Effect of oxygen and ozone on p-type doping of ultra-thin WSe2 and MoSe2 field effect transistors

Abstract

We report on the p-type doping effect of oxygen and ozone molecules on mono- and few-layer WSe₂ and MoSe₂ field effect transistors. We show that adsorption of oxygen and ozone under ambient conditions results in subtantial doping and corresponding enhancement in the hole conductivity of the devices. Ozone-induced doping is found to be rapid and efficient, saturating within minutes of exposure whereas oxygen-induced doping occurs over a period of days to reach the equivalent level of doping. Our observations reveal that the water adlayer on the material surface plays a crucial role in solubilizing oxygen and ozone and in forming a redox couple with a large chemical potential.