Optical, Structural and Electrical Properties of Aluminum Doped Zinc Oxide Thin Films by MOCVD Technique

Thin films of aluminum-doped ZnO (AZO) were deposited by metal organic chemical vapor deposition from a single solid source precursor, aluminum zinc acetylacetonate. The AZO thin films were deposited on a sodalime glass substrate at different substrate temperatures ranging from 390°C to 450°C. Results were characterized using Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM) with energy dispersive x-ray (EDS) facility attached to it, x-ray diffraction (XRD), UV–Visible spectrometry and a four point probe method (with an applied magnetic field). While RBS determined the thickness and elemental composition of the films, the presence of the expected elements in the films was also corroborated by EDS. The average thickness of the thin films was determined to be 133 nm. SEM micrographs revealed that the films were composed of continuously and uniformly distributed crystalline grains without any cracks. XRD analysis showed that the films were polycrystalline with a structure belonging to ZnO hexagonal wurtzite and grain size ranging from 27.50 nm to 41.30 nm. The optical transmittance of AZO films deposited at different temperatures varied from 75% to 95% in the range of wavelength 400–700 nm, with an optical band gap energy value between 3.27 eV and 3.30 eV. The electrical characterization of AZO films deposited at different substrate temperatures revealed resistivity values between 0.07 Ω cm and 0.01 Ω cm. The mobility was not the same for all the films, so also carrier concentration. The physico-chemical characterization showed that the AZO film deposited at temperature 420°C possessed the best properties among the three samples.