Unveiling the Direct Correlation between the CVD-Grown Graphene and the Growth Template

Abstract

Chemical vapor deposition (CVD) is known to produce continuous, large-area graphene sheet with decent physical properties. In the CVD process, catalytic metal substrates are typically used as the growth template, and copper has been adopted as the representative material platform due to its low carbon solubility and resulting monolayer graphene growth capability. For the widespread industrial applications of graphene, achieving the high-quality is essential. Several factors affect the qualities of CVD-grown graphene, such as pressure, temperature, carbon precursors, or growth template. In this work, we provide detailed analysis on the direct relation between the metallic growth substrate (copper) and overall properties of the resulting CVD-grown graphene. The surface morphology of copper substrate was modulated via simple chemical treatments, and its effect on physical, optical, and electrical properties of graphene was analyzed. Based on these results, we propose a simple synthesis route to produce high-quality, continuous, monolayer graphene sheet, which can facilitate the commercialization of CVD graphene into reality.

Graphene-Based Gas Sensors with High Sensitivity and Minimal Sensor-to-Sensor Variation

“…The graphene samples without CH 4 during the cooling process show larger amounts of PMMA residue. The results are consistent with previous studies that reported high-quality graphene by cooling down with carbon precursor. , …”

“…The results are consistent with previous studies that reported high-quality graphene by cooling down with carbon precursor. 30,38 We performed Raman spectroscopy and electrical measurements to further characterize each graphene sample and ultimately to find correlation between the quality of graphene and the performance of graphene gas sensors. In the Raman spectra (Figure 1d) the intensity ratios of the D-band (∼1350 cm −1 ) to G-band (1580 cm −1 ), or I D /I G , are smaller than 0.1, suggesting negligible defects in all four types of graphene.…”

“…With a Cu substrate (Alfa Aesar, 13382) inserted into a furnace, the temperature was raised to 1000 °C under 10 sccm H 2 , followed by introducing CH 4 at 20 sccm for 30 min (∼30 mTorr) as described previously. , After removing the Cu substrate in 0.5 M ammonium persulfate (APS) solution overnight, the synthesized graphene was transferred onto a silicon substrate with 300 nm thick thermal oxide by the polymer-assisted wet transfer method using 9% poly­(methyl methacrylate) in anisole. PMMA was then removed either by acetone rinse or by thermal annealing at 400 °C in Ar (300 sccm) and H 2 (300 sccm) atmosphere for 2 h.…”

Chemical Vapour Deposition of Graphene—Synthesis, Characterisation, and Applications: A Review

“…It was claimed that forming a smooth Cu (111)-oriented surface during pre-annealing leads to the formation of monolayer graphene with improved uniformity and nearly perfect centimetre-scale samples [ 127 ]. Another substrate treatment that modifies surface morphology is using nitric acid for etching the as-received Cu foil using short exposure time (30 s) showing that it improves the quality of the produced graphene film [ 128 ]. The effect of using nitric acid was also reported by Kim et al when Cu foil was annealed first under the flow of hydrogen, followed by etching using nitric acid.…”

“…Nitric acid was also used by several groups for an effective substrate’s pre-treatment. Lee et al have used different exposure times of Cu substrate immersed in nitric acid and studied its effect on the substrate morphology and the grown graphene [ 128 ].…”