Formation of hexagonal phase 9R-Si in SiO2/Si system upon Kr+ ion implantation

Hexagonal silicon polytypes are attracting significant attention from the scientific community due to their potential applications in next-generation electronics and photonics. However, obtaining stable heterostructures based on both cubic and hexagonal polytypes is a complicated task. In the present work, the possibility of formation of hexagonal silicon of the 9R-Si phase using the traditional method of microelectronics, i.e. ion implantation, is shown. Implantation of Kr+ ions was carried out through a SiO2 layer, the thickness of which was approximately twice the projected range of Kr+ followed by high temperature annealing. High resolution transmission electron microscopy reveals that a thin amorphous layer forms in a Si substrate at the interface with the SiO2 film under implantation, upon recrystallization of which the formation of the 9R-Si polytype occurs during annealing. It is assumed that mechanical stresses are created during implantation through the oxide layer, that contributes to hexagonalization during high-temperature annealing. The dependence of the efficiency of hexagonalization on the substrate orientation is established. In addition to the formation of the 9R-Si phase, at the implantation and annealing parameters used, light-emitting defects are formed in silicon, the photoluminescence of which at a wavelength of ∼1240 nm is observed up to a temperature of ∼120 K. The obtained results can stimulate and expand the range of applications of ion-irradiated silicon in micro-, nano-, and optoelectronics