Saari Jesse, Ali-Löytty Harri, Honkanen Mari, Tukiainen Antti, Lahtonen Kimmo, Valden Mika
Surface Science Group, Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 692, FI 33014 Tampere, Finland.
Tampere Microscopy Center, Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 692, FI 33014 Tampere, Finland.
ACS Omega. 2021 Oct 7;6(41):27501-27509. doi: 10.1021/acsomega.1c04478. eCollection 2021 Oct 19.
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 HO 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.
二氧化钛（TiO₂）可保护光电化学（PEC）器件免受腐蚀，但制备具有长期稳定性的高质量TiO₂涂层仍具有挑战性。在此，我们比较了硅片清洗和沉积后退火温度对使用四（二甲基氨基）钛（TDMAT）和H₂O作为前驱体在100℃生长温度下通过原子层沉积（ALD）生长的TiO₂/n-Si光阳极性能的影响。我们表明，如果需要过度的沉积后退火来诱导结晶，那么在碱性PEC水分解条件下，在ALD之前去除原生氧化硅并不能改善TiO₂涂层性能。沉积态的TiO₂涂层是非晶态的，易发生光腐蚀。然而，在400℃热处理使非晶态TiO₂结晶为锐钛矿TiO₂后，发现TiO₂涂层在10小时的时间段内是稳定的。在ALD生长过程中未形成界面氧化硅，但在热处理过程中，所有样品的界面氧化硅厚度增加到1.8nm。将ALD生长温度提高到150℃可在300℃实现结晶，这导致界面氧化硅生长减少，随后光电流起始电位提高70mV。
