Titanum Carbide MXene Flakes as Novel 2D Metallic Solution-Processed Films
Authors: Mariano Marina , Mashtalir Olha , Antonio Francisco , Ryu Won-Hee , Deng Bingchen , Xia Fengnian , Gogotsi Yuri , Taylor André D. 
Published: February 2020

Two-dimensional (2D) materials have opened up a field for developing the next generation of optoelectronic devices thanks to their novel properties such as ultrafast charge injection/extraction, strong light-matter interactions (despite being atomically thin) and quantum confinement(1). In addition, recent advancements in liquid phase exfoliation has revealed a new scalable route to investigate these materials(2). A good example is the fabrication of graphene oxide (GO) where the high resistive precursor of graphene that has to be reduced to recover its favorable optoelectronic properties. In most cases, ultra-high temperature (>1000ºC) and toxic chemicals (hydrazine) have to be used. In this talk, we will present a novel solution-processed film containing T3C2Tx monolayers, a 2D crystal from the recently discovered family of MXenes(3). This new MXene 2D family can be synthetized by selectively etching the A element of the MAX phase and formed into stacks of transition metal carbides and carbonitrides. Indeed, MXenes have recently gained attention due their a hydrophilic behavior, high metallic conductivity and excellent mechanical properties(4).

Herein, we explore the use of freestanding nanometer-thin films of T3C2Tx for solution-processed transparent conductive electrodes. We demonstrate that our T3C2Tx films possess half of the sheet resistance (437 Ohm/sq) of the best reduced graphene oxide by produced solution-processed methods(5) while preserving an 80% of its transmission. In this talk, we will show that by using a simple spin-coating technique we can control the number of flakes forming the film (Figure 1a) and optimize the optoelectronic properties of our films so that they exhibit a figure of merit twice as large as reduced-GO (Figure 1b). The novelty of our approach is our in deep understanding of the limiting factors in the resistivity of the films such as heat treatments and functional end-groups. In addition, we will illustrate their metallic behavior by on-chip measurements and report for the first time the experimental measurement of their work function, which is crucial for advanced device design.

This demonstration of a novel metallic and solution-processed 2D material with high conductivity using T3C2Txflakes with low-temperature fabrication provides a new possible pathway towards scalable manufacturing of ultrathin film devices.

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5. H. A. Becerril et al., Evaluation of Solution-Processed Reduced Graphene Oxide Films as Transparent Conductors. ACS Nano
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Figure 1