First principles calculations of transport properties in Si nanowires: The role of crystal orientation

The electron transport properties of Si nanowires along four different orientations (〈110〉, 〈111〉, 〈100〉,〈112〉) are investigated by density functional theory and non-equilibrium Green’s function methods. It is found that electron transport property depends sensitively on the crystal orientation. The transmission probability of 〈110〉-oriented nanowires displays a smaller conductance gap than that of other directions. Orientation induced orbital overlap reflected from PDOS indicates that 〈110〉 wires have smaller band gap than those along other directions due to larger “electrode-molecule” overlap. The current–voltage characteristic confirms that 〈〉〈110〉-oriented nanowires present larger conductance at low bias than that of others. Moreover, a large negative differential resistance appears in 〈110〉 nanowires, which shows potential advantage as Si based nano-functional electronic device.

Highlight
► Electron transport of Si nanostructures is preferred along [1 1 0] orientations.
► Orientation directed hybridization may reduce energy gap.
► The mechanism underlying the favorable orientation is due to energy preferred space overlap of sp3 hybridization.