Role of Oxide Defects in ALD grown TiO2 Coatings on Performance as Photoanode Protection Layer
Tutkimustuotos: Konferenssiesitys, posteri tai abstrakti ›
|Tila||Julkaistu - 29 toukokuuta 2018|
|Tapahtuma||Optics & Photonics Days 2018 - Jyväskylä, Suomi|
Kesto: 28 toukokuuta 2018 → 30 toukokuuta 2018
|Conference||Optics & Photonics Days 2018|
|Ajanjakso||28/05/18 → 30/05/18|
In this work, structural, optical and photoelectrochemical properties of the ALD grown TiO2 films were studied in as-deposited condition and after annealing in air at 500 °C. TiO2 films were grown on n-type phosphorus-doped silicon and fused quartz by ALD at 200 °C using tetrakis(dimethylamido)titanium (TDMAT) and deionized water as precursors. The properties of TiO2 were investigated by X-ray photoelectron spectroscopy (XPS), ellipsometry and UV/Vis/NIR spectrophotometry. In addition, results from X-ray diffraction (XRD), Raman spectroscopy and photoelectrochemical (PEC) cell are discussed.
Based on the results, as-deposited TiO2 is amorphous and absorbs visible light as ''black'' TiO2. After annealing in air at 500 °C TiO2 crystallizes as rutile and becomes ''white'' TiO2 that absorbs light only in the UV region. As-deposited TiO2 contains significant amount of Ti3+/2+ oxygen vacancies that are oxidized as Ti4+ upon annealing in air. In addition, nitrogen is found only in as-deposited titanium dioxide. As-deposited TiO2 is not chemically stable under PEC conditions. In contrast, the annealed TiO2 is chemically stable and showed 0.20 % ABPE efficiency for water splitting reaction.
As a conclusion, Ti3+ defects induce photocorrosion of ALD TiO2 under PEC conditions. After annealing in air at 500 °C ALD TiO2 is chemically stable and it can be used as a photoanode protection layer. In the future, research will be focused on optimizing the properties of ALD TiO2/Si interface and studying the structure of the surface after deposition of nickel electrocatalysts on TiO2/Si photoanode.