Abstract
Deposition and study of calcium films were achieved under ultrahigh vacuum. The latter was obtained with the use of an ion pump and a helium cryopump. The temperature of the substrate ranged between 90 and 400 K. The electrical resistance was measured with the use of a four-probe method with a constant current. Film thicknesses were in the range between 20 and 300 nm. To obtain a stable film structure, samples were annealed to a temperature near 400 K. The electrical resistivity of the annealed films exhibited a linear and reversible variation with temperature. It was shown to be thickness dependent. For the thickest deposits, electrical resistivity reached a constant value which no longer depended on the thickness, but was a function of the film-deposition temperature. With the help of electron photomicrographs and with use of the conduction model proposed by Mayadas and Schatzkes, we calculated the fraction of electrons which are specularly reflected at the surface of the film and the parameter depending on the reflection on grain boundaries. The influence of grain boundaries was calculated and the mean free path was deduced from these results.
- Received 18 February 1981
DOI:https://doi.org/10.1103/PhysRevB.26.5416
©1982 American Physical Society