Thermoelectric properties of graphane, silicane, germanane, and stanane: Hydrogenation effects

Hydrogenation is a well-recognized technique for modifying the electronic characteristics of nanostructured materials. Here, we investigate the hydrogenation effects on the electronic properties, particularly the thermoelectric properties, of two-dimensional (2D) hexagonal group-IV based on density functional theory combined with Boltzmann transport theory. Hydrogen atoms successfully passivate the dangling bonds of the pristine 2D hexagonal group-IV. As a result, they are no longer semimetallic and have gapped energy bands. Their energy band gaps lead to the increase of the Seebeck coefficients and further enhance the thermoelectric performances. We found that, at T =500 K, silicane has the largest ZTmax followed by stanane. The former, however, could only be achieved with large doping, while ZTmax = 1.8 of the latter one only needs a reasonable p-type doping, i.e. about 0.2 − 0.3 eV. Moreover, ZTmax up to ∼3.0 is also possible to be achieved at T = 800 K. Our results indicate that hydrogenation could be effective to improve the electronic properties of pristine 2D hexagonal group-IV, and further enhance their thermoelectric performances.