Films of sodium and argon have been formed on substrates held at 5 K. As composition is varied, a metal-nonmetal transition is observed which is qualitatively different from previously reported measurements on the sodium-argon system.
Bibliographical noteFunding Information:
The present investigations were undertaken in conjunction with studies of the sodium-ammQnia system in which the conductivity was found to vary in an anomalous fashion with composition \[3\].F ilms were formed from vapor produced in a small molecular beam oven suspended in a vacuum chamber whose walls were cooled to 4 K by liquid helium. Details of the experimental arrangement are reported in ref. \[3\]. The total pressure in the oven was such that it was operated well into the molecular beam region permitting precise control of both the flow rate and the composition. Plots of film conductance against time were linear, confirming the constant rate of deposition. The argon pressure was controlled to +1 × 10 -4 torr and the oven temperature to -+0.1 K. This resulted in a relative compositional uncertainty of +0.2%. Compositions which are reported are nominal in that they are comPuted from oven para .meters under the assump- * Supported in part by USERDA under contract EY-76-S-02-1569 and by the Graduate School of the University of Minnesota.
Copyright 2014 Elsevier B.V., All rights reserved.