Abstract
Based on first-principles calculations, we propose a novel two-dimensional (2D) germanium carbide, tetrahex-GeC2, and determine its electronic and optical properties. Each Ge atom binds to four C atoms, in contrast to the known 2D hexagonal germanium carbides. Monolayer tetrahex-GeC2 possesses a narrow direct band gap of 0.89 eV, which can be effectively tuned by applying strain and increasing the thickness. Its electron mobility is extraordinarily high (9.5 × 104 cm2/(V s)), about 80 times that of monolayer black phosphorus. The optical absorption coefficient is ∼106 cm–1 in a wide spectral range from near-infrared to near-ultraviolet, comparable to perovskite solar cell materials. We obtain high cohesive energy (5.50 eV/atom), excellent stability, and small electron/hole effective mass (0.19/0.10 m0). Tetrahex-GeC2 turns out to be a very promising semiconductor for nanoelectronic, optoelectronic, and photovoltaic applications.
Highlights
Since the first experimental realization of graphene,[1] twodimensional (2D) materials have attracted attention due to exotic structural and electronic properties.[2−5] Belonging to the class of group 14 2D materials, silicene[6] and germanene[7] show low buckled honeycomb structures and Dirac dispersions similar to graphene
First-principles calculations are performed using the Vienna ab initio simulation package (VASP),[38,39] with the electron−ion interactions represented by projector-augmented wave pseudopotentials and the exchange-correlation potential described by the Perdew−Burke− Ernzerhof functional in the structure optimizations
We discover a novel 2D material, tetrahex-GeC2, and predict its mechanical, electronic, and optical properties
Summary
Since the first experimental realization of graphene,[1] twodimensional (2D) materials have attracted attention due to exotic structural and electronic properties.[2−5] Belonging to the class of group 14 2D materials, silicene[6] and germanene[7] show low buckled honeycomb structures and Dirac dispersions similar to graphene. The fabrication of layered g-SiC with a thickness down to 0.5−1.5 nm has stimulated interest in binary 2D group 14 materials,[15−18] as band gap opening has been predicted for this class of materials.[19] Unlike silicene and germanene, the honeycomb structures of g-SiC and g-GeC are not buckled. Despite this structural similarity to graphene, g-SiC and g-GeC realize no massless Dirac fermions but sizeable band gaps. No additional stable structures of 2D germanium carbides have been identified
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