Highly Conductive Optical Quality Solution-Processed Films of 2D Titanium Carbide

• Published in: Advanced functional materials 2016-06, Vol.26 (23), p.4162-4168
• Main Authors: Dillon, Andrew D., Ghidiu, Michael J., Krick, Alex L., Griggs, Justin, May, Steven J., Gogotsi, Yury, Barsoum, Michel W., Fafarman, Aaron T.
• Format: Article
• Language: English
• Subjects: 2D materials; Alignment; Conductivity; Constituents; MXenes; Nanostructure; Optical properties; Plasmonics; Resistivity; solution-processed; transparent conductors; Two dimensional
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201600357

MXenes comprise a new class of solution‐dispersable, 2D nanomaterials formed from transition metal carbides and nitrides such as Ti3C2. Here, it is shown that 2D Ti3C2 can be assembled from aqueous solutions into optical quality, nanometer thin films that, at 6500 S cm−1, surpass the conductivity of other solution‐processed 2D materials, while simultaneously transmitting >97% of visible light per‐nanometer thickness. It is shown that this high conductivity is due to a metal‐like free‐electron density as well as a high degree of coplanar alignment of individual nanosheets achieved through spincasting. Consequently, the spincast films exhibit conductivity over a macroscopic scale that is comparable to the intrinsic conductivity of the constituent 2D sheets. Additionally, optical characterization over the ultraviolet‐to‐near‐infrared range reveals the onset of free‐electron plasma oscillations above 1130 nm. Ti3C2 is therefore a potential building block for plasmonic applications at near‐infrared wavelengths and constitutes the first example of a new class of solution‐processed, carbide‐based 2D optoelectronic materials. An aqueous colloidal Ti3C2‐based MXene is assembled by spincasting into highly aligned, optical‐quality films with a conductivity of 6500 S cm−1. The electrical and optical properties of this material are measured revealing that it is plasmonic in the near‐infrared. Comparison of the in‐plane DC conductivity and the optical conductivity indicates that the macroscopic material is nearly as conductive as the constituent nanosheets.