(439e) Wrinkled MoS2 Field-Effect Transistors

Manipulating the band structure through local-strain is an effective route for tailoring properties of 2D transition metal dichalcogenides (TMDs). Here, we show that wrinkles (wavelength = 100 nm - 10 μm) can induce uniaxial strain in multilayer MoS₂ flakes (more than 20 layers), a resultant phonon softening (2 cm^-1/% strain for Raman E¹_2g mode), and reduction of the optical bandgap (40 meV/% strain). We also report on the influence of the geometric shapes (symmetric, asymmetric and folded) of wrinkles on the strain and optical band gap in the wrinkled MoS₂. In the field-effect transistor and optoelectronic device studies, a larger transport barrier (= 0.815 meV) is exhibited in the transverse direction of the MoS₂ wrinkle, a 1000-fold improvement of on/off ratio in dark, and a 10-fold photocurrent enhancement compared to the flat MoS₂ devices are also observed. This is attributed to the exciton funnel effect and built-in potential induced by band gap reduction and doping variation in wrinkled devices. The wrinkle induced tunability of bandgap and transport in thin film devices can potentially evolve flexible electronic and optoelectronic devices based on 2D TMDs.