Area of research
Materials Chemistry · Electrical and Electronic Engineering
Research interest
Research topics from publications: Photoconductivity of few-layered p -WSe 2 phototransistors via multi-terminal measurements; Evidence for impact ionization in vanadium dioxide. Representative work: Recently, two-dimensional materials and in particular transition metal dichalcogenides (TMDs) have been extensively studied because of their strong light-matter interaction and the remarkable optoelectronic response of their field-effect transistors (FETs). Here, we report a photoconductivity study from FETs built from few-layers of p-WSe2 measured in a multi-terminal configuration under illumination by a 532 nm laser source. The photogenerated current was measured as a function of the incident optical power, of the drain-to-source bias and of the gate voltage. We observe a considerably larger photoconductivity when the phototransistors were measured via a four-terminal configuration when co Pump-probe optical spectroscopy was used to investigate proposed charge-carrier multiplication via impact ionization in the ${M}_{1}$ insulating phase of ${\mathrm{VO}}_{2}$. By comparing the transient reflectivities of the film when pumped at less than and then more than twice the band-gap energy, we observed a larger ultrafast response with the higher energy pump color while the film was still transiently in the insulating phase. We additionally identified multiple time scales within the charge dynamics and analyzed how these changed when the pump and probe wavelengths were varied. This experiment provided evidence that a fast carrier multiplication process, i.e., impact ionization, acts e