Laser-stimulated photodetachment of electrons from planar surfaces

The charging and discharging dynamics of non-conductive materials by plasmas are essential for plasma-surface interactions. While secondary electron emission (SEE) induced by ions and electrons has been well-studied, electron detachment stimulated by photons is less explored. We showed that the laser-stimulated photodetachment (LSPD) from the surface of glow discharge plasma charged (negatively) dielectric substrates induces a nonlinear time-dependent charge decay with subsequent laser shots [1]. The photodetachment yield is defined by not only the type of the material, and laser wavelength but also by the initial density of electrons on the surface. The LSPD yield and cross-section values were experimentally obtained for the Al₂O₃, h-BN, and SiO₂, and they do not follow the expected tabulated electron affinities. This unexpected behavior is attributed to the dependence of yield on initial surface charge density and the existence of electronic states (charge traps) on the surface of insulating materials. The obtained results might pave the way towards controlling surface charge density or its full elimination by properly adjusting the flux of low-energy laser photons, with less damage to the surface, which would be crucial in gas discharge plasma and electron beam applications.