Stability of III–V and IV–VI nanowires—A theoretical study

The properties and the stability of III–V (GaAs, InAs) and IV–VI (PbTe) nanowires are studied by ab initio methods. The calculations show that very thin III–V nanowires are most stable when adopting the wurtzite structure along (0 0 0 1) direction, even though the bulk crystallographic structure of the studied compounds is zinc-blende. This theoretical result has been confirmed by experimental observation of pure wurtzite structure in NWs with diameters up to ca 10 nm. Next, by lateral growth on the side surfaces of such thin wires, thicker wurtzite III–V wires (with diameters up to 40 nm) without stacking faults were obtained. In contrast to the case of III–V nanowires, the most stable PbTe whiskers have the same (rock-salt) crystallographic structure as the bulk crystal for all studied diameters. The energy cost of adopting by such wires another (e.g., CsCl) structure is by few hundred of meV per atomic pair higher, what makes different crystallographic phases unlikely to occur in these wires and points to PbTe as a perfect semiconductor material for growing stacking fault free NWs.