Work function changes of clean and contaminated metal films in vacuum and in mercury vapour

Abstract

Considering the important industrial applications of mercury it is remarkable that so little work has been carried out on the characteristics of mercury surfaces. Prior to the present work, the last determination of the work function of mercury was determined over thirty years ago with some what unsophisticated apparatus.
In the present investigation contact potential difference techniques have been developed which enabled the work functions of solid and liquid mercury films to be measured.
The occurrence of impurity layers floating on top of liquid mercury surfaces is demonstrated, and their origin is traced to the contaminating action of the borosilicate glass are. Using liquid nitrogen techniques the impurity layers were frozen and subsequently submerged below clean condensed mercury films.
It has been demonstrated that the work function of mercury-free gold films is approximately O.5eV higher than previous determinations made in conventional ultra high vacuum systems employing mercury diffusion pumps.
In the course of this work a new measuring technique was developed which enables the work functions of volatile liquids and solids to be measured.
The clean surfaces were produced by condensing evaporated beams onto glass and metal substrates under residual gas pressures of less than 10-9 torr. The measurements were carried out in both conventional glass ultra-high vacuum systems and demountable stainless steel systems.