Electron and hole doping of two-dimensional MoS2 for enabling heterojunction nanoelectronic devices

In this work, we have performed mechanical exfoliation of MoS2 from the bulk crystal using blue-tac tape to exfoliate MoS2 multiple times before transferring them onto the silicon dioxide substrates by viscoelastic stamping. We used the electron beam lithography process to pattern contacts onto the flakes before depositing 10 nm Ti/Au 100 nm contact using electron beam evaporation. We imparted n and p-type doping to the flakes using 1,2 dichloroethane and UV ozone treatment respectively. The n-type doping caused by 1,2, dichloroethane is due to the replacement of chlorine atoms by sulfur vacancies. The p-type doping by UV ozone is due to the solvation of ozone molecules by the water adlayer on MoS2. We have also discussed the impact of dopants and broadband lights as an external stimulus on the electrical behavior of MoS2. We see a difference in the behavior of the broadband lights on the electrical signal when doped via 1,2 dichloroethane compared to UV ozone. We saw significantly higher currents after doping in 1,2 dichloroethane even at low voltages attributed to the n-type doping effect. The broadband lights suppress the electrical response after 1,2 dichloroethane doping. We also saw a reduction in current levels for the lights off measurements after UV ozone doping compared to the doping by chloride molecules attributed to higher defect concentration in UV ozone generating excess charge carrier concentration attributing this effect.