To detect charge distributions on insulating films, a hydrocarbon (HC) replica method had been applied [1] and indicated the distribution of absorption and accumulation of positively or negatively ionized hydrocarbon molecules in residual gases in a TEM column [2, 3]. Figure 999 shows a hydro-carbon contamination layer formed on a Si₃N₄ membrane in thickness of 30 nm. The accelerating voltage of the electron beam used to irradiate on the Si₃N₄ membrane was 75 kV. The charge distributions consist of three zones around the beam irradiation point at the center:
       i) Zone I which is positively charged by high-density irradiation electrons because of generation of SEs (secondary electrons). The HC layer is thicker on the top (entrance) surface than the bottom (exit) surface of the TEM sample because more SEs are generated from the top surface than bottom surface of the TEM sample. (see page4835)
       ii) Zone II which is neutralized by balancing the scattered and absorbed SEs.
       iii) Zone III which is negatively charged by absorbed SEs.

[1] Ken Harada, Keiko Shimada, Kodai Niitsu, Teiji Katsuta, Teruaki Ohno, and Daisuke Shindo1, Transmission Electron Microscope Observation of Charge Distribution on Insulating Thin Films by Hydro-carbon Deposition, Microsc. Microanal. 23 (Suppl 1), 2017.
[2] J. T. Fourie, Optik 44 (1975) p. 111.
[3] J. J. Hren, Ultramicroscopy, 1 (1979) p. 375.
[4] Ken Harada, Keiko Shimada, Kodai Niitsu, Teiji Katsuta, Teruaki Ohno, and Daisuke Shindo, Transmission Electron Microscope Observation of Charge Distribution on Insulating Thin Films by Hydro-carbon Deposition, Microsc. Microanal. 23 (Suppl 1), 1826, (2017).