Polymer Dopants for Work Function Tuning of 2-D Materials

Poster Session: 

B

Presenter: 

Ryan Selhorst

Authors: 

Ryan Selhorst, Peijian Wang, Ashwin Ramasubramaniam, Michael Barnes, Todd Emrick

Author Affiliation: 

University of Massachusetts Amherst

Abstract: 

We present polymers bearing sulfur-rich moieties capable of both n- and p- doping semiconducting molybdenum disulfide (MoS2). Kelvin probe force microscopy (KPFM) reveals that polymer n-dopants, containing tetrathiafulvalene (TTF), decrease the work function after a thin layer of the polymer is applied to the surface of MoS2. These polymers further stabilize suspensions of MoS2 nanosheets demonstrating strong physisorption of TTF to the basal plane of MoS2, hypothesized to facilitate charge transfer. Similarly, we show the synthesis of polyurethanes containing bithiazolidinylidene (BT), a novel sulfur-rich electron acceptor, and its p-doping effect on MoS2. Utilizing substrates of different dielectric constants significantly enhances the magnitude of work function modulation, exercising further control over the electronic properties of MoS2. These experiments present a facile alternative to conventional irreversible and damaging doping methods for semiconductors and demonstrate bidirectional control over the work function of MoS2.