THRESHOLD ENERGY IN ELECTRON BOMBARDMENT CONDUCTIVITY OF DIELECTRIC FILMS

Cathode rays induce steady-state conduction in amorphous dielectric films only if their energy exceeds a threshold. A comparison between values for the threshold and theoretical data for the differential dissipation of energy of fast electrons in solids shows that at the threshold the electrons penetrate only half the thickness of the films. The space charge which develops under these conditions and which is made responsible for the occurrence of the threshold is studied by experiments in which both sides of self-supporting films of arsenic trisulphide are exposed to cathode rays. The interpretation of the results is discussed.