Reflectivity of very low energy electrons (< 10 eV) from solid surfaces: Physical and instrumental aspects

The impact of very low energy electrons (VLEE) on solid surfaces plays an important role in various fields of modern technology. Plasma physics, space research and particle-accelerators and progress in these fields are based partly on investigation of VLEE emission and reflection properties as obtained from laboratory measurements. Here the influence of the material composition and of the angle of incidence on the reflectivity, R, of VLEE is derived by the use of simple quantum mechanical arguments showing a rapid decrease of R from 100% when the incident energy of electrons increases from 0 eV while the surface sensitivity increases. The measurements depend significantly on the potential referencing between the electron source, the sample, and the detector, as well as of the energy spread of the incident electrons. VLEE thin film transmission is briefly considered and various practical consequences of the contrasts (crystalline, topographic, doping) as reported in scanning low energy electron microscopy (SLEEM) are discussed. The present developments may be transposed easily to any kind of solid sample and the possibility of imaging the local vacuum level (or work function) change with a minimum of radiation damage is suggested. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3691956]