We investigate novel oxide shape memory films and corresponding nanoactuators based on the reversible monoclinic / tetragonal transformation in vanadium oxide (VO2) and (V-M)O2 compounds. Among the known functional ceramics exhibiting the shape memory effect, VO2 is of special interest, as it combines multifunctional properties like a metal-insulator transition at 68°C, thermoelasticity and superelasticity with a large effect size. Transformation strains of 1% in c-, -0.6% and -0.1% in a- and b-direction of the rutile structure, respectively, and a high Young’s modulus of 140 GPa promise large force and high work density. Nanofabrication processes are developed using these films as base materials to realize free-standing (V-M)O2 nanoactuators with lateral dimensions down to 100 nm. Their coupled electro-thermo-mechanical performance is characterized by novel in-situ methods in order to understand the scaling and size-dependence of structure, shape memory effect and superelasticity.
Rastjoo, Sanaz PhD student
Fechner, Randy PhD student