Electron micrographs of discontinuous Au films deposited on NaCl substrates have been obtained. Specimens include both films which have been subjected to externally applied voltages as well as films which have not had an external voltage applied. The micrographs offer direct photographic evidence of island distribution, size, and morphology which are highly supportive of injected charges affecting the film morphology in the vicinity of the electrodes.

In discontinuous films the difference between the electrostatic energy of a charge at rest on an island and a charge which has just been placed on an island by tunneling must be accounted for in a phenomonological explanation of the conduction mechanism. This energy difference can exceed the static electrostatic energy which is normally assumed to give rise to the thermally activated resistance experimentally observed in such films. It is also shown that the initial charge creation in discontinuous films may be more likely to arise from carrier injection at the electrodes than from island ionization in the middle of the film because of a lowered energy barrier height and an enhanced electric field in the vicinity of the electrodes. Under suitable conditions electrode injection will show a barrier energy lowering proportional to the square root of the applied field as is experimentally observed. Experimental results which may be indicative of electrode injection are presented.

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