Oxidation of a c-Tb2O3(111) thin film by the sequential formation of stoichiometric phases

SURFACE SCIENCE

卷:694

Article

Lee, Christopher J.¹  Vashishtha, Saumye¹  Sayal, Ameen¹  Weaver, Jason F.¹ 

[1] Univ Florida, Dept Chem Engn, Gainesville, FL 32611 USA

关键词: Terbium oxide;    Oxide thin film;    Ceria;    Oxygen vacancies;    Oxidation;   

DOI  :  10.1016/j.susc.2019.121555

来源: Elsevier

【 摘 要 】

used temperature-programmed desorption (TPD), low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS) to investigate the oxidation of a well -ordered c-Tb2O3(111) thin film supported on Pt(111) by gaseous oxygen atoms in ultrahigh vacuum. Our results provide evidence that the c-Tb2O3 film oxidizes through the sequential development of the stoichiometric (1)-Tb7O12 and delta-Tb11O20 phases, followed by the formation of a variable oxygen concentration alpha-TbOx phase up to x = 2. The 1 and 8-phases decompose to yield sharp O-2 TPD peaks at about 780 and 640 K, while the a-phase evolves O-2 between similar to 450 and 600 K during TPD. Quantitative analysis shows that changes in the XPS Tb 3d and 4d spectra caused by oxidation agree well with our estimates of the Tb-x film stoichiometry determined from TPD. We observe a well-defined LEED pattern for (1)-Tb7O12(111) after heating the oxidized film to similar to 700 K. In contrast, several observations, including incomplete 1 -> delta conversion, lack of an observable LEED pattern for the delta-Tb11O20 phase, and sensitivity of alpha-phase formation to thermal aging of the film, indicate that the delta and alpha-phases develop under kinetic control for the conditions studied, such that the phases decompose in UHV at temperatures lower than those needed for these phases to stabilize into more crystalline and uniform arrangements.

【 授权许可】

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