Substrates For Graphene Growth Research Articles

Low-Temperature Direct Growth of Nanocrystalline Multilayer Graphene on Silver with Long-Term Surface Passivation.

A wide variety of transition metals, including copper and gold, have been successfully used as substrates for graphene growth. On the other hand, it has been challenging to grow graphene on silver, so realistic applications by combining graphene and silver for improved electrode stability and enhanced surface plasmon resonance in organic light-emitting diodes and biosensing have not been realized to date. Here, we demonstrate the surface passivation of silver through the single-step rapid growth of nanocrystalline multilayer graphene on silver via low-temperature plasma-enhanced chemical vapor deposition (PECVD). The effect of the growth time on the graphene quality and the underlying silver characteristics is investigated by Raman spectroscopy, X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and cross-sectional annular dark-field scanning transmission electron microscopy (ADF-STEM). These results reveal nanocrystalline graphene structures with turbostratic layer stacking. Based on the XPS and ADF-STEM results, a PECVD growth mechanism of graphene on silver is proposed. The multilayer graphene also provides excellent long-term protection of the underlying silver surface from oxidation after 5 months of air exposure. This development thus paves the way toward realizing technological applications based on graphene-protected silver surfaces and electrodes as well as hybrid graphene-silver plasmonics.

Crystallographic Texture and Applications of Pure Cu Formed by Shot Peening

In article number 2100550, Hisashi Sato and co-workers have investigated the deformation texture formed by shot-peening of pure Cu. The process that leads to the observed deformation texture is clarified. It is found that the {110} plane of the pure Cu crystal is strongly aligned on the peened surface. It is expected that the pure Cu with this crystal orientation distribution can be applied as a substrate for graphene growth. A growth test by chemical vapor deposition shows high-quality graphene on the shot-peened Cu specimen.

Boron-doped graphene from boron-doped copper substrate for self-powered photodetector

We investigate a method to prepare boron-doped graphene (BG) using a boron-doped copper film as both the substrate for graphene growth and the boron dopant source. About 1.6 at.% of boron was incorporated in the BG film. The BG had a bilayer structure, whereas the undoped pristine graphene (PrG) had a monolayer structure. The graphene films were transferred to the surface of n-type Si to fabricate PrG/n-Si and BG/n-Si diodes. The BG/n-Si diode had a slightly larger Schottky barrier height than the PrG/n-Si, indicating p-type doping in the BG film. Both the BG/n-Si and PrG/n-Si exhibited self-powered photodetection to 0.3 mW/cm2 of 365 nm UV light, and the ON/OFF ratio was 1.5 × 104 for the BG/Si diode and 2.9 × 103 for the PrG/Si diode. Compared with the PrG/n-Si diode, the BG/n-Si had a higher ON/OFF ratio due to its lower dark current and a higher barrier height.

Native and graphene-coated flat and stepped surfaces of TiC

Titanium carbide attracts growing interest as a substrate for graphene growth and as a component of the composite carbon materials for supercapacitors, an electrode material for metal-air batteries. For all these applications, the surface chemistry of titanium carbide is highly relevant and being, however, insufficiently explored especially at atomic level is a subject of our studies. Applying X-ray photoelectron spectroscopy (XPS) to clean (111) and (755) surfaces of TiC, we were able to obtain the detailed spectroscopic pattern containing information on the plasmon structure, shake up satellite, the peak asymmetry and, finally, surface core level shift (SCLS) in C 1s spectra. The latter is essential for further precise studies of chemical reactions. Later on, we studied interface between TiC (111) and (755) and graphene and found the SCLS variation due to strong chemical interaction between graphene and substrate. This interaction is also reflected in the peculiar band structure of graphene probed by angle-resolved photoelectron spectroscopy (ARPES). Based on LEED data the structure is close to (7√3 × 7√3)R30°, with graphene being slightly corrugated. We found that similarly to the graphene on metals, the chemical interaction between graphene and TiC can be weakened by means of intercalation of oxygen atoms underneath graphene.

Single Crystalline Metal Films as Substrates for Graphene Growth

AbstractSingle crystalline metal films deposited on YSZ‐buffered Si(111) wafers were investigated with respect to their suitability as substrates for epitaxial graphene. Graphene was grown by CVD of ethylene on Ru(0001), Ir(111), and Ni(111) films in UHV. For analysis a variety of surface science methods were used. By an initial annealing step the surface quality of the films was strongly improved. The temperature treatments of the metal films caused a pattern of slip lines, formed by thermal stress in the films, which, however, did not affect the graphene quality and even prevented wrinkle formation. Graphene was successfully grown on all three types of metal films in a quality comparable to graphene grown on bulk single crystals of the same metals. In the case of the Ni(111) films the originally obtained domain structure of rotational graphene phases could be transformed into a single domain by annealing. This healing process is based on the control of the equilibrium between graphene and dissolved carbon in the film. For the system graphene/Ni(111) the metal, after graphene growth, could be removed from underneath the epitaxial graphene layer by a pure gas phase reaction, using the reaction of CO with Ni to give gaseous Ni(CO)4.

Alloyed surfaces: New substrates for graphene growth

We report a systematic ab-initio density functional theory investigation of Ni(111) surface alloyed with elements of group IV (Si, Ge and Sn), demonstrating the possibility to use it to grow high quality graphene. Ni(111) surface represents an ideal substrate for graphene, due to its catalytic properties and perfect matching with the graphene lattice constant. However, Dirac bands of graphene growth on Ni(111) are completely destroyed due to the strong hybridization between carbon pz and Ni d orbitals. Group IV atoms, namely Si, Ge and Sn, once deposited on Ni(111) surface, form an ordered alloyed surface with 3×3-R30° reconstruction. We demonstrate that, at variance with the pure Ni(111) surface, alloyed surfaces effectively decouple graphene from the substrate, resulting unstrained due to the nearly perfect lattice matching and preserves linear Dirac bands without the strong hybridization with Ni d states. The proposed surfaces can be prepared before graphene growth without resorting on post-growth processes which necessarily alter the electronic and structural properties of graphene.

High-quality graphene synthesis on amorphous SiC through a rapid thermal treatment

Synthesizing high-quality graphene by catalytic transformation from amorphous silicon carbide (a-SiC) through a rapid thermal treatment (RTT) method is reported. SiO2/Si substrates are coated by a-SiC films followed by Cu and Ni films deposited sequentially. The samples are then thermally annealed by RTT for the synthesis of high-quality graphene in only 3 min. The synergistic effect of Cu and Ni catalyst is observed. We conjecture that the inserted copper film acts not only as a catalyst or substrate for graphene growth but also as a barrier for carbon diffusion to facilitate the synthesis of monolayer graphene, while the nickel film acts as another catalyst and forms Cu-Ni alloy to lower the catalytic temperature. In this paper, we present a simple and time-saving way in preparation of high-quality graphene and put forward a brief theoretical model for the growth of graphene.

Induction heating-assisted repeated growth and electrochemical transfer of graphene on millimeter-thick metal substrates

Chemical vapor deposition in a hot wall reactor is the most common technique for the production of large area single layer graphene. However, growth in this type of reactors is time consuming and the results are limited by the surface quality of the widely used catalytic metal foils as growth substrates. In this work we demonstrate the use of millimeter-thick Cu and Pt substrates for graphene growth via inductive magnetic heating, which allows for fast temperature ramps during heat up and cooling. Based on a detailed growth study, a two-step growth process resulting in continuous monolayer graphene films of high crystal quality with grain size of larger than 90μm is established. An electrochemical transfer process is used to separate the graphene film from the metallic substrate, yielding excellent results in terms of defect density, doping and residual contamination. Back-gated graphene field-effect transistors fabricated on Si/SiO2 structures exhibit a high reproducibility with a peak mobility higher than 4000cm2/Vs. The combination of the highly time efficient graphene growth and electrochemical transfer together with the reusability of the growth substrates and the possibility of applying novel surface pretreatments pave the way for the use of high quality substrates in industrial applications.

The pre-treatment of copper for graphene synthesis

Graphene synthesis by chemical-vapor-deposition (CVD) has attracted great interest. As the substrates for graphene growth, copper has become a common choice because its capacity could produce high-quality and uniform monolayer graphene. Morphology and surface conditions of the copper foil have great influence on the quality of the graphene grown on it. Here we report a rapid and effective copper pre-treatment method to improve the quality of graphene. After a pre-etching in 1 mol/L Fe(NO3)3 aqueous solutions for 90 s, the quality of the copper foil surface has been improved. Compared with the HCl treatment and electro-chemical polishing, Fe(NO3)3 pre-etching can generate a better result and has been verified to have general applicability for different types of copper foils.

リアルタイム光電子分光によるグラフェン・オン・ダイヤモンド形成過程の観察

Graphene-on-insulator structures are required for fabrication of the graphene transistor. Diamond has been attracted as the substrate for graphene growth because it has a larger band gap and break down voltage compared with SiC. The detail of graphitization on a diamond surface has not yet been clarified because the nondestructive evaluation for graphene on diamond (GOD) structure was hard. In this study, we have developed the evaluation method of GOD based on the photoemission spectroscopy using synchrotron radiation focusing the shift of photoelectron spectra due to band bending. We can clearly determine the graphitization temperature on the diamond C(111) surface as approximately 1120 K, which is lower than that on an SiC substrate. It is also confirmed from C 1s photoelectron spectra, there is the buffer layer at the interface between the grapheme layer and the diamond substrate.