STRUCTURAL AND PHOTOLUMINESCENCE STUDY OF ZINC OXIDE THIN FILMS GROWN BY LASER INDUCED PLASMA
Usman Ilyas 1,2, R. S. Rawat 1, G. Roshan 1, T.L. Tan 1, P. Lee 1, S.V.Springham 1, R. Chen 3, H. D. Sun 3, Li Fengji 4 and Sam Zhang 4
1 SSE, NIE, Nanyang Technological University, 1 Nanyang Walk, Singapore
2 Department of Physics, University of Engineering & Technology Lahore, Pakistan.
3 School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore
4 School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore
Abstract. The structural, compositional and optical properties of thin films grown by laser-induced plasma (LIP) were studied as a function of post-deposition annealing. Nanocrystalline powder of ZnO was prepared through a wet chemical method using zinc acetate dihydrate (Zn(CH3COO)2.2H2O) and potassium hydroxide (KOH) as precursors. The X-ray diffraction (XRD) spectra showed the improved crystalline quality at elevated temperatures with a temperature-dependent variation in lattice parameters, pointing the activation of zinc and oxygen related point defects at various annealing temperatures. X-ray photoelectron spectroscopy (XPS) of Auger Zn L3M4,5M4,5 and O 1s peaks revealed the reversion of zinc interstitials to crystal lattice as zinc lattice sites at different annealing temperatures leading to strong Zn-O bonding. The origins of near band edge (NBE) and deep level emission (DLE) in room temperature photoluminescence (PL) spectra, pointing out the activation of temperature-dependent intrinsic defects states are briefly discussed. Among all the thin films under investigation, ZnO thin films annealed at 700 °C were found to have strong Zn-O bonding with maximum contribution of oxygen interstitials that is favorable to form un-doped p-type ZnO essential for optoelectronic and spintronic devices.
Key Words: ZnO, Laser induced plasma (LIP), Wet chemical method.