Giant Photo-Induced Chirality in Thin Film Ge2Sb2Te5 (GST)
Research by the Electron Image Analysis Group and collaborators from the Clarendon Laboratory, Department of Engineering Science, Optoelectronics Research Centre, Diamond Light Source and Institute of Materials Research and Engineering (A*STAR), as reported in physica status solidi (RRL), demonstrates that chirality can be rapidly imprinted in originally achiral amorphous GST thin films by illuminating the films with pulsed circularly polarised (chiral) laser light for less than 2μs in total. The laser-treated GST films display a giant chiral signal as measured by synchrotron circular dichroism spectroscopy. The effects of laser fluence and film thickness on the signal are reported and the optical observations are correlated with structural studies by electron diffraction and model simulations. It is suggested that alignment of reamorphized fragments in the crystallized film along the electric field vector of the light forms the chiral centers responsible for the observed signal. This work has wide-ranging implications for chirality induction in other materials and potential applications in chiral switching and sensing in optoelectronics.