Catalyst-free growth of high-quality ZnO nanorods on Si(100) substrate by two-step, off-axis pulsed-laser deposition

We demonstrate the growth of ZnO nanorods on a Si(100) substrate through a two-step process, annealing and off-axis pulsed laser deposition (PLD), without a catalyst. ZnO powder was first dispersed on the Si substrate, and annealed to form seeds for ZnO nanorod growth for 2.5 h. In the second step, ZnO was deposited on the seeds by PLD for 1 h. It was experimentally confirmed that the surface morphology after annealing acts as growth nuclei of nanorods. Controlling growth parameters during deposition enables the adjustment of the sizes of nanorods, namely, diameter and length. The diameters of the grown nanorods are 50-700nm and the lengths are 2-10μm. Cathode luminescence (CL) spectra were used to evaluate the states of defects within the ZnO nanorods. According to the CL measurement results, the thinnest nanorod arrays were found to have fewer detects, and more detects were introduced as nanorods became thicker.