運動電荷能量損失之表面效應

Abstract

在本論文中, 我們導出平行於固體表面運動的帶電粒子的非彈性倒數平均自由徑( DIMFP )的計算公式. 這個DIMFP可以分為體項及表面項, 對於在固體外行進的電子, 只有表面項對電子與固體之間的非彈性交互作用有貢獻. 對於在固體內部行進的電子, 表面電漿激發及體電漿激發都出現, 且發現表面效應侷限於一個由真空—固體介面向兩側延伸的表面層. 我們使用廣義 Drude 介電函數來描述非彈性交互作用. 利用鏡象反射模型 ( SRM ) 及半古典無限大壁壘模型, 我們發現了能量與動量守恆的限制是相當重要的. 此外, 我們也導出對固體以局域型介電函數描述的解析公式. 我們也討論了先前的非彈性散射對目前的能量損失機率分佈的影響, 且導出阻止本領( Stopping Power )的解析表示式. 結果發現此記憶效應對較小的阻尼係數的介電質與低能的入射粒子有較明顯的效應.

A new, general expression for the differential inverse mean path (DIMFP) of an electron moving parallel to the interface of two semi-finite media is derived. This DIMFP can been divided up into a bulk and a surface term. For the electron moving outside the solid, only the surface term contributed to the inelastic interaction between the solid and the external electron. For the electron moving inside the solid, both surface and bulk excitation exist. It is found that surface effect is restricted to a surface layer extending on both sides of the vacuum-solid interface. The extended Drude dielectric function (Kwei et al. 1993) describes the inelastic scattering in solid very well. Using specular reflection model (SRM) and semi-classical infinite barrier model (SCIBM), we found the momentum and energy conservation restriction is important and the analytic formulae under the local dielectric function approximation is derived. Attention is paid to the influence of previous inelastic scattering on the instantaneous interaction between the external electron and the solid. The analytic expression of stopping power is derived. This “ memory “ is found to be important for the dielectric with the small damping constant.