Hexagonal wurtzite InN nanowires are grown via a vapor-liquid-solid (VLS) mechanism with an Au catalyst. Microstructure characterizations of a large number of nanowires demonstrate that the growth direction of InN nanowires is governed by variable NH_3 flux. InN nanowires at a NH_3 flux of 10 standard cubic centimeters per minute (sccm) grow preferentially in a hexagonal close-packed (hcp) 〈?1001〉 direction, while those at 100sccm NH_3 flux favor the hcp 〈0001〉 direction. A free energy minimization model is proposed to interpret this phenomenon. The first-principles calculations reveal that the 〈 10?10〉 oriented nucleus has the lowest energy at the lower NH_3 flux. In contrast, when NH_3 flux is high, the 〈0001〉 oriented nucleus has the lowest energy.
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