Detection and analysis of structural changes in MoO3/Ag heterostructure by ultrafast transient absorption spectroscopy

Ultrafast transient absorption spectroscopy (UFTS) is a widely used technique to determine the change in optical parameters on laser irradiation and can highlight the pathways and the lifetime of decay of the charge carriers. Here, UFTS was used to detect the structural changes occurring in a MoO₃/Ag heterostructure because of dewetting and dealloying. A comparative study of transient absorption behavior of samples exposed to different temperatures indicated a change in phase and crystallinity of the film. Later through GI-XRD, it was concluded that the MoO₃ film has become crystalline at 350 °C along α-(110) plane. A wide plasmonic band in UFTS data of dealloyed sample followed by FESEM showed randomly distributed Ag-Mo nanoporous clusters (315 nm - 6 μm). Tuning of surface plasmon resonance (~19 nm) was seen with etching time. This study proves UFTS's suitability for correlating the structural change in a film or heterostructure of films with spectroscopic results.