High quality and large-area graphene synthesis with a high growth rate using plasma-enhanced CVD

Abstract

attempt to develop high throughput plasma-enhanced CVD for high quality graphene.[8]- [16] 2 Preparation of a substrate for graphene synthesis and suppression of impurity incorporation.In the case of CVD of graphene using a copper foil substrate, surface cleaning technique of copper foil before CVD is especially important. Also in the case of plasma-assisted CVD (plasma CVD), it is necessary to prevent contamination such as impurities released from the reaction chamber by plasma exposure, particularly silicon, which originate from the quartz of antenna units for exciting plasma.Commercially available copper foil surfaces are subjected to anticorrosive treatment in order to prevent oxidation. Moreover, even foil with anticorrosive treatment has a surface that is still covered with a thin copper oxide layer. For high-quality graphene synthesis, it is necessary to remove these copper oxide and anticorrosive treatment carefully. In thermal CVD of graphene, electrolytic cleaning and successive high-temperature treatment at about 1000 °C of the copper foil substrate in the reaction chamber are effective for removing copper oxide and the anticorrosive treatment layer. Furthermore, in order to flatten the copper foil surface, chemical polishing (CMP) before electrolytic cleaning and annealing treatment is effective.[17] [18] On the other hand, electrolytic cleaning is a wet process and thus there is a possibility of recontamination before CVD. Therefore, cleaning methods consistent with CVD are desirable. IntroductionGraphene [1] is a single atomic sheet in which carbon atoms are arranged in a hexagonal honeycomb lattice. Graphene has a very unique band structure (zero bandgap, linear dispersion), and thereby it shows brilliant electronic and optical characteristics such as extremely high carrier mobility and light absorption which does not depend on wavelength. (2.3 % absorption per layer.) Moreover graphene has the property of flexibility which indium tin oxide (ITO) [2] does not possess, and an attempt has been made to use a few layers of graphene(FLG) as transparent electrodes in such devices as flexible organic light-emitting diode (OLED), solar batteries, and displays.For transparent electrode application of graphene, it is necessary to establish production technology of high quality and high throughput for large area graphene. Among the various methods of graphene production such as mechanical exfoliation of bulk graphite, [1][3] exfoliation of graphene oxide in liquid phase, [4] thermal decomposition of SiC, [5] etc., chemical vapor deposition (CVD) on catalytic transition metal surfaces, in particular on a copper surface, has great promise as a production method for transparent electrode application. Recently, high conductivity graphene has been synthesized on copper substrates by energetic development of the thermal CVD method.[6] [7] On the other hand, since throughput of the thermal CVD method is insufficient, synthesis time needs to be significantly shortened for transparent electrode application. In this p...

Impedance Characteristics of Monolayer and Bilayer Graphene Films with Biofilm Formation and Growth

“…In the past, we confirmed the relatively high susceptibility to biofilm formation [31,[36][37][38][39]. In those cases, we used monolayer graphene on copper substrates produced by CVD [40], since the process could produce reproducible and high quality (high covering ratio) graphene films. However, the mechanical strength of monolayer graphene is relatively weak and the coverage is generally not so high.…”

“…The graphene layer forms on 10 µm copper foil. The thickness of graphene films were confirmed by their transparency, since the transparency for monolayer and bilayer graphene were already fixed [40,41]. On the other hand, the 100 µm polyester film (detachable by heating) exists on the other side of the copper foil.…”

Camphor-Based CVD Bilayer Graphene/Si Heterostructures for Self-Powered and Broadband Photodetection

“…Therefore, the carrier mobility (1.8 × 10 3 cm 2 /V·s) of the camphor-based CVD bilayer graphene was obtained from the room temperature Hall measurement. Compared to the conventional CVD graphene (mobility: 100~1000 cm 2 /V·s) [ 41 , 42 ], the camphor-based CVD graphene shows a higher mobility. However, the biggest issue of CVD graphene is that its carrier mobility is much lower than that of graphene obtained from the exfoliation of graphite.…”