Maskless Micro/Nanopatterning and Bipolar Electrical Rectification of MoS Flakes Through Femtosecond Laser Direct Writing.

Molybdenum disulfide (MoS) micro/nanostructures are desirable for tuning electronic properties, developing required functionality, and improving the existing performance of multilayer MoS devices. This work presents a useful method to flexibly microprocess multilayer MoS flakes through femtosecond laser pulse direct writing, which can directly fabricate regular MoS nanoribbon arrays with ribbon widths of 179, 152, 116, 98, and 77 nm, and arbitrarily pattern MoS 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 MoS, 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 MoS 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 MoS 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 MoS such as logic circuits, complementary circuits, chemical sensors, and p-n diodes.