Neděla Vilém, Tihlaříková Eva, Runštuk Jiří, Hudec Jiří
Environmental electron microscopy group, Institute of Scientific Instruments of the CAS, v.v.i., Královopolská 147, 612 64 Brno, Czechia.
Environmental electron microscopy group, Institute of Scientific Instruments of the CAS, v.v.i., Královopolská 147, 612 64 Brno, Czechia.
Ultramicroscopy. 2018 Jan;184(Pt A):1-11. doi: 10.1016/j.ultramic.2017.08.003. Epub 2017 Aug 12.
A new Combined System for high-efficiency detection of Secondary and Backscattered Electrons (CSSBE) in the ESEM consists of three detectors: an ionisation SE detector, an improved scintillation BSE detector, and a new Ionisation Secondary Electron Detector with an electrostatic Separator (ISEDS). The ISEDS optimizes conditions for electron-gas ionisation phenomena in the ESEM to achieve a strongly amplified signal from the secondary electrons with a minimal contribution from backscattered and beam electrons. For this purpose, it is originally equipped with an electrostatic separator, which focuses signal electrons towards a detection electrode and controls the concentration of positive ions above the sample. The working principle of the ISEDS is explained by simulations of signal electron trajectories in gas using the EOD program with our Monte Carlo module. The ability to detect the signal electrons in a selected range of energies is described with Geant4 Monte Carlo simulations of electron-solid interactions and proven by experimental results. High-efficiency detection of the ISEDS is demonstrated by imaging a low atomic number sample under a reduced beam energy of 5 keV, very low beam currents of up to 0.2 pA, and gas pressure of hundreds of Pa.
环境扫描电子显微镜（ESEM）中用于高效检测二次电子和背散射电子的新型组合系统（CSSBE）由三个探测器组成：一个电离二次电子探测器、一个改进的闪烁背散射电子探测器以及一个带静电分离器的新型电离二次电子探测器（ISEDS）。ISEDS优化了ESEM中电子-气体电离现象的条件，以实现来自二次电子的强放大信号，同时背散射电子和束流电子的贡献最小。为此，它最初配备了一个静电分离器，该分离器将信号电子聚焦到检测电极，并控制样品上方正离子的浓度。使用带有我们蒙特卡罗模块的EOD程序，通过对气体中信号电子轨迹的模拟来解释ISEDS的工作原理。通过Geant4蒙特卡罗模拟电子与固体相互作用来描述在选定能量范围内检测信号电子的能力，并通过实验结果得到验证。在5 keV的降低束能量、高达0.2 pA的极低束电流以及数百帕的气体压力下对低原子序数样品进行成像，证明了ISEDS的高效检测能力。
