Evidence of lattice deformation induced metal-insulator transition in Ti2O3

We synthesized Ti(2)O(3 )epitaxial films with continuously varying ratios of the c -axis to a -axis lattice constants (c/a ratios) on 4H-SiC (0001) substrates and investigated their structural and electronic properties. Ti2O3 films with a wide range of c/a ratios were fabricated in a controllable fashion by changing the growth temperature. As the c/a ratio at room temperature increased, the metal-insulator transition (MIT) temperature systematically de-creased and eventually the MIT disappeared. Detailed analyses revealed that the MIT occurred at a critical c/a ratio of 2.68. The critical c/a ratio for the occurrence of the MIT was also reproduced by density functional theory calculations. These results provide evidence for the origin of the MIT in Ti2O3. The MIT is not a Mott transition induced by temperature, but a gradual semimetal-to-semiconductor transition induced by lattice deformation.