Unexpected metal-insulator transition in thick Ca1-xSrxVO3 film on SrTiO3 (100) single crystal

作者：Takayanagi Makoto; Tsuchiya Takashi; Namiki Wataru; Ueda Shigenori; Minohara Makoto; Horiba Koji; Kumigashira Hiroshi; Terabe Kazuya; Higuchi Tohru

来源：Applied Physics Letters, 2018, 112(13): 133106.

DOI：10.1063/1.5021618

Epitaxial Ca1-xSrxVO3 (0 <= x <= 1) thin films were grown on (100)-oriented SrTiO3 substrates by using the pulsed laser deposition technique. In contrast to the previous report that metal-insulator transition (MIT) in Ca1-xSrxVO3 (CSVO) was achieved only for extremely thin films (several nm thick), MIT was observed at 39, 72, and 113K for films with a thickness of 50 nm. The electronic structure was investigated by hard and soft X-ray photoemission spectroscopy (HX-PES and SX-PES). The difference between these PES results was significant due to the variation in an escape depth of photoelectrons of PES. While HX-PES showed that the V2p(3/2) spectra consisted of four peaks (V5+, V4+, V3+, and V2+/(1+)), SX-PES showed only three peaks (V5+, V4+, and V3+). This difference can be caused by a strain from the substrate, which leads to the chemical disorder (V5+, V4+, V3+, and V2+/1+). The thin film near the substrate is affected by the strain. The positive magnetoresistance is attributed to the effect of electron-electron interactions in the disorder system. Therefore, the emergence of MIT can be explained by the electron-electron interactions from the chemical disorder due to the strain. Published by AIP Publishing.

• 出版日期2018-3-26