Growth of Au-catalyzed and self-catalyzed ZnO nanowires using chemical vapor deposition technique

With the ongoing miniaturization of devices such as FETs, the synthesis of ZnO NWs (building blocks) has attracted extensive research interest. ZnO NWs have been synthesized via different routes by many research groups. In order for these building blocks to be incorporated into functional nano-devices, controlled synthesis of the ZnO NWs to obtain features such as the desired size, shape and alignment should be fulfilled. This is a rather challenging task. A better understanding of the growth mechanism of ZnO NWs may be helpful to resolve these uncertainties. This paper investigates the growth of ZnO NWs by chemical vapor deposition (CVD) technique. For self-catalyzed ZnO NWs, highly c-oriented ZnO films, which was pre-deposited by atomic layer deposition (ALD) technique, have been used as seed layer to facilitate the aligned growth of NWs. The crystal structure of ZnO NWs has been analyzed by HRTEM/SAED. In contrary, Au-catalyzed ZnO NWs are grown on Si substrates pre-sputtered a thin layer of Au film (5 nm thick). Au alloy nanoparticles could be clearly identified at some of the NWs. The effect of synthesis parameters such as distance between Zn precursor and substrates, oxygen flow rate, synthesis duration and amount of Zn powder, on the growth of ZnO NWs are studied systematically. In addition, Au catalyst promoted higher growth rate on Au-catalyzed ZnO NWs as compared to self-catalyzed ZnO NWs. A model to explain the growth of both self-catalyzed and Au-catalyzed ZnO NWs has been proposed.