| Transparent conductive oxide films(TCOs)have a wide range of applications,and TiO2 thin films have been widely studied and studied as a new type of transparent conductive films(TCOs).TiO2 needs to improve the electrical properties by ion doping in order to meet the special requirements of TCOs materials.In this paper,TiO2:Nb thin films were prepared by sol-gel method and post-annealled in given conditions.The effects of sol-gel parameters,ion doping concentration and heat treatment conditions on the grain parameters and electrical and optical properties of Nb/Ta-doped TiO2 films were investigated.The effects of oxygen vacancy and Nb ion doping on the conduction mechanism of the thin films were studied.Experiments improve the conductivity by adjusting the niobium concentration and introducing the oxygen vacancy defect Vo to increase the transparency of the TiO2:Nb thin film.The precursor composition and the sol ratio are adjusted to improve the preparation process to optimize the Nb element incorporation rate.The structure,morphology,composition and valence state,electrical properties and optical properties of the transparent conductive films were characterized by a variety of tests and evaluations.Experimental results show that:(1)When the annealing temperature is 250?,the TiO2 film is amorphous,and the anatase phase is formed at 300?-700?.When the temperature is over 700?,the rutile phase is formed.The best crystallinity,microstructure and electrical properties of Ti02 thin films were the best when annealed at 600 ?.The multiple annealing process is more efficient than the single crystal,and it is more efficient to generate anatase phase and Nb5+ doping to replace Ti4+.The rapid cooling of the film is better than that of the cooling with the furnace,and the film is refined at a high temperature for a long time,which is susceptible to carrier transport.The thickness of the film is better when the spin coating speed is 1800 rpm and the spin coating speed is 900 rpm,but the crystallinity is better and the electrical performance is better.Solder concentration is too small will deteriorate the crystallinity of polycrystalline thin film,sol concentration is too large to make the thickness of the film is too large,is not conducive to carrier transport.When the sol concentration is 0.05M,the film obtains the best crystallinity and electrical properties.(2)The optimum doping concentration of Nb in the film is 10%,and the solubility of tantalum atom in TiO2 lattice is higher and the optimal doping concentration is 8%.When the doping concentration is too high,the Nb element is easy to oxidize.The same doping concentration of TiO2:Ta film only exists TiO2 phase.The tantalum doped TiO2 film has a higher carrier mobility ?H,with obvious advantages over niobium doping.Ta is more soluble in Ti02 lattice so Ta-doped TiO2 films can reduce the impurity scattering center and reduce ionization impurity scattering and have larger visible light transmission.The emissivity of tantalum doped TiO2 thin films is also lower than that of niobium doped TiO2 films.(3)H2 annealing can effectively optimize the crystallinity and conductivity of Ti1-xMxO2 thin films.Compared with ordinary atmosphere,high vacuum,H2 gas and N2 gas atmosphere,the microstructure of the films annealed in H2 atmosphere are the best and the film thickness is the largest.The conductivity is the highest and the visible light transmittance is the highest.The electrical property is best because of owing the maxmun Ti3+.Under the negative pressure,the oxygen vacancy is the main reason for the Ti:O atomic ratio less than 1:2.The reduction of the atmosphere is the main factor affecting the conductivity of the film and the average visible light transmittance.The Ta5+ and the reducing atmosphere determine the conductivity of Ti1-xO2 thin films. |
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