Growth of ZnO Thin Films by Spray Plasma Technique: Correlation Between Spectroscopic Measurements and Film Properties

Nanostructured ZnO thin films have been deposited on glass substrate at low substrate temperature (200 °C) using the Spray Plasma technique. The zinc nitrate or zinc chloride precursors (droplets) are injected in a low-pressure Ar/O2 radio-frequency inductive discharge. The O2 fraction and the distance between the inductive coil and the substrate holder were varied, and the resulting effect on the deposited film properties was investigated by means of X-ray diffraction, atomic force microscopy, transmittance electron microscopy and UV–visible spectroscopy. It was shown that the c-axis orientation growth depends on these two parameters but not on the precursor nature. The quality of the deposited film is optimal for 5 % O2 in argon when the inductive coil-substrate distance is small. The Ar/O2 plasma was also diagnosed by optical emission spectroscopy. The oxygen atom relative concentration was monitored by optical emission actinometry and the rotational spectrum of OH was recorded to estimate the gas temperature.