Abstract
直接決定表面原子幾何排列結構是近來表面科學最基本的研究課題。因為原子幾何排列結構是了解晶体表面的物理及化學性質之基礎。然而目前面科學中所用的一些直接決定原子結構的技術,如 STM、HRTEM、FIM 及GIXRD,都有它們的極限。所以本論文主要是研究發展一較實用且方便的直接決定表面原子結構的技術。既我們利用多重能量的菊池電子繞射圖型經由多重能量相位相加法可以直接且快速地重建單晶表面及覆蓋層表面的三度空間原子影像,完全不需要任何原子模型的假設。如Ag(001),Ag(111),Si(001)(2x1)及Si(111)-r3xr3R30度-Au的表面原子結構都可以經由此種菊池電子全像術完全直接成像而得,而且其解析度可達到一埃.並且此研究結果是全世界第一個可以很清楚地直接成像Si(001)(2x1)表面原子對及Si(111)-r3*r3R30度-Au表面金原子所形成的 "trimer",其解析度遠比STM,HRTEM好.所以此論文研究証明了我們所發展出來的菊池電子全像術很有潛力成為一個無鏡式的電子顯微鏡.Direct imaging of three-dimensional atomic structures of cleanand adsorbated surfaces by numerical Fourier transforming themultiple-energy diffraction patterns of Kikuchi (quasi-elastically scattered) electrons is first demonstratedexperimentally. Examples of the 3D holographic images ofAg(001), Ag(111) and Si(001)(2x1) clean surfaces as well asSi(111)-r3xr3 R30 degree - Au adsorbate-covered surface arepresented. The 3D holographic images reconstructed with anintegral-energy phase-summing method are high-fidelity andartifact-free. The resolution of the reconstructed images is 1angstrom in all spatial directions. The atoms down to threelayers below the source atoms are three-dimensionally imaged.And we directly imaged, for the first time, the various dimeratoms on Si(001)(2x1) surface and the individual Au trimeratoms on Si(111) -r3xr3 R30 degree - Au surface in 3D realspace with the atomic-resolution Kikuchi electron holography.Moreover, the 3D registry of surface atoms to the topmostatomic layer of substrates was clearly revealed withoutambiguity. Espescially for the study on Si(111) -r3xr3R30degree - Au surface, the 3D atomic-image informations,obtained from various incident angles, clearly support the Autrimer structural model without any theorical modeling. Thus,Kikuchi electron holography offers a great potential to developa lensless atom-imaging microscopy.