Low temperature electronic transport properties of ultrathin, single crystal WC and W₂C nanoplates

Transition metal carbides (TMCs) have historically been studied in bulk, non-layered morphologies and applied for high hardness, chemical stability, and electrocatalytic activity. This family has received renewed interest with the development of novel top-down and bottom-up approaches to isolate layered (MXenes)¹ and ultrathin, non-layered TMCs (UThTMCs).² While the MXene family has a wide range of applications,³ electronic transport properties can be difficult to probe owing to small domain size. UThTMCs were shown to be isolated as single crystal nanoplates, such as molybdenum² and tungsten carbide⁴ which were shown to exhibit quasi-2D electronic states. Following recent works in bottom-up synthesis of UThTMCs,^4,5 we isolate WC and W₂C using liquid-metal-assisted chemical vapor deposition. We identify crystal phase using a combination of X-ray and electron diffraction. Atomic force microscopy reveals that the thickness of these crystals is below 50 nm. We find that down to 10 mK, WC does not enter a superconducting state. In W₂C, we observe a superconducting transition, discuss the temperature dependence of the critical fields, and extract Ginzburg-Landua coherence lengths both in and out-of-plane.

1: Naguib et al. Adv. Mater. 23, 4248-4253 (2011)

2: Xu et al. Nat. Mater. 14, 1335-1141 (2015)

3: Y. Gogotsi and Q. Huang ACS Nano 15, 5775-5780 (2021)

4: Wang et al. Adv. Electron. Mater. 5, 1-7 (2019)

5: Zeng et al. Nano Energy 33, 356-362 (2017)