Carbon Implantation Research Articles

Optimisation of carbon implantation pre-treatments on the adhesion strength of amorphous carbon coatings on AISI 440C steel substrates

The effect of carbon ion implantation pre-treatment conditions (implantation energy and substrate etched depth) on the adhesion strength of amorphous carbon coatings deposited onto hardened AISI 440C steel substrates was investigated. Based on the scratch test and the X-ray photoelectron spectroscopy analysis, the most influential factor on the adhesion strength was found to be the carbon concentration on the outmost surface of the implanted steel substrates. A carbon concentration of 20–30 at.% led to the highest carbide concentration and thus the highest adhesion strength between the coatings and the substrates. By optimising the implantation energy and the etched depth to expose the highest carbide bonds on the steel substrates, well-adherent carbon coatings of different thickness (0.5–2.0 μm) could be obtained. The carbon coatings possessed a high scratch resistance with a critical load over 70 N even at a coating thickness of 2.3 μm. In addition, the coatings also exhibited a good tribological performance in the ball-on-disk wear test with friction coefficients below 0.1, which was maintained constantly over 1×10 6 rotation cycles (a sliding distance of 18.8 km) of unlubricated sliding against a WC–6%Co ball.

Chemical Modification of Titanium Nitride Films via Ion Implantation

Titanium nitride, TiN is a typical ceramic coating film for cutting tools and dies; it often suffers from low oxidation temperature and high friction coefficient and wear volume. Its wearing and oxidation resistance is drastically improved by chemical modification via ion implantation. Carbon-, aluminum- and chlorine-ion implantation is introduced to describe the difference in the modified microstructure at the vicinity of surface. Ion-plated TiN films on a high-speed tool steel substrate are employed as a common specimen to be implanted. Each modified titanium nitride has its intrinsic, as-implanted nanostructure to the selected species. In the carbon implantation, the near-surface structure of TiN film is modified to have the layered bonding state with Ti-C/C-C/Ti-C. The Al-implantation modifies TiN to have non-equilibrium solid solution phase of (Ti, Al) N and metallic aluminum cluster. No change is seen in the chlorine implanted TiN except for increase of dislocations or point defects. The wear resistance is improved by the above as-implanted nano-structuring in the case of carbon implantation. Al- and Cl-implantation significantly improves the original oxidation and wearing resistance of TiN by the post-implantation nano-structuring. The stable, dense aluminum oxide layer is in-situ formed as a tight protective shield during the oxidation test by surface reaction between penetrating oxygen and diffusing aluminum. The lubricious titanium oxide film is also in-situ formed in the wear track at the presence of chlorine to sustain low friction and wear rate even in dry, severe wearing conditions.

Diamond formation in cubic silicon carbide

High-dose carbon implantation (3×1017 and 1×1018 ions/cm2) into cubic SiC on Si was carried out at elevated temperatures (600 to 1200 °C) and different dose rates (1×1013 to 1.5×1014 cm−2 s−1). Transmission electron microscopy revealed the formation of either graphite or diamond precipitates, depending on the implantation parameters. In all cases, the diamond grains were epitaxial to the SiC lattice, while the graphite was textured. The minimum temperature for diamond formation was 900 °C, while graphite formed at 600 °C. The synthesized phase depends as well on the dose rate; graphite was formed at 900 °C with a high dose rate. Obviously, a critical temperature for diamond formation exists and increases with increasing dose rate. This behavior is explained by the competition between the accumulation and dynamic annealing of radiation defects in the SiC lattice, which acts as a template for diamond nucleation. Diamond grains with diameters as large as 10 nm have been observed after implantation at 1200 °C.

Ion enhanced deposition by dual titanium and acetylene plasma immersion ion implantation

Plasma immersion ion implantation and deposition (PIII–D) offers a non-line-of-sight fabrication method for various types of thin films on steels to improve the surface properties. In this work, titanium films were first deposited on 9Cr18 (AISI440) stainless bearing steel by metal plasma immersion ion implantation and deposition (MePIII–D) using a titanium vacuum arc plasma source. Afterwards, carbon implantation and carbon film deposition were performed by acetylene (C2H2) plasma immersion ion implantation. Multiple-layered structures with superior properties were produced by conducting Ti MePIII–D + C2H2 PIII successively. The composition and structure of the films were investigated employing Auger electron spectroscopy and Raman spectroscopy. It is shown that the mixing for Ti and C atoms is much better when the target bias is higher during Ti MePIII–D. A top diamond-like carbon layer and a titanium oxycarbide layer are formed on the 9Cr18 steel surface. The wear test results indicate that this dual PIII–D method can significantly enhance the wear properties and decrease the surface friction coefficient of 9Cr18 steel.

Origins of field enhancement in electron field emission from ion beam synthesized SiC layers

SiC layers were synthesized by high-dose carbon implantation into silicon. Their electron field emission properties were studied and correlated with results from atomic force microscopy (AFM) and conducting AFM measurements. It is clearly demonstrated that there are two types of field enhancement mechanisms responsible for the improvement of the electron field emission properties of these ion beam synthesized SiC layers. In the as-implanted samples, the local field enhancement effect is attributed to electrical inhomogeneity due to the existence of small conducting graphitic clusters embedded in the layer. On the other hand, in the annealed samples, the dominant field enhancement mechanism is attributed to a surface morphology effect due to the formation of small protrusion structures at the surface.

Improvement of oxygen barrier of polyethylene terepthalate film by plasma-source ion implantation of carbon

The surface of polyethylene terepthalate (PET) film has been successfully modified to amorphous carbon by plasma source ion implantation (PSII) as a means of improving the oxygen barrier characteristics of the PET film. The process was performed using high negative pulsed voltage in an radio frequency field with C2H2 gas. The amorphous carbon layer is found to consist primarily of graphite crystal with C–H, C–H2 and C–H3 components, and to reduce the oxygen transmission rate of the film by up to 100 times that of unmodified PET film at a thickness of only 70–300 nm. Raman spectra reveal that the amorphous carbon layer has diamond-like carbon characteristics, yet is soft compared to other diamond-like carbon films with hydrogen contents of >20 at. %. A stronger graphite character in the x-ray photoelectron spectroscopy spectra is found to represent the fineness of the carbon structure and correlate well with the improvement of oxygen barrier characteristics.

XPS studies on silicon carbonitride films prepared by sequential implantation of nitrogen and carbon into silicon

Silicon carbonitride films are synthesized by sequential implantation of nitrogen and carbon into silicon. The evolution of the chemical bonding states between silicon, nitrogen and carbon is investigated as a function of implantation sequence and ion dose using X-ray photoelectron spectroscopy. Nitrogen ion implantation into silicon saturates upon the formation of a stoichiometric silicon nitride film. Successive implantation of carbon into this film leads to the formation of a complex of silicon carbonitride and pure carbon. The formation of CN bond is insignificant. Carbon ion implantation into silicon leads to a continuous increase in carbon concentration till the formation of a nearly pure carbon film at the surface. Successive implantation of nitrogen into this film first forms a film dominated by CC and CN bonds. With increase in nitrogen ion dose, it evolves into a silicon nitride film containing a small fraction of CC, CN and CSi bonds. The formation of CN bond is due to the existence of large amount of pure carbon.

Ion implantation into inner wall surface of millimeter size diameter steel tube by plasma source ion implantation

Nitrogen and carbon ions were implanted into the inner wall surface of 304 austenitic type stainless steel and Ni tubes with inner diameters of 0.9, 2 and 1.6 mm, by a plasma source ion implantation (PSII). These 30 mm long substrate tubes were fixed to an alumina ceramic tube in a vacuum chamber, fed with nitrogen and acetylene gases. A 2.45 GHz microwave was supplied to an antenna in the alumina ceramic tube and plasma was produced by a coaxial electron cyclotron resonance (ECR) discharge in this tube. A negative high voltage pulse of 15 kV (1 kHz, 10 μs) was applied to the steel and Ni tubes to extract ions from the generated plasma. The compositional and structural characterizations of the implanted surfaces were carried out using Auger electron spectroscopy and Raman spectroscopy. The results showed that uniform nitrogen ion implantation into the millimeter size inner wall surface of metal tubes was achieved by the PSII. Carbon implantation and subsequent diamond like carbon (DLC) coating was confirmed for the inner wall surface treated by acetylene PSII.

Successive ion implantation of high doses of carbon and nitrogen on steels

HSS and stainless steel samples were successively implanted with high doses of carbon and nitrogen. Different sequences of implantation (C +, C ++N 2 +, N 2 ++C + and N 2 ++C ++N 2 +) were carried out in order to achieve C x N y layers of ultra-high hardness. The bonded states of carbon and nitrogen were studied by XPS spectroscopy. The tribological behaviour was measured by means of ball-on-disc and microhardness tests. The microhardness tests showed that increases in hardness are highly influenced by the implantation order. None of the sequences tested led to a hardness increase higher than that for simple carbon implantation. When nitrogen was implanted into carbon-implanted steel, the result was a huge decrease in surface hardness. Ion implantation of high doses of nitrogen and carbon brought about a decrease in the friction and wear coefficients. The samples for which carbon was implanted in the last step showed the lowest friction and wear coefficients.

Dependence of critical damage energies in diamond on electronic stopping

Damage profiles in diamond due to implantation of argon and krypton ions at liquid nitrogen temperature were determined by α-particle channeling in a backscattering geometry. Energies and fluences were chosen to obtain similar damage energies in the surface region as obtained for a 75 keV carbon implant, investigated and discussed in a previous paper. The damage profiles before and after annealing at 1500 K were compared with those of the carbon implants. Raman spectroscopic analyses and channeling results prove that, contrary to the carbon implants, no irreversible transition to the graphitic phase takes place at comparable damage energies. Critical damage energies are obviously higher for argon and krypton ions than for the lighter carbon ions. This can be explained by a strong annealing effect of the combined inelastic energy transfer by the ion and its associated recoil atoms due to electronic stopping.

The effects of MEVVA ion implantation on the tribological properties of PVD-TiN films deposited on steel substrates

The effects of post-deposition metal vapour vacuum arc (MEVVA) ion implantation into TiN films were studied as part of a continuous effort to improve the wear performance of coatings used for cutting tools. This is a first account on the tribological behaviour of PVD-TiN coatings deposited on steel substrates and treated by MEVVA ion implantation. Two types of species were selected, C and W, one light and one heavy. In all cases, after implantation, tribological improvements were observed: The friction coefficient of the PVD-TiN against ruby was significantly reduced from 0.75 to 0.18 with carbon implantation at a dose of 10 17 cm −2 and the lifetime to spalling was improved by more than 200%. (Untreated films detached after approx. 5000 cycles, whereas implanted films were still well adhered after 19 000 cycles.) For C-implanted samples, an increase in nano-hardness in the near surface region was also observed. These effects are attributed to the formation of a carbonaceous layer on the surface, accompanied by the formation of TiC in the sub-surface region, as detected by XRD. In contrast, W implantation improved coating wear life, but not friction coefficient or nano-hardness. The results are compared to those obtained for MEVVA implantation into CVD-TiN and to conventional implantation.

Field Enhancement Mechanisms and Electron Field Emission Properties of Ion Beam Synthesized and Modified SiC/Si Heterostructures

ABSTRACTSiC/Si heterostructures were synthesized by high dose carbon implantation into silicon using a metal vapor vacuum arc ion source. Their electron field emission properties were studied and correlated with results from other characterization techniques including atomic force microscopy (AFM), conducting AFM, Fourier transform infrared absorption spectroscopy, x-ray diffraction and photoelectron spectroscopy. It is clearly demonstrated that there are two types of field enhancement mechanisms responsible for the improvement of the electron field emission properties of these ion beam synthesized SiC/Si heterostructures, namely, the surface morphology effect and the local electrical inhomogeneity effect. The dependence of the FE properties on the carbon implant dose and thermal annealing conditions could be understood in terms of these two field enhancement mechanisms. It is also demonstrated that improvement in the FE properties can be achieved by implanting tungsten ions into these SiC/Si heterostructures.

Effects of carbon implantation on the electrical properties of amorphous In 2O 3 thin film

Carbon ions with an energy of 30 keV have been implanted into amorphous In 2O 3 thin films at doses of 1×10 15–2×10 16 cm −2 . After implantation the films were annealed in air and subsequently in a vacuum at 350 °C for 1 h. The electrical resistivities of carbon-implanted films decreased due to the increase in the carrier concentration. However, the whole properties were not much improved compared to a previous experiment by the use of crystalline In 2O 3 film as a starting material. The relation between the crystal structure and the electrical property will be discussed.

Formation and annealing of periodically arranged amorphous SiC x nanoclusters in silicon

The formation of a continuous amorphous layer upon high-dose carbon implantation into silicon at elevated temperatures is preceded by the formation of periodically arranged amorphous SiC x nanoclusters and lamellae. The dose and temperature dependence of their formation and the annealing behavior is studied after 180 keV C + implantations at temperatures of 150–350 °C and doses of 1– 9×10 17 C/ cm 2 mainly by cross-sectional transmission electron microscopy (XTEM). Annealing of the nanoclusters at temperatures closely above the crystallization temperature of SiC is shown to result in the partial recrystallization of lamellae into chains of spherical SiC x nanoclusters and in the formation of cavities and crystalline inclusions. The observations are discussed on the basis of a simple model.

Wear reduction effect on ultra-high-molecular-weight polyethylene by application of hard coatings and ion implantation on cobalt chromium alloy, as measured in a knee wear simulation machine

The most important factor affecting performance and longevity of hip joint and knee implants is the wear rate of the ultra-high-molecular-weight polyethylene (UHMWPE) component. UHMWPE wear debris has been linked to complications including tissue inflammation, bone loss (osteolysis) and implant loosening. Reduction of debris has been addressed by investigating new polyethylene formulations, manufacturing and finishing processes, including surface treatments and coatings both on plastic and metallic components. There have been many studies on the effect of surface treatments and hard coatings on cobalt chromium and titanium alloys for prosthetic applications. However, most of them have used laboratory tribo-testers without much correlation to articulating movements in human joints. In this work, hard coatings (TiN and DLC) and surface treatments (nitrogen ion implantation) have been investigated as potential candidates to reduce wear of UHMWPE, when applied on the counter face cobalt chromium alloy. Also the effect of applying nitrogen ion implantation on the UHMWPE surface itself has been investigated. To evaluate wear performance a special knee wear simulator has been used with a combined rolling-sliding movement that corresponds to the most unfavourable situation in the knee. As testing materials, conventional coated and uncoated Co–Cr as well as Al 2O 3 femoral heads were used against UHMWPE plates to obtain comparative data. Testing was carried out at 50 MPa using distilled water at 37±2°C as a lubricant. Wear measurements on UHMWPE were made following ASTM F732 standard by weight loss measurements and also by laser profilometry. The results, up to 5 million wear cycles that represent approximately 3 years of implant life, clearly have demonstrated the beneficial effects of diamond-like carbon (DLC) and ion implantation (both on Co–Cr and UHMWPE) in reducing wear of UHMWPE. Similar values were also obtained for Al 2O 3 ceramic material. A wear reduction up to approximately five times was obtained by the former materials, in comparison with the uncoated control specimen. However, the ion plated TiN coating increased significantly wear on the UHMWPE. Transference of UHMWPE to the ball was very evident with the uncoated control and TiN coated Co–Cr, as observed by SEM, but with DLC and the ceramic material this occurred to a much lesser extent. Some micro-delamination at the worn surface of the UHMWPE was observed when wearing against uncoated Co–Cr, but was not clear in the rest options. Ion implantation and DLC can thus be two good candidate treatments to reduce wear of UHMWPE in cobalt chromium knee and hip joint implants in substitution of a more expensive ceramic material. This DLC has passed all biocompatible tests in accordance with FDA regulations and ISO 10993 standards for implantable devices. An example of a uniformly DLC coated femoral head and knee implant is shown.

Low-energy carbon and nitrogen ion implantation in silicon

Silicon wafers have been implanted with C+, N+, and C++N+ ions at low energies to form buried insulating layers. Buried silicon nitride layers with Si or SiC small crystalline clusters were segregated after annealing at high temperature, leaving a high-crystalline-quality overlayer on top. In the samples implanted with C+ alone, after annealing, the silicon overlayer exhibits a lattice contraction of about 0.04%. In the N+-implanted samples this contraction is between 0.08% and 0.13%. The C++N+ implantation leads to relaxation of the lattice after annealing, with no reduction of the lattice constant.

On the influence of carbon implantation on the structural properties of hard TiN coatings studied by glancing incidence X-ray diffraction

In this work, we investigate the structural properties and, in particular, the residual stress of carbon-implanted TiN coatings by means of glancing incidence X-ray diffraction and secondary ion mass spectrometry techniques. The coatings were grown by ion-beam physical vapor deposition on steel substrates and subsequently implanted at 100 keV with carbon doses of 1×10 17,3×10 17 and 7×10 17 ions/ cm 2 . The carbon depth profiles obtained by secondary ion mass spectrometry enable us to choose the more appropriate X-ray beam incidence angles in order to detect the structural variations in proximity to the implanted region. The X-ray results indicate notable variations both in the crystallinity and in the residual stress and such modifications depend on the carbon dose and penetration depth. In particular, in the coating implanted with a dose of 1×10 17 ions/ cm 2 the initial compressive residual stress is reduced until a penetration depth of at least 400 nm. In addition, the lattice is re-crystallized in the first 100 nm. The coatings implanted with doses of 3×10 17 and 7×10 17 ions/ cm 2 have a surface region (100 nm thick) in the tensile stress state and a peak of compressive stress well above the non-implanted value at a depth between R p and 2 R p. Moreover, the effect of C + implantation is to reduce the lattice parameters for all the investigated samples. Such results can be explained by considering the defect distribution induced by the implantation process and the competition between the implantation amorphization and the self-annealing behavior.

Ion beam synthesis of buried SiC layers in silicon: Basic physical processes

For the ion beam synthesis (IBS) of buried stoichiometric epitaxial layers of 3C–SiC in silicon, a complicated structure in the as-implanted state has been identified as a favourable starting structure prior to annealing. It consists of a nearly rectangular depth distribution of equally sized, oriented 3C–SiC nanocrystals sandwiched between two amorphous zones. The basic physical processes leading to such a distribution of amorphous and crystalline phases during high-dose, high-temperature carbon implantation into silicon are reviewed in this article. In particular, the precipitation of carbon in a self-organized lattice of amorphous inclusions, the formation of stable 3C–SiC nuclei via precursors, beam-induced nucleation of SiC in amorphous Si:C, the different growth of crystalline SiC precipitates in crystalline and amorphous silicon and the ballistic destruction of SiC nanoclusters by the continued bombardment with energetic ions – resulting in a carbon-induced amorphization at elevated temperatures – are described.

High dose nitrogen and carbon shallow implantation in Si by plasma immersion ion implantation

We have performed plasma immersion ion implantation (PIII) processing to dope Si (0 0 1) wafers with nitrogen and carbon at high doses, relying on two different PIII systems: one at the Institute for Ion Beam Physics at Dresden and the other at INPE. In the first system based on an ECR plasma source, we carried out nitrogen and carbon implantation in Si samples at 35 keV, with delivered doses (DD) ranging from 0.6×10 17 to 3.1×10 18 cm −2. On the other hand, nitrogen implantation in Si samples at 12 keV with doses from 1.2×10 17 to 2.4×10 18 cm −2 were conducted in the second system with a glow discharge plasma source. Surface characterizations of these samples based on Auger electron spectroscopy (AES), surface profiler, Fourier transform infrared (FTIR) spectroscopy and a high-resolution X-ray diffractometer indicated different implanted profiles, maximum implanted depths, stresses and etching depths, as well as characteristic surface colors, depending on the doped species, energies and used delivered doses. Comparisons of these results and their interrelationship are discussed in this paper.

High pressure annealing of defects induced by ion implantation on graphite

The aim of this work was to investigate, by Raman spectroscopy, the effect of high pressure on the annealing of the surface disorder induced by hydrogen, carbon and nickel ion implantations on graphite samples. In the case of H implantation, the induced disorder decreased after annealing at 650°C for 7.7 GPa. For C implantation, the defect annealing started at 500°C for 7.7 GPa, while in the case of Ni implantation, it started at 850°C for the same pressure. For the three cases studied, there was practically no annealing effect for temperature treatments in vacuum up to 1100°C. The results indicated that high pressure plays an important role in the defect annealing, accelerating the graphitization process, probably due to the large volume of the defective ion implanted phase. Despite the annealing at high pressure being conducted deep inside the thermodynamic region of stability of diamond, the graphite phase was recovered, indicating that the nucleation barrier for diamond is indeed very high as compared to graphite.