Graphene/Mo2C heterostructure directly grown by chemical vapor deposition

Abstract

Graphene-based heterostructure is one of the most attractive topics in physics and material sciences due to its intriguing properties and applications. We report the one-step fabrication of a novel graphene/Mo 2 C heterostructure by using chemical vapor deposition (CVD). The composition and structure of the heterostructure are characterized through energydispersive spectrometer, transmission electron microscope, and Raman spectrum. The growth rule analysis of the results shows the flow rate of methane is a main factor in preparing the graphene/Mo 2 C heterostructure. A schematic diagram of the growth process is also established. Transport measurements are performed to study the superconductivity of the heterostructure which has potential applications in superconducting devices.

CVD synthesis and characterization of thin Mo2C crystals

“…In addition to the Mo‐C peaks at 228 and 231.2 eV, the peaks at binding energies of 228.4, 232.2, 232.7, 235.5 eV are assigned to Mo +4 and Mo +6 species, which can be attributed to the surface oxidation of Mo 2 C in air 33,34 . The high resolution C 1s spectra (Figure 2B) of the sample can be well‐fitted into two peaks, indicating the formation of graphene (sp 2 hybridized C‐C at 284.3 eV) 35 along with Mo 2 C (Mo‐C at 284.2 eV), 33 in line with previous works where they demonstrated the formation of graphene along with Mo 2 C crystals at a high ratio of CH 4 to H 2 flow rate (≥1:60) 14‐16 …”

“…Secondly, CH 4 flow rate is also very critical not only because it is the carbon source in Mo 2 C, but also the excess amount results in the formation of graphene, which may act as an additional diffusion barrier in the supply of Mo atoms 17 . Although various groups have mentioned simultaneous growth of graphene and Mo 2 C, there are conflicts in the positional relationship between graphene and Mo 2 C as well as their formation mechanism 14‐17,24 . For example, while Geng et al claims the evolution of graphene beneath 2D Mo 2 C, 14 with similar growth conditions, Deng et al suggests the formation of graphene on top of Mo 2 C crystals 15 …”

“…CVD has been a promising technique to achieve large area and high quality thin layers of Mo 2 C 3,13,22,[14][15][16][17][18][19][20][21] . In this method, Cu foil is placed on a Mo substrate and heated.…”

“…17 Although various groups have mentioned simultaneous growth of graphene and Mo 2 C, there are conflicts in the positional relationship between graphene and Mo 2 C as well as their formation mechanism. [14][15][16][17]24 For example, while Geng et al claims the evolution of graphene beneath 2D Mo 2 C, 14 with similar growth conditions, Deng et al suggests the formation of graphene on top of Mo 2 C crystals. 15 In short, the effects of reaction temperature, duration, copper thickness, and CH 4 flow rate on the final morphology and thickness of Mo 2 C crystals were studied to some extent, but there are discrepancies and conflicting data in literature.…”

Preliminary study of the surface reactivity of 2D α‐Mo2C crystallites

“…Furthermore, their advanced TEM data show that the thin layers are single crystals of orthorhombic α‐Mo 2 C and that they are free of defects . Geng et al, Geng et al, and Deng et al reported similar AFM, optical microscopy, and TEM data on the structure and morphology of 2D‐α‐Mo 2 C/graphene hybrid materials …”