Carbon Implantation Research Articles

Installation of ion implantation beam line for 3 MV Tandem Pelletron

An MeV energy beam line for ion implantation of carbon and silicon to fashion optically-active nanocrystals has been constructed at the Ion Beam Modification and Analysis Laboratory at the University of North Texas (UNT). The implantation line is at 15° and consists of a set of slits to define the beam, a doublet quadrupole focusing lens, a 40kV electrostatic ion beam raster scanner and target chamber for 2cm diameter circular implants. A 1.95m drift section between the scanner and target is sufficient to accommodate 10MeV carbon and silicon ions. It was determined that the separation between the slits and quadrupole should be at least 10cm to achieve point-to-parallel focusing in the beam line. It was also determined that, for a slit opening of 2mm, the distance between the upstream bending magnet and the analyzing slit should be at least 20cm to allow only single isotopes of carbon to pass into the beam line.

Carbon ion-implanted optical waveguides in Nd:YLiF 4 crystal: Refractive index profiles and thermal stability

We report on the optical planar waveguides in Nd:YLiF 4 laser crystals fabricated by 6.0 MeV C 3+ ion implantation at doses of 1 × 10 15 or 2.5 × 10 15 ions/cm 2, respectively. The refractive index profiles, which are reconstructed according to the measured dark mode spectroscopy, show that the ordinary index had a positive change in the surface region, forming non-leaky waveguide structures. The extraordinary index is with a typical barrier-shaped distribution, which may be mainly due to the nuclear energy deposition of the incident ions into the substrate. In order to investigate the thermal stability of the waveguides, the samples are annealed at temperature of 200–300 °C in air. The results show that waveguide produced by higher-dose carbon implantation remains relatively stable with post-irradiation annealing treatment at 200 °C in air.

Influence of electronic stopping on amorphization energies

The effect of electronic stopping on amorphization energies in germanium and silicon carbide is investigated by determining critical damage energies from the boundary positions of buried amorphous layers of carbon implants and relating them to the accompanying inelastic energy densities. Additional results were obtained by re-analyzing previously published results of damage profiles obtained by other workers for different ions in silicon, indium phosphide and gallium arsenide. Results show that electronic stopping reduces damage efficiency in mono-elemental targets, although this effect becomes less important with increasing target mass. Contrary to this, an enhancement of damage efficiency is observed in the lighter two binary targets, while a rather weak reduction is observed in gallium arsenide.

Silicon carbide and boron carbide thin films formed by plasma immersion ion implantation of hydrocarbon gases

Samples of silicon wafers and boron films on silicon were immersed in RF plasmas of methane and toluene. They were pulse-biased at different pulse durations and repetition rates at voltages up to − 45 kV. After the process, the samples were analyzed by Rutherford Backscattering Spectrometry for their composition, and by X-ray diffraction for their microstructure. The results show that under all conditions the silicon carbide and the boron carbide films were amorphous. The carbon depth profile depended on the process parameters, mainly on the number of applied pulses and the pulse repetition rate. The carbon implantation process was accompanied by deposition of a carbon film as a concurrent process. While in the case of toluene the deposition process dominated, in the case of methane it was possible to implant carbon in depth. The implantation process could be enhanced by increasing the pulse repetition rate.

Characterization of surface mechanical properties of H13 steel implanted by plasma immersion ion implantation

Abstract AISI H13 steel samples were implanted with nitrogen using plasma immersion ion implantation (PIII) at 320 or 380 °C. In addition, PIII was used for simultaneous implantation of carbon and nitrogen into H13 steel at 380 °C. Treated and untreated samples were studied by wear-friction testing, microhardness measurement, atomic force microscopy and glancing angle X-ray diffraction (XRD) diagnosis. Experimental results indicated that the hardness and wear resistance were improved by increasing the PIII treatment temperature, whereas the presence of C ions does the opposite. It is explained by a nitride formation and a lattice expansion between 1.7 and 2.23%.

Reduction of traps and improvement of carrier lifetime in 4H-SiC epilayers by ion implantation

The authors report a significant reduction in deep level defects and improvement of carrier lifetime in 4H-SiC material after carrying out carbon or silicon ion implantation into the shallow surface layer of 250nm and subsequent annealing at 1600°C or higher temperature. Reduction of Z1∕2 and EH6∕7 traps from 3×1013cm−3 to below the detection limit (5×1011cm−3) was observed by deep level transient spectroscopy in the material 4μm underneath the implanted layer. Minority carrier lifetime almost doubled in the implanted samples compared to the unimplanted samples. The authors propose that the implanted layer acts as a source of carbon interstitials which indiffuse during annealing and accelerate annealing out of grown-in defects in the layer underneath the implanted region.

On the correlation between nuclear and electronic stopping of heavy ions in light targets

Interatomic potentials for Au–C system, calculated with density-functional theory (DFT) method, have been used to obtain the range parameters of gold in carbon at energies of about 1–1000keV and for the inverse implantation of carbon in gold between 5 and 40keV. The range parameters have been evaluated by the standard transport theory and by Monte–Carlo simulations. Good agreement between the computed range parameters and available experimental data does not confirm the existence of correlation effects between the nuclear and electronic stopping in the studied interval of energies.

Optical channel waveguides by proton and carbon implantation in Nd:YAG crystals

In this work the formation of optical channel waveguides in Nd:YAG crystals by either proton or carbon implantation is reported. The channel waveguides were obtained by a single implantation process through an electroformed mask of nickel-cobalt alloy. Experimental measurements of the optical properties of these waveguides are presented.

Electroluminescence of nanopatterned silicon with carbon implantation and solid phase epitaxial regrowth

Electroluminescence at 1.28mum is observed in a nanopatterned silicon test structure that has been subjected to carbon implantation followed by solid-phase epitaxial regrowth for recrystalization. The sub-bandgap luminescence comes from a di-carbon complex known as 'G center'. Enrichment of silicon with carbon atoms has been achieved in a procedure consisting of two implantations and solid-phase epitaxial regrowth. Nanopatterning was done using an anodized aluminum oxide membrane as a mask for reactive ion etching. Along with the electroluminescence, an enhanced photoluminescence was measured.

Monte Carlo simulation study of a selforganisation process leading to ordered precipitate structures

Periodically arranged, selforganised, nanometric, amorphous precipitates have been observed after high-fluence ion implantations into solids for a number of ion/target combinations at certain implantation conditions. A model describing the ordering process based on compressive stress exerted by the amorphous inclusions as a result of the density change upon amorphisation is introduced. A Monte Carlo simulation code, which focuses on high-fluence carbon implantations into silicon, is able to reproduce experimentally observed nanolamella distributions as well as the formation of continuous amorphous layers. By means of simulation, the selforganisation process becomes traceable and detailed information about the compositional and structural state during the ordering process is obtained. Based on simulation results, a recipe is proposed for producing broad distributions of ordered lamellar structures.

Dosage dependence of Ge quantum dots grown on carbon-implanted Si substrates

Carbon implantation effects on self-assembled Ge quantum dots (QDs) have been investigated. Carbon atoms were implanted at different dosage, 9.0×10 14, 4.5×10 15, and 9.0×10 15 ions/cm 2 using the same acceleration energy of 20 keV. A nominal amount, 6 monolayer (ML), of Ge was grown on the substrate at different growth temperatures ranging from 500 to 600 °C using solid source molecular beam epitaxy. The smallest Ge QDs with a 13 nm mean lateral diameter, a 1.2 nm mean height, and an areal density of 2.0×10 11 cm −2 were obtained using the lowest dosage substrate at 550 °C. Raman measurement is carried out to investigate the optical phonons and strain.

Relevance of surface roughness to tungsten sputtering and carbon implantation

Tungsten sputtering and carbon layer growth by carbon ion bombardment has been investigated by experiments with thin W layers. Preparation of tungsten layers by magnetron deposition allows one to control the surface roughness by choosing appropriate substrates. The fluence dependent elemental composition of the bombarded surface has been studied in situ with ion beam analysis allowing separate measurements of the areal densities of tungsten and carbon atoms. In contrast to weight-loss measurements, this approach is much less affected by nonuniformities of the incident flux and therefore allows one to determine the dependency of the principal physics processes on input parameters with much higher accuracy. After bombardment, ex situ scanning electron microscopy has been used for the qualitative understanding of the evolution of the surface topography with increasing fluence. The experiments clearly show the influence of surface roughness, leading to increased tungsten sputter yields and strongly reduced carbon implantation rates. Comparison of the experimental results with simulations by the Monte Carlo code TRIDYN has verified the validity of the kinematic description for the interaction of carbon ions with mixed carbon-tungsten surfaces. At the same time, chemical effects, such as carbide formation, can be neglected in comparison with the contribution of surface roughness to the dynamics of sputtering and implantation.

Synthesis and characterization of embedded SiC phase

Synthesis of embedded silicon carbide (SiC) has been carried out in n-type silicon (Si) samples having (100) and (111) orientations using high dose implantation of 150keV carbon (C+) ions at room temperature. The dose is varied from 4×1017ions-cm−2 to 8×1017ions-cm−2 in different samples of both orientations. Post-implantation annealing at 1000°C is performed in order to anneal out the implantation induced defects and to get a buried silicon carbide layer. Detailed Fourier transform infrared (FTIR) spectroscopy analysis and X-ray diffraction (XRD) studies confirm the formation of cubic SiC precipitates (β-SiC) in the layer. The SiC precipitates have been found to exhibit a better crystalline order in Si (100) samples than in Si (111) samples. X-ray diffraction results also indicate the amorphization of ion beam bombarded region of the Si samples. After annealing the amorphized region is recrystallized into a polycrystalline phase of Si.

Process control and melt depth homogenization for SiC-on-Si structures during flash lamp annealing by carbon implantation

Flash lamp annealing in the millisecond regime of heteroepitaxial silicon carbide on silicon structures involves melting the silicon below the SiC layer, but the deep faceted nature of the liquid-solid interface leads to unacceptable surface roughness. This paper describes a method of controlling melting by implanting a high dose of carbon at a controlled depth below the Si∕SiC interface, which significantly alters the melting characteristics of the silicon. This technology has also been applied to SiC and Si multilayer heterostructures. Results confirm the effectiveness of this approach for increasing surface uniformity, making liquid phase processing compatible with standard device fabrication techniques. A thermal model has also been developed to describe this process and results indicate that the theoretical work is consistent with the experimental evidence. The model is a valuable tool for predicting the onset of melting, maximum temperatures, and process windows for controlled liquid phase epitaxy.

Effect of ion implantation layer on adhesion of DLC film by plasma-based ion implantation and deposition

High adhesive diamond-like carbon (DLC) film on SUS304 was obtained using carbon ion implantation between DLC film and substrate material by plasma-based ion implantation and deposition (PBIID). Implantation of mixed silicon and carbon ions to the substrate resulted in much higher adhesion strength than that of the epoxy resin. Effect of ion implantation on adhesion of DLC film was studied by cross sectional STEM observation and EDS element analysis. Enhancement in adhesive strength by ion implantation of mixed carbon and silicon was ascribed to the formation of the multilayer interface consisting of mixed carbon and silicon ion implanted layer and the amorphous layer of carbon and silicon.

Pyrolytic Carbon Proximal Interphalangeal Joint Resurfacing Arthroplasty

To evaluate the clinical results of a pyrolytic carbon resurfacing proximal interphalangeal joint (PIPJ) arthroplasty in patients with osteoarthritis. A retrospective review of 18 PIPJ arthroplasties in 8 women with severe osteoarthritis performed by a single surgeon was completed with an average follow-up period of 13 months. Clinical assessment included range of motion (ROM), stability, and deformity. Radiographs were reviewed for evidence of loosening, subsidence, fracture, and osseointegration. Six patients, representing 16 joints, answered a questionnaire regarding pain relief, appearance, and overall satisfaction with the arthroplasty. Complications also were recorded. The average preoperative ROM was 10 degrees to 63 degrees, and the average postoperative ROM was 18 degrees to 71 degrees. Although the average arc of motion was unchanged, 9 joints had an increase in ROM and 9 joints had a decrease in ROM. All joints were stable laterally. Radiographic review indicated 2 joints with loosening at 4 months after surgery. Complications included 8 squeaky joints, 5 joint contractures, and 2 dislocations. Pain was relieved completely in 8 joints, and the pain rating on a visual analog scale was 3.6 out of 10 for the 8 patients who had residual pain. Patients were satisfied completely with the results of 9 joints. Although there was residual deformity in 4 joints, patients believed that 15 of 16 joints had improved in appearance. Five of 6 patients responded that they would have the surgery again. There have been no secondary procedures performed by us. The insertion of pyrolytic carbon implants for PIPJ arthroplasty is a technically demanding procedure, but it has the potential to achieve pain relief, stability, satisfactory ROM, and correction of the deformity; however, the results in this review were unpredictable and may not be superior to those achieved with other methods of arthroplasty. Therapeutic, Level IV.

Characterization of austenitic stainless steel after plasma immersion nitrogen and carbon implantation

It has been shown in the literature that plasma immersion ion implantation (PIII) can increase the wear resistance of austenitic stainless steel without losing its corrosion resistance. In this work, the effect of PIII treatment with C ions introduced into the chamber during the process on the tribological properties of AISI 316 L stainless steel has been studied and the results compared.

Enhancement of adhesion strength and tribological performance of pure carbon coatings on Ti-6Al-4V biomaterials with ion implantation pre-treatments

A novel method to increase the adhesion strength of pure carbon coatings on Ti-6Al-4V biomaterials is reported. In the early stage of the experiment, ion implantation of carbon was carried out by metal vapour vacuum arc (MEVVA) in order to create a gradient composition interlayer in the Ti-6Al-4V substrate for subsequent coating depositions. The pure carbon coatings were deposited in a closed-field unbalanced magnetron sputtering system. It was found that the coatings prepared on the carbon-implanted substrates could provide a significant enhancement of adhesion strength, impact and wear resistance. The greatly increased performance could be explained by the increase in hardness of the carbon-implanted substrate and the formation of Ti–C bonds.

Optical waveguides formed in Nd:YVO4 crystals by C2+ implantation

This work reports the formation of planar and channel waveguides in Nd:YVO4 by carbon implantation, using doses as low as 5 × 1014 ions/cm2. The analysis includes refractive index profiles, propagation losses and spectroscopic properties. The results indicate that there is an index convergence, the ordinary index increases while the extraordinary index decreases. The spectroscopic studies show that emission bands coming from the 4F3/2 level are not altered by the ion beam process, shedding light on the potential of carbon implanted waveguides for laser integrated devices.

Oxidation of plasma surface modified zirconium alloy in pressurized high temperature water

Oxidation of a zirconium-alloy, zircaloy-2 in the untreated (non-surface treated) condition and after ion implantation with nitrogen, carbon, and oxygen has been examined after exposure for 168 h to an environment of pressurized water at 25 MPa at temperatures of 300 and 500 °C. At this pressure, water is in subcritical state at 300 °C and supercritical state at 500 °C. Cross-sectional scanning electron microscopy showed that oxidation occurred in the form of mainly an oxygen diffusion layer for the 300 °C exposure, but for the 500 °C exposure a uniform stoichiometric oxide layer and a sub-surface oxide diffusion layer were observed. For the 300 °C exposure, carbon and nitrogen ion implantation resulted in a thinner oxygen affected layer compared to the untreated alloy. The oxygen ion implanted samples showed a thicker oxygen affected layer, but this included the thickness contributions from both thermal oxidation and prior oxygen ion implantation. After exposure at 500 °C, the carbon and nitrogen ion implanted samples exhibited a thicker, and the oxygen ion implanted samples a thinner oxygen affected layer compared to the untreated alloy. A separate experiment involving exposure to supercritical water at 400 °C for 168 h showed lower levels of oxidation in zircaloy-2 samples that were sputter coated with an yttrium film and subsequently bombarded with xenon ions prior to exposure.