From Electric Doping Control to Thermal Defect Nucleation in Perovskites

Simultaneous optical microscopy and electric transport measurements on
La0.7Sr0.3MnO3 nanobridges, grown on SrTiO3 (STO), show direct evidence
of directional oxygen vacancy migration under large voltage bias. Comparative
study on discontinuous structures, with voltages applied across a
micron-scale gap, demonstrates that high electric fields induce electrolytic
modifications confined to the anode. Extensive electromigration is shown to
induce the formation of linear surface scars on the STO substrate, following
well defined crystallographic directions. The reproducible triggering of these
surface dislocations is demonstrated, unveiling their thermal rather than electrical
origin and it is shown that they do not represent electroformed conduction
channels. High-resolution scanning transmission electron microscopy
imaging reveals that the scars correspond to nanometer scale steps caused
by (101) gliding planes in the STO caused by the proliferation of edge dislocations
and local lattice expansion. These findings shed light on selective
electrically-controlled atom migration and its role in structural modification of
functional oxides, opening a unique avenue for ionotronic device design.