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 ( 〈 1 1 0 〉 , 〈 1 1 1 〉 , 〈 1 0 0 〉 , 〈 1 1 2 〉 ) 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 〈 1 1 0 〉 -oriented nanowires displays a smaller conductance gap than that of other directions. Orientation induced orbital overlap reflected from PDOS indicates that 〈 1 1 0 〉 wires have smaller band gap than those along other directions due to larger “electrode-molecule” overlap. The current–voltage characteristic confirms that 〈〉 〈 1 1 0 〉 -oriented nanowires present larger conductance at low bias than that of others. Moreover, a large negative differential resistance appears in 〈 1 1 0 〉 nanowires, which shows potential advantage as Si based nano-functional electronic device.