Simulation Study of Auger Electron Emission Features in Tip–Sample Electric Field Region for Scanning Probe Electron Energy Spectrometer

Abstract

A simulation study of the emission features of the Auger electrons in the electric field region localized within the cylindrical tip shield of a scanning probe electron energy spectrometer (SPEES) are reported. By taking into account synthetically the influence of every detailed factor, the relative intensity distributions for the outgoing Auger electrons are calculated by simulation. The results show that only those Auger electrons emitted from an annulus on sample surface with a width less than its radius can escape from the tip-sample electric field region. This provides a possible way for SPEES to improve the spatial resolution beyond the size of near-field emission electron beam from the tip. The distribution of the emission direction and the vertical height of the outgoing Auger electrons at the edge of the electric field have also been studied, revealing that most of the outgoing Auger electrons are parallel to the sample surface, and their vertical heights are constrained to a small range. These results are significant for improving the detection efficiency, the energy and spatial resolutions of the SPEES, and also provide instructive data for the designing of the tip shield and the electronic optical system in the tip-sample region for an SPEES.

Nanoscale spectroscopic mapping by scanning probe electron energy spectroscopy

“…Using this instrument, they compared the electron spectra obtained by a W (100) field-emission tip of STM with that by a conventional electron gun, and found that the high electric field introduced by the STM tip approaching near the surface would suppress the electron emitted from the sample surface and deform the measured spectra. This effect was confirmed and studied in the subsequent researches [3,[7][8][9]27], and a consensus was reached that the STM tip should be well shielded to obtain a quality electron spectrum by SPEES. A number of experiments were preformed to improve the shielding effect for the tip [4-8, 11, 24, 25, 28], and the most effective ones were achieved by Palmer's group [24] and our group [28] in different ways.…”

A double toroidal analyzer for scanning probe electron energy spectrometer

“…However, early attempts to develop such an instrument encountered great difficulties, [10][11][12][13][14] mainly due to the strong electric field introduced by the tip bias, which greatly compresses the backscattered electrons and reduces the count rate. [15] Therefore, a novel electron energy analyzer with high detection efficiency is required.…”