Electron donor or acceptor behavior of a AuCl3 dopant manipulated by dip-pen nanolithography on a MoS2 thin-film transistor

Gold (III) chloride (AuCl3) is a well-known electron acceptor (p-type dopant). Here, the electron donor or acceptor behavior of a AuCl3 dopant on a molybdenum disulfide (MoS2) thin-film transistor (TFT) is demonstrated by line patterning a concentration-adjusted AuCl3 ink with dip-pen nanolithography (DPN). At a low ink concentration (c(low)) (< 3 mM AuCl3), the Au molecules (Au-0) are transferred and contact with the MoS2 , resulting in an electron donor effect on the MoS2. In contrast, at a high ink concentration (c(high)) (>= 3 mM), the Au3+ is transferred from the AuCl3 salt loaded on the DPN tip probe and reacts with the MoS2 , resulting in an electron acceptor effect. For a c(low) , the mobility of the MoS2 TFT increases when the Au coverage is larger than 10%. For a c(high) , the mobility decreases regardless of the Au coverage. This DPN patterning of the concentration-adjusted AuCl3 inks can be applied to fabricate junction in the local area of MoS2 devices without using complicated lithography. As a result, enhancement of the photoresponse as well as increasing the rectifying behavior of MoS2 devices are demonstrated with the bandgap controlled junction obtained by two direct DPN line patterning operations with the concentration-adjusted AuCl3 inks.