  The thermoelectric properties of cubic zincblend silicon carbide nanowires
(SiCNWs) with nitrogen impurities and vacancies along [111] direction are
theoretically studied by means of atomistic simulations. It is found that the
thermoelectric figure of merit ZT of SiCNWs can be significantly enhanced by
doping N impurities together with making Si vacancies. Aiming at obtaining a
large ZT, we study possible energetically stable configurations, and disclose
that, when N dopants locate at the center, a small number of Si vacancies at
corners are most favored for n-type nanowires, while a large number of Si
vacancies spreading into the flat edge sites are most favored for p-type
nanowires. For the SiCNW with a diameter of 1.1 nm and a length of 4.6 nm, the
ZT value for the n-type is shown capable of reaching 1.78 at 900K. The
conditions to get higher ZT values for longer SiCNWs are also addressed.
