Light-emitting 9R-Si phase formed by Kr+ ion implantation into SiO2/Si substrate

Light-emitting layers of hexagonal 9R silicon were synthesized by ion implantation into SiO2/Si substrates. Using cross-sectional transmission electron microscopy, the formation of a 9R phase in a cubic silicon substrate near the interface with silicon dioxide under irradiation with Kr+ ions (80 keV) and subsequent annealing at 800 °C is demonstrated. Arguments explaining how the new phase is formed through hexagonalization of the initial cubic silicon are presented. The synthesized 9R-Si layers are characterized by a low-temperature photoluminescence line with the maximum at a wavelength around 1240 nm. First-principles calculations of the 9R-Si electronic band structure showed that this material is an indirect-gap semiconductor with the bandgap value of 1.06 eV, which is in good agreement with the spectral position of the experimentally observed photoluminescence line. Believing that the proposed approach can be extended to other semiconductors, we calculated the electronic band structure of 9R germaniu...