Static and Dynamic Charging of Thin Films at the Solid-vacuum Interface: Behavior as Nano-capacitor and Its Role in Photo and Electron Induced Reactivity

Abstract

ABSTRACTCharging of amorphous solid water (ASW) films has been characterized using high resolution, low energy positive ions (Ar+) and electrons at 1-50 eV energy range. This system responds to charging as a nano-capacitor and has been studied for its static electric field effect on electron-induced-desorption from top layers and internally trapped molecules within ASW film. In addition we have investigated the role of electron energy on chemical reactivity of trapped methyl chloride molecules as model for outer space surface chemistry.Dynamic charging at inner pores of porous silicon (PSi) has been studied as the origin of highly efficient photo-induced desorption (PID) of adsorbates such as Xe, CO and N2O. Wavelength and laser power dependence suggest that cross sections for PID, 3 orders of magnitude larger than on non-porous surfaces, originate from dynamic charging of nanometer scale tips at inner pores. These have lead to transient negatively charged species that undergo an Antoniewitz-like PID mechanism.