Surface morphology and thickness dependence of the properties ofMgB2 thin films by hybrid physical–chemical vapor deposition

Abstract

The influence of growth parameters in hybrid physical–chemicalvapor deposition (HPCVD) on surface morphologies ofMgB2 thinfilms, and the dependence of their properties on film thickness are systematically studied. As the HPCVDMgB2 films grow in the Volmer–Weber mode, where islands coalesce into continuousfilms, the grain size has an important influence on the film morphology. We foundthat films deposited with higher growth rates have larger grains, and a largergrain size appears to correspond to a larger film roughness. Under optimizeddeposition conditions, the surface root mean square (RMS) roughness is 1.2 nm over a1 µm × 1 µm area for a 100 nm thick film. The surface morphology does notdirectly affect the structural and superconducting properties of theMgB2 films. The resultsof ultrathin MgB2 films, as thin as 10 nm, with excellent superconducting properties are also presented in thispaper.