Amorphous Hydrogenated Carbon Nitride Films Research Articles

Chemical synthesis and surface morphology of amorphous hydrogenated carbon nitride film deposited by N2/CH4 dielectric barrier discharge plasma

A dielectric barrier discharge of N2:CH4 mixture was operated at 500 mbar was employed to deposit poly-amide (HCN x ) film, under low input power and atmospheric pressure. The top surface layer of amorphous hydrogenated carbon nitride (a-HCN x ) is analyzed by X-ray photoelectron spectroscopy (XPS). Bulk a-HCN x is analyzed by means of fourier transform infrared (FTIR) spectroscopy. The deposited polymer having triple bond (–C≡N/–C≡C–) at ∼2180 cm−1 and carbonyl-amide group –(C=O)NH– at ∼1680 cm−1, were synthesized by FTIR spectroscopy to elucidate the nature of the products formed from N2/CH4 mixture. The nitrile group (–C≡N/–) is decreasing with the elevated annealing temperature is obtained from FTIR spectrum. Shake-up satellite peaks are observed in XPS spectrum at room temperature. The shake-up peaks disappear gradually as the annealing temperature is increased from 50 to 300 °C. Simultaneously, the chemical shift of 1s electron shifted to its own advantageous position. The surface roughness (Root Mean Square, RMS) of the HCN x film is changing from 5.3 to 28.2 nm as the annealing temperature increases from room temperature to 300 °C.

Deposition of Amorphous Hydrogenated Carbon Nitride Films with a Dielectric Barrier Discharge

AbstractThin amorphous carbon nitride (CNx) films have been deposited by DBD plasma. Deposition experiments have been performed on flat silicon (100) substrates using a C2H6/N2 gas mixture and deposition times of up to 6 h. The C2H6/N2 gas ratio has been varied between 1:1 and 1:5 to observe the influence of the feeding gas mixture on the chemical composition of the deposited films. The experiments were performed at gas pressures of 300 and 500 mbar. The chemical composition and bond structure of the deposited CNx films were evaluated by X‐ray photoelectron spectroscopy and by attenuated total reflectance‐Fourier transform infrared spectrometry. The results show that the chemical composition of amorphous CNx thin films depends on the working gas composition. Films deposited with higher nitrogen gas concentrations show a larger N/C ratio, an increase of C=N and C≡N bonds, and become harder.magnified image

Thermal expansion coefficient, mechanical and structural properties of hydrogenated carbon nitrides

Amorphous hydrogenated carbon nitride films (a-C:H:N) deposited by plasma enhanced chemical vapor deposition of methane (CH4) and nitrogen (N2), under low (−200V) and high (−800V) bias voltage are investigated. The nitrogen content was obtained from X-ray photoelectron spectroscopy and nuclear reaction analysis. Raman measurements were performed at 514nm (visible) and 244nm (UV) wavelengths. Mechanical properties (Young's modulus and hardness) and thermal expansion coefficient (TEC) were studied using the bending beam method. Raman spectroscopy shows that the incorporation of nitrogen in a-C:H reduces the disorder in the film, independent of the initial structure of the a-C:H films (tetrahedral-, diamond-, or graphitic-like). The TEC is related to the Raman parameters associated with the degree of sp2 ordering (aromatic rings) in the film structure, increasing with the nitrogen incorporation.

The chemical composition and bonding structure of amorphous hydrogenated carbon nitride film on aluminum surface deposited by electrodeposition

AbstractAmorphous hydrogenated carbon nitride films with excellent adhesion to the substrates were deposited on the surfaces of aluminum plates by electrodeposition with acetonitrile as carbon source. The as‐obtained films were detailed characterized by Raman, XPS and FTIR. The results show that the as‐obtained films are mainly made up of sp2 C, sp3 C, CN, CN bonds and a spot of sp3CH2, sp3CH3, sp3CH and sp2CH bonds. The atomic ratio of N/C is evaluated to be about 2.98 at.% by XPS. Raman analysis indicated that ID/IG ratios decreased from 0.827 to 0.675 when the deposition time increased from 10 to 20 h. At the end, on the basis of the detailed analysis, results of Raman, FTIR and XPS, the possible deposition mechanism was discussed. Copyright © 2010 John Wiley & Sons, Ltd.

Cancer cells (MCF-7, Colo-357, and LNCaP) viability on amorphous hydrogenated carbon nitride film deposited by dielectric barrier discharge plasma

Atmospheric pressure dielectric barrier discharge plasma in CH4/N2 (1:1) gas mixture has been employed to deposit amorphous hydrogenated carbon nitride (aH–CNx) film. In vitro studies with three different cancer cell lines were carried out on the coated surfaces. Preliminary biocompatibility and effect of CH4/N2 films have been investigated by measuring cell proliferation. Three different cancer cell (MCF-7, Colo-357, and LNCaP) suspensions have been exposed on the surface of aH–CNx film to investigate the effect of deposited films on viability of cells. Results from the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H- tetrazolium, inner salt) proliferation assays indicated that the deposited aH–CNx film is cytotoxic to cancer cell lines. Time course cell viability assay indicated maximum cell death at 24 h after seeding the cells. This effect is dependant on physicochemical and mechanical properties of the deposited films. The deposited film has been characterized by x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results confirm the presence of C–N, C≡N, C–Hx, C–O, N–O, overlapping NH, and OH bonds in the film.

Cytocompatibility of amorphous hydrogenated carbon nitride films deposited by CH4/N2 dielectric barrier discharge plasmas with respect to cell lines

Special amorphous hydrogenated carbon nitride (a-H–CNx) films have been prepared on glass substrates for the investigation of adhesion and proliferation of different mammalian cell lines. CH4/N2 dielectric barrier discharge plasmas were applied to deposit a-H–CNx coatings at half of the atmospheric pressure. Film quality was modified by varying the CH4:N2 ratio and deposition duration. Chemical composition was determined by x-ray photoelectron spectroscopy and Fourier transformed infrared spectroscopy. The N/C ratio was in the range of 0.20–0.55. A very small surface roughness was verified by atomic force microscopy. Human embryonic kidney (HEK) and rat adrenal pheochromocytoma (PC12) cells were cultivated on the a-H–CNx films to investigate the cytocompatibility of these surfaces. The microscopic images show that both kinds of cells lines were unable to survive. The cells did not adhere to the surfaces, and most of the cells died after certain time spans. Increased amounts of nitrogen in the film induce an accelerated cell death. It is concluded, that the deposited CNx film behaves cytotoxic to HEK and PC12 cell lines.

Amorphous hydrogenated carbon-nitride films prepared by RF-PECVD in methane–nitrogen atmospheres

In this work, films are deposited by PECVD-RF plasma using a gas mixture of CH 4, N 2 and He or Ar. The Ar/CH 4 and He/CH 4 ratio is kept constant, while the nitrogen flow is allowed to vary. The samples were arranged in the anode plate as well as in the cathode plate. The effect of nitrogen addition on the films optical and structural properties of the films was analyzed by FTIR spectroscopy, UV–VIS–NIR spectroscopy, profilometry, ellipsometry and RBS. The intensities of the CN (1600 cm −1), CN (2300 cm −1) and NH (3250 cm −1) absorption bands, in the IR spectra, increase with the N 2/CH 4 flow ratio. Samples deposited in the grounded electrode, show a decrease in the CH n stretching band for increasing N 2/CH 4 flow ratio, while the NH absorption bond increases, indicating that hydrogen is preferentially bonded to nitrogen. The CN absorption increases for increasing N/C ratio; indicating that a nitrile phase is also formed. For the samples deposited in the powered electrode (Fig. 5), the CNH absorption band (1000–1700 cm −1) is much larger than the other bands (CH n and NH). The increasing signal in the 1000–1300 cm −1 region suggests an increase in nitrogen bonding with sp 3 C. The CN absorption is very small compared with the samples deposited in the grounded electrode. This behavior could be attributed to the increase in the methane and nitrogen radicals caused by stronger ion bombardment in the active electrode.

Surface Damage of Whisker-Type Cold Emitter after Overload Test

An overload test of a new type of ceramic field emitter, ZnO:Al whisker covered with amorphous hydrogenated carbon nitride film, was performed. The aim of this study is to investigate surface damage of the whisker-type cold emitter under overload conditions. The morphologies of the emitter surface before and after operation were compared using scanning electron microscopy. The emission was terminated after the generation of surge current that severely damaged the emission surface.

Structure modification of hydrogenated carbon nitride films by high-energy HE 2+ Irradiation

It is well known that amorphous carbon and related films consist of nano-sized carbon clusters. With the incorporation of hydrogen into these films, the hydrogen termination limits the cluster size and decreases the bond strength among clusters. In this study, dehydrogenation from amorphous hydrogenated carbon nitride films was accomplished using 3.75 MeV-He 2+ irradiation. The hydrogen atoms forming methyl and ethylene groups were mainly removed from the film during the irradiation procedure. With the progress of dehydrogenation from methyl and ethylene groups, the degree of order of the atomic configuration became large, resulting in an increase of the cluster size. The mechanical properties of amorphous films were improved due to cluster growth.

Dehydrogenation of Nitrogen-Containing Carbon Films by High-Energy He2+ Irradiation

It is well known that amorphous carbon and related films consist of nano-sized carbon clusters. With the incorporation of hydrogen into these films, the hydrogen termination limits the cluster size and decreases the bond strength among clusters. In this study, dehydrogenation from amorphous hydrogenated carbon nitride films was accomplished using 3.75 MeV-He2+ irradiation. The hydrogen atoms forming methyl and ethylene groups were mainly removed from the film during the irradiation procedure. With the progress of dehydrogenation from methyl and ethylene groups, the degree of order of the atomic configuration became large, resulting in an increase of the cluster size. The mechanical properties of amorphous films were improved due to cluster growth.

Infrared optical properties of amorphous hydrogenated carbon nitride film

The microstructure and optical properties of nitrogen-doped hydrogenated carbon DLC:N films deposited by the rf plasma-enhanced chemical vapor deposition (PECVD) method were studied by atomic force microscopy (AFM), Raman, Fourier-transform infrared (FTIR) and infrared ellipsometric (IRE) spectrometry. The absorption intensities of the peaks CNH (1600 cm −1), CN (2200 cm −1) and NH (3250 cm −1) in the IR spectra increase with the N 2/CH 4 flux ratio. Raman spectra show that the shape of the D and G bands of DLC:N film varies slightly with the increase of N content, which means that the main structures of N-doped films are still diamond-like carbon (DLC). However, four Gaussian decomposition results show that the peak of the G band widens and shifts to the low wavenumber with increased nitrogen content in Raman spectra due to amorphous C 3N 4 structure being formed in the nitrogen-doped DLC film. AFM topographies and lateral force microscopy (LFM) images of DLC:N film confirm that the amorphous C 3N 4 exists as particles several tens of nanometers in size in the film. IRE spectral analysis results show that the refractive index of the film in the infrared region (2–14 μm) decreases slightly from 1.8 to 1.6 with increased nitrogen content.

Growth of amorphous hydrogenated carbon nitride films in radio-frequency plasma

Amorphous hydrogenated carbon nitride films are deposited both on the cathode and anode in N2–CH4 atmosphere by radiofrequency plasma chemical vapor deposition. The species of the plasma are detected by optical emission spectroscopy and ionization-threshold mass spectroscopy. The effects of varying the N2 partial pressure on plasma states and film properties have been investigated. The results of plasma diagnosis indicate that reactive nitrogen radicals are more easily generated than methane-derived radicals and they increase as the N2 partial pressure in plasma. The films grown on the cathode and anode definitely show different properties. It seems that CN and CNH species in plasma do not contribute to film growth directly. The efficient bombardment of nitrogen ions on growing surface leads to the formation of the film which has lower hydrogen content and more CN bond constructions.

Amorphous hydrogenated carbon nitride films deposited via an expanding thermal plasma at high growth rates

An expanding thermal plasma of argon and nitrogen into which acetylene is injected, was used to deposit amorphous hydrogenated carbon nitride (a-C:N:H) films. In the absence of an external bias high growth rates (up to 37 nm/s) were achieved. The growth rate and refractive index of the films were studied in situ with HeNe-ellipsometry. Fourier transform infrared (FTIR) absorption spectroscopy was used to investigate the different bondings. The changes observed in the infrared absorption spectrum with increasing N 2/C 2H 2 ratio in the plasma indicate an increase in dehydrogenation of the films leading to polymerization, and possibly also to graphitization. The microhardness and Young’s modulus, as determined by nano-indentation measurements, show a strong respectively overall increase with increasing acetylene flow, and appear to decrease on addition of N 2. This is attributed to the increase in the polymerization of the films on incorporation of nitrogen. Evaluation of the chemical composition by Rutherford back scattering (RBS) and elastic recoil detection analysis (ERDA) reveals that a deposition mechanism should be considered in which N and H are in competition with each other during growth.

Structural and optical properties of amorphous hydrogenated carbon nitride films prepared by plasma-enhanced chemical vapor deposition

Thin films of amorphous hydrogenated carbon nitride ( a-CN x :H) were deposited from CH 4 and N 2 gases by plasma-enhanced chemical vapor deposition using a helical resonator discharge. The effects of substrate temperature on the structural and optical properties of the films have been systematically investigated by Raman spectroscopy and transmission ultraviolet-visible spectroscopy. The optical band gap of the a-CN x :H films was found to decrease from 1.72 to 0.95 eV as the substrate temperature is increased to 250°C. Through the relationship between optical band gap and Raman studies, it could be concluded that a progressive graphitization of the films occurs with increasing the substrate temperature.

Characterization of amorphous hydrogenated carbon nitride films prepared by plasma-enhanced chemical vapor deposition using a helical resonator discharge

Amorphous hydrogenated carbon nitride thin films (a-CNx:H) have been prepared by plasma-enhanced chemical vapor deposition of N2 and CH4 gases using a helical resonator discharge. The structural and optical properties of the deposited a-CNx:H films have been systematically studied as a function of the substrate temperature and radio frequency (rf) substrate bias. The chemical structure and elemental composition of the a-CNx:H films were characterized by Fourier transform infrared spectroscopy (FT-IR), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The optical properties of the films were evaluated using transmission ultraviolet–visible spectroscopy. The morphology of the films was investigated by scanning electron microscopy and atomic force microscopy. The FT-IR and XPS studies demonstrate the presence of carbon–nitrogen bonds with hydrogenated components in the films. The film composition ratio N/C was found to vary from 0.127 to 0.213 depending on the deposition conditions. The Raman spectra, showing the G and D bands, indicate that the a-CNx:H films have a graphitic structure. It can be found that the optical band-gap Eg of a-CNx:H films is associated with graphitic clusters, while the decrease in Eg is correlated with an increase in the size and number of graphitic clusters. Combining the results of Raman and optical measurements, it can be concluded that a progressive graphitization of the films occurs with increasing the substrate temperature and rf substrate bias power, corresponding to bias voltage.

Amorphous hydrogenated carbon nitride films obtained by plasma-enhanced chemical vapour deposition

Amorphous hydrogenated carbon nitride (a-CN x :H) films grown by plasma-enhanced chemical vapour deposition using methane-nitrogen mixtures as precursor gas were characterized by a combination of several techniques: MeV ion beam techniques (Rutherford backscattering, nuclear reaction analysis and elastic recoil detection analysis), secondary ion mass spectrometry, Raman spectroscopy and positron annihilation spectroscopy (Doppler broadening method). The Vickers hardness and the internal stress of the films were also measured. Finally, the thermal stability of the films was investigated. Our results indicate that the incorporation of nitrogen into the amorphous carbon network increases the void density and the number (or size) of graphitic domains. These microstructural modifications and the decrease in the average coordination number may account for the observed reduction of the internal stress of the films. For annealing temperatures higher than 300 °C we observe hydrogen and nitrogen losses as well as the progressive graphitization of the films.

Investigation of voids distribution in amorphous hydrogenated carbon nitride films by positron annihilation and thermal gas evolution experiments

An investigation of the voids distribution in hard amorphous carbon nitride films (a-CN X:H) and carbon (a-C:H) films deposited by self-bias glow-discharge was carried out by means of thermal gas evolution analysis and positron annihilation spectroscopy. Internal stress measurements were also performed. Our results for the carbon nitride films indicate a clear correlation between the noticeable reduction of the internal stress of the films and the increase of the voids concentration. The concentration of voids increases with the amount of incorporated nitrogen.