Drastic change in electronic domain structures via strong elastic coupling inVO2films

Visualization of local phase transition behaviors near dislocations in epitaxial VO2/TiO2 thin films

“…[http://dx.doi.org/10.1063/1.4934943] VO 2 shows a tetragonal-monoclinic structural phase transition (SPT) as well as a metal-insulator transition (MIT) near room temperature. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Due to this unique feature, both Mott transition and Peierls instability have been considered as key theoretical components in explaining this intriguing phase transition phenomenon. [1][2][3][4][5][6][7][8][9] The structural distortion, occurring during the SPT, affects the orbital occupancy which directly changes the electron-electron correlation.…”

“…[6][7][8][9][10] Thus, strain states of VO 2 can significantly modify the MIT behaviors, as reported in many thin film studies; additionally, strain states can be controlled by varying the substrates and/or thickness of the samples. [7][8][9][10][11][12][13][14][15] Thick films, especially samples with a large lattice mismatch, may have nonuniform strain states and contain structural defects. [10][11][12][13][14] Local phase transition behaviors may vary depending on the lattice spacing at specific locations and the interaction with nearby regions.…”

“…[7][8][9][10][11][12][13][14][15] Thick films, especially samples with a large lattice mismatch, may have nonuniform strain states and contain structural defects. [10][11][12][13][14] Local phase transition behaviors may vary depending on the lattice spacing at specific locations and the interaction with nearby regions. Thus, contributions from all nanoscopic domains exhibiting diverse transition behaviors determine the overall macroscopic physical properties (e.g., MIT temperature and resistivity) of the thin films.…”

“…Ultrathin epitaxial VO 2 films on the TiO 2 (001) substrates can have large-sized grains, due to the small lattice mismatch (À0.86%). [7][8][9][10][11][12][13][14][15] As the thickness increases, the strain relaxation in the VO 2 /TiO 2 heterostructures is known to create cracks and dislocations. 11,12 Cracks deform the VO 2 lattice in their vicinity, which may alter the local phase transition behaviors.…”

Controlling phase separation in vanadium dioxide thin films via substrate engineering

“…IR near-field imaging studies revealed that the phase transition temperature and the microscopic phase separation patterns of VO 2 films vary considerably when grown on different substrates [10,13]. These distinct substrate and film thickness dependent mesoscopic patterns in highly oriented transition metal oxide thin films originate from the epitaxial strain due to lattice mismatch [10,[14][15][16]. For example, in VO 2 films on a (110) R TiO 2 substrate with an in-plane rutile c R axis, stripe-like unidirectional phase separations are evident [11].…”