Vanadium dioxide (VO 2 ) is an archetypal Mott material with a metal-insulator transition (MIT) near room temperature. In thin films, this transition is affected by substrate-induced strain but, as film thickness increases, the strain is gradually relaxed and the bulk properties are recovered.Epitaxial films of VO 2 on (001)-oriented rutile titanium dioxide (TiO 2 ) relax substrate strain by forming a network of fracture lines that crisscross the film along well-defined crystallographic directions. This work shows that the electronic properties associated with these lines result in a pattern that resembles a "street map" of fully strained metallic VO 2 blocks separated by insulating VO 2 stripes. Each block of VO 2 is thus electronically self-insulated from its neighbors and its MIT can be locally induced optically with a laser, or electronically via the tip of a scanning probe microscope, so that the films behave functionally as self-patterned pixel arrays.

The morphological and microstructural evolution associated with an exsolution driven selfnanostructuration process of La 0.7 Sr 0.3 MnO 3 films, is investigated using scanning force microscopy, reciprocal space mapping and transmission electron microscopy. The focus is placed on the misfit strain relaxation mechanism. Surfaces with atomically flat terraces are already developed after 1hour at 1000 ºC while first fingerprints of phase exsolution do not appear until 9-10 hours. X-ray diffraction reciprocal-space mapping reveals that 24 nm thick films remain strained during the whole microstructural evolution, while 12 hour annealed films undergo almost total plastic relaxation of the misfit strain at a thickness of 60 nm. Overall, these results point to a kinetic limitation of dislocation mechanisms. It is argued that chemical relaxation provides a significant contribution to misfit strain relief.

In the past decade, the rich physics exhibited by solid interfaces combining octahedral framework structures of transition-metal oxides has fascinated the materials science community. However, their behavior still eludes the current understanding of classical semiconductor and metal epitaxy. The reason for that is rooted in the surprising versatility of linked coordination units to adapt to a dissimilar substrate and the strong sensitivity of strongly correlated electron oxides to external perturbations. The confluence of atomic control in oxide thin film epitaxy, state of the art high spatial resolution characterization techniques, and electronic-structure computations, has allowed in recent years to obtain first insights on the microscopic mechanisms governing the epitaxy of these complex materials.

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