Unusual growth direction and controllable wettability of W-catalyzed AlN nanowires

Abstract

Metal W is employed as an efficient catalyst to grow AlN nanowires. High-density nanowires have been synthesized with a W catalyst cap at the tip. Transmission electron microscopy further reveals that the W-catalyzed AlN nanowires have an unusual [1 0 1] growth direction. The growth process of the nanowires has been studied by adjusting the experimental conditions and a growth kinetics model is proposed to describe the growth process of the W-catalyzed AlN nanowires. In addition, the surface wettability of a nanowire film is also observed and the sample shows smart wetting behavior. First, the as-grown sample exhibits a self-dewetting property with a water CA (contact angle) spontaneous transition from initial superhydrophilicity to final superhydrophobicity in the air. Then, the superhydrophilic surface can be recovered by illumination with UV light. The surface oxidation state of the catalyst may be responsible for the transition of the wettability.