Nanostructured Fe2O3 Processing via Water‐Assisted ALD and Low‐Temperature CVD from a Versatile Iron Ketoiminate Precursor

Abstract

Vapor phase deposited iron oxide nanostructures are promising for fabrication of solid state chemical sensors, photoelectrodes for solar water splitting, batteries, and logic devices. The deposition of iron oxide via chemical vapor deposition (CVD) or atomic layer deposition (ALD) under mild conditions necessitates a precursor that comprises good volatility, stability, and reactivity. Here, a versatile iron precursor, namely [bis(N‐isopropylketoiminate) iron(II)], which possesses ideal characteristics both for low‐temperature CVD and water‐assisted ALD processes, is reported. The films are thoroughly investigated toward phase, composition, and morphology. As‐deposited ALD grown Fe2O3 layers are amorphous, while the CVD process in the presence of oxygen leads to polycrystalline hematite layers. The nanostructured iron oxide grown via CVD consists of nanoplatelets that are appealing for photoelectrochemical applications. Preliminary tests of the photoelectrocatalytic activity of CVD‐grown Fe2O3 layers show photocurrent densities up to 0.3 mA cm−2 at 1.2 V versus reversible hydrogen electrode (RHE) and 1.2 mA cm−2 at 1.6 V versus RHE under simulated sunlight (1 sun). Surface modification by cobalt oxyhydroxide (Co‐Pi) co‐catalyst is found to have a highly beneficial effect on photocurrent, leading to maximum monochromatic quantum efficiencies of 10% at 400 nm and 4% at 500 nm at 1.5 V versus RHE.