電子非彈性表面散射截面之記憶效應探討

Abstract

過去的理論模式，總是將每一次電子與固體的非彈性碰撞過程，視為獨立的事件。這意味著每次散射截面，對於前次散射行為不具有任何記憶效力 ；然而我們推測，散射事件應該會藉由電子能量在固體內之轉移，影響下一次電子散射的行為。這個研究的主要目標，就是要建立一個可靠的模式來呈現「連續非彈性交互作用間的記憶效應」。 根據介電理論和柏桑定律，我們針對一個以平行軌跡運動於固體外的測試電子之邊界問題，利用柏桑方程式之解，建立了考慮記憶效應的微分非彈性反平均自由行程與非彈性反平均自由行程公式。 我們計算了發生一次非彈性散射，而損失部分能量且平行於銅及矽表面運動之電子，其發生連續非彈性交互作用之微分非彈性反平均自由行程與非彈性反平均自由行程。我們關注能量範圍在300 - 1000電子伏特的電子，與固體非彈性交互作用的記憶效應，並探討記憶效應所造成的影響。

It was generally assumed that two successive inelastic interactions between an electron and the solid are independent of each other. This means that the electron keeps no memory on its previous interactions. However, any previous interaction should have some influence on the succeeding interaction due to the energy loss of the electron in its previous interaction. The aim in this work was to establish a reliable model to describe the memory effect between successive inelastic interactions. Based on the dielectric response theory and the Poisson law, we set up formulae for the differential and the total inelastic inverse mean free paths with memory effect, by solving the Poisson equation and matching the boundary conditions for a probe electron with a parallel trajectory outside the solid. The differential and the total inelastic inverse mean free paths for the successive interactions were calculated for electrons moving parallel to the surface of Cu and Si by considering the memory effect. The memory effect in the energy loss of inelastic interactions for electrons with energies 300 – 1000 eV was investigated. The effect was observable.