Growth and domain structure of GeTe ferroelectric thin films on miscut silicon substrates: the key role of atomic steps

A significant progress toward next-generation electronic devices that combine memory and processing functions could involve the electrical manipulation of charge carrier spin textures in semiconductors. In this context, GeTe has recently emerged as a promising ferroelectric Rashba semiconductor, exhibiting a giant spin splitting in its band structure. This remarkable property stems from the inversion symmetry breaking induced by its ferroelectric polarization. Here we address the control of the domain structure of GeTe thin films grown on miscut silicon substrates. We show that the domain structure of GeTe thin films is strongly influenced by the miscut direction with respect to nominal Si(111) substrate. Considering miscut in the $\left [\overline{1}\overline{1}2\right ]$ direction, highly crystallized GeTe films are grown without twins and the domain structure exhibits two-fold symmetry. In the case of $\left [11\overline{2}\right ]$ miscut direction we evidence that thin films exhibit a predominance of twins and a complex ferroelectric structure that is affected by a large density of interfacial defects. Our results also show that the miscut direction plays a key role in the growth morphology of GeTe thin film. All these results support the view that atomic steps on silicon substrates have a profound effect on the structure and growth morphology of GeTe thin films as well as on the domain structure via local stress relaxation mechanisms.