Evolution of Structural and Electrical Properties of Carbon Films from Amorphous Carbon to Nanocrystalline Graphene on Quartz Glass by HFCVD

Abstract

Direct growth of graphene films on glass is of great importance but has so far met with limited success. The noncatalytic property of glass results in the low decomposition ability of hydrocarbon precursors, especially at reduced temperatures (<1000 °C), and therefore amorphous carbon (a-C) films are more likely to be obtained. Here, we report the hydrogen influence on the structural and electrical properties of carbon films deposited on quartz glass at 850 °C by hot-filament chemical vapor deposition (HFCVD). The results revealed that the obtained a-C films were all graphitelike carbon films. Structural transition of the deposited films from a-C to nanocrystalline graphene was achieved by raising the hydrogen dilution ratios from 10 to over 80%. On the basis of systematic structural and chemical characterizations, a schematic process with three steps including sp chain aggregation, aromatic ring formation, and sp bond etching was proposed to interpret the structural evolution. The nanocrystalline graphene films grown on glass by HFCVD exhibited good electrical performance with a carrier mobility of 36.76 cm/(V s) and a resistivity of 5.24 × 10 Ω cm over an area of 1 cm. Temperature-dependent electrical characterizations revealed that the electronic transport in carbon films was dominated by defect, localized, and extended states, respectively, when increasing the temperature from 75 to 292 K. The nanocrystalline graphene films presented higher carrier mobility and lower carrier concentration than those of a-C films, which was mainly attributed to their smaller conductive activation energy. The present investigation provides an effective way for direct growth of graphene films on glass at reduced temperatures and also offers useful insights into the understanding of structural and electrical relationship between a-C and graphene.

Kinetics of graphitization of thin diamond-like carbon (DLC) films catalyzed by transition metal

“…The carrier density given by equation 3is quoted to around 10 20 -10 21 cm -3 . It must be noted that the transport properties obtained, with mobility of around 20 cm 2 /V.s at the best, are quite comparable with a recent publication on ta-C:H samples annealed at higher temperatures [35].…”

Optimizing the tribological performance of DLC-coated NBR rubber: The role of hydrogen in films

“…So, hydrogen atoms can promote the topological order of the graphite phase and the increase of the aromatic hydrocarbon bond. Besides, the amorphous property and poor thermal conductor of NBR rubber may accumulate sufficient plasma activation energy and lead to random nuclei of graphite phase [34]. The load-displacement curves further demonstrate that DLC films prepared by the increasingly hydrogenated CH 4 gas discharge plasma own relatively inferior mechanical properties (Fig.…”

“…, thereby producing small grain size and impairing the mechanical properties of the film [34]. In addition, the previous results demonstrate that hydrogen atoms passivate the dangling bonds generated on the friction interfaces and prevent the adhesive component [22].…”

Controlling the Nucleation and Growth Orientation of Nanocrystalline Carbon Films during Plasma-Assisted Deposition: A Reactive Molecular Dynamics/Monte Carlo Study

“…The many favorable properties of nanocrystalline carbon films have allowed for a great development in a wide range of applications, such as surface modification, , electric and thermal conductivity modulation, , and energy storage and conversion. − In these applications, the grain size and growth orientation of nanocrystals can significantly impact their physical and chemical properties. For instance, researchers have found that by changing the grain size and growth orientation of graphite-like nanocrystals, nanocrystalline carbon films may exhibit very different properties of through-film resistance − and atmospheric surface absorption. , However, despite that, many techniques including substrate catalysis, , ion bombardment, , and electron ,, and laser irradiations have been developed to increase the nucleation density of graphene-based nanocrystals, as researchers continue seeking more effective and precise methods to accelerate the nucleation process and to control the grain size and growth orientation of nanocrystalline carbon films.…”

“…Plasma-assisted depositions, mainly including plasma enhanced chemical vapor deposition (PECVD) and magnetron sputtering deposition in combination with an unbalanced magnetron configuration, , have become major techniques in the preparation of nanocrystalline carbon films. Since these bottom-up growth processes always involve the Ostwald’s ripening of carbon nuclei, whether the initial carbon nuclei are crystallized can significantly influence the final microstructures of nanocrystalline carbon films.…”