A new two-dimensional semiconducting carbon allotrope with direct band gap: a first-principles prediction

Two-dimensional (2D) carbon materials with an appropriate band gap play important roles in the various electronics fields. Here, based on first-principles calculations, we predict a new 2D carbon allotrope containing 32 atoms, consists of pentagonal, hexagonal, octagonal and decagonal rings. This new allotrope is named as Po-C32, which possesses P4/MMM symmetry with a tetragonal lattice and has a vertical distance of 2.22 Å between the uppermost and undermost atoms. The cohesive energy, phonon band structure,ab initiomolecular dynamics simulations and elastic constants fitting confirm Po-C32 has high stabilities. The fitted in-plane Young's modulus and Poisson's ratio alongaandbdirections areY_a=Y_b= 244 N m^-1andv_a=v_b= 0.14, respectively, exhibiting the same mechanical properties alongaandbdirections. Interestingly, Po-C32 is a semiconductor with a direct band gap of 2.05 eV, comparable to that of phosphorene, exhibiting great potential in nanoelectronics. Moreover, two stable derivative allotropes are also predicted based on Po-C32. Po-C24-3D is an indirect narrow band gap (1.02 eV) semiconductor, while Po-C32-3D possesses a wider indirect band gap of 3.90 eV, which can be also applied in optoelectronic device.

Electronic, Mechanical and Elastic Anisotropy Properties of X-Diamondyne (X = Si, Ge)

The three-dimensional (3D) diamond-like semiconductor materials Si-diamondyne and Ge-diamondyne (also called SiC4 and GeC4) are studied utilizing density functional theory in this work, where the structural, elastic, electronic and mechanical anisotropy properties along with the minimum thermal conductivity are considered. SiC4 and GeC4 are semiconductor materials with direct band gaps and wide band gaps of 5.02 and 5.60 eV, respectively. The Debye temperatures of diamondyne, Si- and Ge-diamondyne are 422, 385 and 242 K, respectively, utilizing the empirical formula of the elastic modulus. Among these, Si-diamondyne has the largest mechanical anisotropy in the shear modulus and Young's modulus, and Diamond has the smallest mechanical anisotropy in the Young's modulus and shear modulus. The mechanical anisotropy in the Young's modulus and shear modulus of Si-diamondyne is more than three times that of diamond as determined by the characterization of the ratio of the maximum value to the minimum value. The minimum thermal conductivity values of Si- and Ge-diamondyne are 0.727 and 0.524 W cm-1 K-1, respectively, and thus, Si- and Ge-diamondyne may be used in the thermoelectric industry.

TE-C36 carbon: a new semiconducting phase with an all-sp3 bonding network

TE-C36 carbon, possessing an all-sp³ bonding network, is a semiconductor with a direct band gap of 2.25 eV.

New carbon allotropes with metallic conducting properties: a first-principles prediction

Combining density functional theory computation and the global minimum structural search, we have found new α-, β-, and δ-phographene carbon allotropes.