Physico-Chemical Characterization of Anodic Oxides on Hf as a Function of the Anodizing Conditions. Issue 9 (1st January 2016)

• Record Type: Journal Article
• Authors: Zaffora, Andrea; Tranchida, Giada; Franco, Francesco Di; Quarto, Francesco Di; Santamaria, Monica
• Is Part Of: Journal of the Electrochemical Society. Volume 163:Issue 9(2016)
• Page Start: C563
• Page End: C570
• Publication Date: 2016-01-01
• Subjects: Anodic oxides -- Electrochemical Impedance Spectroscopy -- Growth kinetics -- HfO2 -- Photoelectrochemistry; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0871609jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Anodic films were grown to 5 V (Ag/AgCl) on mechanically polished Hf in 0.1 M ammonium biborate and 0.1 M NaOH. Independent of the anodizing conditions, the photoelectrochemical characterization allowed the observation of optical transitions at 3.25 eV, i.e. at photon energy lower than the bandgap of HfO2 . They are attributed to localized states inside the gap of the oxide induced by the presence of oxygen vacancies. From the cathodic photocurrent spectra, it was possible to estimate an energy threshold of ∼2.15 eV for internal electron photoemission phenomena. The impedance measurements proved the formation of insulating oxides with ɛ = 19. The anodizing occurs under a high field regime with an activation energy of 1.1 eV and an activation distance of 3.8 Å.