CNx Films Research Articles

Effect of N2 flow rate on the properties of CNx thin films prepared by radio frequency plasma enhanced chemical vapor deposition from ethane and nitrogen

Carbon nitride (CNx) thin films were deposited using radio frequency plasma enhanced chemical vapor deposition (rf PECVD) from a mixture of nitrogen (N2) gas and either methane (CH4) or ethane (C2H6) gases. The CH4 and C2H6 flow rates were kept constant, while the N2 flow rate was varied. The effects of nitrogen incorporation on the growth rate and structural properties of the films were studied. The use of these two hydrocarbon precursors was also compared. It was found that the effects of N incorporation are significant for films deposited from the CH4 mixture and it greatly affects the bonding and optical properties of the films. In contrast, the effects of N incorporation on the films produced from C2H6 are not as significant, though these films appear to be more uniform and show lower film porosity. Generally, the photoluminescence (PL) intensities increase with the increase in N incorporation for film deposited from both hydrocarbon mixtures. However, the PL properties of these CNx films are enhanced by the use of C2H6 as compared to CH4 since the films produced show lower defects.

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

X-Ray Photoelectron Spectroscopy and Raman Spectroscopy Studies on Thin Carbon Nitride Films Deposited by Reactive RF Magnetron Sputtering

Thin carbon nitride (CNx) films were synthesized on silicon substrates by reactive RF magnetron sputtering of a graphite target in mixed N2/Ar discharges and the N2 gas fraction in the discharge gas, F N, varied from 0.5 to 1.0. The atomic bonding configuration and chemical composition in the CNx films were examined using X-ray photoelectron spectroscopy (XPS) and the degree of structural disorder was studied using Raman spectroscopy. An increase in the nitrogen content in the film from 19 to 26 at% was observed at FN = 0.8 and found to influence the film properties; normality tests suggested that the data obtained at FN = 0.8 are not experimental errors. The interpretation of XPS spectra might not be always straightforward and hence the detailed and quantitative comparison of the XPS data with the information acquired by Raman spectroscopy enabled us to interpret the decomposed peaks in the N 1s and C 1s XPS spectra. Two N 1s XPS peaks at 398.3 and 399.8 eV (peaks N1 and N2, respectively) were assigned to a sum of pyridine-like nitrogen and -C≡N bond, and to a sum of pyrrole-like nitrogen and threefold nitrogen, respectively. Further, the peaks N1 and N2 were found to correlate with C 1s XPS peaks at 288.2 and 286.3 eV, respectively; the peak at 288.2 eV might include a contribution of sp3 carbon.

Structural and Mechanical Properties of CN<sub>X </sub>and CP<sub>X </sub>Thin Solid Films

The inherent resiliency, hardness and relatively low friction coefficient of the fullerene-like (FL) allotrope of carbon nitride (CNx) thin solid films give them potential in numerous tribological applications. In this work, we study the substitution of N with P to grow FL-CPx to achieve better cross- and inter-linking of the graphene planes, improving thus the material’s mechanical and tribological properties. The CNx and CPx films have been synthesized by DC magnetron sputtering. HRTEM have shown the CPx films exhibit a short range ordered structure with FL characteristics for substrate temperature of 300 °C and for a phosphorus content of 10-15 at.%. These films show better mechanical properties in terms of hardness and resiliency compared to those of the FL-CNx films. The low water adsorption of the films is correlated to the theoretical prediction for low density of dangling bonds in both, CNx and CPx. First-principles calculations based on Density Functional Theory (DFT) were performed to provide additional insight on the structure and bonding in CNx, CPx, and a-C compounds.

Evaluation on Structure and Tribological Properties of Carbon Nitride Films Deposited on YG8 Carbide Alloy Substrates

CNx films were deposited on YG8 carbide alloy (WC+8%Co) substrates by DC or RF magnetron sputtering. The composition, bonding state, adhesion, and tribological behavior of CNx films were researched. X-ray Photoelectron spectroscopy results showed that C-N, C=N and C≡N bond existed in CNx films. RF magnetron sputtering is in favor of the bonding of C and N, the adhesion and the wear resistance of CNx films. DC magnetron sputtering is in favor of lubricating ability of CNx films. Substrate bias has some effect on the bonding of C and N, the adhesion of the films, decrease of adhesive wear and the friction coefficient of films.

Improvement of orthodontic friction by coating archwire with carbon nitride film

In order to reduce frictional resistance between archwire and bracket during orthodontic tooth movement, carbon nitride (CNx) thin films were deposited on the surface of archwires with ion beam assisted deposition (IBAD). The energy-dispersive X-ray spectrometer (EDS) analysis showed that the CNx film was successfully deposited on the surface of the orthodontic wires. X-ray photoelectron spectroscopy (XPS) analysis suggested that the deposited CNx film was sp 2 carbon dominated structures, and diversiform bonds (N C, N C, et al.) coexisted in the film. The friction tests indicated that the CNx film significantly reduced the wire-bracket friction both in ambient air and in artificial saliva. The sp 2C rich structure of the CNx film as well as its protection function for the archwire was responsible for the low friction of the wire-bracket sliding system.

Improvement of Tribological Behaviour of Biomedical Nanocrystalline Titanium by Magnetron Sputtered CNx/SiC Double Layer Films

The nano-indentation response and the friction and wear properties of the CNx/SiC (carbon nitride /silicon carbon) double layer thin films (SiC films as interlayer) deposited on nanocrystalline titanium substrate using magnetron sputtering technique at room temperature were investigated. The results show that the CNx films exhibited a low nano-hardness of 8.0 GPa and Young's modulus of 55.0 GPa but a high hardness-to-modulus ratio of 0.146. As sliding against Si3N4 (silicon nitride) ball under Kokubo simulation body fluid (SBF) at room temperature, the CNx films exhibited the superior tribological properties with the friction coefficients of about 0.1 and the special wear rate of about 1.6×10−6 mm3/Nm.

Liquid Phase Deposition of Carbon Nitride Films for Application as Low-k Insulating Materials

CNx films are fabricated using liquid phase deposition by applying a DC bias voltage to Si substrates immersed in acrylonitrile. X-ray photoelectron spectra reveal that C, N, and O are major components of the deposited films. From analysis of C 1s and N 1s spectra, the major bonding state in the CNx film is attributed to a mixture of C≡N and partially hydrogenated C=N bonds. Metal–insulator–semiconductor capacitors incorporating the CNx insulating layers are fabricated to evaluate the electrical properties of the deposited films. The lowest dielectric constant k of the CNx film is determined to be 2.6 from the accumulation capacitance and the thickness of the film, suggesting that the CNx film formed by liquid phase deposition is a promising low-k material for use in ultralarge-scale integration multilevel interconnections.

Study on the tribological properties of hard films deposited on biomedical NiTi alloy

Hard films including carbon nitride (CNx), diamond-like carbon (DLC), and titanium nitride (TiN) were respectively deposited on the biomedical NiTi alloy substrate by using reactive direct current magnetron sputtering. A Ti transition layer was pre-deposited in order to strengthen the adhesion between the hard films and NiTi alloy substrate. The tribological properties of the deposited hard films were systematically investigated by using scratch tester and friction wear tester. It was shown that the tribological performance of NiTi alloy substrate was improved effectively after the deposition of gradient films. The deposition of Ti transition layer benefited in increasing the adhesion strength between the NiTi substrate alloy and the inorganic hard films, especially for the CNx film. Among the three types of gradient films, Ti/CNx film possessed the best tribological performance (with the minimum friction coefficient of 0.092 and the maintenance of smooth and intact surface after the friction and wear tests).

Characterization of CN<sub>x</sub>/Si Using RBS, NRA and AES Techniques

Carbon nitride films were synthesized by pulsed laser ablation of graphite target under nitrogen ambience. The third harmonic of a pulsed Nd-YAG laser of 355 nm wavelength and 7 ns pulse duration was focused onto a rotating target at an incidence angle of 45°. The laser fluence at the target surface was set at 30 J/cm2. The carbon nitride films were deposited on (100) silicon substrate kept at room temperature and placed at a distance of 40 mm from the target surface. The CNx films were grown under N2 gas in the pressure range of 5×10-3 to 4×10-1 mbar. The deposited films composition was investigated by different techniques RBS, NRA and AES. We found an N/C ratio equal to 0.4 in the pressure range cited above.

The Effect of Current Density on CNx Crystal Grain Growth in Electrochemical Deposition

The effect of charge current density on the growth of CNx films by electrolysis of a methanol-urea solution is investigated experimentally. It is seen that the C-C3N4 phase grains in the films are about 200–300 nm for a density of 55 mA/cm2 and dendrite growth takes place with grains as large as 7 μm formed when density is about 70 mA/cm2.

Effect of deposition temperature on chemical composition and electronic properties of amorphous carbon nitride ( a-CNx) thin films grown by plasma assisted pulsed laser deposition

The effect of deposition temperature and nitrogen inclusion in amorphous carbon ( a-C) films, deposited by plasma enhanced pulsed laser deposition, on chemical composition and electronic transport has been studied. a-CNx films were deposited on Si (100) by pulsed ArF laser ablation of a graphite target, under N 2 atmosphere. A radiofrequency (13.56 MHz RF) apparatus was used to generate plasma of excited nitrogen species, and its effect on nitrogen uptake and CNx film formation has been studied. Chemical and micro-structural changes associated to increased deposition temperature and nitrogen incorporation were examined by x-ray photoelectron spectroscopy; electrical properties were analyzed by the four-point-probe methods. Temperature-dependent conductivity measurements are tentatively interpreted and discussed in reference to chemical composition.

Nanoindentation and Friction/Wear Behaviors of a Magnetron Sputtered Cnx/Sic Films on Magnesium Alloy

The interface adhesion, nano-indentation and friction/wear properties of the CNx films in CNx/SiC (carbon nitride/silicon carbon) double layer films (SiC as interlayer) deposited on Mg alloy (AZ91D) substrate by using magnetron sputtering technique at room temperature were investigated. The results show that the interface between CNx film and SiC film and the interface between SiC film and Mg substrate both showed obvious and gradual element diffusions as well as high adhesion. The CNx films exhibited low nano-hardness (3.85 GPa) and Young's modulus (30.46 GPa) but high hardness-to-modulus ratio (0.126). As sliding against Si3N4 (silicon nitride) ball (4 mm in diameter) using ball-on-disc friction and wear tester under dry sliding condition at 200g load, the CNx films exhibited the friction coefficient of about 0.20 and the special wear rate in the order of magnitude of 10−6 mm3 m−1 N−1 without film cracking and interface delaminating.

Composition, Bonding state, and Electrical Properties of Carbon Nitride Films Formed by Electrochemical Deposition Technique

ABSTRACTComposition, bonding state, and electrical properties of CNx films formed by electro-chemical deposition using liquid acrylonitrile were studied. X-ray photoelectron spectra reveal that C, N, and O are major components of the deposited films. From analysis of C 1s and N 1s spectra, the major bonding state in the CNx film is attributed to a mixture of C≡N and partially hydrogenated C=N bond. Metal-insulator-semiconductor capacitors incorporating the CNx insulating layers are fabricated to evaluate the electrical properties of the deposited films. The lowest dielectric constant k of the CNx film is determined to be 2.6 from the accumulation capacitance and the thickness of the film. It is demonstrated that the CNx film formed by electrochemical deposition is a promising low-k material for use in ultralarge-scale integration multilevel interconnections.

Micro/nanomechanical behavior of magnetron sputtered Si–C–N coatings through nanoindentation and scratch tests

Si–C–N/Si based MEMs are advantageous to conventional MEMS because of their ease of fabrication and high temperature sustainability. The failure mechanism of such systems has to be known for their efficient performance. Nanoindentation and scratch behavior were performed on Si–C–N coatings deposited on silicon substrates by RF magnetron sputtering. Crack growth and propagation were studied using optical and SEM views of the deformed region. Different failure mechanisms were observed and analyzed. The crack deflection was due to nanocrystalline phases in the Si–C–N nanocomposite film, as no such deflection was observed in the amorphous CNx film. A different failure mechanism in the form of tensile and conformal cracking was observed. The films' failure mechanism changes from cohesive failure at lower loads to adhesive failure at higher loads during nanoscratching.

Synthesis, structure and mechanical properties of fullerene-like carbon nitride films deposited by DC magnetron sputtering

Carbon nitride (CNx) films were deposited by direct current magnetron sputtering at different N2 fractions and a substrate temperature of 450°C. The composition and microstructure of CNx films were investigated by high resolution transmission electron microscopy, X-ray absorption near-edge spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The CNx films change from amorphous to fullerene-like nanostructure as the N2 fraction is ranged from 0.05 to 0.1, and then to nitridized graphite nanocrystals in amorphous matrix at pure N2, and the curvature of the basal planes decreases with the increase of N content in CNx films. Meanwhile, the structural analysis provides the identification of spectral signatures related with the formation and promotion of FL arrangements, and the formation of C-sp3 sites has been generally considered as the cross-linking path in fullerene-like CNx. Their mechanical and tribological properties were also investigated in detail, aiming at illustrating excellent mechanical, friction and wear behaviours of the fullerene-like CNx film with respect to its high hardness and elastic recovery and less dependence on humidity and oxygen as compared with the amorphous CNx film.

Influence of deposition parameters on the microstructure and properties of nitrogen-doped diamondlike carbon films

CN x films were prepared on cemented carbide substrates by a pulsed bias arc ion-plating method with two graphite targets and using N2/Ar mixture gases. The effects of the deposition parameters, such as substrate negative-bias voltage, duty cycle, and nitrogen flow rate, on the structures and properties of CNx films were investigated using Raman spectra and nanoindentation. The properties of CNx films are closely related to the film structures. For CNx films deposited at a different bias voltage, the CNx film deposited at a bias voltage of −300 V had the highest hardness. The ID/IG ratio and G peak position decreased and then increased with increasing bias voltage, and the minimum values, which correspond to the highest sp3 content, were obtained at a bias voltage of −300 V. For the CNx films deposited at different duty cycles, the hardness and elastic modulus decreased with increasing duty cycle. For the CNx films deposited at different nitrogen flow rates, the results show that first the ID/IG ratio decreases and sp3 content increases with increasing nitrogen flow rate, and then the ID/IG ratio increases and sp3 bond content decreases after the nitrogen flow rate exceeds 10 SCCM (SCCM denotes cubic centimeter per minute at STP). The hardness and elastic modulus of the CNx film prepared at a nitrogen flow rate of 10 SCCM reached the maximum values of 32.1 and 411.8 GPa, respectively.

Improving mechanical properties of a-CNx films by Ti–TiN/CNx gradient multilayer

Amorphous carbon nitride (a-CNx) films with functional gradient Ti–TiN/CNx underlayer were deposited by direct current magnetron sputtering. Microstructure and composition of the films were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, atomic force microscope (AFM) and transmission electron microscopy (TEM). Mechanical and tribological properties were investigated by nanoindenter, scratch and ball-on-disk tribometer. The a-CNx-based films suffer a graphitization process with the increasing deposition temperature, thus the hardness and elastic modulus decrease. With the design of the Ti–TiN/CNx gradient underlayers, some important advantages of relatively thick CNx films can be achieved, such as increased hardness, improved adhesion strength, and the wear resistance of the a-CNx-based films can be also improved significantly.

Structure evolution from nanocolumns to nanoporous of nitrogen doped amorphous carbon films deposited by magnetron sputtering

Different nitrogen doped amorphous carbon (CNx) films were obtained by magnetron sputtering of carbon target in argon and nitrogen atmosphere at the increasing negative bias voltages from 0 to 150 V. The films structures have experienced great change, from the novel column to nanoporous structure at the bias voltage of 0 V to the porous structure at 150 V. The proposed growth process was that the CNx nuclei grew at 0 V acted as the “seeds” for the growth of the nanocolumns, and ion etching effects at 150 V induced the formation of nanoporous structures. Furthermore, a comparison study showed that the field emission properties of the CNx films were related with the introduction of the nitrogen atoms, the size and concentration of sp 2 C clusters and the surface roughness. The films with rougher surface have lower threshold field.

Industrial-scale deposition of highly adherent CNx films on steel substrates

Highly adherent carbon nitride (CNx) films were deposited using a novel pretreatment with two high power impulse magnetron sputtering (HIPIMS) power supplies in a master–slave configuration: one to establish the discharge and one to produce a pulsed substrate bias. During the pretreatment, SKF3 (AISI 52100) steel substrates were pulse-biased in the environment of a HIPIMS Cr plasma in order to sputter clean the surface and to implant Cr metal ions. Subsequently, CNx films were prepared at room temperature by DC unbalanced magnetron sputtering from a high purity graphite target in a N2/Ar discharge at 3 mTorr. All processing was done in an industrial CemeCon CC800 system. A series of depositions were obtained with samples at different bias voltages (DC and pulsed) in the range of 0–800 V. Scanning transmission microscopy (STEM) and high resolution transmission electron microscopy (HRTEM) show the formation of an interface comprising a polycrystalline Cr layer of 100 nm and an amorphous transition layer of 5 nm. The adhesion of CNx films evaluated by the Daimler-Benz Rockwell-C reach strength quality HF1, and the scratch tests gives critical loads of 84 N. Adhesion results are correlated to the formation of an optimal interfacial mixing layer of Cr and steel.