ULTRASONIC SPRAY-ASSISTED CVD GROWTH OF HIGHLY TRANSPARENT AND CONDUCTIVE ALUMINUM-DOPED ZnO

Zinc oxide (ZnO), undoped and Al-doped thin films have been synthesized by the ultrasonic spray-assisted chemical vapor deposition (USCVD) system. The films were deposited on glass substrates. The precursor solution was prepared dissolving zinc chloride in distilled water. First, the precursor concentrations were investigated and optimized before studying Al doped, after we have studied the Al-doped influence on ZnO films especially optical and electrical properties for use as a transparent conductive oxide (TCO) in solar cell electrodes. The characterizations have been carried out using X-ray diffraction technique, UV-vis spectrophotometry, Hall Effect measurement (ECOPIA), atomic force microscopy (AFM, VEECO Dimension 3100) and scanning electron microscopy (SEM). X-ray diffraction (XRD) results showed that ZnO and Al-doped ZnO (AZO) films were crystallized in the hexagonal wurtzite structure with (002) orientation. Optical measurements have shown that all films exhibit, along the visible range, high transmittance and that optical band gap depends strongly to Al-doped concentration. Hall-effect measurement indicates that the highest carrier concentration (1.2×1020cm-3) and the lowest resistivity (2.7×10−2Ωcm) are obtained for the 4% AZO sample. The SEM shows that the microstructures of ZnO and AZO are homogeneous and the AFM images prove their microcrystallinity with grains orthogonal to the film surface.