Growth and characterization of ZnO Nanorods Nanowalls and Nanochains using pulsed laser deposition

Abstract

Recently, ZnO has attracted increasing interest because of its strong potential applications in nano (electronics, nano (optolectronics, nano (piezotronics, gas/chemical sensing and field emission display devices. ZnO is a II VI wide band gap material has a direct band gap of 3.4 eV in the near(UV spectral region, and a large exciton binding energy of 60 meV, so that exciton related emission processes can persist at or even above room temperature. Novel ZnO nanostructures including nanorods, nanowires, nanowalls, nanobelts, nanohelix, nanotubes, nanonails and nanoplates/sheets have been reported using various physical and chemical methods. Among them, one of the most versatile approaches to grow oxide thin film is pulsed laser deposition (PLD). In the present investigation, vertically aligned ZnO nanorods were grown on Si (100) substrate by optimizing the deposition parameters such as substrate temperature, target to substrate distance, oxygen partial pressure and wavelength of the laser. The influence of substrates including GaN (0001), Al2O3 (0001) and Si (100) on the growth of_aligned ZnO nanorods has been discussed. The vertically aligned hexagonal(pyramidal ZnO nanorods were obtained on the Al2O3 and Si substrates whereas interlinked ZnO nanowalls were obtained on the GaN substrates. A growth mechanism for the formation of ZnO nanowalls has been proposed based on the different growth rates of ZnO polar and non(polar planes. Novel ZnO chain(like structures have been synthesized by high(pressure PLD technique. A study of micro(Raman on these low dimensional structures has confirmed the good crystallinity. In this study,_ the weight ratio of ZnO:Mg was varied as 49:1, 33:1 and 24:1. The diameter of nanochains increases with the increase of the Mg concentration. The effect of substrate temperature on the growth of ZnO nanochains has been discussed in detail newline