skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Unusual Changes in Electronic Band-Edge Energies of the Nanostructured Transparent n-Type Semiconductor Zr-Doped Anatase TiO 2 (Ti 1–x Zr x O 2 ; x < 0.3)

Authors:
; ;
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Center for Bio-Inspired Solar Fuel Production (BISfuel)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1369666
DOE Contract Number:
SC0001016
Resource Type:
Journal Article
Resource Relation:
Journal Name: Inorganic Chemistry; Journal Volume: 55; Journal Issue: 13; Related Information: BISfuel partners with Arizona State University.
Country of Publication:
United States
Language:
English

Citation Formats

Mieritz, Daniel G., Renaud, Adèle, and Seo, Dong-Kyun. Unusual Changes in Electronic Band-Edge Energies of the Nanostructured Transparent n-Type Semiconductor Zr-Doped Anatase TiO 2 (Ti 1–x Zr x O 2 ; x < 0.3). United States: N. p., 2016. Web. doi:10.1021/acs.inorgchem.6b00712.
Mieritz, Daniel G., Renaud, Adèle, & Seo, Dong-Kyun. Unusual Changes in Electronic Band-Edge Energies of the Nanostructured Transparent n-Type Semiconductor Zr-Doped Anatase TiO 2 (Ti 1–x Zr x O 2 ; x < 0.3). United States. doi:10.1021/acs.inorgchem.6b00712.
Mieritz, Daniel G., Renaud, Adèle, and Seo, Dong-Kyun. 2016. "Unusual Changes in Electronic Band-Edge Energies of the Nanostructured Transparent n-Type Semiconductor Zr-Doped Anatase TiO 2 (Ti 1–x Zr x O 2 ; x < 0.3)". United States. doi:10.1021/acs.inorgchem.6b00712.
@article{osti_1369666,
title = {Unusual Changes in Electronic Band-Edge Energies of the Nanostructured Transparent n-Type Semiconductor Zr-Doped Anatase TiO 2 (Ti 1–x Zr x O 2 ; x < 0.3)},
author = {Mieritz, Daniel G. and Renaud, Adèle and Seo, Dong-Kyun},
abstractNote = {},
doi = {10.1021/acs.inorgchem.6b00712},
journal = {Inorganic Chemistry},
number = 13,
volume = 55,
place = {United States},
year = 2016,
month = 7
}
  • We have investigated the electronic structure changes and the origin of the enhanced optical properties of N-doped anatase TiO{sub 2} using first-principles density-functional theory calculations. To determine the band gap variations induced by N-doping, we developed a new approach to locate the effective valence band maximum (VBM) by characterizing the degree of localization of the N-induced states in the band structures of various N-doped TiO{sub 2} systems. Our calculations show that the band gap variations are largely affected by the local bonding structures and doping concentration of the substitutional N atoms. As the N content is up to certain level,more » some local bonding structures can indeed cause band gap reduction due to the formation of band-like delocalized states above the VBM of TiO{sub 2}, while other local bonding configurations may simply form localized impurity states in the band gap. Accordingly, the N-induced localized and delocalized electronic states can exist simultaneously to contribute to the enhanced optical properties of anatase TiO{sub 2}. Our computational approach also provides a new way to investigate the band gap engineering of other wide band gap semiconductor material systems.« less
  • This paper proposes a novel sputter-based method for the direct growth of transparent conducting Ti{sub 1-x}Nb{sub x}O{sub 2} (TNO) polycrystalline films on glass, without the need for any postdeposition treatments, by the use of an initial seed-layer. Anatase TNO epitaxial films grown on LaAlO{sub 3} (100) substrates under a reducing atmosphere exhibited a low resistivity (rho) of (3-6)x10{sup -4} OMEGA cm. On glass, however, highly resistive rutile phase polycrystalline films (rhoapprox100 OMEGA cm) formed preferentially under the same conditions. These results suggest that epitaxial stabilization of the oxygen-deficient anatase phase occurs on lattice-matched substrates. To produce a similar effect onmore » a glass surface, we deposited a seed-layer of anatase TNO with excellent crystallinity under an increased oxygen atmosphere. As a result, anatase phase TNO polycrystalline films could be grown even under heavily reducing atmospheres. An optimized film exhibited rho=1.1x10{sup -3} OMEGA cm and optical absorption lower than 10% in the visible region. This rho value is more than one order of magnitude lower than values reported for directly deposited TNO polycrystalline films. This indicates that the seed-layer method has considerable potential for producing transparent conducting TNO polycrystalline films on glass.« less
  • W-doped anatase TiO{sub 2} films were deposited on glass substrate by magnetron cosputtering. The minimum resistivity, 1.5x10{sup -2} {Omega} cm, for Ti{sub 1-x}W{sub x}O{sub 2} film (x=0.063) was obtained. X-ray photoelectron spectroscopy analysis shows W incorporated in the Ti lattice position is mostly in the W{sup 6+} state. Theoretical calculations based upon the density-functional theory were applied to analyze the electronic structure and conducting mechanism. The strong hybridization of Ti 3d states with W 5d states is the dominate factor to cause the shifting in Fermi level into conduction band. Our results suggest that tungsten is a favorable dopant tomore » form TiO{sub 2}-based transparent conducting oxide materials.« less
  • The effect of Niobium doping and size of crystallites on highly transparent nano-crystalline Niobium doped Titanium Dioxide (NTO) thin films with stable anatase phase are reported. The Nb doping concentration is varied within the solubility limit in TiO{sub 2} lattice. Films were annealed in controlled environment for improving the crystallinity and size of crystallites. Elemental and thickness analysis were carried out using Rutherford backscattering spectrometry and cross sectional field emission scanning electron microscopy. Structural characteristics reveal a substitutional incorporation of Nb{sup +5} in the TiO{sub 2} lattice which inhibits the anatase crystallites growth with increasing the doping percentage. The micro-Ramanmore » (MR) spectra of films with small size crystallites shows stiffening of about 4 cm{sup −1} for the E{sub g(1)} mode and is ascribed to phonon confinement and non-stoichiometry. In contrast, B{sub 1g} mode exhibits a large anomalous softening of 20 cm{sup −1} with asymmetrical broadening; which was not reported for the case of pure TiO{sub 2} crystallites. This anomalous behaviour is explained by contraction of the apical Ti-O bonds at the surface upon substitutional Nb{sup 5+} doping induced reduction of Ti{sup 4+} ions also known as hetero-coordination effect. The proposed hypotheses is manifested through studying the electronic structure and phonon dynamics by performing the near edge x-ray absorption fine structure (NEXAFS) and temperature dependent MR down to liquid nitrogen temperature on pure and 2.5 at.% doped NTO films, respectively.« less