Analysis of hydrogen plasma in a microwave plasma chemical vapor deposition reactor

Shivkumar, Gayathri; Tholeti, Siva Sashank; Alrefae, Majed A.; Fisher, Timothy S.; Alexeenko, Alina

doi:10.1063/1.4943025

Cited by 41 publications

(28 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As shown in Figure. 6, increasing the microwave power from 340 to 580 W, as the pressure is increased simultaneously increases the H 2 rotational temperatures from 930 to 1340 K. This result is explained by two interdependent simultaneous effects: (i) because the gas temperature depends on the energy transferred from the electric field to the gas molecules by electrons during collisions, increasing the plasma power increases the gas temperature; (ii) increasing the pressure increases the collision frequency in the plasma and then the energy transfer between electrons and gas molecules. These results are in good agreement with the OES measurements suggested that the gas temperature has weak dependence on power and very strong dependence on pressure [77]. Rotational energy, E J' (cm -1 ) Figure 6.…”

Section: A Experimental Resultssupporting

confidence: 89%

“…Since atoms, ions and molecules create a unique emission spectrum specific to each element, OES enables their identification. OES has the advantage of being noninvasive and has already been used to monitor the state of plasma in situ and to determine the concentration of the species and different plasma parameters, such as the electron densities and temperatures of diamond [85][86][87][88][89][90][91][92][93], carbon nanotubes [94] and, more recently, graphene [77]. Since an important step in achieving control of defect-free and few-layers graphene synthesis involves understanding the role of plasma properties, OES can help to identify the species responsible for graphene growth.…”

Section: B Plasma Optical Emission Spectroscopymentioning

confidence: 99%

“…For a rotational transition within a particular electronic state and vibrational band that follows a Boltzmann distribution, the emission intensity can be rewritten from Eq. (1) for a given wavelength  as [77] (2)…”

Section: Determination Of the H 2 Rotational Temperaturementioning

confidence: 99%

“…The literature contains few studies involving plasma diagnostics and CVD modeling. Shivkumar et al proposed a numerical model to simulate hydrogen plasma inside a microwave plasma CVD cavity used for graphene growth [77]. Their model solves fully coupled Maxwell and heat-transfer equations to predict the electric field, electron number density, electron temperature, and gas temperature in a 2D axisymmetric configuration.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Pashova

Hinkov

Aubert

et al. 2019

Plasma Sources Sci. Technol.

View full text Add to dashboard Cite

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.

show abstract

Section: A Experimental Resultssupporting

confidence: 89%

Section: B Plasma Optical Emission Spectroscopymentioning

confidence: 99%

Section: Determination Of the H 2 Rotational Temperaturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Pashova

Hinkov

Aubert

et al. 2019

Plasma Sources Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…The rotational temperatures of

{normalN}_{2}^{+} (B \to X)

and

{normalH}_{2} true({normald}^{3} {normalΠ}_{u} \to {normala}^{3} {normalΣ}_{g}^{+} true)

were extracted from their emission spectra and interpreted as the gas temperature in the plasma, as shown in Figure c. A Boltzmann plot is used to derive the rotational temperatures of these two species . In the center region of the plasma, H 2 has a relatively higher emission intensity and lacks perturbation from other rotational lines, making it a clearer signal for determining the temperature.…”

Section: Resultsmentioning

confidence: 99%

Roll‐to‐Roll Production of Graphitic Petals on Carbon Fiber Tow

2018

Self Cite

View full text Add to dashboard Cite

A scalable roll-to-roll process is employed to produce graphitic petals. A 1-meter sample of graphitic petals on carbon fiber tow is produced with a roll-to-roll radio-frequency plasma chemical vapor deposition method. Microscale characterization reveals increasingly graphitic carbon structures with production time. Correspondingly, macroscale characterization shows enhanced functional performance with production time: decreasing electrical resistance and increasing capacitance. Using optical emission spectroscopy, important species in the plasma are studied and used to determine the plasma gas temperature. The results demonstrate that 1) successful cost-driven production of graphitic petals is possible, 2) a plasma diagnostic technique is capable of real-time process monitoring, and 3) meaningful material characterization methods are amenable to a production setting. Finally, valuable experiential learnings are shared to inform future equipment design and process development.

show abstract

Covalently‐Bonded Diaphite Nanoplatelet with Engineered Electronic Properties of Diamond

Zhai,

Zhang,

Chen

et al. 2024

Adv Funct Materials

View full text Add to dashboard Cite

Diamond, as a highly promising “extreme” semiconductor material, necessitates electronic property engineering to unleash its full potential in electronic and photonic devices. In this work, the diaphite nanoplatelet, consisting of (11) planes of diamond nanoplatelet covalently bonded with graphite (0001) planes, is facilely synthesized using one‐step microwave plasma enhanced chemical vapor deposition method. The high‐energy plasma created by the pillar plays a crucial role in the formation. Importantly, altered electronic and optical properties are determined in the diaphite nanoplatelet through electron energy loss spectrum, density functional theory calculations, and cathodoluminescence spectroscopy. It is revealed that the strong sp3/sp2‐hybridized interfacial covalent bonding in the diaphite nanoplatelet induces the electron transfer from diamond to graphite. This modulates the electronic structure of the near‐interface layer of diamond and triggers a new local trapping band below the conduction band minimum within the bandgap. Consequently, the covalently‐bonded diaphite exhibits a different optical emission characteristic ranging from 2.5 to 3.64 eV, featuring a significant peak blueshift of 430 meV compared to the H‐terminated diamond. This work demonstrates a novel method to engineer the electronic properties of diamond, opening avenues for functional semiconductor device applications of diamond.

show abstract

Analysis of hydrogen plasma in a microwave plasma chemical vapor deposition reactor

Cited by 41 publications

References 34 publications

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

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

Roll‐to‐Roll Production of Graphitic Petals on Carbon Fiber Tow

Covalently‐Bonded Diaphite Nanoplatelet with Engineered Electronic Properties of Diamond

Contact Info

Product

Resources

About