Laser trimming for lithography-free fabrications of MoS₂ devices

Single-layer MoS₂ produced by mechanical exfoliation is usually connected to thicker and multilayer regions. We show a facile laser trimming method to insulate single-layer MoS₂ regions from thicker ones. We demonstrate, through electrical characterization, that the laser trimming method can be used to pattern single-layer MoS₂ channels with regular geometry and electrically disconnected from the thicker areas. Scanning photocurrent microscope further confirms that in the as-deposited flake (connected to a multilayer area) most of the photocurrent is being generated in the thicker flake region. After laser trimming, scanning photocurrent microscopy shows how only the single-layer MoS₂ region contributes to the photocurrent generation. The presented method is a direct-write and lithography-free (no need of resist or wet chemicals) alternative to reactive ion etching process to pattern the flakes that can be easily adopted by many research groups fabricating devices with MoS₂ and similar two-dimensional materials.