Stable, highly-responsive and broadband photodetection based on large-area multilayered WS2 films grown by pulsed-laser deposition

Abstract

The progress in the field of graphene has aroused a renaissance of keen research interest in layered transition metal dichalcogenides (TMDs). Tungsten disulfide (WS₂), a typical TMD with favorable semiconducting band gap and strong light–matter interaction, exhibits great potential for highly-responsive photodetection. However, WS₂-based photodetection is currently unsatisfactory due to the low optical absorption (2%–10%) and poor carrier mobility (0.01–0.91 cm² V⁻¹ s⁻¹) of the thin WS₂ layers grown by chemical vapor deposition (CVD). Here, we introduce pulsed-laser deposition (PLD) to prepare multilayered WS₂ films. Large-area WS₂ films of the magnitude of cm² are achieved. Comparative measurements of a WS₂-based photoresistor demonstrate its stable broadband photoresponse from 370 to 1064 nm, the broadest range demonstrated in WS₂ photodetectors. Benefiting from the large optical absorbance (40%–85%) and high carrier mobility (31 cm² V⁻¹ s⁻¹), the responsivity of the device approaches a high value of 0.51 A W⁻¹ in an ambient environment. Such a performance far surpasses the CVD-grown WS₂-based photodetectors (μA W⁻¹). In a vacuum environment, the responsivity is further enhanced to 0.70 A W⁻¹ along with an external quantum efficiency of 137% and a photodetectivity of 2.7 × 10⁹ cm Hz^1/2 W⁻¹. These findings stress that the PLD-grown WS₂ film may constitute a new paradigm for the next-generation stable, broadband and highly-responsive photodetectors.