Interface Engineering of TiO 2 Photoelectrode Coatings Grown by Atomic Layer Deposition on Silicon

• Published in: ACS omega Vol. 6; no. 41; pp. 27501 - 27509
• Main Authors: Saari, Jesse, Ali-Löytty, Harri, Honkanen, Mari, Tukiainen, Antti, Lahtonen, Kimmo, Valden, Mika
• Format: Journal Article
• Language: English
• Published: United States 19.10.2021
• ISSN: 2470-1343; 2470-1343
• DOI: 10.1021/acsomega.1c04478

Titanium dioxide (TiO ) can protect photoelectrochemical (PEC) devices from corrosion, but the fabrication of high-quality TiO coatings providing long-term stability has remained challenging. Here, we compare the influence of Si wafer cleaning and postdeposition annealing temperature on the performance of TiO /n -Si photoanodes grown by atomic layer deposition (ALD) using tetrakis(dimethylamido)titanium (TDMAT) and H O as precursors at a growth temperature of 100 °C. We show that removal of native Si oxide before ALD does not improve the TiO coating performance under alkaline PEC water splitting conditions if excessive postdeposition annealing is needed to induce crystallization. The as-deposited TiO coatings were amorphous and subject to photocorrosion. However, the TiO coatings were found to be stable over a time period of 10 h after heat treatment at 400 °C that induced crystallization of amorphous TiO into anatase TiO . No interfacial Si oxide formed during the ALD growth, but during the heat treatment, the thickness of interfacial Si oxide increased to 1.8 nm for all of the samples. Increasing the ALD growth temperature to 150 °C enabled crystallization at 300 °C, which resulted in reduced growth of interfacial Si oxide followed by a 70 mV improvement in the photocurrent onset potential.