Observing femtosecond laser damage failure of a MoS2 thin film as an ultrafast photoacoustic transducer

Abstract

Utilizing a femtosecond laser pump–probe system, we perform a failure test of laser damage with a 55-nm-thick MoS2 as an ultrafast photoacoustic transducer. By increasing pump laser fluence until the laser damage occurs, the longitudinal coherent acoustic phonon oscillation of MoS2 layers and the emitted picosecond acoustic pulse have been simultaneously measured and analyzed. Laser excitation and damage thresholds of 27.58 and 579.18 μJ/cm2 have been measured, respectively. Dramatic photothermal effects are further observed with increasing pump fluences, which lead to MoS2 lattice softening and MoS2/glass interface annealing. When the pump fluence is increased to 579.18 μJ/cm2, the laser damage suddenly occurred and created a nanohole on MoS2, indicating a damage mechanism of the plasma explosion facilitated by photothermal effects. Our results provide insight into the rational design and thermal management of next-generation ultrafast photoacoustic transducers with 2D layered semiconductors.