Experimental data and model simulations of beam spread in the environmental scanning electron microscope

Abstract

Summary: This work describes the comparison of experimental measurements of electron beam spread in the environmental scanning electron microscope with model predictions. Beam spreading is the result of primary electrons being scattered out of the focused beam by interaction with gas molecules in the low-vacuum specimen chamber. The scattered electrons form a skirt of electrons around the central probe. The intensity of the skirt depends on gas pressure in the chamber, beam-gas path length, beam energy, and gas composition. A model has been independently developed that, under a given set of conditions, predicts the radial intensity distribution of the scattered electrons. Experimental measurements of the intensity of the beam skirt were made under controlled conditions for comparison with model predictions of beam skirting. The model predicts the trends observed in the experimentally determined scattering intensities; however, there does appear to be a systematic deviation from the experimental measurements.

Use of Environmental Scanning Electron Microscopy to image poly(N-isopropylacrylamide) microgel particles

“…The scattered electrons out of the focused beam by interaction with gas molecules in the lowvacuum sample chamber form a ''skirt" of electrons around the central probe. This scattering (skirt formation) depends on gas pressure in the chamber, beam-gas path length, beam energy, and gas composition and must be considered and controlled to avoid degrading the image resolution [47,48]. Beam damage [49,50] and charging effects [51] have also been analyzed.…”

Skirting effects in the variable pressure scanning electron microscope: Limitations and improvements

“…In this case, the production of signals such as secondary electrons, backscattered electrons and X-rays, is not neglected. The presence of a gaseous environment in the VP-SEM modifies the primary electron beam profile then the electron beam can be generally divided into two fractions: (1) un-scattered beam, which retain the same distribution profile and also the same diameter as the original electron probe; (2) scattered beam, which affects the trajectory of the primary electron beam and distributed around it to forms what is known as a "beam skirting", usually spreads over the size of the electron probe diameter (Danilatos, 1988;Wight, 2001;Wight and Zeissler, 2000). It is of a paramount importance to know the magnitude and the extent of the electron beam skirt and how closely the scattered fraction can affect the spatial resolution of X-ray microanalyses and the BSE imaging in the VP-SEM.…”

Monte Carlo Study of the Interaction Volume Changes by the Beam Skirt in VP-SEM

“…Indeed, many works have studied the problems caused by the skirt phenomenon [1][2][3][4][5][6][7][8][9][10][11]. The most of the earlier studies on the topic were dedicated essentially to measure the amplitude of deflected beam [12][13][14] and to evaluate its impact on the analysis. Recent works propose some experimental equipment and methods to minimize the effect of the gas interaction electron beam and to study the dielectric samples [15].…”