帶電粒子平行於雙層系統運動之能量損失

Abstract

一個帶電粒子平行於固體表面運動時，由於此粒子和固體表面電子之交互作用，使得粒子感受到激發電位之影響。粒子因受到感應電場之作用，造成能量損失。目前，有一些相關的理論研究報告，但僅侷限於半無限大的固體。 本論文將理論研究延伸至由薄膜及半無限大基質組成之雙層系統。我們將利用介面之邊界條件，根據介電理論來解帕松方程式，以得到含真空-薄膜介面及薄膜-基質介面激發之電位解。我們將得到滿足能量動量守恆定律的激發電位及阻擋力的公式。 我們將仔細的探討質子平行於一真空-銅-矽組成的系統運動，其激發電位的空間分佈情形。阻擋力以及質子所在位置的感應電位與薄膜厚度、粒子速度以及粒子與固體表面間的距離之間的關係將被仔細研討。

An energetic charged particle moving parallel to a solid surface experiences a wake potential arising from the interaction of this particle with surface electrons. The gradient of the wake potential will act back on the charged particle and cause it to lose energy. A number of theoretical works has been reported. However, such works are restricted to semi-infinite solids. This thesis intends to extend theoretical studies to overlayer systems composed of thin films and semi-infinite substrates. Based on the dielectric theory, a formulation of surface (vacuum-film contact) excitations and interface (film-substrate contact) excitations will be developed by solving the Poisson equation and taking into account the boundary conditions. Expressions for the induced potential and the stopping force will be set up with the consideration of energy-momentum conservation laws and using the extended Drude model including spatial dispersion for the dielectric function. The wake potential as a function of space is studied for a proton moving parallel to a vacuum-Cu-Si system. The dependence of stopping forces and the induced potential at the instantaneous position of the proton are investigated on the film thickness, the distance of the proton from the surface, and the velocity of the proton.