Maskless Micro/Nanopatterning and Bipolar Electrical Rectification of MoS₂ Flakes through Femtosecond Laser Direct Writing

Molybdenum disulfide (MoS₂) micro/nanostructures are desirable for tuning electronic properties, developing required functionality, and improving the existing performance of multilayer MoS₂ devices. This work presents a useful method to flexibly microprocess multilayer MoS₂ flakes through femtosecond laser pulse direct writing, which can directly fabricate regular MoS₂ nanoribbon arrays with ribbon widths of 179, 152, 116, 98, and 77 nm, and arbitrarily pattern MoS₂ flakes to form micro/nanostructures such as single nanoribbon, labyrinth array, and cross structure. This method is mask-free and simple and has high flexibility, strong controllability, and high precision. Moreover, numerous oxygen molecules are chemically and physically adsorbed on laser-processed MoS₂, attributed to roughness defect sites and edges of micro/nanostructures that contain numerous unsaturated edge sites and highly active centers. In addition, electrical tests of the field-effect transistor fabricated from the prepared MoS₂ nanoribbon arrays reveal new interesting features: output and transfer characteristics exhibit a strong rectification (not going through zero and bipolar conduction) of drain-source current, which is supposedly attributed to the parallel structures with many edge defects and p-type chemical doping of oxygen molecules on MoS₂ nanoribbon arrays. This work demonstrates the ability of femtosecond laser pulses to directly induce micro/nanostructures, property changes, and new device properties of two-dimensional materials, which may enable new applications in electronic devices based on MoS₂ such as logic circuits, complementary circuits, chemical sensors, and p-n diodes.