Deposition and characterization of spinel indium zinc oxide thin films

Spinel indium zinc oxide (IZO) has been theoretically predicted by density function theory simulations but its growth in significant quantities has not yet been studied before. In this work we report the deposition of spinel IZO with In:Zn cation concentration ratios equal to 2:1, by co-sputtering. The deposition of spinel IZO crystallites was first achieved on SiO2 by employing a substrate temperature of 200 °C and an Ar/O2 sputtering gas mixture with an O2 partial pressures (RO2) equal to 45%, at a chamber pressure of approximately 0.4 mTorr. The use of pulsed DC power in combination with low chamber pressures and high RO2  improved the crystallization into the spinel structure, due to the enhanced bombardment of the substrate with high-energy O-. Transmission electron microscopy (TEM) and precession electron diffraction (PED) measurements suggested that the spinel IZO crystallites were embedded inside a quasi-amorphous phase of IZO. The use of a polycrystalline spinel gallium zinc oxide (GZO) template was found to induce the growth of polycrystalline films that predominantly consist of spinel IZO grains. The TEM and PED measurements indicated that the texture of the GZO template was transferred to spinel IZO, resulting in the growth of textured grains with the (111) planes oriented parallel to the surface of the sample. The results of this work contribute to the development of high-mobility and electrically stable semiconducting oxides for several thin-film transistor applications.