Photoemission study of ZnO nanocrystals: Thermal annealing in UHV and induced band bending
2013 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 612, 10-15 p.Article in journal (Refereed) Published
ZnO nanocrystals distributed by spin-coating on SiO2/Si surfaces were annealed in UHV and studied in situ by synchrotron radiation based X-ray Photoelectron Spectroscopy. Changes in chemical composition and electronic structure of ZnO nanocrystal surfaces were found with increasing annealing temperatures. Annealing at 650 °C reduces the surface contaminant levels without any observed de-composition of ZnO. After annealing at 700 °C an initial de-composition of ZnO together with further reduction of contaminants was observed. As a result, 650 °C is found to be the optimal annealing temperature for thermal cleaning of ZnO nanocrystals. Chemical changes and induced point defect formation cause changes in the band structure of the ZnO/SiO2/Si system. An upward band bending of 0.7 eV on the surfaces of the ZnO nanocrystals was found after annealing at 300 °C. The bands on the surfaces of ZnO nanocrystals gradually bend downwards with increasing annealing temperatures. A downward band bending of 1.4 eV is the result after annealing at 750 °C for 1 h. This large downward band bending is explained as due to the change in balance of oxygen vacancies and zinc vacancies on the surfaces of ZnO nanocrystals.
Place, publisher, year, edition, pages
Amsterdam: Elsevier , 2013. Vol. 612, 10-15 p.
ZnO, Nanocrystals, XPS, Annealing, Band bending
Research subject Physics
IdentifiersURN: urn:nbn:se:kau:diva-27016DOI: 10.1016/j.susc.2013.02.001ISI: 000317809100005OAI: oai:DiVA.org:kau-27016DiVA: diva2:617224