Abstract
With a combination of outstanding properties and a wide spectrum of applications, graphene has emerged as a significant nanomaterial. However, to realize its full potential for practical applications, a number of obstacles have to be overcome, such as low-temperature, transfer-free growth on desired substrates. In most of the reports, direct graphene growth is confined to either a small area or high sheet resistance. Here, an attempt has been made to grow large-area graphene directly on insulating substrates, such as quartz and glass, using magnetron-generated microwave plasma chemical vapor deposition at a substrate temperature of 300 °C with a sheet resistance of 1.3k Ω/□ and transmittance of 80%. Graphene is characterized using Raman microscopy, atomic force microscopy, scanning electron microscopy, optical imaging, UV–vis spectroscopy, and X-ray photoelectron spectroscopy. Four-probe resistivity and Hall effect measurements were performed to investigate electronic properties. Key to this report is the use of 0.3 sccm CO2 during growth to put a control over vertical graphene growth, generally forming carbon walls, and 15–20 min of O3 treatment on as-synthesized graphene to improve sheet carrier mobility and transmittance. This report can be helpful in growing large-area graphene directly on insulating transparent substrates at low temperatures with advanced electronic properties for applications in transparent conducting electrodes and optoelectronics.
Highlights
A huge number of publications have been reported on various synthesis methods and possible future applications of graphene after successful exfoliation of single-layer graphene by Geim et al in 2004, revealing significant electrical, optical, and chemical properties.[1−10] Among various synthesis methods, thermal chemical vapor deposition (TCVD) has proven to be the simplest and cost effective for industrial grade graphene synthesis.[11−15] the use of catalysts during graphene growth in TCVD has created extra challenges for researchers, such as removal of the catalyst and transfer of graphene from such catalyst materials on to desired substrates.[16−19] Much awaited future applications of graphene, such as transparent conductive electrodes, have been delayed due to use of a catalyst and the inevitable transfer process during graphene synthesis using TCVD
Synthesized films on glass and quartz were first characterized by Raman spectroscopy
The D peak seen in the Raman spectrum can be attributed to defects, such as lattice disorders and unintentional impurity substitutional doping in synthesized graphene lattice.[35]
Summary
A huge number of publications have been reported on various synthesis methods and possible future applications of graphene after successful exfoliation of single-layer graphene by Geim et al in 2004, revealing significant electrical, optical, and chemical properties.[1−10] Among various synthesis methods, thermal chemical vapor deposition (TCVD) has proven to be the simplest and cost effective for industrial grade graphene synthesis.[11−15] the use of catalysts during graphene growth in TCVD has created extra challenges for researchers, such as removal of the catalyst and transfer of graphene from such catalyst materials on to desired substrates.[16−19] Much awaited future applications of graphene, such as transparent conductive electrodes, have been delayed due to use of a catalyst and the inevitable transfer process during graphene synthesis using TCVD. Researchers are still in the process of finding a better alternative to synthesize graphene at lower temperatures directly on desired substrates to end the search of an alternative to indium tin oxide for 20 years.[20]. To overcome these problems, many researchers have tried direct graphene growth on insulating substrates using TCVD. We have attempted to grow large-area graphene directly on insulating substrates, such as quartz, SiO2/Si, and glass, using magnetron-generated microwave plasma CVD (PCVD) at a substrate temperature of 300 °C and the effect of ozone (O3) treatment on as-synthesized graphene has been studied to improve sheet resistance and transmittance of graphene
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