Microstructure of epitaxial scandium nitride films grown on silicon

Epitaxial scandium nitride films (225 nm thick) were grown on (1 1 1)-oriented silicon substrates by molecular beam epitaxy (MBE), using ammonia as a reactive nitrogen source. Film microstructure was investigated using X-ray diffraction (XRD). The (1 1 1) v-scan FWHM of 0.5518 obtained for films grown at 850 8C is the lowest reported so far for ScN thin films. The principal orientation of ScN with respect to Si is (1 1 1)ScN// (1 1 1)Si and [1¯10]ScN//[0¯11]Si, representing a 608 in-plane rotation of the ScN layer with respect to the Si substrate. However, some twinning is also present in the films; the orientation of the twinned component is (1 1 1)ScN//(1 1 1)Si and [1¯10]ScN//[1¯10]Si, representing a ‘cube-on-cube’ orientation. The volume percentage of these twins in the films decreases with increasing film growth temperature.