Microstructure of epitaxial scandium nitride films grown on silicon

Epitaxial scandium nitride films (225nm thick) were grown on (111)-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 (111) ω-scan FWHM of 0.551 deg. obtained for films grown at 850 deg. C is the lowest reported so far for ScN thin films. The principal orientation of ScN with respect to Si is (111)ScN//(111)Si and [11-bar 0]ScN//[01-bar 1]Si, representing a 60 deg. 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 (111)ScN//(111)Si and [11-bar 0]ScN//[11-bar 0]Si, representing a 'cube-on-cube' orientation. The volume percentage of these twins in the films decreases with increasing film growth temperature