Grazing incidence X-ray diffraction studies of ferroelectric ScAlN thin films

In principle, the intrinsic dipole nature of wurtzite III-nitrides (GaN, AlN, InN) should allow polarity inversion by an external electric field. However, due to the giant switching energy barrier such behavior has never been achieved (until very recently for AlN). Theoretically predicted 20 years ago, the incorporation of scandium atoms into AlN induces a distortion of the wurtzite structure that flattens the energy landscape and thus enables ferroelectric polarization switching. The first experimental evidence of ferroelectricity in ScAlN was reported in 2019. While sputtering is largely used to elaborate ScAlN films, its epitaxial growth is still limited. The ¿perfect¿ epitaxial growth is limited to the thickness of about 15 nm followed by a columnar-like growth. The goal is to explore the strain, strain gradients, and grain sizes in ScAlN thin films via Williamson-Hall analysis by performing specular XRD and grazing incidence X-ray diffraction.