Influence of Mg doping on the ultrafast electron dynamics of VO2 films

Broadband time-resolved measurements of pristine and Mg-doped vanadium dioxide (VO2) films are presented herein. The two films were synthesized on float glass and K-glass (SnO2 coated) substrates, respectively. Spectral and temporal dynamics of the insulator to metal transition are accessed via femtosecond pump-probe spectroscopy. Reflection and transmission signals were recorded during sample perturbation by high photon energy, 3.1 eV, laser pulses for below and above the transition threshold values of the excitation fluence. Changes of the spectral dynamics due to photoexcitation are tracked throughout the visible spectrum by use of broadband white-light supercontinuum pulses. The study demonstrates a faster temporal response of the Mg-doped film across the probed spectrum. The system is photoexcited to the metallic state reaching a plateau value in signal transmission within less than 5 ps post-pulse perturbation. These optimized trends of the Mg-doped VO2 films hold promise for applications necessitating ultrafast optical switching capabilities.