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Effect of total gas pressure and O2/N2 flow rate on the nanostructure of N-doped TiO2 thin films deposited by reactive sputtering

Baker, MA, Fakhouri, H, Grilli, R, Pulpytel, J, Smith, W and Arefi-Khonsari, F (2014) Effect of total gas pressure and O2/N2 flow rate on the nanostructure of N-doped TiO2 thin films deposited by reactive sputtering Thin Solid Films, 552. pp. 10-17.

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Abstract

N-doped TiO2 thin films have been deposited by reactive RF magnetron sputtering at different total gas pressures and varying O 2/N2 gas flow rates at 300 C. The thin film nanostructure has been studied by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy (XPS). Increasing the deposition pressure leads to reduced crystallinity of the thin films and a higher N2 flow rate was required to incorporate N into the growing film. This is attributed to the lower energy ion bombardment of the surface and N adatom chemical reactivity being reduced at higher total gas pressures. Ar+ ion sputtering of the deposited N-doped TiO2 thin films has enabled a detailed XPS investigation of the surface and bulk N species to be performed. Adsorbed N species have been identified on all the deposited thin film surfaces, with the most prevalent adsorbed N species occurring at a binding energy of approximately 400 eV, shown to originate from atmospheric contamination, most probably N containing organic species. The bulk N content varies between 0.6 and 6.0 at.% and N is located predominantly at substitutional sites in the TiO2. The presence of interstitial N, in the form of NO species, has been identified by XPS in some thin films deposited at higher deposition pressures. Hence, varying the total gas pressure may provide a route for tailoring the location of N in the bulk structure. At higher N contents (> 3 at.%), TiN is found as a secondary phase within the bulk structure and the presence of TiN leads to a sharp reduction in the band gap. Post-deposition annealing of low N containing films results in an N-doped TiO2 single phase anatase structure. © 2013 Elsevier B.V.

Item Type: Article
Subjects : Mechanical Engineering Sciences
Divisions : Faculty of Engineering and Physical Sciences > Mechanical Engineering Sciences
Authors :
AuthorsEmailORCID
Baker, MAUNSPECIFIEDUNSPECIFIED
Fakhouri, HUNSPECIFIEDUNSPECIFIED
Grilli, RUNSPECIFIEDUNSPECIFIED
Pulpytel, JUNSPECIFIEDUNSPECIFIED
Smith, WUNSPECIFIEDUNSPECIFIED
Arefi-Khonsari, FUNSPECIFIEDUNSPECIFIED
Date : 3 February 2014
Identification Number : 10.1016/j.tsf.2013.11.111
Additional Information : © 2014. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Depositing User : Symplectic Elements
Date Deposited : 29 Jan 2016 12:28
Last Modified : 29 Jan 2016 12:28
URI: http://epubs.surrey.ac.uk/id/eprint/809773

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