Preparation And Characterization Of Titanium Dioxide Films On MgAl₂O₄ And LaAlO₃ Substrates

Transparent electronics and transparent oxide optoelectronics have caused widespread attention and rapid development since they came into notice,which makes the wide bandgap oxide semiconductor materials more and more popular.As an wide bandgap oxide semiconductor material,TiO₂ has many good properties such as a high dielectric constant,a large refractive index,a high photochemical activity and stable physicochemical properties,and therefore is widely used in many fields such as flat panel displays,photocatalysis,transparent conducting oxides?TCOs?,field effect transistors?FETs?,solar cells and gas sensors.In this paper,anatase TiO₂ thin films were grown on MgAl₂O₄ and LaAlO₃ substrates by MOCVD.High pure Ti?N?CH₃?₂?₄,N₂ and O₂ were used as titanium organic source,carrier gas and oxidant in the experiment,respectively.TiO₂ films were prepared successfully on the above substrates at the organic source molar flow rate of 4.03 �10^-7 mol/min.The substrate temperatures were 500?.550?.600? and 650?,respectively.The key research work and results are as following:1.Preparation and characterization of TiO₂ thin films on MgAl₂O₄?100?substrates:The structural analyses indicated that the TiO₂ film prepared at 600? had the best single crystalline quality with no twins.The out-of-plane and in-plane epitaxial relationships of the film were a-TiO₂?001??MgAl₂O₄?100?and TiO₂[100]?MgAl₂O₄[100],respectively.A uniform and compact surface with stoichiometric composition was also obtained for the 600?-deposited sample.The average transmittance of all the TiO₂ films in the visible range exceeded 91%and the optical band gap of the films varied from 3.31 to 3.41 eV.2.Preparation and characterization of TiO₂ thin films on MgAl₂O₄?111?substrates:The structural analyses showed that the films were highly?004?oriented with tetragonal anatase structure and the epitaxial relationship was given as a-TiO₂?004??MgAl₂O₄?111?.The sample prepared at 600? exhibited the best crystallization with a single-crystalline epitaxial film.The average transmittance of every TiO₂ film in the visible range exceeded 90%excluding the influence of the substrate.The morphology and composition of the TiO₂ films have also been studied in detail.3?Preparation and characterization of TiO₂ thin films on LaAlO₃?001?substrates:The structural studies revealed that the TiO₂ film prepared at 600? had the best single crystalline quality with no twins.The out-of-plane and in-plane epitaxial relationship of the films were a-TiO₂?004??LaAlO₃?001?and TiO₂[100]?LaAlO₃[100],respectively.The optical band gap of the films ranged from 3.30 to 3.37 eV.The morphology and composition of the TiO₂ films have also been studied in detail.