Low-temperature reactively sputtered iron oxide for thin film devices

The development of a low-temperature reactive-sputtering process for producing high-quality hematite films was explored. Iron oxide thin films were sputter-deposited under different conditions of oxygen partial pressure and at substrate temperatures up to 200 °C, and characterized for comparison. Although all sample films exhibited structural and compositional characteristics consistent with polycrystalline rhombohedral Fe2O3 (hematite), it was found that the detailed grain features and morphology, as well as the optical and electrical properties, were significantly altered by process parameter variations. Average grain size increased with deposition temperature and decreased with oxygen partial pressure. Measured film conductivities ranged from 10−9 S/cm in 100 °C samples up to 5×10−4 S/cm in the 200 °C samples. Highest conductivities were found in the sample films exhibiting the largest grains, which is attributed to the effects of mobility enhancement through reduced inter-grain scattering.