The formation of ScAlN nanowires on ScN/6H-SiC(0001) by hydride vapor phase epitaxy (HVPE) was analyzed. The diameters and lengths of the nanowires were 50 to 150 nm and 1 µm, respectively. The nanowires had a Al/Sc metal ratio of 95/5 as measured by energy dispersive analysis of X-rays (EDX). The 4.84 Å unit cell periodicity along the length of the ScAlN nanowires was similar to that of pure AlN (4.98 Å), as measured by Fourier transforms of high resolution transmission electron microscopy images of a single nanowire. Only the (111) and (222) peaks of the ScN continuous film and the (0006) of the 6H-SiC substrate were detected by θ-2θ X-ray diffraction. A tentative model, based on catalyst-induced growth, is proposed to explain the unintentional formation of nanowires on the ScN film. This model is based on the production of volatile Al (possibly AlCl) by the reaction of the scandium metal source with the alumina reactor tube and subsequent reaction with hydrogen chloride. This reacts with ammonia in the deposition zone to create ScAlN nanowires, catalyzed by small ScAl clusters, which are spontaneously formed on the ScN film before the nanowire growth.
SEM images of the ScAlN nanowires.