Study On Preparation, Electrical And Optical Properties Of ZnO Thin Films

ZnO material with hexagonal wurtzite structure has been widely used in piezoelectric, optoelectronic devices and sensors due to its unique electrical and optical properties. In this paper, two methods, sol-gel and RF magnetron sputtering, were employed to fabricate ZnO thin films. The structural, electrical and optical characteristics of ZnO films were investigated using XRD, AFM, SEM, EDS and photoluminescent (PL) measurements.Li+, Mg2+ and Li+/Mg2+ doped ZnO films were prepared on lime-glass substrate by sol-gel method using zinc acetate, 2-methoxyethanol and monoethanolamine as starting materials, and the effects of processing parameters such as dopants, solution concentration, postheating temperature and the film thickness on the properties of ZnO films were discussed. The results showed that proper amount of Li+ or Mg2+ dopants could obviously improve the cystallization and the preferential C-orientation, as well as the resistivity of ZnO films. For the Li/Mg co-doped ZnO film (Li/Zn=0.10, Mg/Zn=0.04) annealed at 610℃, the oriented degree of (002) plane(OD002) and the resistivity reached 0.961 and 6.0×107?cm, respectively. The photoluminescent results showed that the 403nm PL peak was induced by Li acceptor level (about 0.29eV), and for the Li-doped ZnO films the NBE peak near 371nm disappeared. The intensities of DLE peaks near 452nm and 470nm decrease with the increase of Li or Mg dopants.The ZnO (100) thin film with OD100 of 0.752 was successfully deposited on lime-glass substrate under extremely high RF power (550W) by magnetron sputtering, while deposited under low RF power (100~380W), the film preferentially oriented along (101) with OD101 of 0.799. However, when the substrate heated to 250℃, the films deposited at 200W preferably grew along (002) with the OD002 of 0.742. The XRD results indicated that the cell parameters of ZnO film with C-orientation was smaller than that with (100) and (101) orientation, which was probably due to the different amount of defects in the three kinds of films. The PL spectra also proved that...