Early stage morphology of quench condensed Ag, Pb and Pb/Ag hybrid films

TL;DR

This study uses STM to analyze the early morphology of quench condensed Ag, Pb, and Pb/Ag films on inert substrates, revealing substrate influence on grain size and electrical properties.

Contribution

It demonstrates that substrate type affects grain size and conduction thresholds in quench condensed metal films, a novel insight into film morphology.

Findings

Ag grain size depends on substrate type

Pb/Ag films have higher critical conduction thickness

Substrate influences grain morphology and electrical properties

Abstract

Scanning Tunneling Microscopy (STM) has been used to study the morphology of Ag, Pb and Pb/Ag bilayer films fabricated by quench condensation of the elements onto cold (T=77K), inert and atomically flat Highly Oriented Pyrolytic Graphite (HOPG) substrates. All films are thinner than 10 nm and show a granular structure that is consistent with earlier studies of QC films. The average lateral diameter, $\bar {2r}$, of the Ag grains, however, depends on whether the Ag is deposited directly on HOPG ($\bar {2r}$ = 13 nm) or on a Pb film consisting of a single layer of Pb grains ($\bar {2r}$ = 26.8 nm). In addition, the critical thickness for electrical conduction ($d_{G}$) of Pb/Ag films on inert glass substrates is substantially larger than for pure Ag films. These results are evidence that the structure of the underlying substrate exerts an influence on the size of the grains in QC films. We propose a qualitative explanation for this previously unencountered phenomenon.