Materials Science and Engineering

Biography

Biography: Sirikanjana Thongmee

Abstract

The effects of substituting Ag³⁺ into Ag-doped ZnO NR’s, Zn_1-xAg_xO (x =0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) are investigated. X-Ray Diffraction (XRD) patterns do not indicate that the Ag ions are systematically replacing the Zn ions but instead are forming into nano Ag particles. Since the radius of the Ag³⁺ ions (0.126 nm) is much greater than that of Zn²⁺ (0.072 nm), there would be a tremendous amount of lattice distortion if at the higher level of Ag doping if the Ag ions replaced the Zn ions at the lattice sites.  In the XRD patterns for the pure and x = 0.1 NR’s, we did not observe any peaks of the fcc crystal structure of Ag. When Ag was increased to x  ³ 0.3, we see the reflection from the Ag (1 1 1) and Ag (2 0 0) planes. SEM shows the morphologies of NR’s are changing along with the shape of the rods as the level of Ag substitute increase. For pure ZnO, the rods are orientated perpendicular to the plane appear to be hexagonal. The SEM images of the 1% Ag doped ZnO NR’s still show the presence of rod shaped particles. The morphologies of the 2% Ag doped ZnO NR’s are quite different. Some of them appear to star shape with a few arms emanating from a central point.  SEM image of 5% Ag doped NR’s showed ZnO NR’s appear to be “broccoli” shaped. 

The results from PL spectrum revealed that the visible light emission of the undoped ZnO NR’s are somewhat suppressed but becomes strongly enhanced (in the region between 450 – 600 nm) as the level of Ag doping is increased to 1%, then to 2%.  This could be taken as evidence that more defects were being created as the Ag ions were replacing the Zn in their sites in the wurtzite structure.