High resolution X-ray diffraction studies of epitaxial ZnO nanorods grown by reactive sputtering

Vertically aligned and highly c-axis oriented ZnO nanorods were epitaxially grown on c-sapphire by dc reactive sputtering of zinc target in argon-oxygen atmosphere. Scanning electron microscopy shows that substrate temperature critically controls the morphology of sputtered ZnO films, eventually causing the formation of laterally oriented ZnO nanorods at higher temperatures (700 °C–750 °C), as confirmed by ϕ-scan measurements. High resolution X-ray diffraction was used to obtain the micro-structural parameters of ZnO columnar films/nanorods from Williamson-Hall plots of ω and ω-2θ scans, and rocking curves of asymmetric reflections. These results show that epitaxially grown ZnO nanorods exhibit substantially superior micro-structural parameters, namely, tilt (0.4°), twist (0.5°), and micro-strain (4 × 10−4), compared to columnar ZnO films grown at 500 °C–600 °C. The reciprocal space maps of (0002), (0004), 10 1 ¯ 1, 10 1 ¯ 4 , and ( 11 2 ¯ 0 ) planes of ZnO nanorods were carried out to obtain the lattice ...