Chemical vapor deposition (CVD) has shown great promise for the large-scale production of high-quality graphene films for industrial applications. Atomic-scale theoretical studies can help experiments to deeply understand the graphene growth mechanism, and serve as theoretical guides for further experimental designs. Here, by using density functional theory calculations, ab-initio molecular dynamics simulations, and microkinetic analysis, we systematically investigated the kinetics of hydrogen constrained graphene growth on Cu substrate. The results reveal that the actual hydrogen-rich environment of CVD results in CH as the dominating carbon species and graphene H-terminated edges. CH participated island sp² nucleation avoids chain cyclization process, thereby improving the nucleation and preventing the formation of non-hexameric ring defects. The graphene growth is not simply C-atomic activity, rather, involves three main processes: CH species attachment at the growth edge, leading to a localized sp³ hybridized carbon at the connecting site; excess H transfer from the sp³ carbon to the newly attached CH; and finally dehydrogenation to achieve the sp² reconstruction of the newly grown edge. The threshold reaction barriers for the growth of graphene zigzag (ZZ) and armchair (AC) edges were calculated as 2.46 and 2.16 eV, respectively, thus the AC edge grows faster than the ZZ one. Our theory successfully explained why the circumference of a graphene island grown on Cu substrates is generally dominated by ZZ edges, which is a commonly observed phenomenon in experiments. In addition, the growth rate of graphene on Cu substrates is calculated and matches well with existing experimental observations.

Transition metal catalyzed chemical vapor deposition (CVD) is considered as the most promising approach to synthesize high-quality graphene films, and low-temperature growth of defect-free graphene films is long-term challenged because of the high energy barrier for precursor dissociation and graphitization. Reducing the growth temperature can also bring advantages on wrinkle-free graphene films owing to the minimized thermal expansion coefficient mismatch. This work focuses on density functional theory (DFT) calculations of the carbon source precursor with hydroxyl group, especially CH₃OH, on low-temperature CVD growth of graphene on Cu and CuNi substrate. We calculated all the possible cleavage paths for CH₃OH on transition metal substrates. The results show that, firstly, the cleavage barriers of CH₃OH on transition metal substrates are slightly lower than those of CH₄, and once CO appears, it is difficult to break the C–O bond. Secondly, the CO promotes a better formation and retention of perfect rings in the early stage of graphene nucleation and reduces the edge growth barriers. Thirdly, these deoxidation barriers of CO are reduced after CO participates in graphene edge growth. This paper provides a strategy for the low-temperature growth of wrinkles-free graphene on transition metal substrates using CH₃OH.

The transfer of graphene from metallic substrates onto application-specific substrates is usually inevitable for the applications of high-quality graphene films derived from chemical vapour deposition (CVD) approaches. Commonly used to support the graphene films during the transfer, the coating of the polymer would produce the surface contaminations and hinder the industrially compatible transfer. In this work, through the thermal imidization of polyamide acid (PAA) to polyimide (PI) and tuning of the concentration of dangling chains, we achieved the ultraclean and crack-free transfer of graphene wafers with high electronic quality. The resulting contamination-free and hydrophilic surface also enabled the observed improved cell viability in a biomedical applications. By avoiding aqueous etching or the usage of strong bases, our proposed transfer method is industrially compatible for batch transfer of graphene films towards the real applications.

With the continuous advancements in electronics towards downsizing and integration, efficient thermal dissipation from chips has emerged as a critical factor affecting their lifespan and operational efficiency. The fan-less chip cooling system has two critical interfaces for thermal transport, which are the contact interface between the base and the chip dominated by thermal conduction, and the surface of the fins dominated by thermal radiation. The different thermal transfer modes of these two critical interfaces pose different requirements for thermal management materials. In the study, a novel approach was proposed by developing graphene thermal transport functional material whose morphology could be intentionally designed via reformed plasma-enhanced chemical vapor deposition (PECVD) methods to meet the diverse requirements of heat transfer properties. Specifically, graphene with multilevel branching structure of vertical graphene (BVG) was fabricated through the hydrogen-assisted PECVD (H₂-PECVD) strategy, which contributed a high emissivity of ~ 0.98. BVG was deposited on the fins’ surface and functioned as the radiation enhanced layer to facilitate the rapid radiation of heat from the heat sinks into the surrounding air. Meanwhile, the well-oriented vertical graphene (OVG) was successfully prepared through the vertical electric field-assisted PECVD process (EF-PECVD), which showed a high directional thermal conductivity of ~ 53.5 W·m⁻¹·K⁻¹. OVG was deposited on the contact interface and functioned as the thermal conduction enhanced layer, allowing for the quick transmission of heat from the chip to the heat sink. Utilizing this design concept, the two critical interfaces in the chip cooling system can be jointly enhanced, resulting in a remarkable cooling efficiency enhancement of ~ 30.7%, demonstrating that this novel material possessed enormous potential for enhancing the performance of cooling systems. Therefore, this research not only provided new design concepts for the cooling system of electronic devices but also opened up new avenues for the application of graphene materials in thermal management.

Recently, graphene has drawn considerable attention in the field of electronics, owing to its favorable conductivity and high carrier mobility. Crucial to the industrialization of graphene is its high-quality microfabrication via chemical vapor deposition. However, many problems remain in its preparation, such as the not fully understood cracking mechanism of the carbon source, the mechanism of its substrate oxidation, and insufficient defect repair theory. To help close this capability gap, this study leverages density functional theory to explore the role of O in graphene growth. The effects of Cu substrate oxidation on carbon source cracking, nucleation barriers, crystal nucleus growth, and defect repairs are discussed. O_Cu was found to reduce energy change during dehydrogenation, rendering the process easier. Moreover, the adsorbed O in graphene or its Cu substrate can promote defect repair and edge growth.

Vapor catalysis was recently found to play a crucial role in superclean graphene growth via chemical vapor decomposition (CVD). However, knowledge of vapor-phase catalysis is scarce, and several fundamental issues, including vapor compositions and their impact on graphene growth, are ambiguous. Here, by combining density functional theory (DFT) calculations, an ideal gas model, and a designed experiment, we found that the vapor was mainly composed of Cu_i clusters with tens of atoms. The vapor pressure was estimated to be ~ 10⁻¹²–10⁻¹¹ bar under normal low-pressure CVD system (LPCVD) conditions for graphene growth, and the exposed surface area of Cu_i clusters in the vapor was 22–269 times that of the Cu substrate surface, highlighting the importance of vapor catalysis. DFT calculations show Cu clusters, represented by Cu₁₇, have strong capabilities for adsorption, dehydrogenation, and decomposition of hydrocarbons. They exhibit an adsorption lifetime and reaction flux six orders of magnitude higher than those on the Cu surface, thus providing a sufficient supply of active C atoms for rapid graphene growth and improving the surface cleanliness of the synthesized graphene. Further experimental validation showed that increasing the amount of Cu vapor improved the as-synthesized graphene growth rate and surface cleanliness. This study provides a comprehensive understanding of vapor catalysis and the fundamental basis of vapor control for superclean graphene rapid growth.

Suppressing the formation of amorphous surface carbon and contaminants during the preparation of graphene by chemical vapor deposition remains an ongoing issue. Herein, we analyzed how substrate characteristics affect graphene quality by simulating margin extension, the nucleation process, and defect pegging configurations on mono-crystalline oriented metal substrates with the aim of enhancing graphene cleanliness. Defect formation energy and nucleation potential, which are indirect substrate–graphene interaction features, were found to appropriately evaluate graphene quality. The crystallographic orientation of the metal substrate was discovered to be critical for producing superclean graphene. A low graphene defect density and high nucleation rate on the Cu (100) facet guarantee growth of high-quality graphene, especially in terms of suppressing the formation of amorphous carbon. In addition, rapid kink growth and self-healing on the Cu (100) facet facilitate rapid graphene synthesis, which is also promoted by rapid kink splicing and margin self-repair on this facet. This study provides theoretical insight useful for the synthesis of superclean graphene.

Carbon source precursor is a critical factor governing chemical vapor deposition growth of graphene films. Methane (CH₄), has been the most commonly used precursor in the last decade, but it presents challenges in terms of decomposition efficiency and growth rate. Here we thoroughly evaluated acetylene (C₂H₂), a precursor that is probably for providing carbon dimer (C₂) species, for fast growth of large-scale graphene films. We find that the graphene growth behaviors fueled by C₂H₂ exhibit unconventional localized growth behavior with significant advantages in terms of high growth rate, which mainly ascribe to the as-decomposed C₂ species. Therefore, a C₂-fueled scanning growth strategy is proposed, and the fast scanning growth rate of 40 cm/min was experimentally demonstrated. This growth strategy is compatible with the approach of unidirectional growth of single-crystal graphene films, and the as-grown graphene films are of high-quality. This work demonstrates a reliable and promising strategy for the rapid synthesis of high-quality graphene film and may pave the avenue to cost-effective mass production of graphene materials in the roll-to-roll system.

Gaseous promotors have readily been adopted during the direct synthesis of graphene over insulators to enhance the growth quality and/or boost the growth rate. The understanding of the real functions of carbon-containing promotors has still remained elusive. In this study, we identify the critical roles of a representative CO₂ promotor played in the direct growth of graphene. The comparative experimental trials validate CO₂ as an effective modulator to decrease graphene nucleation density, improve growth kinetics, and mitigate adlayer formation. The first-principles calculations illustrate that the generation of gas-phase OH species in CO₂-assisted system helps decrease the energy barriers of CH₄ decomposition and carbon attachment to the growth front, which might be the key factor to allow high-quality direct growth. Such a CO₂-promoted strategy enables the conformal coating of graphene film over curved insulators, where the sheet resistance of grown graphene on quartz reaches as low as 1.26 kΩ·sq⁻¹ at an optical transmittance of ~ 95.8%. The fabricated endoscope lens based on our conformal graphene harvests an apoptosis of 82.8% for noninvasive thermal therapy. The work presented here is expected to motivate further investigations in the controllable growth of high-quality graphene on insulating substrates.

Chemical vapor deposition (CVD) in conjunction with batch-to-batch manufacturing process is considered as the most promising technical route for mass-production of high-quality graphene films. To improve the space utilization of the CVD chamber and increase the throughput per batch, stacking of the Cu foil substrates is efficient, but suffers from the problems of adjacent fusion and the poor mass-transfer. Here, we demonstrate an efficient strategy for high-throughput and rapid growth of high-quality graphene by alternate stacking of Cu foils and porous carbon fiber paper (CFP). Relying on the unhindered mass-transfer through the pores of CFPs, full-covered high-quality graphene films on compact-stacked Cu foils were achieved within 2 min. Computational fluid dynamics (CFD) simulation and isotope labeling technique were performed to explore the gas diffusion and graphene growth process in the confined space of the Cu-CFP stacks. This work provides a feasible method for industrial production of graphene films, which may also be used for batch production of other two-dimensional materials.