Low temperature atomic layer deposition of highly photoactive hematite using iron(iii) chloride and water

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 1; no. 38
• Main Authors: Klug, Jeffrey A., Becker, Nicholas G., Riha, Shannon C., Martinson, Alex B. F., Elam, Jeffrey W., Pellin, Michael J., Proslier, Thomas
• Format: Journal Article
• Language: English
• Published: United States Royal Society of Chemistry 01.01.2013
• Subjects: MATERIALS SCIENCE
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c3ta12514a

Nanostructured hematite (α-Fe2O3) has been widely studied for use in a variety of thin film applications including solar energy conversion, water oxidation, catalysis, lithium-ion batteries, and gas sensing. Among established deposition methods, atomic layer deposition (ALD) is a leading technique for controlled synthesis of a wide range of nanostructured materials. In this work, ALD of Fe2O3 is demonstrated using FeCl3 and H2O precursors at growth temperatures between 200 and 350 °C. Self-limiting growth of Fe2O3 is demonstrated with a growth rate of ~0.6 Å per cycle. As-deposited, films are nanocrystalline with low chlorine impurities and a mixture of α- and γ-Fe2O3. Post-deposition annealing in O2 leads to phase-pure α-Fe2O3 with increased out-of-plane grain size. Photoelectrochemical measurements under simulated solar illumination reveal high photoactivity toward water oxidation in both as-deposited and post-annealed films. Planar films deposited at low temperature (235 °C) exhibit remarkably high photocurrent densities ~0.71 mA cm-2 at 1.53 V vs. the reversible hydrogen electrode (RHE) without further processing. Films annealed in air at 500 °C show current densities of up to 0.84 mA cm-2 (1.53 V vs. RHE).