Aligned AlN nanowires by self-organized vapor–solid growth

Abstract

Highly oriented AlN single crystal nanowires with aspect ratio up to 600, diameter in the range of 40–500 nm,and 100 µm lengths, have been synthesized via a vapor–solid growth mechanism. The results were obtained at1750 °C and 850 mbar nitrogen pressure on vicinal SiC substrates pretreated by SiC sublimationepitaxy in order to attain distinguishable terraces. It was found that the nanowires changein thickness after they have reached a critical length, and this fact contributes to anunderstanding of the growth mechanism of AlN nanowires. The nanowires are hexagonallyshaped and perfectly aligned along the [0001] direction with a small tilt given bythe substrate vicinality. Under nitrogen excess a preferential growth along thec-axis of the wurtzite structure takes place while below some critical value of nitrogenpressure the growth mode switches to lateral. The AlN nanowires are shown to have adislocation free wurtzite crystal structure. Some possible applications are discussed.