The Structure of Extremely Thin Layers Evaporated in Kinetic Vacuum Systems

Abstract

In a commercial electron diffraction camera some alkaline earth metals (from Be to Sr) or Al, Ni, or Mo were evaporated onto outgassed metal sheets or glass slides, using the starting pressure of 0.1μ of mercury. The diffraction patterns of the thinnest layers (to about 10³A) presented, regardless of the evaporation speed used, the pattern of the oxide of the evaporated metal exclusively. The diffraction pattern of the metal space lattice itself was growingly observed with Be, Al, Ni, and Mo only after uninterrupted evaporation until layer thicknesses of about 1μ were reached. When Mg, Ca, and Sr were evaporated, no patterns without, at least, the most intensive oxide rings could be attained under the vacuum conditions given in the apparatus. The results are in accord with some earlier findings of Langmuir, Beeching, Darbyshire, and Beischer, and clear up some hitherto not fully explained effects with stepwise evaporated layers. The appearance of oxide patterns is always accompanied by strong improvements of the vacuum in the evaporation compartment by the arising metal vapors, i.e., by the well‐known gettering effect.