Annealing and polycrystallinity effects on the thermal conductivity of supported CVD graphene monolayers

Enhancing Thermal Management of Graphene Devices by Self-Assembled Monolayers

Two-dimensional graphene has emerged as a promising competitor to silicon in the post-Moore era due to its superior electrical, optical, and thermal properties. However, graphene undergoes a strong degradation in its in-plane thermal conductivity when it is coupled to an amorphous substrate. Meanwhile, the weak van der Waals interaction between graphene and the dielectric substrate leads to high interfacial thermal resistance. Severe challenges in the device's heat dissipation rise, resulting in elevated hotspot and deteriorated electrical performance. Here, we applied self-assembled monolayers (SAMs) to modify the interface between graphene and the oxide substrate and mitigate the thermal issues in the device. The -NH2 terminated SAM demonstrates enhanced interfacial coupling strength between graphene and substrate, increasing the interfacial thermal conductance. The -CH3 terminated SAM effectively suppresses the substrate phonon scattering, preserving the high in-plane thermal conductivity of graphene. Particularly, the -NH2 terminated SAM significantly enhances the heat dissipation efficacy of graphene field-effect transistors and alleviates the self-heating issues. Enhancements of 28.1% and 48.2% were observed in the devices' current-carrying capacity and maximum power density, respectively. Our research provides a highly attractive platform for incorporating SAMs to improve thermal management in two-dimensional electronic devices.

Plasma Assisted Reduction of Graphene Oxide Films

The past decade has seen enormous efforts in the investigation and development of reduced graphene oxide (GO) and its applications. Reduced graphene oxide (rGO) derived from GO is known to have relatively inferior electronic characteristics when compared to pristine graphene. Yet, it has its significance attributed to high-yield production from inexpensive graphite, ease of fabrication with solution processing, and thus a high potential for large-scale applications and commercialization. Amongst several available approaches for GO reduction, the mature use of plasma technologies is noteworthy. Plasma technologies credited with unique merits are well established in the field of nanotechnology and find applications across several fields. The use of plasma techniques for GO development could speed up the pathway to commercialization. In this report, we review the state-of-the-art status of plasma techniques used for the reduction of GO-films. The strength of various techniques is highlighted with a summary of the main findings in the literature. An analysis is included through the prism of chemistry and plasma physics.

Influence of Humidity on Contact Resistance in Graphene Devices

The electrical contact resistance at metal-graphene interfaces can significantly degrade the properties of graphene devices and is currently hindering the full exploitation of graphene's potential. Therefore, the influence of environmental factors, such as humidity, on the metal-graphene contact resistance is of interest for all graphene devices that operate without hermetic packaging. We experimentally studied the influence of humidity on bottom-contacted chemical-vapor-deposited (CVD) graphene-gold contacts, by extracting the contact resistance from transmission line model (TLM) test structures. Our results indicate that the contact resistance is not significantly affected by changes in relative humidity (RH). This behavior is in contrast to the measured humidity sensitivity [Formula: see text] of graphene's sheet resistance. In addition, we employ density functional theory (DFT) simulations to support our experimental observations. Our DFT simulation results demonstrate that the electronic structure of the graphene sheet on top of silica is much more sensitive to adsorbed water molecules than the charge density at the interface between gold and graphene. Thus, we predict no degradation of device performance by alterations in contact resistance when such contacts are exposed to humidity. This knowledge underlines that bottom-contacting of graphene is a viable approach for a variety of graphene devices and the back end of the line integration on top of conventional integrated circuits.

Thermal Transport in Supported Graphene Nanomesh

Graphene is considered as a promising candidate material to replace silicon for the next-generation nanoelectronics because of its superb carrier mobility. To evaluate its thermal dissipation capability as electronic materials, the thermal transport in monolayer graphene was extensively explored over the past decade. However, the supported chemical vapor deposition (CVD) grown monolayer graphene with submicron structures were seldom studied, which is important for practical nanoelectronics. Here we investigate the thermal transport properties in a series of CVD graphene nanomeshes patterned by a hard-template-assisted etching method. The experimental and numerical results uncovered the phonon backscattering at hole boundary (<100 nm neck width) and its substantial contribution to the thermal conductivity reduction.