硅基板上Fe掺杂TiO_2氧敏薄膜的制备、结构与性能研究

Influence of Fe^(3+) Doped on Phase Formation and the Oxygen Sensitivity of TiO_2 Oxygen Sensitive Thin Films Prepared on Silicon Substrate by Sol-Gel Method

采用溶胶-凝胶法,以Ti(OC4H9)4为前驱体,用提拉法在硅基板上制备了掺Fe的TiO2氧敏薄膜,对薄膜物相结构进行了X射线衍射(XRD)测定,利用扫描电镜(SEM)对薄膜微结构进行了观察.结果表明:在硅基板上生长的TiO2薄膜中锐钛矿相为均匀小晶粒分布结构,金红石相以大尺度团聚结构形貌出现.Fe离子的掺杂对硅基板上制备的TiO2薄膜中金红石相的形成有很大的影响.Fe的掺入降低了金红石相的形成温度约100℃,Fe掺量在6mol% 时,形成金红石相的量达到最大,即析晶能力最强.薄膜中形成晶相的晶格常数在<6mol%的低Fe范围内,随较小的Fe离子取代较大的Ti离子,锐钛矿相和金红石相的晶格常数都随之减小;在>6mol%的高Fe掺量范围内,随Fe掺量的增加,体系缺陷过量增加,晶格结构畸变严重,伴随着畸变能的释放,金红石相的晶格常数c轴逐渐增长,n轴略有下降(或基本不变). TiO2氧敏薄膜的氧敏性能受金红石相含量和氧空位浓度控制.当Fe离子掺杂浓度为6mol% 时,金红石相及相应氧空位达到最大值,TiO2氧敏薄膜的氧敏性能也达到最大值,比刚形成金红石相的薄膜的氧敏性能增加近19倍.

The Fe^3＋ doped TiO2 oxygen sensitive thin films deposited on single crystal silicon substrates were prepared by a sol-gel method. The phase structure of the thin films was measured by X-ray diffraction （XRD）. The morphologies were observed by scanning electron microscope （SEM）. The results showed that the anatase phase appeared with a small grain size dispersed homogeneously in the thin film. The rutile phase appeared with a morphology of special clustered grains and large sizes in the thin film. It was exhibited evidently that the formation of the rutile phase in the thin film on a single crystal substrate was dependent on Fe^3＋ doping in the system. The formation temperature was about 100℃ lower with 3mol% Fe^3＋ doped than that without Fe^3＋ doping. The largest content of the rutile phase appeared in the thin film while Fe^3＋ doping of about 6mol%. In addition, the crystal lattice of both the anatas phase and the rutile phase decreased with the substitution of a small size of Fe ions for a large size of Ti ions when doping Fe ions concentrantion below 6mol%. As Fe ions doped was above 6mol%, the c axis of the rutile phase increased while the a axis kept almost constant with the increase of Fe and thus both oxygen vacancy and structure distortion increased. The oxygen sensitivity of Fe doped TiO2 thin films was controled by the concentration of the oxygen vacancies and the content of the rutile phase in TiO2 thin films.The rutile phase and the sensitivity in the Fe doped TiO2 thin film showed maximum while Fe doping was 6mol%, and its oxygen sensitivity was 19 times more than that of the TiO2 thin film with 3mol% Fe doped.