MOLECULAR-ORBITAL THEORY OF FIELD EVAPORATION

We present a theory based on nonempirical molecular orbital calculations for field evaporation. To investigate desorption under a high electric field, a cluster model is constructed for a silicon surface with a hydrogen atom absorbed on top of it. The peripheral dangling bonds of the silicon surface are terminated by hydrogen atoms. We obtained the potential energy surfaces for an absorbed hydrogen atom on a silicon surface under both positive and negative biases. In case the field strength is 20.0 V/nm, the activation energy decreases to 0.6 eV under a negative bias and to 1.5 eV under a positive bias, while it is 11.7 eV for the nonbiased surface. Electron population analysis reveals that the desorbed particles are a proton under a positive bias and a negative hydrogen ion under a negative bias. We employed unrestricted Hartree-Fock calculations with an STO-3G basis set.