Visual Observations on the Malter Effect

Abstract

The thin film field emission (Malter effect) from ${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$ films on Al was investigated (1) by coating the film with a fine dust of willemite and observing the behavior of the primary beam; (2) by forming an electron image of the surface by means of the Malter current from it. The behavior of these films, while exhibiting the Malter effect, may be summarized as follows: 1. The potential of the front surface of the electrode is a saw-tooth function of time at any point, and nonuniform over the surface at any instant. 2. The current density of the primary beam at the surface varies, correspondingly, because of the varying electric field above the surface. 3. A time lag exists between the application of voltage across the film and the establishment of the Malter current. 4. The Malter current issues chiefly from a number of isolated points on the surface, and the current from any one of these points varies with time. 5. The emitting points are scattered over the entire surface of the electrode, with some preferential grouping in the region covered by the primary beam. 6. Some of the electrons constituting the Malter current have a kinetic energy corresponding in order of magnitude to the voltage drop across the film. 7. The Malter electrons leave the film with a wide range of speeds.