A method to provide an article of manufacture of iron oxide on indium tin oxide for solar energy conversion. An atomic layer epitaxy method is used to deposit an uncommon bixbytite-phase iron (III) oxide (β-Fe2O3) which is deposited at low temperatures to provide 99% phase pure β-Fe2O3 thin films on indium tin oxide. Subsequent annealing produces pure α-Fe2O3 with well-defined epitaxy via a topotactic transition. These highly crystalline films in the ultra thin film limit enable high efficiency photoelectrochemical chemical water splitting.