Synthesis of Aligned ZnO Nanorod Array on Silicon and Sapphire Substrates by Thermal Evaporation Technique

High density ZnO nanorods were grown by thermal evaporation of Zn powder at 700°C on Si (100) and sapphire (0001) substrates at atmospheric pressure without adding any catalyst. The nanorods were characterizated in terms of their structural and optical properties. The nanorods grown on Si have a diameter of 350–400 nm and a length of 1.2 μm while those on sapphire have a diameter of 600–800 nm and a length of 2.5 μm. During the structural characterization, it is noticed that the rods grow along the (0002) plane with perfect hexagonal facet. The room temperature photoluminescence spectrum showed a strong UV emission peak at 385 nm with a weak green band emission, which confirms that nanorods have good optical properties. It is observed that the oxygen partial pressure plays an important role to control the shape and size of the nanorods in thermal evaporation growth technique.