On the basis of a model of the real insulating layer within a MIS structure, taking into account small interface regions with trap densities by at least one or two orders of magnitude larger than the trap density of the bulk, electron injection and trap filling of these regions is calculated. Experimental results agree very well with predictions of the trap‐filling model. In thermal SiO2 layers trap densities in the interface region are found to be about 0.6 to 8 × 1010 cm−2 with larger values at the silicon side. The corresponding values of Si3N4 layers are found to be about 6 × 1011 to 6 × 1012 cm−2 with larger values at the metal side. From the time constants of trap filling of about 120 s the widths of the interface regions follow to be about 32 Å.

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DC characteristics of thermally grown SiO2 films of thicknesses between 70 and 120 nm in MOS structures are measured from below 106 V/cm to breakdown. The measuring conditions and the significance of the measured currents are derived from a model of spatial trap distribution which suggests interface regions of higher trap density compared with the bulk. At some samples nearly exact Fowler‐Nordheim characteristics are found whereby the current did not show any measurable decrease with time indicating the SiO2 films to have very low trap density. In the range of field strengths below Fowler‐Nordheim conduction on many samples currents are measured which are in good accordance with j ∼ exp (–B/F1/4). This behaviour is derived by the percolation theory of hopping conduction in amorphous solids. It is suggested that real percolation channels exist in SiO2 films which may be influenced during the preparation of the films. The hopping currents tend to instabilities under electrical stress.

In liquid benzene and anthracene, observation of polarization voltages indicates that the electric current flow produces a coverage of electrodes by adsorbates. With this conception the current/field characteristics can be explained, as well as the observed decrease of the current with time. The amount of coverage is limited because at higher current densities electrohydrodynamic liquid motion begins.