Graphene synthesis by microwave plasma chemical vapor deposition: analysis of the emission spectra and modeling

Abstract

In this article, we report on some of the fundamental chemical and physical processes responsible for the deposition of graphene by microwave plasma-enhanced chemical vapor deposition (PECVD). The graphene is grown by plasma decomposition of a methane and hydrogen mixture (CH 4 /H 2) at moderate pressures over polycrystalline metal catalysts. Different conditions obtained by varying the plasma power (300-400 W), total pressure (10-25 mbar), substrate temperature (700-1000°C), methane flow rate (1-10 sccm) and catalyst nature (Co-Cu) were experimentally analyzed using the in situ optical emission spectroscopy (OES) technique to assess the species rotational temperature of the plasma and the H-atom relative concentration. Then, two modeling approaches were developed to analyze the plasma environment during graphene growth. As a first approximation, the plasma is described by spatially averaged bulk properties, and the species compositions are determined using kinetic rates in the transient zero-dimensional (0D) configuration. The advantage of this approach lies in its small computational demands, which enable rapid evaluation of the effects of reactor conditions and permit the identification of dominant reactions and key species during graphene growth. This approach is useful for identifying the relevant set of species and reactions to consider in a higher-dimensional model. The reduced chemical scheme was then used within the self-consistent two-dimensional model (2D) to determine auto-coherently the electromagnetic field, gas and electron temperatures, heavy species, and electron and ion density distributions in the reactor. The 0D and 2D models are validated by comparison with experimental data obtained from atomic and molecular emission spectra.

Graphene Synthesis by Inductively Heated Copper Foils: Reactor Design and Operation

“…Regarding our preliminary question: to grow graphene from methane should we decompose the gaseous precursor by heating the gas in the volume or can the catalyst directly make this decomposition without the need to heat the overall surrounding gas? We compared temperature profiles issued from our PECVD process with a 2.45 GHz microwave [33,34] with actual calculations in inductive heating process. To depict the influence of the thermal design on the methane decomposition performances of axisymmetric PECVD and inductively heated reactors, we first compared temperature profiles above the substrate in these processes.…”

Graphene Flakes for Electronic Applications: DC Plasma Jet-Assisted Synthesis

“…Electrical properties are a key issue for a wide spectrum of applications. Generally, it should be mentioned that the plasma synthesized materials, including graphene, are characterized by the standpoint of their structural properties, and chemical content of flakes [ 30 , 48 , 49 , 50 , 51 ]. Here, we study the plasma jet-assisted synthesized graphene materials aimed at the development of electronic devices fabricated by printing techniques on a flexible substrate, providing pervasive, light-weight, and cost-effective devices.…”

Advances in Microwave‐Enhanced Chemical Vapor Deposition for Graphene Synthesis

“…Figure 1b shows the type of device as just mentioned. [11] The microwave power, gas flow and reaction temperature could be controlled independently. Additionally, the power can change with gas pressure simultaneously, which makes the excited plasma more stable.…”