Reactive co-sputtering of hematite doped silica (Fe2O3-SiO2) thin films

Abstract Fe 2 O 3 doped silica films were deposited using a reactive cosputtering approach where the power applied to the Fe cathode was systematically varied from 20 to 80 W to change the Fe 2 O 3 content, while SiO 2 was deposited with a constant power of 100 W applied to the Si target. As a result of increases in Fe cathode power, from 20 to 80 W, the fraction of Fe 2 O 3 relative to SiO 2 was shown to increase from 0.01 to 0.15, as measured via x-ray photoelectron spectroscopy (XPS). XPS analysis was also used to analyze the valence states of the compounds present in the films, confirming the presence of both Fe 2 O 3 (Fe 3+ ) cations alongside SiO 2 (Si 4+ ). The observed increases in Fe 2 O 3 content were associated with a rise in refractive index values from n 589 = 1.48 to n 589 = 1.72, while the extinction coefficient, k 589 remained below 0.01. Films deposited using the methods outlined within this work demonstrate Eg values ranging from highly transparent at above 3.5 eV, down to 1.52 eV, within the range for devices requiring efficient absorption of solar energy.