AVS 61st International Symposium & Exhibition
    2D Materials Focus Topic Tuesday Sessions
       Session 2D+AS+BI+PS+SS-TuM

Invited Paper 2D+AS+BI+PS+SS-TuM1
Phase Engineering in 2D Transition Metal Dichalcogenides

Tuesday, November 11, 2014, 8:00 am, Room 310

Session: 2D Materials: Surface Chemistry, Functionalization, Bio and Sensor Applications
Presenter: Manish Chhowalla, Rutgers University
Correspondent: Click to Email
Two-dimensional transition metal dichalcogenides (2D TMDs) — whose generalized formula is MX2, where M is a transition metal of groups 4–7 and X is a chalcogen — exhibit versatile chemistry and consist of a family of over 40 compounds that range from complex metals to semiconductors to insulator. Complex metal TMDs assume the 1T phase where the transition metal atom coordination is octahedral. The 2H phase is stable in semiconducting TMDs where the coordination of metal atoms is trigonal prismatic. Unlike mechanical exfoliation and chemical vapor deposition, chemical exfoliation of semiconducting layered TMDs yields monolayered nanosheets with heterogeneous atomic structure consisting of metallic (1T) and semiconducting (2H) phases. Metal (1T phase) to semiconductor (2H phase) transition can be achieved via mild annealing of exfoliated materials. Semiconductor to metal transitions can be achieved via chemistry. The 1T phase in semiconducting TMDs has scarcely been studied but it deserves urgent attention as it exhibits promise as a hydrogen evolution catalyst and as contact electrode in electronic devices. We will describe these phase transitions in semiconducting TMDs and provide examples of how we have learned to exploit them for covalent functionalization, enhanced catalytic and electronic performance.