中文摘要：

LaTiO3是一种典型的强关联电子材料,其（110）薄膜为通过晶格对称性、应变等的设计调控外延结构的物理性质提供了新的机会.本文研究了SrTiO3（110）衬底表面金属La和Ti沉积所引起的微观结构变化,进而利用电子衍射信号对分子束外延薄膜生长表面阳离子浓度的灵敏响应,发展了原位、实时、精确控制金属蒸发源沉积速率的方法,实现了高质量LaTiO3（110）薄膜的生长和对阳离子化学配比的精确控制.由于LaTiO3中Ti3＋3d电子的库仑排斥作用,氧原子层截止的（110）表面更容易实现极性补偿,因此生长得到的薄膜表面暴露出单一类型的氧截止面.

英文摘要：

Transition metal oxides exhibit abundant physical properties due to the electronic interactions between charge,orbit and spin degrees of freedom. Lanthanum titanate, LaTiO3, a typical strongly correlated electron material, shows Mott-type metal-insulator and antiferromagnetic transitions at low temperature. And these interesting behaviors can be tuned by adjusting the occupation of the t2 g orbit of Ti3＋, or introducing symmetry breaking or lattice strain into the heterointerfaces. Especially on LaTiO3（110） surface, the anisotropic structure as well as the surface polarity allows the flexible control of artificial low-dimensional structure. However, the instability induced by surface polarity hinders the growth of high-quality LaTiO3（110） film. Here we show that by keeping the growing surface reconstructed in the molecular beam epitaxy（MBE） process, the surface polarity can be effectively compensated for, allowing the high-quality layer-by-layer film growth. Moreover, the intensity of reflective high-energy electron diffraction（RHEED）pattern sensitively changes with the surface cation concentration. Therefore the relative deposition rates of La and Ti sources can be monitored and further be precisely calibrated in situ and in real-time. We first prepare the（2 ×16） reconstruction on Sr Ti O3（110） surface by depositing La and Ti（2 ML for each） metals. Further increasing the Ti concentration on（2 × 16）, i. e., the [Ti]/[La] ratio, results in the significant decrease of RHEED ＂1 × ＂ intensity and the increase of ＂2 × ＂ intensity. And the change of RHEED intensity is quantitatively reversible through reducing the[Ti]/[La] ratio by the same amount. We set the evaporation rate of Ti source to be slightly higher than that of La for the MBE film growth. And the shutter state of Ti source is controlled to be open or close, which is determined by the change of RHEED intensity. Precise cation stoichiometry is achieved in the LaTiO3（110） film. X-ray diffraction confirms the si