First-principles calculations of structural, electronic, and thermodynamic properties of monolayer Si_1-xGe_xC sheet

The structural, electronic, and thermodynamic properties of a monolayer honeycomb Si_1-xGe_xC sheet are analyzed using first-principles calculations based on density functional theory. The dynamical stability of our structures is testified by the analysis of phonon dispersion curves. Deviations of the lattice parameter, Young's modulus, and band gap of relaxed structures derived from Vegard's law are investigated; small bowing coefficients are observed except for Young's modulus. The band gaps are found to decrease as the concentration x increases. The T-x phase diagram, which identifies the stable, metastable, and unstable mixing areas, is also calculated and shows a critical temperature T_c of 187.45 K. The results provide a new method to modify the electronic properties of 2D-SiC, which has great importance in its applications for optoelectronic devices.