Growth control of corundum-derivative MnSnO₃ thin films by pulsed-laser deposition

The periodic arrangement of equimolar two cations in the corundum structure produces the ilmenite-type and LiNbO₃-type orderings. The phase (polymorphism) control is one of the important topics in solid-state chemistry. Using a pulsed-laser deposition technique, we examined the formation of MnSnO₃ films as a function of oxygen gas pressure. Under the optimal low oxygen gas pressure, c-axis oriented single-crystalline films of the ilmenite-type MnSnO₃ were synthesized on Al₂O₃ (0001). We found that, with an increase of oxygen gas pressure, x-ray diffraction peaks characteristic of the ilmenite-type ordering disappeared and the c-axis length approached that of the LiNbO₃-type MnSnO₃ while the crystal structure retained basic features of corundum derivatives. The optical bandgap measurement revealed the decrease of bandgap in the LiNbO₃-type (or disordered corundum-type) MnSnO₃. The thin-film approach can add a new degree of freedom in the control of structural and physical properties in corundum-derivative oxides.