CH Species Research Articles

Characterization of Ethanol Plasma Glow Discharge, Decomposition in Several Species and Solid Film Formation

Ethanol plasma produced in low pressure with constant flux has been characterized in situ by optical emission spectroscopy (OES) and a Langmuir probe. From these methods, hydrogen and carbon monoxide are the main products from the ethanol decomposition in the plasma. In addition, C 2 , OH, CH, O + 2 , and H α species were identified. The values obtained for electron density and temperatures were 1.26 × 10 18 m -3 and 1.16 eV, respectively. The mass deposited (MD) on the electrode was analyzed by scanning electron microscopy and Fourier transform infrared spectroscopy (FT-IR) techniques. The morphology of the MD changes as a function of the discharge time from thin film to a cluster formation. The FT-IR results show that the main absorbance corresponds with C-H bonds, indicating that the mass deposit is formed mainly by this molecular fraction, which agrees with the CH species identified as the less abundant molecule in the plasma by OES. In addition, C≡C, O-H, C-H, C=C, and C-O bonds were identified.

Abrupt SiGe and Si Profile Fabrication by Introducing C Delta Layer

Epitaxial SiGe is widely used for many applications e.g. stressor for C-MOS channel (1), NPN HBT base (2) and SiGe superlattice bolometer (3). However, in order to fabricate shallow and abrupt SiGe profiles, diffusion control at Si and SiGe interface is important, especially at high Ge content. To prevent the interdiffusion, a possible solution could be to lower the temperature during and after the SiGe epitaxy, however it is not preferred because flexibility of process integration is restricted. To reduce the interdiffusion, introduction of C delta layer at the interface is reported (4). Here we investigated the influence of the C delta layer on the interdiffusion and crystal quality. Epitaxial Si/SiGe growths are carried out using a single wafer reduced pressure CVD system. After native oxide removal of a Si(001) wafer by 1000oC prebake in H2, ~10 nm thick Si0.5Ge0.5 is deposited using H2-SiH4-GeH4 at 500oC. Then a Si cap layer is deposited at 500oC to 575oC using H2-Si2H6. To discuss the influence of a C delta layer on the interdiffusion and crystallinity, CH3SiH3 exposure with H2 carrier gas is performed at 500oC before/after the SiGe growth. Profiles of Ge content and crystal perfection are simulated by fitting of XRD rocking curves of Si(004) diffraction. Crystal perfection ranges from 1 (ideal crystal) to 0 (amorphous/polycrystalline). Crystal perfection of SiGe with C delta layers at different positions without/with postannealing at 575oC is shown in Fig. 1. In the case of samples without postannealing, the influence of C delta layers on the crystal perfection is minor. On the other hand, in the case of samples after the postannealing at 575oC, suppression of crystallinity degradation is observed only for the samples with C delta layer at the SiGe surface. C delta layer at the interface between Si and SiGe is less impacting on the suppression of crystallinity degradation. The degradation of SiGe crystallinity is also detected by spectroscopic ellipsometry analysis. The C delta layer at the surface seems to be suppressing defect formation of SiGe at 575oC. Further investigation is required for clarifying the mechanism behind. Figure 2 shows crystal perfection of a Si cap layer deposited on SiGe without/with C delta layers at different temperatures. Note that no defects are observed for all Si growth temperatures used if the Si layer is deposited on Si surface. That means the Si2H6 based Si epitaxy for its own is working perfectly. In the case of the sample without C spike at the interfaces, crystal perfection is ~0.8 from 500oC to 550oC, indicating high crystal quality. But at 575oC, crystal perfection becomes zero because Si is grown on defective SiGe. On the other hand, in the case of the sample with C delta layers at the interface, low crystal perfection of Si cap layer is observed at 500oC. With increasing Si cap growth temperature the crystal perfection of the Si cap becomes higher. At above 550oC, crystal perfection reached ~0.9. The high crystallinity of Si cap at 575oC is caused by maintained crystallinity of the SiGe by the C delta layer. A possible interpretation of low crystallinity Si growth at 500oC and improved Si crystal quality at higher temperature is; Adsorbed CH3 species on SiGe surface at 500oC causes probability of disordered Si2H6 adsorption.At higher temperature, hydrogen desorption from the SiGe surface and reallocation are pronounced. The CH3species may react with dangling bond at substitutional site. (C desorption is not evidenced by SIMS measurement). SiGe/Si cap profiles simulated by XRD without and with C delta layers at interface are shown in Fig. 3 (a). By depositing Si cap at 550oC, smearing of SiGe profile is observed for sample without C delta layers. On the other hand, in the case of sample with C delta layer at interface, steep SiGe profile is observed. This diffusion suppression by C delta layer is also detected by SIMS (Fig. 3 (b)). The SiGe interdiffusion process is reported as vacancy mechanism (5). Possible assumption of the diffusion suppression effect is vacancy trap near the interface by C. These results shown here offer the opportunity of interdiffusion control of SiGe/Si interface using C delta doping while maintaining high crystal perfection. References (1) J. Kasim et al. Solid-State Electron. 110 (2015) 19 (2) A. Fox et al. IEEE Electron Device Lett. 36 (2015) 642 (3) L. Zhang et al. DOI: 10.1109/RSETE.2012.6260364 (4) T. Hirano et al. Thin Solid Films 518 6 1 (2011) S222 (5) N. Ozguven et al. J. Appl. Phys 90 (2007) 082109 Figure 1

Tuning the adsorption behaviors and conversions of CHx species on metal embedded graphene surfaces

The stable geometries and adsorption behaviors of CHx (x=0, 1, 2, 3, 4) species on the single-atoms metal embedded graphene (M-graphene) are investigated by first-principles calculations. It is found that the adsorbed CHx species have the different stability on the M-graphene surfaces, and the adsorption energies of CHx species on the Al-graphene are smaller than those on the Au-graphene. Besides, the adsorption of CHx species can regulate the electronic structure and magnetic properties of M-graphene systems. Moreover, the diffusion pathways of CHx (x=0–3) species and the conversion reactions between CHx (x=1–4) species on the M-graphene are analyzed systematically. In the conversion reactions, the adsorbed C and CH species can be more easily converted into the CHx+2 species through the hydrogenation reactions, the broken M-H bond and the formation of new CH bond need overcome the large energy barriers. These results give a clue for designing graphene-based anode materials with high activity and inhibiting carbon deposition.

Abrupt SiGe and Si Profile Fabrication by Introducing C Delta Layer

High quality and steep Si / Si0.5Ge0.5 / Si profile is fabricated by introducing a C delta layer at the interface using reduced pressure chemical vapor deposition system. The Si0.5Ge0.5 and Si layers are deposited by H2-SiH4-GeH4 at 500oC and H2-Si2H6 at 500oC to 575oC, respectively. By introducing a C delta layer at the surface, roughening of the Si0.5Ge0.5 surface is maintained at 575oC due to suppressed surface migration of Si and Ge as well as defect injection into the Si0.5Ge0.5 layer resulting in high crystallinity Si cap layer growth. Adsorbed CH3 species at the surface are preventing the epitaxial Si cap layer growth at 500oC, but it is possible to deposit high quality epitaxial Si at higher temperature because of hydrogen-desorption from adsorbed CH3. Interdiffusion of Si and Ge at the interface is observed at 525oC in the case of sample without C delta layers, but the interdiffusion is suppressed even at 575oC by introducing C delta layers.

New Late Devonian phacopid trilobites from Marhouma, SW Algerian Sahara

Late Devonian phacopid trilobites of the SW Algerian Sahara are recognised as being the most diversified in cratonic North Gondwana. The first trilobites in the Frasnian of Algeria were discovered in the Marhouma S section near Beni Abbes: the new genus Chlupacops with two species Ch. laticeps gen. et sp. nov. and Ch. aff. cryphoides (Richter&Richter) are described from the uppermost part of the Cheffar el Ahmar Formation of mid-Frasnian age. The latter taxon is compared with the type material of Ch. cryphoides (Richter&Richter) from Sessacker (Rhenish Slate Mts). New occurrences of lower Famennian phacopids in the “Argiles de Marhouma” Formation comprise the new genus Enigmapyge with its type species E. marhoumensis gen. et sp. nov., two species of Trimerocephalus: T. mahboubii sp. nov. and T. caecus (Gurich), two species of Trifoliops: Tr. cronierae sp. nov. and Tr. trifolius (Osmolska). In the middle Famennian, pygidia of Dianops cf. algeriensis Cronier were discovered. With the exception of the latter all taxa of the Marhouma S section can be assigned to conodont zones. The Algerian Late Devonian phacopids comprise predominantly blind or reduced-eyed taxa of basinal offshore environment. They are closely related to contemporaneous occurrences on the epicontinental margins of Laurussia as well as in Gondwana derived terranes and as such bear witness of the absence of oceanic barriers.

Adsorption properties of CO, H2 and CH4 over Pd/γ-Al2O3 catalyst: A density functional study

Density functional theory (DFT) calculations were employed to investigate the adsorption characteristics of carbon monoxide (CO), hydrogen (H2), and methane (CH4) on the surface of clean γ-Al2O3 and Pd supported γ-Al2O3, which is of significant for catalytic combustion. The adsorption intensities of the three gas molecules in pure γ-Al2O3 (1 1 0) and Pd/γ-Al2O3 (1 1 0) were in the order of CO>H2>CH4. The corresponding adsorption energies on the Pd/γ-Al2O3 (1 1 0) surface were at least three times higher than those on γ-Al2O3 (1 1 0). Anlysis of Mulliken population and partial density of states (PDOS) showed that the adsorption mechanisms were as follow: (a) CO stably adsorbed on the bridge site of dimer Pd with two CPd bonds because of charges transfer from the surface to CO, and the triple bond (CO) was broken to a double bond (CO); (b) H2 was dissociated into hydrogen atoms on the dimer Pd and produced a stable planar configuration; and (c) the tetrahedral structure of CH4 was destroyed on the surface and formed a CH3 species bonded to the Pd atom, which contributes to the orbital hybridization between C and Pd atoms.

Synthesis of flat sticky hydrophobic carbon diamond-like films using atmospheric pressure Ar/CH4 dielectric barrier discharge

An Ar/CH4 atmospheric pressure dielectric barrier discharge (AP-DBD) was used to synthesize sticky hydrophobic diamond-like carbon (DLC) films on glass surface. The film is formed with plasma treatment duration shorter than 30 s, and water contact angles larger than 90° together with contact angle hysteresis larger than 10° can be achieved. According to Fourier transform infrared spectroscopy and atomic force microscopy analysis, hydrocarbon functional groups are created on the glass substrate, producing coatings with low surface energy (∼35 mJ m−2) with no modification of the surface roughness. To infer the plasma processes leading to the formation of low energy DLC surfaces, optical emission spectroscopy was used. From the results, a direct relationship between the CH species present in the plasma and the carbon concentration in the hydrophobic layer was found, which suggests that the CH species are the precursors of DLC film growth. Additionally, the plasma gas temperature was measured to be below 350 K which highlights the suitability of using AP-DBD to treat thermo-sensitive surfaces.

Unraveling the role of support surface hydroxyls and its effect on the selectivity of C2 species over Rh/γ-Al2O3 catalyst in syngas conversion: A theoretical study

The supported Rh-based catalysts exhibit the excellent catalytic performances for syngas conversion to C2 species. In this study, all possible elementary steps leading to C2 species from syngas have been explored to identify the role of support and its surface hydroxyls over Rh/γ-Al2O3 catalyst; Here, the results are obtained using density functional theory (DFT) method. Two models: Rh4 cluster supported on the dry γ-Al2O3(110) surface, D(Rh4), and on the hydroxylated γ-Al2O3(110) surface, H(Rh4), have been used to model Rh/γ-Al2O3 catalyst. Our results show that CO prefers to be hydrogenated to CHO, subsequently, starting from CHO species, CH and CH2 species are the dominate monomers among CHx(x=1–3) species rather than CH3 and CH3OH on D(Rh4) and H(Rh4) surfaces, suggesting that γ-Al2O3-supported Rh catalyst exhibits the high selectivity towards CHx formation compared to the pure Rh catalyst. On the other hand, D(Rh4) is more favorable for C2 hydrocarbon (C2H2) formation, whereas H(Rh4) surface easily produces C2 hydrocarbon (C2H2) and C2 oxygenates (CHCO,CH2CHO), indicating that the surface hydroxyls of support can affect the selectivity of C2 species over Rh/γ-Al2O3 catalyst in syngas conversion. Moreover, compared to the pure Rh(111) surface, Rh/γ-Al2O3 catalyst can achieve the excellent catalytic performances for syngas conversion to C2 species.

Mechanism studies concerning carbon deposition effect of CO methanation on Ni-based catalyst through DFT and TPSR methods

Ni-based catalysts, which are widely used, have produced promising results for methane formation from syngas. The key to rational design of catalysts and corresponding technological parameters is an understanding of the underlying mechanism of CO methanation at the molecular level. In the present study, the mechanism of CO methanation on Ni (111) and carbon-doped Ni(111) (C-Ni(111)) surfaces was investigated by means of temperature-programmed surface reaction and density functional theory method. Our conclusion is that the energy barrier of CO dissociation decreases significantly on the C-Ni(111) surface. The rate-limiting steps of CO methanation on the Ni(111) and C-Ni(111) surfaces are CO dissociation and CH3 species hydrogenation, respectively. Results from comparison of the activation barriers and rate-limiting steps indicate that CH4 production may be improved by slight deposition of carbon.

Some aspects of speciation and reactivity of mercury in various matrices

Speciation of mercury compounds in environmental and biological samples requires different techniques and different approaches. This speciation is mandatory to explain the toxicity, the reactivity and the bioavailability of mercury. It is dominated by inorganic mercury species Hg(II) and Hg(0), and the organic mercury species CH3Hg and (CH3)2Hg. In this paper, some aspects of mercury speciation are presented in terms of: - mercury reactivity (Hg(II) complexation and reduction), - mercury species distribution in the main compartments of the environment La spéciation du mercure dans les échantillons environnementaux et biologiques nécessite différentes techniques et différentes approches. Cette spéciation permet d’expliquer la toxicité, la réactivité et la biodisponibilité du mercure. Elle est dominée par les espèces de mercure inorganique Hg(II) et Hg(0) et les espèces organiques CH3Hg et (CH3)2Hg. Dans cet article, quelques aspects de la spéciation du mercure sont présentés en termes de : - réactivité du mercure (complexation et réduction de Hg(II)), - distribution des espèces du mercure dans les principaux compartiments de l’environnement.

Metathesis of C5–C8 Terminal Olefins on Re2O7/Al2O3 Catalysts

Primary products of the interaction of terminal olefins C5–C8 with Re2O7/Al2O3 catalysts are established. The rupture of the C=C bond of the olefin occurs with formation of a carbene localized at a rhenium ion, with the alkylidene fragment in the produced carbene being the CH2=group of the terminal alkene molecule. Thus M=CH2 species and lower normal α-olefins are formed.

Origin of Chemical Order in a-SixCyHz: Density-Functional Tight-Binding Molecular Dynamics and Statistical Thermodynamics Calculations

We investigate the growth mechanisms and structures of hydrogenated amorphous silicon carbide (a-SixCyHz) during chemical vapor deposition (CVD) by using density-functional tight-binding molecular dynamics (DFTB MD) and statistical thermodynamics (ST) calculations. Our multiscale modeling from an atomic to an experimental scale allows us to bridge the gap between micro- and macroscopic knowledge. As in any compound, the degree of chemical order in a-SixCyHz is of practical importance. However, the origin of chemical order and effects of composition on the degree of chemical order remain unknown. First, CVD simulations are performed by the impingement of CH3 and SiH3 radicals on a Si(001)-(2 × 1):H surface with DFTB MD. The initial growth process consists of an abstraction-adsorption mechanism, where a CH3 or SiH3 radical abstracts a H atom and forms a dangling bond (DB) on the surface, and a subsequent CH3 or SiH3 radical is adsorbed on the DB. A surface-adsorbed CH2 species with a DB is inserted into a n...

Insight into the mechanism about the initiation, growth and termination of the C-C chain in syngas conversion on the Co(0001) surface: a theoretical study.

The initiation, growth and termination mechanism of the C-C chain from syngas on the Co(0001) surface have been investigated using DFT calculations. Our results show that CHx (x = 1-3) formation is easier than CH3OH, both CH and CH2 species are the dominant forms of CHx (x = 1-3), both CH and CH2 species dominantly interact with CHO to form CHCHO and CH2CHO, and realizes the initial C-C chain formation. Then, CHCHO and CH2CHO prefer to be successively hydrogenated to CH3CHO, followed by C-O bond cleavage to give CH3CH; subsequently, CHO insertion into CH3CH can realize the further chain growth to form CH3CHCHO, followed by dissociation and hydrogenation to give CH3CHCH and CH3CH2CHO, respectively; further, CH3CHCH hydrogenation or CH3CH2CHO dissociation via the C-O bond cleavage can form the CH3CH-like species CH3CH2CH intermediate. Thus, the mechanism of a C-C chain growth cycle has been proposed that starts from a CH3CH2CH intermediate, followed by repeating the above C-C chain growth cycle via CH3CH intermediates, and the C-C chain growth to higher C2+ hydrocarbons and oxygenates can be realized, in which RCH2CH prefers to interact with CHO to form RCH2CHCHO, followed by its C-O bond cleavage and its hydrogenation to form R'CHCH (R' = RCH2) and R'CH2CHO (R' = RCH2), respectively, where R'CHCH hydrogenation and C-O bond cleavage of R'CH2CHO will produce R'CH2CH. Moreover, aldehyde intermediates R'CH2CHO are expected to undergo C-O bond cleavage to five R'CH2CH (R' = RCH2) rather than its desorption and its hydrogenation to alcohol. The C-C chain termination occurs at three possible positions along the growth cycle: R'CH2CHO desorption, R'CHCH with successive hydrogenation steps to alkanes or alkenes, and R'CH2CH hydrogenation to alkanes, in which the relative importance of termination of R'CHCH and R'CH2CH with hydrocarbons will depend strongly on the hydrogen coverage on the metal surface. The results of this work not only illustrate the initiation, growth and termination mechanism of the C-C chain involved in FTS on the Co(0001) surface, but also serve as a basis for the rational design of other Co surfaces toward desirable higher hydrocarbons or oxygenates.

Long term puzzles of the CH and CD energetics and related phenomena revisited; solutions sought through REMPI-photofragmentations of bromomethanes.

Ever since the pioneering work by Herzberg and Johns in 1969 (The Astrophysical Journal, 1969, 158, 399) the spectral assignment and the energetics of the fundamental molecular fragment CH, in the region of 63 000-65 000 cm(-1) (7.81-8.06 eV), have remained a puzzle to a large extent. The dissociation of bromoform and deuterated bromoform following two-photon resonance excitations to molecular Rydberg states forms the fragment species CH* and CD* in the excited state A(2)Δ(v' =0) as well as carbon and bromine atoms in the ground and first excited states, C/C* and Br/Br*. Further (1r + 1i)REMPI of CH* and CD* resonance excites the fragments to the energy region of concern, whereas the atom fragments were identified by further (2r + 1i)REMPI. Analysis based on spectral simulations, isotope shifts and comparison with other data allowed spectral identifications, assignments and partial characterization of four highly excited bound states for each of the molecular fragments (CH**/CD**); including the (3)(2)Π valence state and the (4)(2)Π Rydberg state, for the first time. Perturbations, shown as line-shifts, line-intensity and/or line-width alterations, due to the level-to-level state interactions between the bound states and predissociations by a repulsive state are recognized. Recording of C(+) signals in REMPI of several bromomethanes for a one-photon energy of about 40 333 cm(-1) allows the clarification of a mystery concerning a broad C(+) band frequently observed. This work, presented, demonstrates the usefulness of molecular REMPI for fragment analysis.

Accuracy of atmospheric parameters of FGK dwarfs determined by spectrum fitting

We performed extensive tests of the accuracy of atmospheric parameter determination for FGK stars based on the spectrum fitting procedure Spectroscopy Made Easy (SME). Our stellar sample consists of 13 objects, including the Sun, in the temperature range 5000--6600~K and metallicity range -1.4 -- +0.4. The analysed stars have the advantage of having parameters derived by interferometry. For each star we use spectra obtained with different spectrographs and different signal-to-noise ratios (S/N). For the fitting we adopted three different sets of constraints and test how the derived parameters depend upon the spectral regions (masks) used in SME. We developed and implemented in SME a new method for estimating uncertainties in the resulting parameters based on fitting residuals, partial derivatives, and data uncertainties. For stars in the 5700--6600 K range the best agreement with the effective temperatures derived by interferometry is achieved when spectrum fitting includes the H$\alpha$ and H$\beta$ lines, while for cooler stars the choice of the mask does not affect the results. The derived atmospheric parameters do not strongly depend on spectral resolution and S/N of the observations, while the uncertainties in temperature and surface gravity increase with increasing effective temperature, with minima at 50~K in Teff and 0.1~dex in log g, for spectra with S/N=150--200. A NLTE analysis of the TiI/TiII and FeI/FeII ionisation equilibria and abundances determined from the atomic CI (NLTE) and molecular CH species supports the parameters we derived with SME by fitting the observed spectra including the hydrogen lines.

Effect of Gallium Source Material on the Transparent Conducting Properties of Ga:ZnO Thin Films Through Metalorganic Chemical Vapor Deposition

We present the first experimental comparisons of growth of Ga-doped ZnO (GZO) thin films through metalorganic chemical vapor deposition (MOCVD) using Triethylgallium (TEG) and Trimethylgallium (TMG) as dopant sources with qualified opt-electrical properties. Interestingly, we found the GZO films growth by using TEG source exhibited the preferred orientation of (100) and (110) planes which (100) plane is the dominant orientation as well as the formation of pyramidal texture on the film surface compared to the one using TMG source that is highly (002)-orientated ZnO films and formation of planar structure. Additionally, the total C incorporation into GZO films prepared by TEG is slightly lower than that of using TMG source, indicating the formation of stable C2H4 species during reaction when using TEG source can reduce the C incorporation of GZO films compared to the less stable CH3 species by using TMG source. It also found that the doping efficiency by using TEG as a dopant source was much lower than that of using TMG source due to the different thermal decomposition between two sources. These results indicate clearly that the Ga dopant source is crucial to determine the morphology, structure, carbon incorporation as well as the doping efficiency of GZO films that can motivate further research in this field by using various materials.

Facet Dependence of CO2 Reduction Paths on Cu Electrodes

Experimental results have shown that CO2 electroreduction is sensitive to the surface morphology of Cu electrodes. We used density functional theory (DFT) to evaluate the thermodynamics and kinetics of CO2 reduction pathways on Cu(100) and Cu(111) with the aim of understanding the experimentally reported differences in CO2 reduction products. Results suggest that the hydrogenation of CO* to hydroxymethylidyne (COH*) or formyl (CHO*) is a key selective step. Cu(111) favors COH* formation, through which methane and ethylene are produced via a common CH2 species under high overpotential (<−0.8 V vs RHE). On Cu(100), formation of CHO* is preferred and ethylene formation goes through C–C coupling of two CHO* species followed by a series of reduction steps of the C2 intermediates, under relatively lower overpotential (−0.4 to −0.6 V vs RHE). Further reduction of these C2 intermediates, however, require larger potentials (∼−1.0 V vs RHE) and conflicts with the experimentally observed low potential pathway to C2 ...

Plasma polymerization of acrylic acid onto polystyrene by cyclonic plasma at atmospheric pressure

The cyclonic atmospheric-pressure plasma is developed for chamberless deposition of poly(acrylic acid) film from argon/acrylic acid mixtures. The photoemission plasma species in atmospheric-pressure plasma polymerization was identified by optical emission spectroscopy (OES). The OES diagnosis data and deposition results indicated that in glow discharge, the CH and C2 species resulted from low-energy electron-impact dissociation that creates deposition species, but the strong CO emission lines are related to nondeposition species. The acrylic acid flow rate is seen as the key factor affecting the film growth. The film surface analysis results indicate that a smooth, continuous, and uniform surface of poly(acrylic acid) films can be formed at a relatively low plasma power input. This study reveals the potential of chamberless film growth at atmospheric pressure for large-area deposition of poly(acrylic acid) films.

Diamond synthesis at atmospheric pressure by microwave capillary plasma chemical vapor deposition

Polycrystalline diamond has been synthesized on silicon substrates at atmospheric pressure, using a microwave capillary plasma chemical vapor deposition technique. The CH4/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H2 into the deposition gas chemistry. Electronically excited species of CN, C2, Ar, N2, CH, Hβ, and Hα were observed in the emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T2g phonon at 1333 cm−1 peak relative to the Raman features of graphitic carbon. Field emission scanning electron microscopy images reveal that, depending on the growth conditions, the carbon microstructures of grown films exhibit “coral” and “cauliflower-like” morphologies or well-facetted diamond crystals with grain sizes ranging from 100 nm to 10 μm.

Atmospheric pressure plasma polymerization using double grounded electrodes with He/Ar mixture

In this study, we have proposed the double grounded atmospheric pressure plasma jet (2G-APPJ) device to individually control the plasmas in both fragmentation (or active) and recombination (or passive) regions with a mixture of He and Ar gases to deposit organic thin films on glass or Si substrates. Plasma polymerization of acetone has been successfully deposited using a highly energetic and high-density 2G-APPJ and confirmed by scanning electron microscopy (SEM). Plasma composition was measured by optical emission spectroscopy (OES). In addition to a large number of Ar and He spectra lines, we observed some spectra of C2 and CH species for fragmentation and N2 (second positive band) species for recombination. The experimental results confirm that the Ar gas is identified as a key factor for facilitating fragmentation of acetone, whereas the He gas helps the plume of plasma reach the substrate on the 2nd grounded electrode during the plasma polymerization process. The high quality plasma polymerized thin films and nanoparticles can be obtained by the proposed 2G-APPJ device using dual gases.