Stranski–Krastanov growth of disordered ScNx thin films on MgO(100): Influence of defect densities on electronic structure and transport properties

Abstract

We report a real-time Stranski–Krastanov growth of reactively sputtered ScNx thin films on MgO(100). The epitaxial growth was limited to 5 nm at a substrate temperature (Ts) of ∼25 °C, while the self-sustaining epitaxial nature along the [100] azimuth was retained up to 25 nm in Ts = 250 and 500 °C samples due to enhanced adatom mobility. At Ts = 700 °C, the film showed a half order in situ RHEED pattern, with forbidden (hkl) planes indicating an N-deficient hcp ScN phase. The presence of defect densities, i.e., N vacancies and O interstitials, leads to a disorder in the ScNx system with a weak intergranular tunneling effect and the appearance of Raman relaxed first order transverse and longitudinal optical phonon modes and further leads to a metal like Seebeck coefficient. Higher grain boundaries at Ts = 25 °C and higher N out-diffusion at Ts = 700 °C pave the way for the incorporation of higher oxygen interstitial in these samples.