Electronic and optical properties of strain-locked metallic Ti2O3 films

• Published in: Current applied physics 2023-03, Vol.47, p.9-14
• Main Authors: Lahneman, D.J., Kim, H., Jiang, H., Mathews, S.A., Lock, E., Prestigiacomo, J., Qazilbash, M.M., Rohde, C., Piqué, A.
• Format: Article
• Language: English
• Subjects: Electrical properties; Optical properties; Phase transition; Strained films; Titanium sesquioxide
• ISSN: 1567-1739; 1878-1675
• DOI: 10.1016/j.cap.2022.12.006

We successfully grow corundum structured Ti2O3 films on c-plane sapphire substrates using pulsed laser deposition. Temperature dependent resistivity measurements show that a metal to insulator transition (MIT) is suppressed, showing conducting behavior at all temperatures. Samples still show an increase in resistivity as temperature is decreased, a characteristic indicative of a semiconducting phase. Our films exhibit grain size on the order of 30 nm which induce a strain consistent with nanoparticle Ti2O3 showing a (c/a) ratio of 2.7. The imposed strain causes an increase in the c-axis length as the temperature is decreased, and thereby suppresses the transition to an insulating phase. Our optical data agrees with this result, showing the lack of a band gap and the electronic structure consistent with bulk high temperature metallic Ti2O3 with the a1g - egπ interband transition shifted down to 0.7 eV from its bulk insulating value of ∼1 eV. [Display omitted] •Deposited corundum structured Ti2O3 films on c-cut sapphire substrates.•Metal-insulator transition of Ti2O3 films is suppressed by film strain.•Imposed film strain prevents the band gap from opening in Ti2O3 film.•New electrical and optical properties of Ti2O3 films compared to bulk form.