Layer exchange synthesis of multilayer graphene

Abstract

Low-temperature synthesis of multilayer graphene (MLG) on arbitrary substrates is the key to incorporating MLG-based functional thin films, including transparent electrodes, low-resistance wiring, heat spreaders, and battery anodes in advanced electronic devices. This paper reviews the synthesis of MLG via the layer exchange (LE) phenomenon between carbon and metal from its mechanism to the possibility of device applications. The mechanism of LE is completely different from that of conventional MLG precipitation methods using metals, and the resulting MLG exhibits unique features. Modulation of metal species and growth conditions enables synthesis of high-quality MLG over a wide range of growth temperatures (350 °C–1000 °C) and MLG thicknesses (5–500 nm). Device applications are discussed based on the high electrical conductivity (2700 S cm−1) of MLG and anode operation in Li-ion batteries. Finally, we discuss the future challenges of LE for MLG and its application to flexible devices.

Impact of the Density and Oxygen Concentration of Initial Amorphous Carbon on Layer Exchange of Multilayer Graphene

“…We found that high-quality MLG was formed from low-density a-C sputtered under high-pressure conditions. This is because poor crystallinity is preferred for the initial a-C in LE, which is consistent with the LE of semiconducting materials such as Si. − Moreover, O in the a-C film suppresses the diffusion of C atoms into Ni, resulting in a lower nucleation frequency of MLG and the formation of larger MLG domains. In Figure d, the lowest annealing temperature at which LE occurred in 10 min of annealing is plotted as a function of P a‑C , which shows that the lowest LE temperature strongly depends on P a‑C .…”

“…42 These results indicate that LE occurred in all samples and that MLG was formed on the SiO 2 substrate after annealing at 800 °C. 37 Figure 2c shows the intensity ratio of the G to D peaks (I G /I D ) in the Raman spectra, which is This I G /I D ratio behavior suggests an enlargement of the MLG domain size. We found that high-quality MLG was formed from low-density a-C sputtered under high-pressure conditions.…”

“…There are no electrical property data for the sample with P a‑C = 0.1 Pa because the resulting MLG is discontinuous and its electrical property could not be evaluated using the van der Pauw method. This could be related to the fact that LE occurs less easily for a-C with higher crystallinity. − Figure a shows that the electron mobility (μ) increases with P a‑C . This μ behavior reflects the enlargement of the MLG domain size, as shown in Raman study (Figure c).…”

Metal-Catalyzed Nanostructured Silicon Films as Potential Anodes for Flexible Rechargeable Batteries

“…We synthesized multilayer graphene (graphite thin films) by adapting LE to carbon. − The anode properties of graphite thin films are strongly dependent on the LE conditions, and our group had demonstrated anode capacities comparable to those of bulk graphite by controlling them. , In this study, we controlled the crystallinity and structure of Si by modulating the growth temperature and film thickness ratio in the Al-induced LE and investigated the effects of the LE conditions on the anode properties. Furthermore, a fine nanostructure was formed using EE.…”

Si1–xGex anode synthesis on plastic films for flexible rechargeable batteries

“…Although graphite is generally synthesized at high temperatures (> 2000 °C), we achieved low-temperature synthesis of graphite thin films (i.e., multilayer graphene (MLG)) on plastic films (polyimide: heat resistance of up to 400 °C) via metal-induced layer exchange (LE) 4 . In LE, an amorphous layer crystallizes through LE between the amorphous layer and metal catalyst layer 5 , 6 . LE will be suitable for microfabrication of devices because it can synthesize crystalline thin films with controlled thicknesses on arbitrary substrates at low temperatures 7 , 8 .…”