Mechanism linking Al grain size to the underlying (In,Fe)As lattice constant

Determine the mechanism by which the grain size of epitaxial Al films is linked to the lattice constant of the underlying strained (In,Fe)As layer, in order to explain the systematic variation of the Al superconducting critical temperature.

Background

The paper reports that the superconducting critical temperature of the Al films varies systematically with the in-plane lattice constant and compressive strain of the underlying (In,Fe)As layer. Atomic-force microscopy shows that both the Al surface roughness and average grain size increase as the compressive strain increases, while the critical temperature decreases. The observed critical-temperature dependence can be fitted using a model for grain-size-enhanced superconductivity in Al films, but this empirical correlation does not establish why the lattice constant or strain of (In,Fe)As controls the Al grain size. The unresolved problem is therefore to identify the microscopic growth or interfacial mechanism connecting the strained ferromagnetic-semiconductor substrate to the Al film morphology and resulting superconducting properties.