Description
Ultrafast excitation can drive distinct structural pathways in thin films, enabling control of lattice order and the associated electronic response. In this poster, we compare GaS and VO2 thin films as two complementary systems for femtosecond-laser-induced structural switching. For GaS, X-ray diffraction measurements combined with ab initio calculations identify an irreversible modification threshold near 10 mJ cm−2 and reveal an atomic rearrangement that preserves the in-plane structure while elongating the c-axis from 23.174 to 25.38 Å. This distortion drives a direct-to-indirect band-gap transition with an increase of about 0.45 eV. Preliminary results on VO2 extend the comparison to a correlated oxide with photoinduced switching behavior. Together, these two systems illustrate how femtosecond excitation can induce different structure–property pathways in thin films, linking excitation conditions, lattice modification, and electronic functionality.
