以蒙地卡羅法探討散射模式對反射電子之影響

Abstract

本論文利用蒙地卡羅法完成反射電子能量損失能譜以及彈性峰電子能譜之 計算。為了獲得正確的結果，我們的模擬包含了較為完整的電子與物質交 互作用模式。在處理彈性散射方面，我們在分波法中考慮了固態效應對電 子密度分佈之影響，以及電子互換和極化作用對靜態位勢之修正。而且， 本論文使用有限差分法來精確計算由彈性散射所引起的相移。至於非彈性 散射，無論固態內部或表面之激發皆為考慮。為了能在蒙地卡羅法中加入 表面電漿激發效應，我們發展了一個模擬方法，採用帕松統計原理來計算 入射電子穿越真空和固態界面之能量損失。此外，我們還探討了不同的交 互作用模式對反射電子能量損失能譜以及彈性峰電子能譜之影響。除了分 析散射位勢模型對彈性背向散射電子角度分佈之效應外；我們藉著表面電 漿激發對彈性反射係數以及反射電子能量損失能譜之影響，來分別確認此 種激發與電子能量和穿越角之相關性。我們所得結果與實驗相當吻合，且 印證了本論文所採交互作用模式和方法之正確性。 The REELS and EPES were constructed by Monte Carlo simulations. To obtain the results accurately, more complete interaction models were included in our simulations. In treating the elastic scattering, we have taken into account solid state effect on the atomic electron density distribution and corrections of exchange and polarization effects to the static potential in the partial wave analysis. As regards the inelastic scattering, both volume and surface excitations were considered. We have developed a method to include the surface plasmon excitation in our simulations by adopting the Poisson statistics when primary electrons were passing through the vacuum-solid interface. Besides, the influences of different interaction models on the REELS and EPES were explored. The effect of scattering potential models on the angular distribution of elastically backscattered electrons was analyzed. Then the influences of surface excitations on the elastic reflection coefficient and the REELS were presented to assure the dependence of electron energies and passing angles of this excitation. The agreement of our results with experimental data has sugggested the validity of the interaction models and approaches we applied.