On‐axis and off‐axis growth of zinc oxide nanostructures via pulsed laser deposition

Abstract

The comparison of surface morphology of ZnO at two different regions on n‐type Si substrate surface (off‐axis and on‐axis pulsed laser deposition) is reported. Nanostructures were grown by ablating ZnO pellet with second harmonic Q‐switched Nd:YAG laser. The nanostructures were synthesized by two‐step processes where first ZnO seed layers were grown on Si‐substrate at 300 °C and 0.2 mbar O2 pressure followed by the growth of nanostructures at different O2 pressures keeping the substrate temperature fixed at 450 °C. The growth of these morphologies (particles and thin‐walled nanostructures) is attributed to difference in the kinetic energy of the plasma at different angles of emission from the target surface. Structural property was studied by XRD spectra and the optical properties of the nanostructures were investigated by photoluminescence and Micro‐Raman spectroscopy. Recorded photoluminescence spectra shows near band edge emission along with visible emissions related to the defect levels in ZnO. Micro‐Raman spectra confirm the crystalline nature of the nanostructures and the presence of defects related to oxygen vacancy and interstitial zinc of grown nanostructures.

Band gap engineered zinc oxide nanostructures via a sol–gel synthesis of solvent driven shape-controlled crystal growth

“…10 However, synthesis of defect free 1D ZnO nanostructures, with desired morphology and composition, has been challenging as most growth techniques involve either high-cost fabrication processes or high temperature wet-chemical syntheses performed in highly toxic solvents. Among such fabrication techniques, chemical vapor deposition (CVD), 18 pulse-laser deposition (PLD), 19 molecular beam epitaxy (MBE), 20 and electro-chemical deposition 21 have been utilized to grow ZnO nanostructures directly onto the substrate. In addition to these thin lm deposition techniques, sol-gel and solvothermal methods are two of the most common chemical solution methods, which show the promise in terms of scalability, energy efficiency, and cost-effectiveness for the preparation of catalyst-free metal oxide nanostructures with better control over the growth conditions and morphology.…”