The influence of geometry and specific electronic and nuclear energy deposition on ion-stimulated desorption from thin self-supporting membranes

TL;DR

This study examines how geometry and energy deposition influence ion-stimulated desorption from thin silicon membranes, highlighting electronic sputtering as the main mechanism and the combined effects of electronic and nuclear energy depositions on ion yields.

Contribution

It provides detailed experimental insights into the roles of electronic and nuclear energy depositions and the influence of geometry on ion yields in ion-stimulated desorption from silicon membranes.

Findings

Electronic sputtering governs desorption of surface species.

Nuclear energy deposition enhances ion yields, especially in transmission geometry.

Heavier ions and specific geometries increase secondary ion production.

Abstract

We investigate the dependence of the yield of positive secondary ions created upon impact of primary He, B and Ne ions on geometry and electronic and nuclear energy deposition by the projectiles. We employ pulsed beams in the medium energy regime and a large position-sensitive, time-of-flight detection system to ensure accurate quantification. As a target, we employ a single crystalline Si(100) self-supporting 50 nm thick membrane thus featuring two identical surfaces enabling simultaneous measurements in backscattering and transmission geometry. Electronic sputtering is identified as the governing mechanism for the desorption of hydrogen and molecular species found on the surfaces. Nevertheless, larger energy deposition to the nuclear subsystem by heavier projectiles as well as due to the directionality of the collision cascade appears to act in synergy with the electronic energy deposition leading to an overall increase in secondary ion yields. A higher yield of ions sputtered from the matrix is observed in transmission geometry only for B and Ne ions, consistent with the observed role of nuclear stopping.