Search

In this work, an attempt has been made to compare the physical properties of conductive films of Nb-doped TiO2 deposited on Kapton polyimide, glass and silicon substrates. Thin films were deposited by radio frequency sputtering at room temperature and subsequently characterized using X-ray diffraction, X-ray photoelectron spectroscopy, UV-VIS-NIR spectroscopy and Hall Effect measurement. Structurally, the films grown on the flexible substrate exhibit more strain and had inferior crystallinity (crystallite size ∼ 13.8 nm) compared to the films deposited on glass and silicon substrates (crystallite size ∼ 27 nm). The film on glass had a resistivity value around 1. 6 7 × 1 0 − 3   Ω ⋅ cm while the resistivity of the films grown on polyimide was found about five-fold higher. Furthermore, the films deposited on glass substrate showed optical transparency of > 80% in the visible range (400–750 nm). The inferior electrical transport properties of the films grown on polyimide were correlated with the poor crystallinity and cracks induced during the annealing process. Furthermore, various possible routes have been discussed to improve crystallinity and control cracks in the films. [ABSTRACT FROM AUTHOR]

Oxide-based films and nanostructures have emerged as important materials for a wide range of applications such as photovoltaics, optoelectronics, gas sensing and electronics. To develop an appropriate understanding of the properties of these oxides, it is necessary to address the material preparation methods and defect probing issues. This work reports on the synthesis processes of TiO 2 based transparent conductive films, their stoichiometry control and defect identifying, in relation with their electrical and optical properties. Un-doped and TiO 2 :Nb films were deposited by RF co-sputtering from TiO 2 and Nb 2 O 5 targets in Ar plasma. The chemical species present in the plasmas used in deposition process were investigated by optical emission spectroscopy, which was later on correlated with the defects structure of the films. Analysis by X-ray photoelectron spectroscopy shed more light on the nature of the vacancies and on the effect of the latter on the optical and electrical properties of the films. In terms of results, we measured electrical resistivity in the range 10 − 2 –10 − 3 Ω cm for the intrinsically and extrinsically doped films (films doped with oxygen vacancies and Nb + 5 respectively) while the lowest resistivity was obtained for intrinsically-extrinsically co-doped TiO 2 films (7.4 × 10 − 4 Ω cm). The films transparency was also actively determined by the defects in the lattice and highly transparent films (65–85% in the visible range) were obtained by controlling the density of defects. The approach adopted in this work for the generation of oxygen vacancies could be useful for other oxide-based films, where the oxygen vacancies-dependent properties are crucial, for room temperature ferromagnetism and photocatalytic applications. [ABSTRACT FROM AUTHOR]

The authors report a method of enhancing the conductivity of TiO 2 films by controlling their structural phases. Thin films of Nb:TiO 2 (TNO) were prepared on glass and silicon substrates by RF sputtering with varying Nb content at 200 °C. It is shown that fine control over the structural phases of TiO 2 is critical for achieving low resistivity. The resistivity values of the films doped with oxygen vacancies and Nb +5 decreased from 3.8 × 10 −1 to 4.1 × 10 −3 Ω cm when the weight percent of rutile in anatase-rutile phase mixture decreases from 52.8% to 32%. Furthermore, the lowest resistivity value of 2.37 × 10 −3 Ω cm was obtained for the doped TiO 2 films having single phase anatase structure. The physical processes responsible for the diverse electrical properties are discussed and are associated with the growth conditions. Our result indicates that highly conductive doped-TiO 2 film can be obtained by controlling the anatase phase formation via the growth temperature. The obtained results can significantly contribute to the development of transparent electrodes by RF sputtering, a suitable technique for coating large area substrates. [ABSTRACT FROM AUTHOR]

The authors report a comparative study of the electrical and optical properties of Nb:TiO 2 thin films (TNO) in relation with their chemical properties. Two types of niobium containing targets, Nb metal and Nb 2 O 5 oxide were employed simultaneously with ceramic TiO 2 target for the films growth, in Ar and Ar-O 2 discharge. Niobium is found to incorporate easily and substitutionally into titanium lattice site when deposited from oxide targets in oxygen-deficient discharge (Ar plasma). Consequently, the TNO film exhibits lowest resistivity of 1.4×10 −3 Ω cm with optical transparency of more than 80% in the visible region. On the contrary, doping was not effective in case the TNO films were grown from Nb metal and TiO 2 targets in Ar and Ar-O 2 plasma, probably due to the growth of niobium sub-oxide phases and lack of oxygen vacancies. The possible reasons of diverse electrical properties are discussed and are link with the growth conditions. Our result indicates that highly conductive and transparent doped-TiO 2 film can be obtained by choosing appropriate target material and sputtering gas. The obtained results can significantly contribute to the development of transparent electrodes by RF sputtering, a suitable technique for coating on large area substrates. [ABSTRACT FROM AUTHOR]