Electrical resistivity of thin films of potassium at 100°K

Abstract

The electrical resistivity of thin potassium films at 100°K has been measured as a function of thickness in the range 148–1600 Å. The experimental results are in excellent agreement with Fuchs's theoretical predictions in the range 500–1600 Å and show that the scattering of the electrons at the film surfaces is completely diffuse. Comparison of experimental and theoretical curves gives a bulk resistivity parameter of 1·85 μΩ-cm, a mean free path of 1180 Å, and an electron to atomic density ratio of 1·0. The films were deposited on a Pyrex substrate from a beam of potassium vapor in a vacuum chamber which had a pressure less than 5 × 10 −8 mm Hg. The film thickness, in each case, was computed from a known beam intensity, exposure time, and film density. A surface ionization detector was used to calibrate the beam intensity ( J 1) as a function of effusion oven temperature ( T 0). The linear plot of log ( J 1 T 0 1 2 ) versus T 0 −1 gave a heat of sublimation for potassium at 450°K of 21·1 kcal mole , in good agreement with Brewer's value of 21·4 kcal mole within our experimental error.