Writing monolithic integrated circuits on a two-dimensional semiconductor with a scanning light probe

The development of complex electronics based on two-dimensional (2D) materials will require the integration of a large number of 2D devices into circuits. However, a practical method of assembling such devices into integrated circuits remains elusive. Here we show that a scanning visible light probe can be used to directly write electrical circuitry onto the 2D semiconductor molybdenum ditelluride (2H-MoTe2). Laser light illumination over metal patterns deposited onto 2D channels of 2H-MoTe2 can convert the channels from an n-type semiconductor to a p-type semiconductor, by creating adatom-vacancy clusters in the host lattice. With this process, diffusive doping profiles can be controlled at the submicrometre scale and doping concentrations can be tuned, allowing the channel sheet resistance to be varied over four orders of magnitudes. Our doping method can be used to assemble both n- and p-doped channels within the same atomic plane, which allows us to fabricate 2D device arrays of n-p-n (p-n-p) bipolar junction transistor amplifiers and radial p-n photovoltaic cells.