Low-Temperature Nitrogen Doping of Nanocrystalline Graphene Films with Tunable Pyridinic-N and Pyrrolic-N by Cold-Wall Plasma-Assisted Chemical Vapor Deposition

Abstract

We report a viable method to produce nanocrystalline graphene films on polycrystalline nickel (Ni) with enhanced N doping at low temperatures by a cold-wall plasma-assisted chemical vapor deposition (CVD) method. The growth of nanocrystalline graphene films was carried out in a benzene/ammonia/argon (C6H6/NH3/Ar) system, in which the temperature of the substrate heated by Joule heating can be further lowered to 100 °C to achieve a low sheet resistance of 3.3 kΩ sq–1 at a high optical transmittance of 97.2%. The morphological, structural, and electrical properties and the chemical compositions of the obtained N-doped nanocrystalline graphene films can be tailored by controlling the growth parameters. An increase in the concentration of atomic N from 1.42 to 11.28 atomic percent (at.%) is expected due to the synergetic effects of a high NH3/Ar ratio and plasma power. The possible growth mechanism of nanocrystalline graphene films is also discussed to understand the basic chemical reactions that occur at such low temperatures with the presence of plasma as well as the formation of pyridinic-N- and pyrrolic-N-dominated nanocrystalline graphene. The realization of nanocrystalline graphene films with enhanced N doping at 100 °C may open great potential in developing future transparent nanodevices.

Epitaxy of III-nitrides on two-dimensional materials and its applications

“…The growth conditions of CVD were often harsh because the growth process required high-temperature cleavage of carbon precursors followed by rapid cooling to form graphene. In recent years, many scholars had conducted a lot of researches on these growth factors, and the CVD growth parameters of graphene had been optimized continuously, and now there are some feasible methods to synthesize high-quality graphene films at low temperature, [60] low pressure, [61] and metal-free substrates, [62] which gradually got rid of the constraints of strict growth conditions and expanded the applicability of CVD methods. After the research of our group, we found that the defects of graphene were directly influenced by the growth conditions, and in plasma enhanced chemical vapor deposition (PECVD), the defect type of graphene changed from vacancy to boundary type with the increase of ion source power; the morphology of graphene changed from 2D to 3D with the increase of temperature or ion source power, [63] which was beneficial for us to prepare especial graphene on non-catalytic substrate, such as sapphire, GaN, and AlN substrates.…”

Nanocrystalline Materials: Synthesis, Characterization, Properties, and Applications

“…This method of production is very costefficient for the bulk synthesis of CNTs. Juggernauth et al [95] used the CVD process and adopted step-wise control of various process variables such as gas flow, pressure, and time for the growth of films. This allowed them to successfully deposit the vanadium ox- Although the basic principle of the CVD process remains the same, a lot of research modification has been done over the past few years to cater to different kinds of NC materials.…”

“…The process parameters to produce these CNT-mediated vanadium oxide structures could easily be altered for a variety of functional applications such as electrochemical cells, physical and chemical sensors, etc. Ariffin et al [95] also reported a novel method. They used a cold-wall plasma-assisted CVD process to synthesize nitrogen-doped NC graphene layers on a polycrystalline Ni substrate at considerably lower temperatures of around 100 • C. This process could be used to develop transparent nano-scale devices soon.…”

Semitransparent Solar Cells Employing n-Type Graphene on LaVO3

“…For high-performance semitransparent solar cells, a method to improve the conductivity while maintaining excellent T of Gr is required. Chemical doping is one of the techniques to reduce the sheet resistance ( R s ) of Gr simply, − but the R s of Gr increases over time due to deterioration in air. Therefore, it is very important to find a dopant that can maintain the R s of Gr for a long time at room temperature.…”