The technique of the total reflection of x rays has been applied to the study of thin films of Cu, Ni, Ge, and Se vacuum-deposited onto polished glass substrates. Starting with fresh films, ``smooth'' enough to exhibit pronounced x-ray interference fringes in the region just beyond the critical angle, the effects of vacuum anneal and oxidation were studied. Changes in the reflection curves are interpreted in terms of possible structural changes in the films. Reflection from layers of particles of carbon or polystyrene latex deposited onto ``smooth'' substrates was also studied for comparison.
Density measurements have been made on vacuum-deposited copper films in the thickness ranges 50 to 150 A and 500 to 1000 A. To obtain the density, an analysis was made of the relation between the reflection coefficient and the glancing angle of incidence for 1.54 A x-rays. For films in the range 500 to 100 A, this analysis was augmented by a chemical determination of the average mass per unit area. Although there is evidence of nonuniform density with depth in the film, especially for the very thin films, the average density of a film thicker than about 300 A was found within the limits of the experimental accuracy to be equal to the bulk density. This conclusion is in disagreement with some previously published work; the discrepancy appears to lie in differences between the x-ray method of measuring film thickness and the conventional optical interference method.
Absolute photoelectric yields of Ni, Cu, Pt, Au, W, Mo, Ag, and Pd are presented for the spectral region from 1400 to 473 A. Measurements were obtained for commercially pure polycrystalline surfaces which were treated in various ways including heat treatment in vacuo and in various gas atmospheres at reduced pressures. Surfaces, heat treated in vacuo, gave reproducible yields ranging from 10−3 electrons per photon at 1400 A to 10−1 electrons per photon at 500 A. Although untreated samples exhibited a maximum in the region studied, this maximum disappeared after heat treatment resulting in most cases in a broad plateau extending from 1000 A to 500 A. At wavelengths longer than 1000 A a decrease in yield was observed. Representative experiments with a Ni cathode, heat treated in vacuo then exposed to O2 at reduced pressures, indicated that the maxima for untreated surfaces were caused by adsorbed gases and metallic oxide formation. The absolute error in the values of the photoyields was estimated to be within ±15%.
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