Bilayer MoS2 phototransistor deposited on a flexible substrate

A new phototransistor with a MoS2 bilayer deposited on a polyimide substrate was fabricated using pulsed-laser deposition technique. The structural and optical properties of the bilayer MoS2 films were characterized by Raman, photoluminescence and optical absorption spectroscopy. The photocurrent generated by a laser light with the wavelength of 532 nm in the top gate flexible field effect transistor was determined for specified drain and gate voltages. The photoresponsivity of the device could be adjusted over a wide range by controlling the gate and drain voltages. At this, the photoresponsivity value could exceed 12.5 mA/W. The structure showed switching behavior with a characteristic time of approximately 10 ms in response to pulsed illumination. The photocurrent changed significantly due to compressive or tensile strain induced by the bent substrate, which affected the band-gap value of the ultrathin MoS2 layers. The proposed structure may find potential applications in flexible electronics, such as e.g. for nanoscale flexible photodetectors or stress sensors.