Variable-deceleration-ratio wide-acceptance-angle electrostatic lens for two-dimensional angular and energy analysis

High-Performance Compact Pre-Lens Retarding Field Energy Analyzer for Energy Distribution Measurements of an Electron Gun

The energy distribution of an electron gun is one of the most important characteristics determining the performance of electron beam-based instruments, such as electron microscopes and electron energy loss spectroscopes. For accurate measurements of the energy distribution, this study presents a novel retarding field energy analyzer (RFEA) with the feature of an additional integrated pre-lens, which enables an adjustment of beam trajectory into the analyzer. The advantages of this analyzer are its compact size and simple electrode configuration. According to trajectory simulation theories, the optimum condition arises when the incident electron beam inside the RFEA is focused on the center of a retarding electrode. Comparing I–V curves depending on whether the pre-lens working or not, it is confirmed that the use of the pre-lens dramatically improves the energy resolution and efficiency of the signal acquisition process. The pre-lens RFEA was applied to characterize a Schottky electron gun under various temperatures and extraction voltages as operational conditions. When the tip temperature was increased by 50 K, we were able to measure an energy distribution broadening of 13.8 meV with the proposed pre-lens RFEA. The relative standard deviation of energy distribution was 0.7% for each working condition.

Study and design of a lens-type retarding field energy analyzer without a grid electrode

A retarding field energy analyzer (RFEA) for measuring the energy distribution of charged particles offers the advantages of a simple structure and suitability for simultaneous observations of beam patterns in two dimensions. In this study, lens-based RFEAs without a grid electrode were theoretically investigated with regard to the geometry and lens condition to achieve high performance. The simulation results show that the proposed RFEA can achieve a resolution of 2.6 meV at an energy level of 500 eV. In addition, performance, which is the ratio of the resolution to the beam energy, reached 5.2×10^-6. These results indicate that the RFEA designed in this study is capable of high-performance outcomes. The findings here demonstrate that the most important factors when attempting to realize a high-resolution RFEA design are to reduce the sagging effect of the electron beam through the focusing lens and ensure that V″(z) in the retarding electrode is close to zero. The design of the lens-based RFEAs is described in detail.

Acceptance-cone-tunable electron spectrometer for highly-efficient constant energy mapping

We have developed an acceptance-cone-tunable (ACT) electron spectrometer for the highly efficient constant-energy photoelectron mapping of functional materials. The ACT spectrometer consists of the hemispherical deflection analyzer with the mesh-type electrostatic lens near the sample. The photoelectron trajectory can be converged by applying a negative bias to the sample and grounding the mesh lens and the analyzer entrance. The performance of the present ACT spectrometer with neither rotating nor tilting of the sample is demonstrated by the wide-angle observation of the well-known π-band dispersion of a single crystalline graphite over the Brillouin zone. The acceptance cone of the spectrometer is expanded by a factor of 3.30 when the negative bias voltage is 10 times as high as the kinetic energy of photoelectrons.