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Epitaxial La-doped BaSnO 3 films were grown in an adsorption-controlled regime by molecular-beam epitaxy, where the excess volatile SnO x desorbs from the film surface. A film grown on a (001) DyScO 3 substrate exhibited a mobility of 183 cm 2 ·V -1 ·s -1 at room temperature and 400 cm 2 ·V -1 ·s -1 at 10 K, despite the high concentration (1.2×10 11 cm -2 ) of threading dislocations present. In comparison to other reports, we observe a much lower concentration of (BaO) 2 Ruddlesden-Popper crystallographic shear faults. This suggests that in addition to threading dislocations that other defects-possibly (BaO) 2 crystallographic shear defects or point defects-significantly reduce the electron mobility.

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First-principles calculations based on density functional theory have been used to calculate the temperature-dependent dilute tracer diffusion coefficients for 47 substitutional alloying elements in hexagonal closed packed (hcp) Mg by combining transition state theory and an 8-frequency model. The minimum energy pathways and the saddle point configurations during solute migration are calculated with the climbing image nudged elastic band method. Vibrational properties are obtained using the quasi-harmonic Debye model with inputs from first-principles calculations. An improved generalized gradient approximation of PBEsol is used in the present first-principles calculations, which is able to well describe both vacancy formation energies and vibrational properties. It is found that the solute diffusion coefficients in dilute hcp Mg are roughly inversely proportional to bulk modulus, which reflects the solutes' bonding to Mg. Transition metal elements with d electrons show strong interactions with Mg and have large diffusion activation energies. Correlation effects are not negligible for solutes Ca, Na, Sr, Se, Te, and Y, in which the direct solute migration barriers are much smaller than the solvent (Mg) migration barriers. Calculated diffusion coefficients are in remarkable agreement with available experimental data in the literature.

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