An original method for revealing the dielectric heterogeneities on an insulating surface has been developed on creation of an electron multiplication cascade inside the insulator placed in an electric field. The steps of the physical process are: (i) excitation of electrons into the conduction band, (ii) electric field acceleration of the conduction electrons, (iii) ionization of the valence levels, (iv) creation of many more new defects in the vicinity of dielectric heterogeneities, (v) charge localization on defects and appearance of a local residual potential. The potential map is observable by scanning electron microscopy after propagation of the ionizing cascade, but only during the first scan which smoothes the surface potential. By electron spectroscopy the energy of the secondary negative particles emitted during the cascade can be analysed.
Vigouroux, J. P.; Duraud, J. P.; Le Gressus, C.; Petite, G.; Agostini, P.; and Boiziau, C.
"Study by Scanning Electron Microscopy and Electron Spectroscopy of the Cascade of Electron Multiplication in an Insulator Submitted to an Electric Field,"
Scanning Electron Microscopy: Vol. 1985
, Article 18.
Available at: https://digitalcommons.usu.edu/electron/vol1985/iss1/18