucleated directly onto the (0001) surface in a melt of CuO saturated with AlO at 1473 K. The excess flux was mostly removed by the capped alumina plate on cooling with a limited amount of residue which can be leached afterward. The CuAlO platelets all have a 3R crystal structure with no line and planar defects observed by TEM. The CuAlO crystals emit a luminescence at 3.49 eV associated with resonant Raman effect resulted from a band-to-band transition in room-temperature PL measurement. The facile fabrication method for growing highly anisotropic CuAlO crystals paves the way for their practical application in photoelectrochemical devices.