In-situ straining with a MEMS device

Researchers from the Microspectroscopy group at PSI in a collaboration with the Politecnico di Milano, the Max-Born-Institute, and the National Cheng Kung University have developed a novel setup for the in situ application of tensile mechanical strains of several percentage points to freestanding ferroic thin films compatible with soft X-ray dichroic ptychography imaging. The work has been published as Editors' suggestion within Physical Review B.

In this work, the researchers have modified a microelectromechanical system (MEMS) device by means of focused ion beam (FIB) milling and subsequently transferred a micrometric lamella cut out of a freestanding thin film between the two cantilevers of the MEMS device. By applying a voltage to the MEMS device, causing the cantilevers to bend outward, a tensile strain up to 10% can be applied to the freestanding film. As the lamella is bridging two separate cantilevers, this setup is compatible with transmission X-ray microscopy.

A proof-of-concept experiment where the performances of the setup were demonstrated was carried out. In this experiment, the ferroelectric and spin cycloidal configuration of a 80 nm thick freestanding (001) BiFeO₃ lamella was imaged by soft X-ray dichroic ptychography as a function of the applied strain. A combined rotation and change in the period of the spin cycloid in the BiFeO₃ could be successfully investigated.