Al2O3 and SiO2 Atomic Layer Deposition Layers on ZnO Photoanodes and Degradation Mechanisms

Qian Cheng, Manpuneet K. Benipal, Qianlang Liu, Xingye Wang, Peter A. Crozier, Candace Chan, Robert J. Nemanich

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Strategies for protecting unstable semiconductors include the utilization of surface layers composed of thin films deposited using atomic layer deposition (ALD). The protective layer is expected to (1) be stable against reaction with photogenerated holes, (2) prevent direct contact of the unstable semiconductor with the electrolyte, and (3) prevent the migration of ions through the semiconductor/electrolyte interface, while still allowing photogenerated carriers to transport to the interface and participate in the desired redox reactions. Zinc oxide (ZnO) is an attractive photocatalyst material due to its high absorption coefficient and high carrier mobilities. However, ZnO is chemically unstable and undergoes photocorrosion, which limits its use in applications such as in photoelectrochemical cells for water splitting or photocatalytic water purification. This article describes an investigation of the band alignment, electrochemical properties, and interfacial structure of ZnO coated with Al2O3 and SiO2 ALD layers. The interface electronic properties were determined using in situ X-ray and UV photoemission spectroscopy, and the photochemical response and stability under voltage bias were determined using linear sweep voltammetry and chronoamperometry. The resulting surface structure and degradation processes were identified using atomic force, scanning electron, and transmission electron microscopy. The suite of characterization tools enable the failure mechanisms to be more clearly discerned. The results show that the rapid photocorrosion of ZnO thin films is only slightly slowed by use of an Al2O3 ALD coating. A 4 nm SiO2 layer proved to be more effective, but its protection capability could be affected by the diffusion of ions from the electrolyte.

Original languageEnglish
Pages (from-to)16138-16147
Number of pages10
JournalACS Applied Materials and Interfaces
Volume9
Issue number19
DOIs
Publication statusPublished - May 17 2017

Fingerprint

Zinc Oxide
Atomic layer deposition
Zinc oxide
Electrolytes
Degradation
Semiconductor materials
Ions
Photoelectrochemical cells
Thin films
Chronoamperometry
Water
Redox reactions
Carrier mobility
Voltammetry
Photoelectron spectroscopy
Photocatalysts
Bias voltage
Ultraviolet spectroscopy
Electrochemical properties
Surface structure

Keywords

  • atomic layer deposition
  • interface electronic structure
  • photoanode
  • photocorrosion
  • photodegradation
  • wide band gap protective layer
  • zinc oxide

ASJC Scopus subject areas

  • Materials Science(all)

Cite this

Al2O3 and SiO2 Atomic Layer Deposition Layers on ZnO Photoanodes and Degradation Mechanisms. / Cheng, Qian; Benipal, Manpuneet K.; Liu, Qianlang; Wang, Xingye; Crozier, Peter A.; Chan, Candace; Nemanich, Robert J.

In: ACS Applied Materials and Interfaces, Vol. 9, No. 19, 17.05.2017, p. 16138-16147.

Research output: Contribution to journalArticle

Cheng, Qian ; Benipal, Manpuneet K. ; Liu, Qianlang ; Wang, Xingye ; Crozier, Peter A. ; Chan, Candace ; Nemanich, Robert J. / Al2O3 and SiO2 Atomic Layer Deposition Layers on ZnO Photoanodes and Degradation Mechanisms. In: ACS Applied Materials and Interfaces. 2017 ; Vol. 9, No. 19. pp. 16138-16147.
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