title: Quantum-trajectory Monte Carlo method for study of electron-crystal interaction in STEM.
abstract: In this paper, a novel quantum-trajectory Monte Carlo simulation method is developed to study electron beam interaction with a crystalline solid for application to electron microscopy and spectroscopy. The method combines the Bohmian quantum trajectory method, which treats electron elastic scattering and diffraction in a crystal, with a Monte Carlo sampling of electron inelastic scattering events along quantum trajectory paths. We study in this work the electron scattering and secondary electron generation process in crystals for a focused incident electron beam, leading to understanding of the imaging mechanism behind the atomic resolution secondary electron image that has been recently achieved in experiment with a scanning transmission electron microscope. According to this method, the Bohmian quantum trajectories have been calculated at first through a wave function obtained via a numerical solution of the time-dependent Schrödinger equation with a multislice method. The impact parameter-dependent inner-shell excitation cross section then enables the Monte Carlo sampling of ionization events produced by incident electron trajectories travelling along atom columns for excitation of high energy knock-on secondary electrons. Following cascade production, transportation and emission processes of true secondary electrons of very low energies are traced by a conventional Monte Carlo simulation method to present image signals. Comparison of the simulated image for a Si(110) crystal with the experimental image indicates that the dominant mechanism of atomic resolution of secondary electron image is the inner-shell ionization events generated by a high-energy electron beam.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China. zjding@ustc.edu.cn.
authors.forename: Z
authors.initials: Z
authors.lastname: Ruan
authors.forename: R G
authors.initials: RG
authors.lastname: Zeng
authors.forename: Y
authors.initials: Y
authors.lastname: Ming
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: B
authors.initials: B
authors.lastname: Da
authors.forename: S F
authors.initials: SF
authors.lastname: Mao
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Ding