Observation of Surface Deformation of Ferroelectric and Ferroelastic Crystals by Atomic Force Microscopy

AFM原子力显微镜（Atomic Force Microscopy，AFM）是观察铁电和铁弹畴结构表面形貌的有效方法之一，因为与表面刻蚀、扫描电镜等方法相比，AFM可以在不对样品表面进行任何修饰或破坏的情况下进行测量。PbTiO_3（LT）、Gd_2（MoO_4）_3（GMO）、NdP_<5p>O_<14>（NDPP）和W_（03）都发生了相变，改变了晶体结构。即，在室温下，BT和LT中由于立方到四方相转变而形成的90度畴结构，GMO中四方相到正交相畴结构，以及NDPP和W0_3中正交相到单斜相畴结构分别被可视化。特别地，还进行了进一步的实验，例如观察BT中施加电场下的90度畴图像，W0_3中的温度依赖的三斜畴图像。

AFM(Atomic Force Microscopy) is one of the useful methods for visualizing the surface morphology due to the ferroelectric and ferroelastic domain configurations, since the measurement is possible without any modification or damage of the sample surface in contrast to other methods such as surface etching, scanning electron microscopy, etc.In this project, we made AFM observations about surface structure of the following five crystals, BaTiO_3(BT), PbTiO_3(LT), Gd_2(MoO_4)_3(GMO), NdP_<5p>O_<14>(NDPP) and W0_3, all of which show phase transitions with alteration of the crystal system. Namely, 90 degree domain structure due to the cubic to tetragonal phase transition in BT and LT, the tetragonal to orthorhoinbic domain structure in GMO, and the orthorhombic to monoclinic domain structure in NDPP and W0_3, were visualized at room temperature, respectively. In particular, further experiments such as observation of the 90 degree domain image under application of electric field in BT, temperature-dependent triclinic-domain images in W0_3 were also made.