Chemical modulation of valance band in delafossite structured CuFeO 2 thin film and its photoresponse

• Published in: Materials research express 2018-01, Vol.5 (1), p.15909
• Main Authors: Bera, Arun, Deb, Krishna, Sinthika, S, Thapa, Ranjit, Saha, Biswajit
• Format: Article
• Language: English
• ISSN: 2053-1591; 2053-1591
• DOI: 10.1088/2053-1591/aaa68a

Using simple spin coating process we report the development of delafossite structured CuFeO 2 ceramic thin film on florine doped tin oxide (FTO) coated glass substrate and found improved electrical conductivity, through possible modulation of valance band with high photoresponse of these structures. The valance band of CuFeO 2 predominantly comprising of localized Cu 3d and O 2p orbitals, has been chemically modulated through post annealing of the film in oxygen rich atmosphere in order to obtain delocalized holes as carriers. During post annealing of the film in the oxygen rich environment for substantially long time (8, 16 and 24 h) oxygen atoms are introduced in the crystal as interstitials, and thus brings a chemical modulation of valance band without any external doping. The crystal structure, optical band gap and p-type conductivity have been studied experimentally, and theoretical first-principle based density functional calculations estimate that the oxygen atoms create mid gap states and are responsible for the states in the conduction band. A fivefold increase in the electrical conductivity was observed upon 24 h of annealing. More interestingly an excellent photoresponse behavior of the CuFeO 2 films in its J – V characteristics have been observed and reported in this article, which must appear very significant in exploring its prospect of application as a p type semiconductor in optoelectronic devices with appropriate energy band gap.