Hydrogenated Carbon Nitride Films Research Articles

プラズマCVD法により作製したSi-CNxHy膜の油中摩擦特性

プラズマCVD法により作製したSi-CNxHy膜の油中摩擦特性

Humidity resistant hydrogenated carbon nitride films

The aim of this study is to prepare the hydrogenated carbon nitrides films which possess good adhesion to silicon substrates and stability in humid surroundings. The films were prepared by magnetron sputtering from pure graphite target in a nitrogen-hydrogen discharge. Two main factors can lead to delamination of the films. The first is the high value of residual stress and the second is the absorption of moisture into the bulk and their affect on films/substrates interface. Both factors were eliminated by adding hydrogen and post-deposition annealing in the vacuum. The influence of annealing (to 200, 400, 600, 800 and 1000°C) on chemical composition and microstructure was studied by various methods. For preparation of humidity (water) resistant films we have added 15% partial pressure of hydrogen to nitrogen discharge and annealed the samples in vacuum to minimum temperature, which was 600°C. The heating to 600°C causes the increasing of carbon – nitride ratio from 2.0 to 2.4 and the relative atomic concentration calculated from XPS data (N 1s peak areas of CN and CN) reveals that amount of CN bonds increases from 49% to 57%. Desorption of absorbed moistures and elements from the film was studied by Thermal Desorption Spectroscopy. Dominant molecules in TDS spectra were HCN and N2, which were correlated with changes in chemical composition, measured by Rutheford Backscattering Spectroscopy and Elastic Recoil Detection Analysis. For observation of films delamination caused by high compressive stress, the Scanning Low Energy Electron Microscopy was used.

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.

Note: Development of fast heating inert gas annealing apparatus operated at atmospheric pressure

Here, we report the development of a simple, small, fast heating, and portable, homemade, inert gas (Ar) atmospheric annealing setup. Instead of using a conventional heating element, a commercial soldering rod having an encapsulated fast heating heater is used here. The sample holder is made of a block of stainless steel. It takes 200 s to reach 700 °C, and 10 min to cool down. The probability of oxidation or surface contamination has been examined by means of x ray photoelectron spectroscopy of virgin Cu sample after annealing at 600 °C. In addition, we compare the annealing of a hydrogenated carbon nitride film (HCN(x)) in both a conventional vacuum and our newly developed ambient Ar atmosphere setup.

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.

S116032 プラズマCVD法を用いたSi-CNxHy膜の密着性の向上と低温処理の実現

S116032 プラズマCVD法を用いたSi-CNxHy膜の密着性の向上と低温処理の実現

Influence of temperature on structure as well as adhesion and friction and wear behavior of hydrogenated carbon nitride films prepared on silicon substrate

Hydrogenated-carbon nitride (CNx:H) films were synthesized on silicon substrate in a large quantity by the pyrolysis of ethylenediamine in a temperature range of 700–950°C. The influence of temperature on the morphology, structure, adhesion to substrate, and friction and wear behavior of CNx:H films was investigated. It has been found that CNx:H films obtained at 700°C and 800°C are amorphous, and those prepared at 900°C and 950°C consist of carbon nitride nanocrystal. Besides, CNx:H film sample obtained at 700°C has the maximum N content of 9.1at.% but the poorest adhesion to Si substrate, while the one prepared at 900°C has the lower N content and the highest adhesion to substrate. As a result, nanocrystalline CNx:H (nc-CNx:H) film synthesized at 900°C possesses the best wear resistance when slides against stainless steel counterpart. N atom is incorporated into the graphitic network in three different bonding forms, and their relative content is closely related to temperature, corresponding to different adhesion as well as friction and wear behavior of the films obtained at different temperatures. Furthermore, the friction coefficient and antiwear life of as-deposited CNx:H films vary with varying deposition temperature and thickness, and the film with thickness of 1.3μm, obtained at 900°C, has the longest antiwear life of over 180,000s.

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.

Characteristics of Ti–Nb, Ti–Zr and Ti–Al containing hydrogenated carbon nitride films

Nanocomposite Me–C–N:H coatings (Me is TiNb, TiZr or TiAl), with relatively high non-metal/metal ratios, were prepared by cathodic arc method using TiNb, TiZr and TiAl alloy cathodes in a CH 4 + N 2 atmosphere. For comparison purposes, a-C–N:H films were also produced through evaporating a graphite cathode in a similar atmosphere. The films were characterized in terms of elemental and phase compositions, chemical bonds, texture, hardness, adhesion and friction behavior by GDOES, XPS, Raman spectroscopy and XRD techniques, surface profilometry, hardness and scratch adhesion measurements, and tribological tests. The nanocomposite films consisted of a mixture of crystalline metal carbonitride and amorphous carbon nitride. The non-metal/metal ratio in the films composition was found to range between 1.8 and 1.9. For the metal containing nanocomposites, grain size in the range 7–23 nm, depending on the metal nature, were determined. As compared with the a-C–N:H, the Me–C–N:H films exhibited a much higher hardness (up to about 39 GPa for Ti–Zr–C–N:H) and a better adhesion strength, while the coefficients of friction were somewhat higher (0.2–0.3 for Me–C–N:H and 0.1 for a-C–N:H).

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.

Correlation between nitrogen incorporation and structural modification of hydrogenated carbon nitride films

The growth and microstructure of hydrogenated carbon nitride a-CNx:H (0⩽x⩽0.10) films deposited by PECVD have been studied. Upon the analysis of FTIR spectra, Raman spectra and XPS, it is concluded that π doping could take place even at a very low percentage of nitrogen, which favors the formation of sp2 carbon clusters. The C 1s peak shifts toward higher binding energy while the N 1s peak remains constant as the nitrogen content in the film increases, which can be considered as a result of the chemical shifts on charge transfer due to the strong electronegativity of the N atom. 3D profile measurements show that there were a great number of particles formed when nitrogen is incorporated in to the films and the particles coalescence when the nitrogen content increases due to enhanced surface diffusion. The stress of the films converts from compressive to tensile stress gradually with increased N content. The elimination of grain boundaries and annihilation of excess vacancies, due to columnar structure increasing by diffusion leads to volume shrinkage of the film, thus causing tensile stress. These analyses were fairly consistent to help understand the effects of nitrogen in hydrogenated carbon films.

The effect of nitrogen incorporation on the bonding structure of hydrogenated carbon nitride films

This work describes the composition and bonding structure of hydrogenated carbon nitride (a-CNx:H) films synthesized by electron cyclotron resonance chemical vapor deposition using as precursor gases argon, methane, and nitrogen. The composition of the films was derived from Rutherford backscattering and elastic recoil detection analysis and the bonding structure was examined by infrared (IR) spectroscopy and x-ray absorption near edge spectroscopy (XANES). By varying the nitrogen to methane ratio in the applied gas mixture, polymeric a-CNx:H films with N/C contents varying from 0.06 to 0.49 were obtained. Remarkably, the H content of the films (∼40 at. %) was rather unaffected by the nitrogenation process. The different bonding states as detected in the measured XANES C(1s) and N(1s) spectra have been correlated with those of a large number of reference samples. The XANES and IR spectroscopy results indicate that N atoms are efficiently incorporated into the amorphous carbon network and can be found in different bonding environments, such as pyridinelike, graphitelike, nitrilelike, and amino groups. The nitrogenation of the films results in the formation of N-H bonding environments at the cost of C-H structures. Also, the insertion of N induces a higher fraction of double bonds in the structure at the expense of the linear polymerlike chains, hence resulting in a more cross-linked solid. The formation of double bonds takes place through complex C=N structures and not by formation of graphitic aromatic rings. Also, the mechanical and tribological properties (hardness, friction, and wear) of the films have been studied as a function of the nitrogen content. Despite the major modifications in the bonding structure with nitrogen uptake, no significant changes in these properties are observed.

Effect of N 2/CH 4 flow ratio on microstructure and composition of hydrogenated carbon nitride films prepared by a dual DC-RF plasma system

Hydrogenated carbon nitride (a-CN:H) films were deposited on n-type (1 0 0) silicon substrates making use of direct current radio frequency plasma enhanced chemical vapor deposition (DC-RF-PECVD), using a gas mixture of CH 4 and N 2 as the source gas in range of N 2/CH 4 flow ratio from 1/3 to 3/1 (sccm). The deposition rate, composition and bonding structure of the a-CN:H films were characterized by means of X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectrometry (FTIR). The mechanical properties of the deposited films were evaluated using nano-indentation test. It was found that the parameter for the DC-RF-PECVD process had significant effects on the growth rate, structure and properties of the deposited films. The deposition rate of the films decreased clearly, while the N/C ratio in the films increased with increasing N 2/CH 4 flow ratio. CN radicals were remarkably formed in the deposited films at different N 2/CH 4 flow ratio, and their contents are related to the nitrogen concentrations in the deposited films. Moreover, the hardness and Young’s modulus of the a-CN:H films sharply increased at first with increasing N 2/CH 4 flow ratio, then dramatically decreased with further increase of the N 2/CH 4 flow ratio, and the a-CN:H film deposited at 1/1 had the maximum hardness and Young’s modulus. In addition, the structural transformation from sp 3-like to sp 2-like carbon–nitrogen network in the deposited films also was revealed.

Influence of flow ratio on mechanical and tribological properties of hydrogenated carbon nitride films prepared by DC-RF-PECVD

Amorphous hydrogenated carbon nitride (a-CN : H) films were deposited onto silicon (n-100) substrates by dual direct current radio frequency plasma enhanced chemical vapour deposition with CH4 and N2 as feedstock at different ratios. The composition and surface morphology of the films were characterized by means of x-ray photoelectron spectroscopy, Raman spectroscopy and atomic force microscopy; while the mechanical and tribological properties of the films were evaluated using nano-indentation and the UMT test system. It was found that the deposition rate of the films decreased significantly but the N/C ratio, the surface roughness and the ID/IG ratio of the films increased as the N2/CH4 flow ratio increased. The nano-hardness and adhesion strength of the films to the silicon substrate sharply increased at first and then decreased with increasing N2/CH4 flow ratio. Moreover, the wear resistance of the films varied with the N2/CH4 flow ratio. The structure transformation from an sp3-like to sp2-like carbon–nitrogen network in the deposited films was also revealed.

Effect of deposition pressure on microstructure and properties of hydrogenated carbon nitride films prepared by DC-RF-PECVD

Hydrogenated carbon nitride (a-CN:H films) were deposited on n-type (1 0 0) silicon substrates making use of dual direct current radio frequency plasma enhanced chemical vapor deposition (DC-RF-PECVD), at working pressure of 2–20 Pa, using a mixed gas of CH 4 and N 2 as the source gas. The growth rate, composition, bonding structure of the deposited films were characterized by means of XPS and FTIR, and the mechanical properties of the deposited films were investigated by nano-indentation test. It was found that the parameters for the DC-RF-PECVD process had significant effects on the growth rate, structure and properties of the deposited films. The growth rate of the deposited films increased at first with increasing deposition pressure, then saturated with further increase of the deposition pressure. The N/C ratio inside the deposited films increased with increasing working pressure except that it was as much as 0.50 at a working pressure of 5.0 Pa. The nano-hardness of the films decreased with increasing deposition pressure. CN radicals were remarkably formed in the deposited films at higher pressures, and their contents are related to the nitrogen concentrations in the deposited films.

Preparation and characterization of hydrogenated carbon nitride films synthesized by dual DC-RF plasma system

Carbon nitride films (CN x films) were deposited on Si(1 0 0) substrates making use of dual direct current radio frequency (DC-RF) plasma enhanced chemical vapor deposition (PECVD), using a mixed gas of CH 4 and N 2 as the source gas. The microstructures, morphologies, and compositions of the resulting CN x films were analyzed by means of atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transformation infrared spectrometry (FTIR), and Raman spectroscopy. The mechanical properties of the CN x films were examined using a nano-indentation test system. The Raman spectrum showed two characteristic bands: a graphite G band and a disordered D band of carbon, which suggested the presence of an amorphous carbon matrix. FTIR and XPS measurements suggested the existence of C NH, C NH, C N, N H, and C H in the CN x films, and the nitrogen to carbon atom ratio (N/C) is as much as 0.50. Moreover, the TEM showed various diffraction rings of different d values, which could confirm the polycrystallites embedded in the CN x matrix. Besides, the quality and elasticity of the CN x films were significantly improved by the incorporation of nitrogen. The films prepared in the present work had much higher hardness and Young's modulus than the DLC films prepared under the same conditions, and the elastic recovery parameter was up to 89%.

Synthesis and mechanical properties of hydrogenated carbon and carbon nitride films prepared by magnetron sputtering

Hydrogenated carbon and carbon nitride films were synthesized by closed field unbalanced magnetron sputtering (CFUBM). The deposition rate, structure and mechanical properties of these films were studied as a function of applied bias voltage and nitrogen partial pressure on substrate during deposition. The film structures were investigated in Raman spectroscopy and FESEM. The hardness and elastic modulus were evaluated by nano-indentation test. Hydrogenated carbon films deposited at a bias of − 200 V exhibited a maximum hardness and a minimum electrical resistivity and hydrogenated carbon nitride films synthesized at a nitrogen partial pressure of 0.2 Pa showed minimum friction coefficient.

ELECTRICAL PROPERTIES OF REACTIVELY-SPUTTERED HYDROGENATED CARBON NITRIDE FILMS

Hydrogenated carbon nitride films have been synthesized on Si (100) by DC reactive sputtering with RF bias. These films are characterized by transmission electron microscopy and atomic force microscopy. Hydrogenated carbon nitride films have low surface roughness. At low hydrogen fraction, the films include small crystallites. High hydrogen fraction promotes the films to be amorphous. The resistivities of the films are measured, which range from 6.35×105 to 1.16×108 Ω· cm . The measured resistivity results indicate that the hydrogenated carbon nitride films have semiconductive properties. The resistivity largely depends on the bonding configurations. Effects of H2 fraction, target current and substrate bias are investigated. All these deposition parameters have influence on the resistivities. High C—H, N—H and C—NH bond fractions result in high resistivity.