Ultimate strength measurements on freestanding SrTiO₃ thin films

The last two decades have seen enormous growth in the field of nanoengineering and nanomechanics using thin sheets owing to the variety of 2D materials available to us (2D Mater. 5, 032005 (2018)). With new advances in thin film growth techniques(Nat. Mater. 15, 1255–1260 (2016)), a new class of functional oxide thin films which are freestanding can be produced and readily incorporated in such nanomechanical implementations. However functional oxides are rigid and brittle in bulk, so it becomes imperative to verify the feasibility of nanomechanical deformations by investigating the breaking strength of these thin films. Here we report measurements of the ultimate strength of SrTiO₃ thin films using an atomic force microscope (AFM) by impinging upon a freestanding drumhead with an AFM tip. We demonstrate that in the sub-20 nm thickness regime of these thin films, SrTiO₃ can withstand an elastic extension of ~ 6% which is more than an order of magnitude higher than that for bulk. Furthermore, we also show that the fracture point of these films with respect to applied force is robust thus demonstrating their potential for use in nanomechanical platforms and devices.