Throttling Aperture as the Gaseous Secondary Electron Detector in the Variable Pressure/Environmental SEM

M. Krysztof and W. Słówko Faculty of Microsystem Electronics and Photonics, Wrocław University of Technology, Z. Janiszewskiego 11/17, 50-372 Wrocław, Poland

Full Text PDF

The authors analysed the conditions of the secondary electron detection with the use of the lower throttling aperture as the electron collector positioned close to the sample, at the distance less, or comparable to the aperture opening. For computer simulations of electron flow under various gas conditions, the software combining the commercial programme SIMION 3D v. 7.0, enabling computations of charged particles trajectories in the electric and magnetic fields, combined with the Monte Carlo one written by the authors was used. The results of the simulations show that the gas amplification of the electron signal and the noise to signal ratio are suitable for imaging at working gas pressures exceeding 1 hPa (100 Pa). The upper limit of the pressure defined by the electron beam scattering by far exceeds 10 hPa and is a question of the accelerating voltage and vacuum units design. The detector unit combined also with the differential pumping system has been designed in the form: of an attachment to the classic scanning electron microscopy and applied in the JSM840 (JEOL) microscope. The simulation results have been proved experimentally.

DOI: 10.12693/APhysPolA.123.880 PACS numbers: 41.85.-p, 52.80.Dy