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在钛酸铋(Bi4Ti3O12)薄膜的制备过程中容易获得晶粒c轴垂直于基片表面的薄膜,而压电和铁电存储器主要利用a轴的自发极化分量,因而制备a轴择优取向的Bi4Ti3O12铁电薄膜具有特别的意义。采用飞秒脉冲激光作用在钛酸铋陶瓷靶上,采用Si(111)作为衬底,制备了a轴择优取向的钛酸铋薄膜。采用X射线衍射(XRD)的薄膜附件和场发射扫描电镜(FSEM)研究了薄膜的结构和形貌;采用傅里叶红外光谱仪测量了室温(20℃)下在石英基片上沉积的样品的光学特性;室温下沉积的钛酸铋薄膜呈c轴择优取向,晶粒的平均大小为20 nm,其光学禁带宽度约为1.0 eV。在500℃沉积的钛酸铋薄膜呈a轴择优取向,晶粒大小在30~300 nm之间,薄膜的剩余极化强度Pr为15μC/cm2,矫顽力Er为48 kV/cm。
In the preparation of bismuth titanate (Bi4Ti3O12) thin films, the c-axis of the crystal grains perpendicular to the surface of the substrate is easily obtained. However, the piezoelectric and ferroelectric memories mainly utilize the spontaneous polarization component of the a-axis, Bi4Ti3O12 ferroelectric thin film has a special significance. A bismuth titanate thin film with a-axis preferred orientation was prepared by using femtosecond pulsed laser on bismuth titanate ceramic target with Si (111) as the substrate. The structure and morphology of the films were investigated by X-ray film diffraction (XRD) and field emission scanning electron microscopy (SEM). The optical properties of samples deposited on quartz substrates at room temperature (20 ℃) were measured by Fourier transform infrared spectroscopy The bismuth titanate films deposited at room temperature have a preferred c-axis orientation with an average grain size of 20 nm and an optical band gap of about 1.0 eV. The bismuth titanate films deposited at 500 ℃ have a preferred orientation along the a-axis, the grain size is between 30 and 300 nm, the remanent polarization Pr of the films is 15 μC / cm2 and the coercivity Er is 48 kV / cm.