High rate deposition of ZnO thin films by a small-scale inductively coupled argon plasma generated in open air

Linear transparent ZnO films were deposited using a millimetre sized inductively coupled argon plasma at atmospheric pressure in open air. Increasing the substrate temperature enabled high growth rates between 200 and 1 νm s^-1 to be obtained. The optical transmission of the obtained films is above 80% in the visible and the roughness of the films had a value of 15 nm. Plasma gas temperatures estimated from the rotational temperature of N ₂ assessed by optical emission spectroscopy suggest values of up to approximately 1800 K. The detected species in the plasma were argon and zinc radicals, but no ions. The high growth rate of the films is attributed to the rapid melting and sputtering of the metallic source filament, the produced species being carried to the substrate surface by the plasma gas. High substrate temperatures as well as high scanning rates are considered crucial to the formation of transparent, dense ZnO films, the first promoting surface migration and the second permitting regulation of the flux of oxygen to the surface.