The growth behavior and properties of atomic layer deposited zinc oxide films using hydrogen peroxide (H2O2) and ozone (O-3) oxidants

Abstract

Two types of zinc oxide (ZnO) films were grown by thermal atomic layer deposition (ALD), each using hydrogen peroxide and ozone gas oxidants. Diethylzinc (DEZ) was used as the zinc precursor for all experiments. The use of hydrogen peroxide oxidant resulted in elevated growth rates by approximately 70% at relatively low temperatures below 200 degrees C, in comparison with films grown using ozone gas. It is suggested that the use of hydrogen peroxide induces the formation of hydroxyl compounds on top of the growing film between each ALD cycle, which promotes better surface adsorption of the DEZ precursor molecules, thus enhancing the surface reaction rate. On the other hand, ozone-assisted growth is rather close to a thermally activated process, where the growth rate is observed to increase gradually with substrate temperature. At a relatively low growth temperature of 150 degrees C, the electrical resistivity of the ZnO films grown using hydrogen peroxide was lower than the films grown using ozone, by approximately three orders of magnitude. The free carrier density was observed to be the major parameter affecting the resistivity, the latter decreasing with growth temperature. The differences in electron mobility and concentration were correlated to the microstructure and atomic bonding states examined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).