The Relationship Between Carrier Mobility And Bicrystalline Grains Boundary Of Rutile TiO₂ Film

Titanium dioxide(TiO₂)exists in nature as Rutile,Anatase and Brookite.Among these three crystal forms,only Rutile TiO₂ has good stability at high temperature,so the research of Rutile TiO₂ in the field of sensors has attracted much attention.However,there are few studies on the mobility of Rutile TiO₂ carriers.The carrier mobility of Rutile TiO₂ is mainly affected by various scattering,especially the grain boundary scattering.The aim of this study is to investigate the relationship between carrier mobility and bicrystalline grains boundary of Rutile TiO₂ film.the following studies were carried out:(1)Rutile TiO₂ thin films are deposited by the traditional DC pulse magnetron sputtering technique and high temperature annealing.With the increase of sputtering power from 150 W to 900 W,the crystal structure of deposited TiO₂ films transform from amorphous to Anatase.Rutile TiO₂ films can be prepared by annealing TiO₂ films with different sputtering power in air at 1000?for 1h.(2)The electrical properties and crystal structure of Rutile TiO₂ films were tested to explore the influence of the mobility of Rutile TiO₂ carriers on the grain boundary.The Hall result shows that,the carrier concentration of all rutile TiO₂ films keeps at(2.16±0.37)×10¹⁶/cm³.On the contrary,with the increase of sputtering power from 150 W to 900W,the carrier mobility of rutile TiO₂ films increase from 0.75 cm²/V·s to 38.88 cm²/V·s.Combining the TEM and SAED results,it is confirmed that the carrier mobility is mainly influenced by the large angle bicrystalline grain boundary.In the case of rutile TiO₂ film with 150 W in sputtering power,the large angle bicrystalline grain boundary exist in the film,which seriously deteriorates the carrier mobility of film.On the contrary,in the case of rutile TiO₂film with 900 W in sputtering power,the low angle bicrystalline grain boundary exist in the film,which has little influence on the carrier mobility of film.(3)TiO₂ thin films were prepared on polyimide substrates.The heat absorption and exothermic behavior of TiO₂ thin films at high temperature was studied by TG and DSC.The results show that there is an obvious heat absorption peak between 800-900?between 150W and 900 W polyimide substrates,because the transition from anatase to rutile TiO₂ begins at this time.However,900 W has a smaller endothermic peak in this region,indicating that900 W has completed the transition from anatase phase TiO₂ to rutile phase TiO₂,and only rutile phase TiO₂ is growing up.