Intrinsic nitrogen-doped CVD-grown TiO2 thin films from all-N-coordinated Ti precursors for photoelectrochemical applications

Sun Ja Kim, Ke Xu, Harish Parala, Radim Beranek, Michal Bledowski, Kirill Sliozberg, Hans Werner Becker, Detlef Rogalla, Davide Barreca, Chiara Maccato, Cinzia Sada, Wolfgang Schuhmann, Roland A. Fischer, Anjana Devi

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

N-doped titanium dioxide (TiO2) thin films are grown on Si(100) and indium tin oxide (ITO)-coated borosilicate glass substrates by metal-organic (MO)CVD. The intrinsic doping of TiO2 thin films is achieved using all-nitrogen-coordinated Ti precursors in the presence of oxygen. The titanium amide-guanidinate complex, [Ti(NMe2)3(guan)] (guan = N,N′-diisopropyl-2-dimethylamidoguanidinato) has been developed to compensate for the thermal instability of the parent alkylamide [Ti(NMe 2)4]. Both of these amide-based compounds are tested and compared as precursors for intrinsically N-doped TiO2 at various deposition temperatures in the absence of additional N sources. The structure and morphology of TiO2 thin films are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Rutherford back scattering (RBS), nuclear reaction analysis (NRA), and secondary ion mass spectrometry (SIMS) analyses are performed to determine N content and distribution in the films. The optical and photoelectrochemical properties of TiO2 thin films on ITO substrates are also examined. N-doped TiO2 thin films, grown from [Ti(NMe 2)3(guan)] at 600 °C, exhibit the lowest optical absorption edge (3.0 eV) and the highest visible light photocurrent response. When compared to undoped TiO2, while in UV light photoconversion efficiency decreases significantly, the intrinsically N-doped TiO2 shows enhanced photocurrents under visible light irradiation. The intrinsic doping of TiO2 thin films with nitrogen by MOCVD and the investigation of the photo-electrochemical properties of the films are reported. N-doped anatase phase TiO2 thin films are grown on Si(100) and ITO substrates under specific processing conditions, using [Ti(NMe2) 4] (1) and [Ti(NMe2)3(guan)] (2) (guan = N,N′-diisopropyl-2-dimethylamidoguanidinato) as precursors. The films grown from [Ti(NMe2)3(guan)] at 600 °C show relatively large surface roughness and lower bandgap related with high N content.

Original languageEnglish
Pages (from-to)45-52
Number of pages8
JournalChemical Vapor Deposition
Volume19
Issue number1-3
DOIs
StatePublished - Mar 2013
Externally publishedYes

Keywords

  • MOCVD
  • N-coordinated Ti precursor
  • N-doping
  • Photocurrent
  • TiO thin films

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