Spontaneous and Position-Controlled Epitaxial Growth of ZnO Nanowires on AlN/Si by CVD

For the integration of ZnO nanowires in future devices, the controlled growth on a Si substrate is of utmost interest. We report the spontaneous and position-controlled epitaxial growth of highly oriented ZnO nanowires on Si using a catalyst-free CVD approach with an AlN buffer and a ZnO seed layer. The length, diameter, and density of the nanowires were analyzed for a wide range of growth parameters, i.e., growth time, substrate temperature, oxygen concentration, and carrier flow rate. Subtle changes lead to variations in nanowire dimensions and density but maintain the nontapered and uniform hexagonal shape. The use of the AlN buffer layer allowed for epitaxial growth of the ZnO seed layer and nanowires on Si, as confirmed by high-resolution X-ray diffraction. The high alignment of nanowires with low crystal tilt and twist was confirmed by ω-scans with a full width at half-maximum of 0.33 and 0.64° of the (0002) and (101̅0) reflection, respectively. Finally, after optimizing growth parameters, catalyst-free, position-controlled growth of ZnO NWs was demonstrated by lithographic patterning and selective etching of the ZnO seed layer.