Strain insensitive flexible photodetector based on molybdenum ditelluride/molybdenum disulfide heterostructure

Flexible electronic and optoelectronic devices are highly desirable for various emerging applications, such as human-computer interfaces, wearable medical electronics, flexible display, etc. Layered two-dimensional (2D) material is one of the most promising types of materials to develop flexible devices due to its atomically thin thickness, which gives it excellent flexibility and mechanical endurance. However, the 2D material devices fabricated on flexible substrate inevitably suffer from mechanical deformation, which can severely affect device performances, resulting in function degradation and even failure. In this work, we propose a strain insensitive flexible photodetector based on MoS2/MoTe2 heterostructure on polyimide substrate, which provides a feasible approach to cancel unpredicted impacts of strain on the device performances. Specifically, the MoS2/MoTe2 heterostructure is deposited with 4 electrodes to form three independent devices of MoS2 FET, MoTe2 FET and MoS2/MoTe2 heterojunction. Among them, the MoS2/MoTe2 heterojunction is used as the photodetector, while the MoS2 FET is used as a strain gauge to calibrate the photo detection result. Such configuration is enabled by the Schottky barrier formed between the electrodes and the MoS2 flake, which leads to obvious and negligible photo response of MoS2/MoTe2 heterojunction and MoS2 FET, respectively, under low source-drain bias (ex. 10 mV). The experimental results show that the proposed mechanism can not only calibrate the photo response to cancel strain effect, but also successfully differentiate the wavelength (with fixed power) or power (with fixed wavelength) of light illumination.