Direct growth of transparent conducting Nb-doped anatase TiO2 polycrystalline films on glass

Abstract

This paper proposes a novel sputter-based method for the direct growth of transparent conducting Ti1−xNbxO2 (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 LaAlO3 (100) substrates under a reducing atmosphere exhibited a low resistivity (ρ) of (3–6)×10−4Ωcm. On glass, however, highly resistive rutile phase polycrystalline films (ρ∼100Ωcm) 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 on 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 ρ=1.1×10−3Ωcm and optical absorption lower than 10% in the visible region. This ρ 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.

Effect of micromorphology on transport properties of Nb‐doped anatase TiO2 films: A transmission electron microscopy study

“…Nb‐doped anatase TiO 2 (TNO) is a newly developed TCO with unique properties, such as excellent chemical stability , high refractive index , and wide conductivity range . Since the discovery of TNO grown by pulsed laser deposition (PLD) , many efforts have been dedicated to fabricate highly conductive TNO on glass substrates with a scalable and industrial deposition method, that is, sputtering . In our previous studies using PLD and sputtering , we observed that TNO films crystallized from amorphous precursors that were deposited on unheated substrates, exhibited high conductivity.…”

Structural and electronic impact of SrTiO3 substrate on TiO2 thin films

“…To overcome the difficulties, much effort has been devoted to the growth of its thin films via a variety of methods, such as the magnetic sputtering [8], molecular beam epitaxy [9], and pulsed-laser deposition [10], where the nature of the film/substrate interface has long been suspected to play an important role in affecting the crystallinity of the thin films. To date, TiO 2 thin films have been deposited onto a wide range of oxide substrates, involving, e.g., the yttria-stabilized zirconia (YSZ) [11], Al 2 O 3 [12], SiO 2 [13], SrTiO 3 (STO) [14], and LaAlO 3 [15].…”

Spectrally selective reflector surfaces for heat reduction in concentrator solar cells: modeling and applications of TiO_2:Nb-based thin films

“…Our initial work used SnO x :F [4][5][6][7], and more recently we have investigated SSRs based on anatase TiO 2 :Nb [8,9]. This latter material was discovered as lately as 2005 [13] and has attracted much interest recently as a high-performance low-cost transparent conductor [14][15][16][17][18]. Our earlier work demonstrated that TiO 2 :Nb backed by Al leads to a reflector with pronounced optical selectivity [8,9].…”