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DOI	10.1039/d0ee02032j
	Failure modes of protection layers produced by atomic layer deposition of amorphous TiO2on GaAs anodes
	Buabthong P.; Ifkovits Z.P.; Kempler P.A.; Chen Y.; Nunez P.D.; Brunschwig B.S.; Papadantonakis K.M.; Lewis N.S.
发表日期	2020
ISSN	1754-5692
起始页码	4269
结束页码	4279
卷号	13 期号:11
英文摘要	Amorphous titanium dioxide (a-TiO2) films formed by atomic layer deposition can serve as protective coatings for semiconducting photoanodes in water-splitting cells using strongly alkaline aqueous electrolytes. Herein, we experimentally examine the mechanisms of failure for p+-GaAs anodes coated with a-TiO2 films (GaAs/a-TiO2). Galvanic displacement of exposed GaAs by Au allowed imaging of pinholes in the a-TiO2 coatings, and enabled collection of quantitative and statistical data associated with pinhole defects. A combination of imaging, electrochemical measurements, and quantitative analyses of corrosion products indicated that extrinsic pinholes were present in the a-TiO2 films before electrochemical operation. During electrochemical operation these pinholes led to pitting corrosion of the underlying GaAs substrate. The dominant source of pinholes was the presence of atmospheric particulate matter on the GaAs surface during deposition of the a-TiO2 layer. The pinhole density decreased substantially when the thickness of the a-TiO2 coating increased beyond 45 nm, and approached zero when the thickness of the film exceeded 112 nm. The density of pinholes in films thinner than 45 nm decreased when the a-TiO2 coating was deposited in an environmentally controlled cleanroom. Pinhole-free GaAs/a-TiO2 devices were also tested via chronoamperometry to quantify the rate of pinhole formation during electrochemistry. The time-to-failure increased with thickness, suggesting that the failure mechanism may involve diffusion or migration through the film. However, other mechanisms may also contribute to the degradation of thicker films (>112 nm). Nevertheless, as previously hypothesized, extrinsic pinhole defects formed during deposition and testing control the short-term protective performance of the a-TiO2 film for GaAs anodes evolving O2 from water. © The Royal Society of Chemistry.
语种	英语
scopus关键词	Anodes; Atomic layer deposition; Chronoamperometry; Gallium arsenide; III-V semiconductors; Magnetic semiconductors; Oxide minerals; Pitting; Protective coatings; Semiconducting gallium; Titanium dioxide; Alkaline aqueous electrolytes; Atmospheric particulate matter; Corrosion products; Electrochemical measurements; Galvanic displacement; Pinhole formation; Protective performance; Thickness of the film; Failure (mechanical); corrosion; deposition; diffusion; electrode; film; particulate matter; performance assessment; statistical data; titanium
来源期刊	Energy and Environmental Science
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/162387
作者单位	Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, CA 91125, United States; Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, United States; Beckman Institute and Molecular Materials Research Center, California Institute of Technology, Pasadena, CA 91125, United States
推荐引用方式 GB/T 7714	Buabthong P.,Ifkovits Z.P.,Kempler P.A.,et al. Failure modes of protection layers produced by atomic layer deposition of amorphous TiO2on GaAs anodes[J],2020,13(11).
APA	Buabthong P..,Ifkovits Z.P..,Kempler P.A..,Chen Y..,Nunez P.D..,...&Lewis N.S..(2020).Failure modes of protection layers produced by atomic layer deposition of amorphous TiO2on GaAs anodes.Energy and Environmental Science,13(11).
MLA	Buabthong P.,et al."Failure modes of protection layers produced by atomic layer deposition of amorphous TiO2on GaAs anodes".Energy and Environmental Science 13.11(2020).