High-aspect-ratio single-crystalline AlN nanowires: Free-catalytic PVT growth and field-emission studies

Abstract

Nanowires (NWs) with high aspect ratios (HARs) have great advantages for the fabrication of nanodevices. Herein, a high-efficiency and simple physical vapor transport (PVT) method is utilized to synthesize the uniform HAR aluminum nitride (AlN) NWs on a tungsten substrate without any catalysts. Synergistic effect of high surface energy of (0001), low saturated vapor pressure and large axial temperature gradient leads to the growth of HAR AlN NWs, which provides new insight for the growth of low-dimensional AlN nanostructures. The as-obtained AlN NWs with super HAR have hexagonal wurtzite structure, the diameters are about 100 nm and the lengths are over 200 μm. The AlN NWs have an intensive deep ultraviolet (DUV) absorption peak at 5.94 eV and exhibit a relatively high electrical conductivity (1.29 × 10−3 Ω−1 cm−1), low turn-on field (6.2 V μm−1) and threshold field (8.5 V μm−1). These results indicate that PVT method is efficient to fabricate HAR AlN NWs and the AlN NWs not only play an important role in DUV photoelectric devices but also have tremendous potential as a candidate for field-emission nanodevices.