Transfer-free Growth Of Graphene Research Articles

GaN LEDs with in situ synthesized transparent graphene heat-spreading electrodes fabricated by PECVD and penetration etching

High-quality and patterned graphene is grown directly on GaN LED arrays for transparent and heat-spreading electrodes. The CVD is done at 600 °C for 2 min. Sacrificial Co acts both as GaN mesa etching mask and transfer-free graphene growth catalyst.

Copper acetate-facilitated transfer-free growth of high-quality graphene for hydrovoltaic generators.

Direct synthesis of high-quality graphene on dielectric substrates without a transfer process is of vital importance for a variety of applications. Current strategies for boosting high-quality graphene growth, such as remote metal catalyzation, are limited by poor performance with respect to the release of metal catalysts and hence suffer from a problem with metal residues. Herein, we report an effective approach that utilizes a metal-containing species, copper acetate, to continuously supply copper clusters in a gaseous form to aid transfer-free growth of graphene over a wafer scale. The thus-derived graphene films were found to show reduced multilayer density and improved electrical performance and exhibited a carrier mobility of 8500 cm2 V−1 s−1. Furthermore, droplet-based hydrovoltaic electricity generator devices based on directly grown graphene were found to exhibit robust voltage output and long cyclic stability, in stark contrast to their counterparts based on transferred graphene, demonstrating the potential for emerging energy harvesting applications. The work presented here offers a promising solution to organize the metal catalytic booster toward transfer-free synthesis of high-quality graphene and enable smart energy generation.

Functional Microarray Platform with Self-Assembled Monolayers on 3C-Silicon Carbide.

Currently available bioplatforms such as microarrays and surface plasmon resonators are unable to combine high-throughput multiplexing with label-free detection. As such, emerging microelectromechanical systems (MEMS) and microplasmonics platforms offer the potential for high-resolution, high-throughput label-free sensing of biological and chemical analytes. Therefore, the search for materials capable of combining multiplexing and label-free quantitation is of great significance. Recently, interest in silicon carbide (SiC) as a suitable material in numerous biomedical applications has increased due to its well-explored chemical inertness, mechanical strength, bio- and hemocompatibility, and the presence of carbon that enables the transfer-free growth of graphene. SiC is also multifunctional as both a wide-band-gap semiconductor and an efficient low-loss plasmonics material and thus is ideal for augmenting current biotransducers in biosensors. Additionally, the cubic variant, 3C-SiC, is an extremely promising material for MEMS, being a suitable platform for the easy micromachining of microcantilevers, and as such capable of realizing the potential of real time miniaturized multiplexed assays. The generation of an appropriately functionalized and versatile organic monolayer suitable for the immobilization of biomolecules is therefore critical to explore label-free, multiplexed quantitation of biological interactions on SiC. Herein, we address the use of various silane self-assembled monolayers (SAMs) for the covalent functionalization of monocrystalline 3C-SiC films as a novel platform for the generation of functionalized microarray surfaces using high-throughput glycan arrays as the model system. We also demonstrate the ability to robotically print high throughput arrays on free-standing SiC microstructures. The implementation of a SiC-based label-free glycan array will provide a proof of principle that could be extended to the immobilization of other biomolecules in a similar SiC-based array format, thus making potentially significant advances to the way biological interactions are studied.

Transfer-Free Layered Graphene on Silica via Segregation through a Nickel Film for Electronic Applications

Transfer-free graphene growth via annealing-induced carbon segregation was investigated on a series of carbon/metal/silica layered samples prepared by sequential deposition of Ni from evaporation o...

Intergrain Diffusion of Carbon Radical for Wafer-Scale, Direct Growth of Graphene on Silicon-Based Dielectrics.

Graphene intrinsically hosts charge-carriers with ultrahigh mobility and possesses a high quantum capacitance, which are attractive attributes for nanoelectronic applications requiring graphene-on-substrate base architecture. Most of the current techniques for graphene production rely on the growth on metal catalyst surfaces, followed by a contamination-prone transfer process to put graphene on a desired dielectric substrate. Therefore, a direct graphene deposition process on dielectric surfaces is crucial to avoid polymer-adsorption-related contamination from the transfer process. Here, we present a chemical-diffusion mechanism of a process for transfer-free growth of graphene on silicon-based gate-dielectric substrates via low-pressure chemical vapor deposition. The process relies on the diffusion of catalytically produced carbon radicals through polycrystalline copper (Cu) grain boundaries and their crystallization at the interface of Cu and underneath silicon-based gate-dielectric substrates. The graphene produced exhibits low-defect multilayer domains ( La ∼ 140 nm) with turbostratic orientations as revealed by selected area electron diffraction. Further, graphene growth between Cu and the substrate was 2-fold faster on SiO2/Si(111) substrate than on SiO2/Si(100). The process parameters such as growth temperature and gas compositions (hydrogen (H2)/methane (CH4) flow rate ratio) play critical roles in the formation of high-quality graphene films. The low-temperature back-gating charge transport measurements of the interfacial graphene show density-independent mobility for holes and electrons. Consequently, the analysis of electronic transport at various temperatures reveals a dominant Coulombic scattering, a thermal activation energy (2.0 ± 0.2 meV), and two-dimensional hopping conduction in the graphene field-effect transistor. A band overlapping energy of 2.3 ± 0.4 meV is estimated by employing the simple two-band model.

Synthesis of transfer-free graphene on cemented carbide surface

Direct growth of spherical graphene with large surface area is important for various applications in sensor technology. However, the preparation of transfer-free graphene on different substrates is still a challenge. This study presents a novel approach for the transfer-free graphene growth directly on cemented carbide. The used simple thermal annealing induces an in-situ transformation of magnetron-sputtered amorphous silicon carbide films into the graphene matrix. The study reveals the role of Co, a binding phase in cemented carbides, in Si sublimation process, and its interplay with the annealing temperature in development of the graphene matrix. A detailed physico-chemical characterisation was performed by structural (XRD analysis and Raman spectroscopy with mapping studies), morphological (SEM) and chemical (EDS) analyses. The optimal bilayer graphene matrix with hollow graphene spheres on top readily grows at 1000 °C. Higher annealing temperature critically decreases the amount of Si, which yields an increased number of the graphene layers and formation of multi-layer graphene (MLG). The proposed action mechanism involves silicidation of Co during thermal treatment, which influences the existing chemical form of Co, and thus, the graphene formation and variations in a number of the formed graphene layers.

Transfer-free growth of graphene on Al2O3 (0001) using a three-step method

The transfer process before graphene device fabrication could worsen the performance of graphene device greatly, so a transfer-free growth method for preparing graphene films is demanded urgently. Herein, we propose a novel three-step method to achieve transfer-free graphene films on Al2O3 (0001) substrates. Cu (111) films and carbon source were co-deposited on α-Al2O3 (0001) substrates by metal-organic chemical vapor deposition (MOCVD) at one step, then graphene was synthesis by a rapid annealing process, transforming the carbon source in copper into graphene films. Finally, a transfer-free graphene film with an ultra-smooth surface (∼3.49 nm) is achieved by etching the copper film on Al2O3(0001). Crystallographic characterization demonstrated the as-deposited Cu films show a nature of epitaxial single crystal, with a smooth surface (∼6.89 nm). Few layer graphene films (3–4 layers) with least defect concentration were grown at annealing time of 20 min.

Transfer-free synthesis of graphene-like atomically thin carbon films on SiC by ion beam mixing technique

Abstract Here we demonstrate the synthesis of graphene directly on SiC substrates at 900 °C using ion beam mixing technique with energetic carbon cluster ions on Ni/SiC structures. The thickness of 7–8 nm Ni films was evaporated on the SiC substrates, followed by C cluster ion bombarding. Carbon cluster ions C4 were bombarded at 16 keV with the dosage of 4 × 1016 atoms/cm2. After thermal annealing process Ni silicides were formed, whereas C atoms either from the decomposition of the SiC substrates or the implanted contributes to the graphene synthesis by segregating and precipitating process. The limited solubility of carbon atoms in silicides, involving SiC, Ni2Si, Ni5Si2, Ni3Si, resulted in diffusion and precipitation of carbon atoms to form graphene on top of Ni and the interface of Ni/SiC. The ion beam mixing technique provides an attractive production method of a transfer-free graphene growth on SiC and be compatible with current device fabrication.

Transfer-free growth of polymer-derived graphene on dielectric substrate from mobile hot-wire-assisted dual heating system

Chemical vapor deposition (CVD) is the most promising, relatively inexpensive approach for the growth of high quality graphene. However, the need to transfer the graphene to dielectric substrates limits its usage in electronic applications. Here, we demonstrate transfer-free growth of graphene on dielectric substrates via mobile hot-wire (MHW) assisted dual heating system (DHS). MHW is utilized as independent heat source over polymer/Ni/SiO2/Si, which is placed on a bottom heater. The hot-wire scan speed (Vw, 0.01–40 mm/min) and temperature (Tw) are varied to control the diffusion kinetics and amount of carbon source into nickel by changing the cooling rate of hot zone where nucleation and growth of graphene occurs between Ni and SiO2. The optimum growth condition for single-layer graphene is further verified through controlling the substrate temperature (Tsub, 430–630 °C). We also improve coverage of graphene by changing polymers as a function of thermal stability. The results show that thermal decomposition temperature determines the amount of the carbon dissolved into nickel for graphene growth. Through our synthesis, we can obtain nearly full-coverage of single-layer graphene. We believe our simple method of growing graphene is potentially scalable and advances the possibility of various electrical and optical applications.

Transfer-Free Growth of Multilayer Graphene Using Self-Assembled Monolayers.

Large-area graphene needs to be directly synthesized on the desired substrates without using a transfer process so that it can easily be used in industrial applications. However, the development of a direct method for graphene growth on an arbitrary substrate remains challenging. Here, we demonstrate a bottom-up and transfer-free growth method for preparing multilayer graphene using a self-assembled monolayer (trimethoxy phenylsilane) as the carbon source. Graphene was directly grown on various substrates such as SiO2/Si, quartz, GaN, and textured Si by a simple thermal annealing process employing catalytic metal encapsulation. To determine the optimal growth conditions, experimental parameters such as the choice of catalytic metal, growth temperatures, and gas flow rate were investigated. The optical transmittance at 550 nm and the sheet resistance of the prepared transfer-free graphene are 84.3% and 3500 Ω/□, respectively. The synthesized graphene samples were fabricated into chemical sensors. High and fast responses to both NO2 and NH3 gas molecules were observed. The transfer-free graphene growth method proposed in this study is highly compatible with previously established fabrication systems, thereby opening up new possibilities for using graphene in versatile applications.

Graphene device array using transfer-free patterned growth on insulator for an electrolyte-gated sensor

We report transfer-free graphene growth on insulated substrates and the fabrication of a sensor array from the synthesized graphene. The insulated substrate coated with amorphous carbon and catalyst metals was annealed under an Ar atmosphere. After annealing, graphene was synthesized between the metal layer and the insulated substrate. We fabricated a sensing array based on the graphene growth method and used it for pH measurements. Our sensor had as a high resolution of pH as that of graphene synthesized by chemical vapor deposition. This technique allows graphene arrays to be synthesized simply and is suitable for industrial sensing applications.

Fast growth of graphene on SiO2/Si substrates by atmospheric pressure chemical vapor deposition with floating metal catalysts

Graphene on dielectric substrates is essential for its electronic applications. Graphene is typically synthesized on the surface of metal and then transferred to an appropriate substrate for fabricating device applications. This post growth transfer process is detrimental to the quality and performance of the as-grown graphene. Therefore, direct growth of graphene films on dielectric substrates without any transfer process is highly desirable. However, fast growth of graphene on dielectric substrates remains challenging. Here, we demonstrate a transfer-free chemical vapor deposition (CVD) method to directly grow graphene films on dielectric substrates at fast growth rate using Cu as floating catalyst. A large area (centimeter level) graphene can be grown within 15 min using this CVD method, which is increased by 500 times compared to other direct CVD growth on dielectric substrate in the literatures. This research presents a significant progress in transfer-free growth of graphene and graphene device applications.

Low-temperature plasma-enhanced chemical vapour deposition of transfer-free graphene thin films

Large area transfer free graphene films were deposited at low substrate temperature of 380°C by plasma-enhanced chemical vapour deposition (PECVD) using a nickel buffer layer. The Raman spectrum indicated a structure of highly disordered sp2-C. The current–voltage characteristics of the films showed ohmic behaviour with sheet resistance of ~10.1kΩ/sq and transmittance of 70% at wavelength of 550nm. This transfer-free graphene growth technique is reproducible and is promising for applications in devices.

Batch Fabrication of Transfer-Free Graphene-Coated Microcantilevers

This letter reports a method for transfer-free graphene growth and its application to batch fabrication of graphene-coated microcantilevers. Transfer-free graphene was synthesized directly on insulating substrates from solid carbon sources of poly(methyl methacrylate) or amorphous carbon. The graphene thickness and quality were controlled by optimizing the amount of solid carbon source, annealing temperature, and growth time. This synthesis method was then used to fabricate more than 100 graphene-coated cantilevers on a silicon substrate of size 2 cm × 2.5 cm. More than 90% of the cantilever surface was coated with high-quality multilayer graphene, and the overall device yield was ~75%.

Transfer-free growth of graphene on SiO2 insulator substrate from sputtered carbon and nickel films

Here we demonstrate the growth of transfer-free graphene on SiO2 insulator substrates from sputtered carbon and metal layers with rapid thermal processing in the same evacuation. It was found that graphene always grows atop the stack and in close contact with the Ni. Raman spectra typical of high quality exfoliated monolayer graphene were obtained for samples under optimised conditions with monolayer surface coverage of up to 40% and overall graphene surface coverage of over 90%. Transfer-free graphene is produced on SiO2 substrates with the removal of Ni in acid when Ni thickness is below 100nm, which effectively eliminates the need to transfer graphene from metal to insulator substrates and paves the way to mass production of graphene directly on insulator substrates. The characteristics of Raman spectrum depend on the size of Ni grains, which in turn depend on the thickness of Ni, layer deposition sequence of the stack and RTP temperature. The mechanism of the transfer-free growth process was studied by AFM in combination with Raman. A model is proposed to depict the graphene growth process. Results also suggest a monolayer self-limiting growth for graphene on individual Ni grains.

Progress of graphene growth on copper by chemical vapor deposition: Growth behavior and controlled synthesis

Recently, chemical vapor deposition (CVD) on copper has been becoming a main method for preparing large-area and high- quality monolayer graphene. In this paper, we first briefly introduce the preliminary understanding of the microstructure and growth behavior of graphene on copper, and then focus on the recent progress on the quality improvement, number of layers control and transfer-free growth of graphene. In the end, we attempt to analyze the possible development of CVD growth of graphene in future, including the controlled growth of large-size single-crystal graphene and bilayer graphene with different stacking orders.

Transfer‐Free Growth of Few‐Layer Graphene by Self‐Assembled Monolayers

Graphene layers are directly synthesized on an oxide substrate without transfer. The catalytic structure aids graphene formation without the vaporization of a self-assembled monolayer (SAM) material and induces direct growth of graphene on the substrate. Film uniformity and the number of graphene layers are modulated. The catalytic structure and growth process provide a robust method for transfer-free graphene growth with uniform thickness.