The distribution of autelectronic emission from single crystal metal points. I. Tungsten, molybdenum, nickel in the clean state

Abstract E. Müller has shown that the angular distribution of field emission from fine metal points can be related to the crystal structure of the metal. He also suggested that the modifications in the pattern from tungsten which took place when the point temperature was raised could be attributed to a movement of the surface atoms which caused local changes in the work function. Further experiments are described in this paper using tungsten, molybdenum and nickel. It is shown that this surface mobility occurs above 1170° K for tungsten, 770° K for molybdenum, and 370° K for nickel. The changes in emission distribution, which are very much more marked for molybdenum and nickel than for tungsten, can be completely explained in terms of a change in the geometrical shape of the point. This is brought about by the action of the high external field upon the mobile surface atoms. The flash-over phenomenon in high vacuum is discussed and an explanation offered in terms of these observations. The effect of small traces of gas is illustrated, and it is shown that the gas film is removed at the relatively low temperature of 620-670° K. Several possible suggestions are put forward to explain the dependence of the emission distribution on the crystal structure of the metal, but no definite conclusion can be reached with the data at present available.