The properties of superconducting thin films were correlated with molecular beam epitaxy deposition parameters. The possibility of using a thermochemical analysis of MgB2 synthesis to predict optimum growth conditions was demonstrated. The growth of stoichiometric films with improved crystalline quality could be achieved at higher temperatures by using high reactant fluxes. High B flux enhanced the sticking coefficient of Mg and facilitated higher growth temperatures and improved structural and electrical properties. With a Mg flux of about 16Å/s and a substrate temperature of 300C, a superconducting transition temperature of 37.7K with a narrow transition width of less than 1K was observed. This work showed that a growth model must include the strong dependence of the Mg sticking coefficient upon B flux.

Thermochemical Analysis of MgB2 Synthesis by Molecular-Beam Epitaxy. J.Kim, R.K.Singh, J.M.Rowell, N.Newman, L.Gu, D.J.Smith: Journal of Crystal Growth, 2004, 270[1-2], 107-12