Energy threshold and ion yield for H − ions ejected from Si( [formula omitted]):H(1×1) during low energy electron collisions: study of ESD process in relation with atom manipulation in STM

Abstract

This paper deals with an experimental study of H − ions desorption out of a well organised silicon crystal surface Si(1 1 1):H(1×1). It mainly concerns the resonant desorption process attributed to a dissociative electron attachment below 12 eV. In situ access to the work function provides an accurate reference of the incident electron energy. The resonant peak for desorption is centred at 8 eV with a corresponding threshold of about 6 eV. For the resonance energy, a probability 2.0×10 −6 ion H − per electron is deduced from both the incident electron density and the spectrometer calibration. Variation in desorption yield with electron dose suggest that hydrogen leaves the surface as neutral also with a probability about 1.1×10 −3 atom per electron. Evaluation of the image charge influence provides a distance 1.2 Å between external silicon atoms and hydrogen. This determination was based on the measured-desorption threshold and the H − ion kinetic energy, as well as on the hydrogen electron affinity and the SiH binding energy deduced from data tables. This distance fairly agrees with ab initio simulations once the jellium extension is included. Comparing most ESD features for H − ions desorption with hydrogen atom manipulation in scanning tunnel microscopy out of the same substrate, we assume that similar energy threshold and yields strongly suggest a common initial electron excitation process. Projected ESD experiments might enlighten the understanding of such surface atom manipulation.