Octahedrally coordinated single layered CaF: robust insulating behaviour.

Using first-principles calculations, the structural, vibrational, and electronic properties of single-layered calcium fluoride (CaF) are investigated. The dynamical stability of 1T-CaF is confirmed by the phonon dispersions. Raman active vibrational modes of 1T-CaF enable its characterization via Raman spectroscopy. In addition, the calculated electronic properties of 1T-CaF confirmed insulating behavior with an indirect wide band gap which is larger than that of a well-known single-layered insulator, h-BN. Moreover, one-dimensional nanoribbons of CaF are investigated for two main edge orientations, namely zigzag and armchair, and it is revealed that both structures maintain the 1T nature of CaF without any structural edge reconstructions. Electronically, both types of CaF nanoribbons display robust insulating behavior with respect to the nanoribbon width. The results show that both the 2D and 1D forms of 1T-CaF show potential in nanoelectronics as an alternative to the widely-used insulator h-BN with its similar properties and wider electronic band gap.