Sp3 Bond Content Research Articles

Effect of ion-beam surface modification technology on the variation of surface texture

Ion-beam surface bombardment modification technology is successfully used to manufacture different kinds of nano-textures on the surface of silicon substrate. Relationship between the morphology and arrangement patterns of nano-textures and the bombarding parameters is studied. Results show that the ion-beam bombardment has a significant impact on surface morphology. Different kinds of textures on silicon substrate can be formed according to the variation of bombardment time. The nanodot array texture is observed on the surface of silicon substrate when the duration of argon ion-beam bombardment is 15 minutes. Simultaneously, the tetrahedral amorphous carbon film is deposited on the silicon substrates that have different kinds of nano-texture. The microstructure of ta-C film deposited on unprocessed and nano-textured silicon substrate is analyzed by X-ray photoelectron spectroscopy. Results indicate that the content of sp3 bonds decreases with increasing bombardment time, and thereafter keeps a steady value. The ta-C films deposited on the nanodot-textured substrate shows the lowest sp3 fraction. It is also observed by friction and wear test that the wear time is enhanced from 10 to 70 min. The tribological properties is highly improved when the coating is deposited on the nano-textured substrate.

Influence of the substrate bias potential on the properties of ta-C coatings deposited using Venetian blind plasma filter

The paper presents the research results on the formation of amorphous ta-C films with a minimum amount of defects, deposited by pulsed vacuum-arc method with the use of a water-cooled electromagnetic Venetian blind plasma filter. The subject of the research was the influence of the substrate bias voltage, in the range of −25 to −200V, on the structural and mechanical properties of ta-C coatings. Dependence of the microstructure and phase composition of ta-C films on the substrate bias voltage were analyzed by Raman and X-ray photoelectron spectroscopy. The results of the structural analysis of coatings showed characteristic changes in the content of the diamond-like sp3 fraction on the substrate potential. Mechanical properties of ta-C films — roughness, adhesion, hardness and Young's modulus were investigated using a profilometer, the scratch tester and a nanoindenter. The highest content of sp3 bonds, of about 63%, was obtained in the coating deposited at the substrate bias potential of −100V, which also showed the minimum surface roughness and maximum hardness and Young's modulus of 50GPa and 371GPa respectively. The ta-C coating synthesized at this bias potential had excellent adhesion — complete film delamination occurs at the load of 41N. Our preliminary studies and the results described in this work enable the use of electromagnetic Venetian blind plasma filter for deposition of thin ta-C coatings with a minimum amount of defects.

Study of protective diamond-like carbon films on GCr15 bearing steel

Hydrogenated diamond-like carbon (H-DLC) were deposited on GCr15 bearing steel by double cathodes pulse glow discharge (DCPGD) plasma vapour deposition at different gas volume ratios. The surface morphology, composition, microstructure, hardness and friction properties of the H-DLC films were observed. It was found that the sp3 bond content and I(D)/I(G) ratio of DLC films were between 58 and 61% and in the range of 0·68–0·88, respectively. When H2∶Ar∶C2H2 gas volume ratio ranges from 4∶1∶1 to 8∶1∶1, the I(D)/I(G) ratio decreases with an increase in the sp3 bond content, the friction coefficient (about 0·1) and wear rate (between 4·5×10−8 and 8·4×10−8 mm3 N−1 m−1) of DLC films were very low. In this study, when H2∶Ar∶C2H2 gas volume ratio is 6∶1∶1, the thickness of the film is 8·13 μm deposited for is 4 h, the hardness reaches a maximum value (22·5 GPa), the friction coefficient and wear rate reduce to a minimum value, 0·094 and 4·5×10−8 mm3 N−1 m−1, respectively.

The Optical Property and Sensitivity of Ag Nanoparticles Deposited Ultra-Thin Diamond-Like Carbon Films

Ag nanoparticles (NPs) had most prominent local surface plasma resonance effect (LSPR) among the all metals. Diamond-like carbon (DLC) film had good biological compatibility, wear resistance, corrosion-resisting and high transmission ability in the visible and near-infrared range. Since the Ag NPs were easily oxidized in air,a new LSPR interface between them and an ultra-thin DLC films was formed by means of a plasma enhanced chemical vapor deposition (PECVD). The morphologies and properties of the Ag NPs deposited ultra-thin DLC films were studied by using Raman spectrometer, X-ray photoelectron spectrometer (XPS) , field emission scanning electron microscope (FESEM) and atomic force microscope (AFM) and so on. And the optical tramsmission sensitivity of the new LSPR interface was also examined. The results indicated that the DLC films deposited in a shorter time had a higher sp3bond content of carbon atoms and more sensitive to refractive index of surrounding media. Moreover, to obtain the optimal morphologies and the sensing property, the deposition time for forming the DLC films should be controlled within 30 seconds.

Improvement of the mechanical properties of single-walled carbon nanotube networks by carbon plasma coatings

Carbon vacuum arc was used to deposit 5–25nm thick carbon coatings on single-walled carbon nanotube (SWCNT) networks. The SWCNT bundles thus embedded in conformal coatings maintained their optical transparency and electrical conductivity. Sheet resistances of the networks were measured during the vacuum arc deposition, revealing initially a 100-fold increase, followed by significant recovery after exposing the samples to an ambient atmosphere. Nanoindentation measurements revealed improved elasticity of the network after applying the carbon coating. Pristine SWCNT networks were easily deformed permanently, but a 20nm carbon coating strengthened the nanostructure, resulting in a fully elastic recovery from a 20μN load applied with a Berkovich tip. In nano-wear tests on selected areas, the coated SWCNT maintained its networking integrity after two passes raster scan at loads up to 25μN. On the other hand, the pristine networks were badly damaged under a 10μN scan load and completely displaced under 25μN. Raman and electron energy loss spectroscopies indicated the carbon coating on bundles to be mainly sp2 bonded. Finite element modeling suggests that the low content of sp3 bonds may be due to heating by the intense ion flux during the plasma pulse.

Investigating the microstructure and mechanical behaviors of DLC films on AISI52100 bearing steel surface fabricated by plasma immersion ion implantation and deposition

The microstructure and mechanical properties of diamond-like carbon (DLC) films fabricated on an AISI52100 bearing steel substrate surface by plasma immersion ion implantation and deposition (PIIID) were studied. Atomic force microscope (AFM) observation reveals that the DLC film has an extremely smooth surface, and high uniformity and efficiency of space filling over large areas. Raman spectroscopy analysis indicates that DLC films are mainly constituted by amorphous and crystalline phases, with a variable ratio of sp2/sp3 carbon bonds, and sp3 bond content of more than 10%. The maximum nanohardness and elastic modulus of the DLC film are 40GPa and 430GPa, and increase by 263.6% and 95.5%, respectively. The friction and wear results exhibit that the friction coefficient against an AISI52100 steel ball decreases from 0.87 to 0.20. The corrosion polarization curves in a 3.5% saturated NaCl solution shows that the corrosion resistance of DLC/AISI52100 samples is much better than that of bearing steel substrate. Compared with the bare bearing steel, the surface mechanical property of the DLC/AISI52100 sample is improved significantly.

Pulsed laser deposition of composite Mo–Se–Ni–C coatings using standard and shadow mask configuration

Thin film Mo–Se–Ni–C coatings for tribologycal applications were prepared by pulsed laser co-deposition from two targets — MoSe2(Ni) and graphite. Two methods of deposition from the MoSe2(Ni) target were used: deposition with unhindered expansion of the laser plume (standard PLD) and deposition of a plume scattered in collisions with Ar gas (pressure 2Pa) in the shadow of a mask (shadow-masked PLD — SMPLD). Doping with carbon by PLD was used in all cases, and carbon content in the composite Mo–Se–Ni–C coatings was varied in the range 35–85.5at.%. Pure MoSex(Ni) coatings were also prepared by PLD and SMPLD. Rutherford backscattering spectroscopy of helium ions, scanning electron and atomic force microscopy, electron probe microanalysis, transmission electron microscopy and micro-diffraction, micro-Raman spectroscopy, X-ray photoelectron spectroscopy and hardness evaluation were all used for comparative studies of the coatings obtained by PLD and SMPLD/PLD. In the PLD coatings, micron-sized particles were found, consisting of pure Ni or MoSe2, as well as nanometre-sized particles of monocrystalline Mo. The nanoparticles were distributed on the surface and in an amorphous matrix in all PLD coatings. Within the amorphous matrix of the Mo–Se–Ni–C coatings, local ordering of atoms was detected, causing the formation of a mixture of amorphous carbon, Mo–C, and Mo–Se phases. Increasing the carbon content caused an increase in the content of sp3 bonds in the carbon phase, and an increase in the hardness of the coatings. SMPLD/PLD coatings had no micro- and nanoparticles, but these coatings were characterized by high selenium content and reduced density. Doping with carbon in the SMPLD/PLD configuration caused the formation of composite coatings containing Mo–Se and amorphous carbon phases as in the PLD coatings, but the hardness of the composite SMPLD/PLD coatings was significantly lower than even the hardness of the pure PLD MoSex(Ni) coatings.

Effect of boron and silicon doping on the surface and electrical properties of diamond like carbon films by magnetron sputtering technique

To improve the surface and electrical properties, silicon (Si) and boron (B) were co-doped in diamond-like carbon (DLC) films prepared on silica substrates by RF magnetron sputtering. In the deposition of a Si, B co-doped DLC film, Si content was controlled by the number of intrinsic Si wafer piece and B content by B target power. The surface roughness and resistivity of film increased by increment in the CC sp3 bond content due to added Si and the surface roughness and resistivity of film decreased by decrement in the CC sp2 bond content due to added B. A CC sp3 bond content in the Si, B co-doped DLC films decreased from 47.4% to 36.5% with increasing B target power compared with from 46.7% to 23.9% in case of the only B doped DLC films. From this result, it can be said that Si can suppress a graphitization of DLC with presence of B. However, the surface roughness and resistivity values of Si, B co-doped DLC films decreased similarly as in only B doped DLC films with an increase in the B target power. These results were caused the SiB sp3 bonds formed smaller than Si sp3 bonds with increase in the B target power as a result of the B-doping effect. In order to minimize the reduction in sp3 bond content over the decrease roughness and resistivity, DLC films were prepared by Si, B co-doping. So, these films can be applied in chemical sensing, electro-synthesis, and electrochemical-based toxic waste detection, remediation, and so on at industrial level.

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.

Effect of thickness on structures of ultrathin diamond-like carbon films

Diamond-like carbon (DLC) films with different thickness were deposited by filtered cathode vacuum arc (FCVA). Vis-Raman and spectroscopic ellipsometry were employed to analyze the structure of DLC films. The wavelength of Vis-Raman is 514.5 nm. Experimental results show that structures of DLC films are affected by film thicknesses. When the film thickness increases from 2 to 30 nm, the G-peak position (G-pos) shifts to higher wavelength, the intensity ratio ID/IG and the extinction coefficient Ks decrease. It is indicated that the content of sp3 bond increases with film thickness. However, when the film thickness increases from 30 nm to 50 nm, ID/IG and Ks increase. The content of sp3 bonds decreases with film thickness.

Experimental Assessment of a New Type of Carbon-Coated ARTECOR® Vascular Prosthesis in Sheep

The aim of the study was to test and verify the characteristics of a new type of carbon-coated ARTECOR® vascular prosthesis developed at the Knitting Research Institute, a.s. Brno. Eight healthy Merino sheep, aged between 2 and 3 years, were implanted four types (A, B, C with diamond-like carbon (DLC) coating and D as a control without DLC) of vascular prostheses. The site of implantation was the common carotid artery; the length of the implant was 7 cm. All sheep received antibiotics prophylactically in accordance with the theory of the so-called “protected coagulum”. Doppler ultrasound examination was performed before finishing the operation to verify the patency of each prosthesis. During the study period the animals were closely observed. Prostheses were extirpated on day +/- 100 in 6 sheep and on day 182 in 2 sheep. Type B prosthesis showed better results according to its postoperative patency. The implant lumen was constantly 7 mm, whereas the use of other types resulted in lumen narrowing. Type B prosthesis has a deposition of DLC coating of a thickness of 20 nm with a high content of sp3 bonds (more diamond-like ones). The experimental type B of prosthesis ARTECOR® appears to be the most successful of the tested prostheses (at the end of the study all B-type prostheses remained patent). This prosthesis appears to better satisfy the rheologic characteristics for healing.

Characteristics of diamond-like carbon film deposited by filter arc deposition

Abstract A diamond-like carbon (DLC) film was successfully deposited on SKD 51 by filter arc deposition (FAD). An interlayer of CrN between the substrate and the DLC film was formed, enhancing the adhesion and the mechanical properties of the film assembly. The film structure exhibited high sp3 bonding under optimal conditions when the cathode current was varied. The process parameters were compared by studying various mechanical properties of the deposited films such as microhardness, adhesion and residual stress. The crystal structure was investigated by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The sp3 bond content dominates at a cathode current of 50 A and is inversely proportional to the cathode current, explaining why damage by the high beam current is associated with more graphitic character. The main contribution of this study is to help understand the relationship between the variation in the cathode current and the relationship between the interlayer (CrN) and DLC.

Nanostructured superhard carbon phase obtained under high pressure with shear deformation from single-wall nanotubes HiPco

Raman spectra of single-wall nanotubes under high pressure combined with shear deformation are investigated in situ in a diamond cell. Shear deformation applied under 35 GPa led to pressure multiplication up to 60 GPa, and increased the intensity of Raman bands more than ten times without essential change of G-mode position while causing its essential broadening. The G-mode remained broad after pressure unloading and shifted to 1534 cm −1. The hardness of the superhard material was 58±6 GPa, comparable to the hardness of carbo-boro-nitride. A broad band appeared in the photoluminescence spectrum with a maximum at about 2 eV, which allowed to assume a high content of sp 3-bonds in the sample. The large dispersion of the G-mode almost vanished after pressure unloading. However, a noticeable dispersion of the D-mode was found, which is a sign of certain ordering in the superhard phase. TEM study of the superhard phase detected clusters with graphene sheets with a size about 1 nm.

Tetrahedral amorphous-carbon thin films for silicon-on-insulator application

The application of a silicon-on-insulator substrate in a high-power integrated circuit is limited by the self-heating effect, caused by the poor thermal conductivity of the buried SiO2. We introduce tetrahedral amorphous-carbon thin films, formed by the filtered arc deposition method, as an alteration. We investigated the surface morphology, microstructure, and electrical properties of these films. The films deposited under a substrate bias of −200 V displayed outstanding surface topography (low surface roughness with the Rrms value under 0.5 nm) and excellent electrical property (breakdown field of 4.7 MV/cm). The film has a high content of sp3 bonds of carbon (87%) and low content of oxygen (<2%).

COMPARATIVE ANALYSIS OF DLC FLIM FINE STRUCTURE BY RAMAN SPECTRA AND X-RAY PHOTOELECTRON SPECTROSCOPY

The diamond-like carbon (DLC) films were deposited under different deposition parameters by using arc technology. The detailed relationship of sp3 structure with the D peak of the DLC films' Raman spectra is discussed. In aid of the discussion, X-ray photoelectron spectroscopy was used to determine the DLC films' C1s binding energy. By comparing the binding energy with the Raman shift of the films, it can be found that the intensity of D peak decomposed from the Raman shift can be increased not only by the graphite cluster, but also by higher content of sp3 bonds. Higher sp3 content of DLC films can be obtained by using 90 degree magnetic filter. The study shows that the C1s binding energy of DLC films, whose Raman spectra have higher intensity of D peak, can be 284.15 or 285.50 eV, which reveals that the DLC films may have higher graphite-like or diamond-like structure, respectively.

Interface investigations by infrared spectroscopy and X-ray reflectivity measurements of cubic boron nitride thin films

Cubic boron nitride thin films were deposited by unbalanced r.f. magnetron sputtering of a hexagonal boron nitride target in a pure argon discharge in combination with r.f. argon ion bombardment. At a flux ratio of the argon ions relative to the film forming boron and nitrogen atoms of 20, and an argon ion energy of 87 eV, the total content of sp3-bonds of a 300 nm film amounts to 92.8%, according to infrared analysis. This film has a hexagonal interface between the silicon substrate and the cubic top layer which is estimated to be 15.6 nm on the basis of infrared spectroscopy as well as X-ray reflectivity. From the infrared investigations of the film thickness dependence it can be concluded that 72% of the sp2-bonds in the 300 nm c-BN film are formed in the hexagonal interface region, and only 18% between the cubic crystallites in the top layer. Consequently, the content of the cubic phase in the top layer amounts to 98.6%, which is in agreement with the density of 3.502 g/cm3 as determined by X-ray reflectivity measurements.

Ion-beam sputtered diamond-like carbon with densities of 2.9 g/cc

Thin films of carbon have been deposited at temperatures ranging from 77 to 1073 K. It has been found that diamond-like properties of the films change with the deposition temperature and the thermal conductivity of the substrate. Densities as high as 2.9 g/cc with an sp3 bond content >40% have been observed. Substrates that have been investigated include graphite, NaCl, Si, Al2O3, fused quartz, and diamond. Density measurements have been made using Rutherford backscattering spectrometry and electron-energy-loss spectroscopy while hydrogen profiling was conducted using forward recoil spectrometry.