A comparative study of electronic and thermoelectric properties of bulk, 2D sheet and 1D wire of Silicon: an ab-initio study

We have made a comparative study of the electronic and thermoelectric properties of bulk, 2D-sheet and 1D atomic wire of Silicon, using the Full Potential Linearized Augmented Plane Wave method (FP-LAPW) within the framework of DFT. The electron exchange correlation was treated with the modified Becke-Johnson exchange potential (PBmBJ) for bulk Silicon and for Si sheet and wire, the most common Generalized Gradient Approximation (GGA) is taken into consideration. The transport coefficients were calculated by a post DFT treatment which involved the semi-classical Boltzmann Theory as implemented in the code BoltzTraP. For Si, we observed that as we move towards lower dimensionality, the thermoelectric efficiency ZT increases significantly (bulk ~ 0.01, Si sheet ~ 1.1 and Si wire ~ 1.65 at 300 K). The increase in ZT is mostly due to the change in phase in going from higher to lower dimension, which increases the electrical conductivity and reduces the thermal conductivity. Results obtained are compared with available theoretical and experimental results.