Transparent and Conducting TiO2 : Nb Thin Films Prepared by Spray Pyrolysis Technique (original) (raw)
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Influence of Thermal Treatment on Electrical Properties of Transparent TiO 2 :Nb Thin Films
Proc. 39th Int. Spring Seminar on Electronics Technology, Pilsen (Czechia), 2016
This study presents electrical behavior of TiO 2 :Nb thin films with niobium concentration up to 13 at. %. The layers were deposited on Corning 7059 glass substrates by unipolar dc pulse magnetron co-sputtering from TiO 2 and Nb composite target. Manufactured films underwent thermal treatment in the ambient air up to the 873 K. Dependencies between the temperature and electrical conductivity as well as thermoelectric force were determined within the range of 300-578 K. An amorphous TiO 2 :Nb films with optical transparency of about 50% in the visible range and resistivity higher than 8 Ωcm were achieved directly after deposition for the target power density discharge in the range of 4.7-5.8 W/cm 2. During the post process air thermal treatment a rapid resistivity decrease (over 1000) was observed up to final value of 1.5×10-3 Ωcm at 300 K. Moreover the conversion from n-type semiconductivity to metallic conductivity was observed.
Nb-doped TiO2 thin films deposited by spray pyrolysis method
Undoped TiO 2 and Nb-doped TiO 2 thin films have been deposited by spray pyrolysis method on ITO/glass substrates. All the as-deposited films are amorphous, as shown by X-Ray Diffraction. Under certain conditions of heat-treatment in air, the films deposited by pyrolysis became pure anatase. The hydrophilic properties of all the films were investigated, and a comparison was made as a function of the heat treatment, and as a function of Nb doping. Contact angles lower then 3 deg. have been obtained, after irradiation times specific for each film
Materials Science in Semiconductor Processing, 2017
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.
Influence of thermal treatment on electrical properties of transparent TiO2:Nb thin films
2016 39th International Spring Seminar on Electronics Technology (ISSE), 2016
This study presents electrical behavior of TiO2:Nb thin films with niobium concentration up to 13 at. %. The layers were deposited on Corning 7059 glass substrates by unipolar dc pulse magnetron co-sputtering from TiO2 and Nb composite target. Manufactured films underwent thermal treatment in the ambient air up to the 873 K. Dependencies between the temperature and electrical conductivity as well as thermoelectric force were determined within the range of 300-578 K. An amorphous TiO2:Nb films with optical transparency of about 50% in the visible range and resistivity higher than 8 Ωcm were achieved directly after deposition for the target power density discharge in the range of 4.7-5.8 W/cm2. During the post process air thermal treatment a rapid resistivity decrease (over 1000×) was observed up to final value of 1.5×10-3 Qcm at 300 K. Moreover the conversion from n-type semiconductivity to metallic conductivity was observed. Simultaneously the layers exhibited the substantial increase in the transparency and decrease in Seebeck coefficient from -160 μV/K to -35 μV/K. Electrical behavior of the films where examined with the use of NiCrSi/Ag thin films contacts pads according to Kelvin method.
Conducting Nb-doped TiO2 thin films fabricated with an atomic layer deposition technique
Thin Solid Films, 2014
Highly conducting Ti 1 − x Nb x O 2 thin films have been grown on glass substrates from TiCl 4 , Nb(OEt) 5 and H 2 O with an atomic layer deposition (ALD) technique. The films become electrically conducting and crystallize with the anatase structure upon a reductive post-deposition annealing. A highly c-axis oriented Ti 0.75 Nb 0.25 O 2 film exhibits room-temperature resistivity as low as 1.4 × 10 −3 Ω cm. The charge carrier density and electron mobility, as estimated from Seebeck and resistivity measurements, are 0.21-1.1 × 10 21 cm −3 and 4.2-22 cm 2 /Vs, respectively. The electrical properties of the ALD-fabricated Nb-doped anatase films are comparable with those of sputter-deposited polycrystalline films on glass.
Volume 3, Issue 1, 2019
This work reports on the influence of niobium on the structural and optical properties of titanium dioxide thin films made by DC Magnetron sputtering. The films were deposited on glass substrates at ambient temperature which stood at below 50 °C in the deposition chamber. Film thickness based on profilometry ranged from 432 nm to 620 nm. Parameters investigated among others include structure, optical constants, grain size and film density. The as-deposited films were found to be amorphous and turn to crystalline upon annealing in air. The film density increased with doping to a maximum estimated to be 5.77 at. % Nb, beyond which a decrease was recorded. It was also observed that the refractive index of the film increased with doping.
Pulsed laser deposited Nb doped TiO2 as a transparent conducting oxide
Thin Solid Films, 2008
Nb doped TiO 2 (Nb:TiO 2 ) is a promising indium-free transparent conducting oxide. We have examined the growth of Nb:TiO 2 thin films by pulsed laser deposition (PLD) on SrTiO 3 , LaAlO 3 , and fused silica. For b004N oriented anatase Nb:TiO 2 films grown on SrTiO 3 by PLD at 550°C, the conductivity can be as high as 2500 S/cm. A nearly thickness independent conductivity for Nb:TiO 2 demonstrates that the conductivity is a bulk property and not a substrate interface effect. In addition, Nb:TiO 2 films deposited at room temperature were annealed at temperatures up to 750°C in either vacuum or 1.3 × 10 − 3 Pa O 2 . For these films, conductivities as high as 3300 S/cm on SrTiO 3 and 85 S/cm on LaAlO 3 substrates were obtained for the highest temperature vacuum anneals, albeit with some loss in transparency. Published by Elsevier B.V.
Direct growth of transparent conducting Nb-doped anatase TiO[sub 2] polycrystalline films on glass
Journal of Applied Physics, 2009
This paper proposes a novel sputter-based method for the direct growth of transparent conducting Ti 1−x Nb x O 2 ͑TNO͒ 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 3 ͑100͒ substrates under a reducing atmosphere exhibited a low resistivity ͑͒ of ͑3-6͒ ϫ 10 −4 ⍀ cm. On glass, however, highly resistive rutile phase polycrystalline films ͑ ϳ 100 ⍀ cm͒ 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 = 1.1ϫ 10 −3 ⍀ cm and optical absorption lower than 10% in the visible region. This 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.
The Role of HiPIMS Pulse Length in Reactive Deposition of Transparent Conductive Oxide Nb:TiO2 Films
Materials Research-ibero-american Journal of Materials, 2023
The present paper sets out to investigate the role of voltage pulse length on the properties of Nb:TiO 2 films deposited by High Power Impulse Magnetron Sputtering (HiPIMS). Several characteristics of the films were investigated, namely, resistivity, transmittance, crystallinity and band gap values of Nb:TiO 2 films. Reactive depositions were carried out in Ar/O 2 plasma with 40 µs, 50 µs, 60 µs, and 70 µs pulses. Increasing the pulse length changes the deposition from compound to metal mode. As it gets closer to metal mode, the deposition rate increases by up to one order of magnitude, while the resistivity of the resulting Nb:TiO 2 film becomes as low as 10-4 Ω.cm, without any significant loss in optical transmittance, which remains close to 90% for a wavelength around 450 nm, but reduction in 25% of heat transmission (above 800 nm) were observed. Results indicate the anatase phase for all deposition conditions, and Ti 3+ states increase with the pulse length, which can be explained by the generation of a second band gap. Both the niobium doping and the Ti 3+ states can contribute to increase the conductivity of the Nb:TiO 2 films in the as-deposited condition.