title: Insights into Interfacial Changes and Photoelectrochemical Stability of In(x)Ga(1-x)N (0001) Photoanode Surfaces in Liquid Environments.
abstract: The long-term stability of InGaN photoanodes in liquid environments is an essential requirement for their use in photoelectrochemistry. In this paper, we investigate the relationships between the compositional changes at the surface of n-type In(x)Ga(1-x)N (x ∼ 0.10) and its photoelectrochemical stability in phosphate buffer solutions with pH 7.4 and 11.3. Surface analyses reveal that InGaN undergoes oxidation under photoelectrochemical operation conditions (i.e., under solar light illumination and constant bias of 0.5 VRHE), forming a thin amorphous oxide layer having a pH-dependent chemical composition. We found that the formed oxide is mainly composed of Ga-O bonds at pH 7.4, whereas at pH 11.3 the In-O bonds are dominant. The photoelectrical properties of InGaN photoanodes are intimately related to the chemical composition of their surface oxides. For instance, after the formation of the oxide layer (mainly Ga-O bonds) at pH 7.4, no photocurrent flow was observed, whereas the oxide layer (mainly In-O bonds) at pH 11.3 contributes to enhance the photocurrent, possibly because of its reported high photocatalytic activity. Once a critical oxide thickness was reached, especially at pH 7.4, no significant changes in the photoelectrical properties were observed for the rest of the test duration. This study provides new insights into the oxidation processes occurring at the InGaN/liquid interface, which can be exploited to improve InGaN stability and enhance photoanode performance for biosensing and water-splitting applications.
authors.affiliation: Institute for Semiconductor Technology and Laboratory for Emerging Nanometrology, TU Braunschweig , Braunschweig 38092, Germany.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Caccamo
authors.affiliation: University of Freiburg , Friedrichstrasse 39, Freiburg im Breisgau 79098, Germany.
authors.forename: Giulio
authors.initials: G
authors.lastname: Cocco
authors.affiliation: LENS-MIND-IN2UB, Departament d'Electronica, Universitat de Barcelona , c/Martı́ Franque's 1, Barcelona 08028, Spain.
authors.forename: Gemma
authors.initials: G
authors.lastname: Martín
authors.affiliation: Institute for Semiconductor Technology and Laboratory for Emerging Nanometrology, TU Braunschweig , Braunschweig 38092, Germany.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Institute for Semiconductor Technology and Laboratory for Emerging Nanometrology, TU Braunschweig , Braunschweig 38092, Germany.
authors.forename: Sönke
authors.initials: S
authors.lastname: Fundling
authors.affiliation: Institute for Semiconductor Technology and Laboratory for Emerging Nanometrology, TU Braunschweig , Braunschweig 38092, Germany.|Inorganic Chemistry Department, National Research Centre (NRC) , Cairo, Egypt.
authors.forename: Alaaeldin
authors.initials: A
authors.lastname: Gad
authors.affiliation: Institute for Semiconductor Technology and Laboratory for Emerging Nanometrology, TU Braunschweig , Braunschweig 38092, Germany.
authors.forename: Matin Sadat
authors.initials: MS
authors.lastname: Mohajerani
authors.affiliation: Institute for Semiconductor Technology and Laboratory for Emerging Nanometrology, TU Braunschweig , Braunschweig 38092, Germany.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Abdelfatah
authors.affiliation: LENS-MIND-IN2UB, Departament d'Electronica, Universitat de Barcelona , c/Martı́ Franque's 1, Barcelona 08028, Spain.
authors.forename: Sonia
authors.initials: S
authors.lastname: Estradé
authors.affiliation: LENS-MIND-IN2UB, Departament d'Electronica, Universitat de Barcelona , c/Martı́ Franque's 1, Barcelona 08028, Spain.
authors.forename: Francesca
authors.initials: F
authors.lastname: Peiró
authors.affiliation: Institute of Energy Research and Physical Technologies, TU Clausthal , Leibnizstrasse 4, Clausthal-Zellerfeld 38678, Germany.
authors.forename: Wanja
authors.initials: W
authors.lastname: Dziony
authors.affiliation: Institute for Applied Physics, TU Braunschweig , Mendelssohnstrasse 2, Braunschweig 38106, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Bremers
authors.affiliation: Institute for Applied Physics, TU Braunschweig , Mendelssohnstrasse 2, Braunschweig 38106, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Hangleiter
authors.affiliation: Fraunhofer Institut für Werkstoffmechanik (IWM) , Wöhlerstraße 11, Freiburg im Breisgau 79108, Germany.
authors.forename: Leonhard
authors.initials: L
authors.lastname: Mayrhofer
authors.affiliation: Institute of Energy Research and Physical Technologies, TU Clausthal , Leibnizstrasse 4, Clausthal-Zellerfeld 38678, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Lilienkamp
authors.affiliation: Fraunhofer Institut für Werkstoffmechanik (IWM) , Wöhlerstraße 11, Freiburg im Breisgau 79108, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Moseler
authors.affiliation: Institute of Energy Research and Physical Technologies, TU Clausthal , Leibnizstrasse 4, Clausthal-Zellerfeld 38678, Germany.
authors.forename: Winfried
authors.initials: W
authors.lastname: Daum
authors.affiliation: Institute for Semiconductor Technology and Laboratory for Emerging Nanometrology, TU Braunschweig , Braunschweig 38092, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Waag
keywords: InGaN layer; X-ray photoelectron spectroscopy; photoelectrochemical stability; surface oxidation; transmission electron microscopy