Action of an electric field on the photoelectric properties of thin films of calcium.

A study was made of the behavior of the photoelectric efficiency of very thin films of calcium-thicknesses between 1 nm and 20 nm-when an electric field was applied to them, of intensity between 2 x 10(3) V and 10(6) V.m(-1), perpendicular to the plane of their substrate. The corresponding work functions and their variations in accordance with the field were determined using Fowler's graphic method. It was seen that when the field increased, the work function relating to the normal photoelectric threshold decreased. This variation depends on the thickness of the thin film; it is greatest for a thickness d(0) of about 5.5 nm. There is a second photoelectric threshold for a thickness less than d(0) even when the field applied perpendicularly to the substrate is zero. The work function Phi(s) relating to it does not vary when the field is increased. When the thickness is greater than d(o), the second threshold no longer exists for a zero applied field; it appears again when the field is higher than a certain value, which is a function of film thickness.