Study Of The Laser Irradiation And Annealing Effects On Visible Luminescence Controlling Of ZnO Thin Films

Zinc oxide (ZnO) is a new type of semiconductor optoelectronic material, thereare extremely wide applications in solar, UV detectors, surface acoustic wave devices,light emitting diodes, and so on. With the deepening of knowledge of ZnO, manyadvanced growth technologies have been applied in preparing ZnO thin films, and theresearches of its optical and electrical properties have become one of the hot topics inmaterials.ZnO thin films were deposited on a sapphire (001) by pulsed laser deposition(PLD) technique. The effects of luminescent properties of ZnO thin film on substratetemperature, atmosphere (oxygen and nitrogen) and gas pressure had been studied.The best growth condition had been found by PL Spectra which characterizes thestrongest visible luminescence of ZnO thin films. The samples with the strongestvisible luminescence were divided into two parts, some of them were annealed atdifferent temperatures, and the others were irradiated with different laser energies.The changes of optical and electrical properties of ZnO thin films had been observed.The origins of UV and visible emissions were investigated; furthermore, theregulation of visible luminescence was performed.Results showed that the ZnO thin films with best visible luminescence propertycan be obtained in O2atmosphere of40Pa pressure at room temperature. The surfacemorphology of annealed and laser irradiated ZnO thin films had a large difference.Comparing with laser irradiation, annealing treatment could improve the structuraland morphological qualities of ZnO thin films. The UV emission had a closerelationship with its surface morphology. Annealing and laser irradiation nearly hadthe common effect on controlling the concentration and type of defects in visibleemission, especially for the concentration of hallow donor defect. The visibleluminescence band was devided into four parts:1.84,2.08,2.22, and2.38eV, whichwere related to Oi, VO++, VZnand VO+defects, respectively. The origin of UV emissionof ZnO thin films was F0X, D0X and D0X-LO radiative recombination. TheConductivity of ZnO thin films improved5orders of magnitude after annealing, andup to6orders of magnitude after laser irradiation, which could be related to theaccumulation of Zni related shallow donor defects. Moreover, laser irradiation caneffectively regulate the visible light color of ZnO thin films, continuous changes fromred-orange to blue-green light, and the glowing shapes can be regulated by the maskswith different shapes.