Functional polymeric passivation-led improvement of bias stress with long-term durability of edge-rich nanoporous MoS2 thin-film transistors

Abstract

Nanoporous patterning of two-dimensional materials using block copolymer lithography has drawn much attention. Lateral edge exposures made by the nanoporous patterning provide electrical and optical characteristics that are different from the original materials. However, nanopatterning processes inevitably generate edge exposure and surface defects that may result in poor reliability and reproducibility of the devices. In this study, we propose a reliable method to passivate nanoporous molybdenum disulfide (MoS2) thin-film transistors (TFTs) using polymer thin films, synthesized by initiated chemical vapor deposition (iCVD) to improve the electrical stability of nanoporous MoS2 TFTs. To this end, functional polymer films of electron-donating poly(1-vinylimidzole) (pVI) and inert poly(1H,1H,2H,2H-perfluorodecyl methacrylate) (pPFDMA) were utilized as passivation layers on nanoporous MoS2 TFTs. An n-type doping effect was observed in the pVI-deposited nanoporous MoS2 film due to the electron-donating imidazole ring, whereas the inert pPFDMA efficiently stabilized the electrical characteristics of the nanoporous MoS2 TFTs. Moreover, the hydrophobic fluoroalkyl chain of the pPFDMA film efficiently prevented oxygen and moisture adsorption on the nanoporous MoS2. The superior passivation effect of the pPFDMA layer was confirmed using gate-bias stress tests and long-term storage tests under ambient conditions.