Structural and electronic properties of two-dimensional atomically thick (100) diamond nanofilms by first-principles calculations

In this work, the structural and electronic properties of two-dimensional (2D) atomically thick (100) diamond nanofilms are investigated by first-principles calculations. The results of phonon dispersion curves and ab initio molecular dynamics simulations indicate that the nanofilms are dynamically and thermally stable with three types of reconstructed surfaces (named 5-MR, 5-7-MR, and 5/5-7-MR). The bandgaps (E-g) of the nanofilms with 5-MR and 5-7-MR patterns are in regions of 1.02-1.40eV and 0.32-0.55eV, respectively, and an oscillatory phenomenon of E-g appears related to parity of the layer number. The nanofilms with the 5/5-7-MR pattern show a metallic feature. The variations in E-g are determined by surface states with different configurations. These novel diamond-based structures may be useful for applications such as 2D semiconductors in diamond-based electronic devices.