Pulsed laser deposited Nb doped TiO2 as a transparent conducting oxide (original) (raw)
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Fabrication of TiO2-Based Transparent Conducting Oxide Films on Glass by Pulsed Laser Deposition
Japanese Journal of Applied Physics, 2007
Nb-doped anatase TiO 2 (Ti 0:94 Nb 0:06 O 2) films with excellent conductivity and transparency were deposited on non-alkali glass by pulsed laser deposition. X-ray diffraction analysis and transmission electron microscopy confirmed that the obtained films were polycrystalline with anatase structure. The films deposited at a substrate temperature of 250 C with subsequent H 2 annealing at 500 C showed a resistivity of 1:5 Â 10 À3 Ácm at room temperature and an optical transmittance of 60-80% in the visible region. These results indicate that anatase Ti 0:94 Nb 0:06 O 2 has great potential as a transparent conducting oxide that could replace Sn-doped In 2 O 3 (ITO).
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.
Transparent conducting properties of anatase Ti0.94Nb0.06O2 polycrystalline films on glass substrate
Thin Solid Films, 2008
We report on transparent conducting properties of anatase Ti 0.94 Nb 0.06 O 2 (TNO) polycrystalline films on glass substrate, and discuss the role of grain crystallinity and grain boundary on resistivity. Thin films of TNO were deposited using pulsed laser deposition at substrate temperature ranging from room temperature to 350°C, with subsequent H 2 -annealing at 500°C. Polycrystalline TNO films showed resistivity of 4.5 × 10 − 4 Ω cm and 1.5 × 10 − 3 Ω cm for films prepared at substrate temperature of room temperature and 250°C, respectively. X-ray diffraction measurements and transmission electron microscopy reveal that grain crystallinity and grain boundary play key roles in conductive films.
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.
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.
Transparent and Conducting TiO2 : Nb Thin Films Prepared by Spray Pyrolysis Technique
American Research Journal of Physics, 2015
To date, only sputtering and pulsed laser deposition (PLD) techniques have been employed successfully to fabricate highly conducting and transparent TiO 2 :Nb (TNO) films. In this article, we demonstrate that transparent and conducting Nb : TiO 2 films can be made by the spray pyrolysis technique. The films were deposited on Corning 7059 glass substrates at 500 15˚C using an alcoholic precursor solution consisting of titanium (iv) isopropoxide and 5 NbCl. The influence of increasing Nb concentration on the electrical, optical and structural properties was investigated. The minimum resistivity, 3.36-3 10 Ω cm, for 2 x x-1 O Nb Ti film (x = 0.15) was obtained after 1 hour post deposition annealing in hydrogen atmosphere at 500˚C. The x-ray diffraction of hydrogen annealed films showed a polycrystalline anatase (004)-oriented phase without any second phases. The optical band gap for undoped and doped films lay in the range 3.38-3.47 eV. Using dispersion analysis, optical constants were determined from spectro-photometric measurements for films on glass.
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.
Fabrication of TiO 2-based transparent conducting oxide on glass and polyimide substrates
Thin Solid Films, 2009
We report on preparation and properties of anatase Nb-doped TiO 2 transparent conducting oxide films on glass and polyimide substrates. Amorphous Ti 0.96 Nb 0.04 O 2 films were deposited at room temperature by using sputtering, and were then crystallized through annealing under reducing atmosphere. Use of a seed layer substantially improved the crystallinity and resistivity (ρ) of the films. We attained ρ = 9.2 × 10 − 4 Ω cm and transmittance of~70% in the visible region on glass by annealing at 300°C in vacuum. The minimum ρ of 7.0 × 10 − 4 Ω cm was obtained by 400°C annealing in pure H 2 .
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.
Journal of Electronic Materials, 2018
Titanium oxide (TiO 2) is a semiconducting oxide of increasing interest due to its chemical and thermal stability and broad applicability. In this study, thin films of TiO 2 were deposited by pulsed laser deposition on sapphire and silicon substrates under various growth conditions, and characterized by x-ray diffraction (XRD), atomic force microscopy (AFM), optical absorption spectroscopy and Hall-effect measurements. XRD patterns revealed that a sapphire substrate is more suitable for the formation of the rutile phase in TiO 2 , while a silicon substrate yields a pure anatase phase, even at high-temperature growth. AFM images showed that the rutile TiO 2 films grown at 805°C on a sapphire substrate have a smoother surface than anatase films grown at 620°C. Optical absorption spectra confirmed the band gap energy of 3.08 eV for the rutile phase and 3.29 eV for the anatase phase. All the deposited films exhibited the usual high resistivity of TiO 2 ; however, when employed as a buffer layer, anatase TiO 2 deposited on sapphire significantly improves the conductivity of indium gallium zinc oxide thin films. The study illustrates how to control the formation of TiO 2 phases and reveals another interesting application for TiO 2 as a buffer layer for transparent conducting oxides.