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Title: In situ study of the electronic structure of atomic layer deposited oxide ultrathin films upon oxygen adsorption using ambient pressure XPS

In this work, ambient pressure X-ray photoelectron spectroscopy (APXPS) was used to investigate the effect of oxygen adsorption on the band bending and electron affinity of Al 2O 3, ZnO and TiO 2 ultrathin films (similar to 1 nm in thickness) deposited on a Si substrate by atomic layer deposition (ALD). Upon exposure to oxygen at room temperature (RT), upward band bending was observed on all three samples, and a decrease in electron affinity was observed on Al 2O 3 and ZnO ultrathin films at RT. At 80 °C, the magnitude of the upward band bending decreased, and the change in the electron affinity vanished. These results indicate the existence of two surface oxygen species: a negatively charged species that is strongly adsorbed and responsible for the observed upward band bending, and a weakly adsorbed species that is polarized, lowering the electron affinity. Based on the extent of upward band bending on the three samples, the surface coverage of the strongly adsorbed species exhibits the following order: Al 2O 3 > ZnO > TiO 2. Lastly, this finding is in stark contrast to the trend expected on the surface of these bulk oxides, and highlights the unique surface activity ofmore » ultrathin oxide films with important implications, for example, in oxidation reactions taking place on these films or in catalyst systems where such oxides are used as a support material.« less
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7]
  1. Soochow Univ., Suzhou (People's Republic of China); Chinese Academy of Sciences, Shanghai (People's Republic of China); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States)
  4. Argonne National Lab. (ANL), Argonne, IL (United States); Yale Univ., New Haven, CT (United States); The Univ. of Chicago, Chicago, IL (United States)
  5. Chinese Academy of Sciences, Shanghai (People's Republic of China); ShanghaiTech Univ., Shanghai (China)
  6. Soochow Univ., Suzhou (People's Republic of China)
  7. Chinese Academy of Sciences, Shanghai (People's Republic of China); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); ShanghaiTech Univ., Shanghai (China)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Catalysis Science and Technology
Additional Journal Information:
Journal Volume: 6; Journal Issue: 18; Journal ID: ISSN 2044-4753
Publisher:
Royal Society of Chemistry
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Materials Sciences and Engineering Division; National Natural Science Foundation of China (NNSFC)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE
OSTI Identifier:
1352564