Carbon Ion Implantation Research Articles

Exploration of Defect Dynamics and Color Center Qubit Synthesis with Pulsed Ion Beams

Short-pulse ion beams have been developed in recent years and now enable applications in materials science. A tunable flux of selected ions delivered in pulses of a few nanoseconds can affect the balance of defect formation and dynamic annealing in materials. We report results from color center formation in silicon with pulses of 900 keV protons. G-centers in silicon are near-infrared photon emitters with emerging applications as single-photon sources and for spin-photon qubit integration. G-centers consist of a pair of substitutional carbon atoms and one silicon interstitial atom and are often formed by carbon ion implantation and thermal annealing. Here, we report on G-center formation with proton pulses in silicon samples that already contained carbon, without carbon ion implantation or thermal annealing. The number of G-centers formed per proton increased when we increased the pulse intensity from 6.9 × 109 to 7.9 × 1010 protons/cm2/pulse, demonstrating a flux effect on G-center formation efficiency. We observe a G-center ensemble linewidth of 0.1 nm (full width half maximum), narrower than previously reported. Pulsed ion beams can extend the parameter range available for fundamental studies of radiation-induced defects and the formation of color centers for spin-photon qubit applications.

Generation of shallow nitrogen-vacancy centers in diamond with carbon ion implantation

The shallow nitrogen-vacancy center of diamond exhibits excellent sensitivity and resolution in the magnetic detection and quantum sensing areas. Compared with other methods, low-energy carbon ion implantation does not need high-purity diamond nor introduce new impurity atoms, but the formation mechanism of nitrogen-vacancy center is not clear. In this work, shallow nitrogen-vacancy centers are created in the diamond by low energy carbon ion implantation and vacuum annealing, and the transformation mechanism of nitrogen-vacancy centers in diamond is studied by Raman spectroscopy, X-ray photoelectron spectroscopy, and positron annihilation analysis. The results show that shallow nitrogen-vacancy centers can be obtained by carbon ion implantation combined with vacuum annealing. After implantation, superficial layer of diamond shows the damage zone including lattice distortion and amorphous carbon, and carbon-vacancy cluster defects (carbon atoms are surrounded by vacancy clusters) are generated. In the vacuum annealing process, the damaged area gradually transforms into the diamond structure through the recovery of the distortion area and the solid-phase epitaxy of the amorphous carbon area, accompanied by the continuous dissociation of carbon-vacancy cluster defects. When samples are annealed at 850 and 900 ℃, the structure of the damaged area is partially repaired. While annealing at 950 ℃, not only the damaged layer is basically recovered, but also nitrogen atoms capture the single vacancy obtained by the dissociation of carbon vacancy clusters, forming the nitrogen-vacancy centers.

Атомно-силовая микроскопия подповерхностных структур

Atomic force microscopy techniques of rapid indentation make it possible to obtain physical and mechanical properties simultaneously with the topography of the surface. In the general case, the obtained relief depends on the load with which the probe indents the surface. The paper presents a method of treatment of the force curves that highlights the changes in the relief at each individual step of the applied load: the surface topography (the moment of the probe touching the material), the transition region, and the sub-surface structures are separated (standard software only provides the topography corresponding to the maximum of the applied load). The proposed approach is illustrated by studying both soft and relatively stiff materials. In the first case, a two-phase polymer (polyurethane) was considered – the fibrillar structure of the polymer hidden by the soft nanolayer was shown; a study of the protein layer deposited on the surface of this polymer revealed a dendritic nanostructure of the protein film under the homogeneous surface layer. In the second case, a polymer modified by plasma implantation of carbon ions was investigated – subsurface inhomogeneities of the implanted carbon layer were shown; deformation-induced nanocracks were found to be first formed under the surface in the stiffest part of the modified layer. The paper proposes a method for estimating the thickness of the soft surface layer. It is also shown that the most complete picture of the subsurface structure does not correspond to the maximum of the applied load. The paper raises the problem of investigating adhesion interactions and the validity of using adhesion in calculating the elastic modulus in cases where the surface of an inhomogeneous material is covered by some nanolayer. The considered methods not only allow one to determine the surface relief and the features of the subsurface structures but also give the knowledge of what the researcher sees when using standard software of the device.

Surface characterisation of brass alloy in the correlation of hardness and electrical resistivity by carbon ion implantation

Material modification, as per demand of era, has been explored by several groups in different areas focusing its engineering prospect for better performance. Carbon ion implantation, using four different doses, has been done on α-brass (64% Cu; 36% Zn) to see its effects on hardness, microstructure and electrical resistivity. Carbon ions distorted the crystalline surface, increased defect density and hardened the surface by 13.2%. The crystallite size was found decreased by 41.15%, which in turn caused a significant increase in electrical resistivity, i.e. 234.8%. Overall, the lattice parameter found increased from 3.680 to 3.688 Å. SEM morphology exhibited nonuniform agglomerations in the form of pits, cracks, voids, cavities, craters, particulates, droplets and petals like structures at the surface by carbon ion implantation.

Favourable tuning of optical absorbance, bandgap and surface roughness of ZnO thin films by C ion implantation at the critical angle

Low energy ion implantation with exquisite control of angle allows manipulating the applications of thin films. Here we present a favourable and efficient strategy of 50 keV Carbon ion implantations on ZnO thin films at three different tilt angles 0°, 30° and 60°. This plays a significant role in tuning of optical absorbance, bandgap, grain size and surface roughness simultaneously. The TRIM simulations are performed to elucidate the theoretical understanding and to compare the modifications in the physical properties using different characterization tools. These experimental results demonstrate that the ion implantations at 30° result in a significant reduction of 89% in the grain size and 35% reduction in the optical transmittance along with an improvement of 25% in the surface roughness of these thin films. The optical bandgap is also tuned from 3.27 to 3.20 eV. These results establish a new approach in designing the exotic materials with lower grain size, lower bandgap and smoother surface along with higher absorbance of ultraviolet (UV) light that will help increasing the data storage capacity and getting higher energy efficiency with reduced UV light emissions.

Carbon ion implantation as healing strategy for improved reliability in phase-change memory arrays

In this paper we investigate the effect of Carbon ion implantation in Ge2Sb2Te5 based Phase-Change Memory (PCM) targeting reliability improvement in 4 kb memory arrays. We show how ion implantation by beam line allows to localize the Carbon in a specific volume of the active layer, demonstrating that a low C concentration (lower than 5 at. %) can be achieved with a high control thanks to dose monitoring. We evidence an outstanding improvement of the PCM cell performances, in both single devices and 4 kb arrays, such as programming window widening and reduced variability of electrical parameters. We support our findings by TEM/EDS analyses demonstrating the healing effects of C ion implantation on interfaces and on retarding the phase-change layer segregation mechanisms.

Enhancement in Corrosion Resistance and Hardness of AZ91D Magnesium Alloy by Carbon Ion Implantation

To improve the mechanical and corrosion resistance of AZ91D magnesium alloy, carbon ion implantation technique has been carried out using 2 MV Pelletron accelerator on the polished magnesium alloy surface. Vickers hardness test, particle induced X-ray emission (PIXE) analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and corrosion tests are employed to analyse the properties. Vickers hardness tests revealed the improvement in surface hardness which we infer is due to the enhancement in dislocation density, as a consequence of carbon ion implantation with varied dose from 1.26×1013 to 8.4×1014 ions-cm-2. That is, the increase in hardness is directly related to the ion dose, variation in lattice parameters, crystallite size, and change in peak intensity, all due to the increase in ion fluence. The non-destructive elemental analysis, PIXE, gave the elemental profile before and after ion implantation. SEM results indicated that singly ionized carbon ion implantation has modified the surface of AZ91D Mg-alloy. XRD results showed that the unexposed and treated samples include ?-Mg and ?-Mg17Al12 phases. XRD results also revealed that after the carbon ion implantation the diffraction peak position and intensity of all the phases shifted. The corrosion tests were carried out using two methods, namely, weight loss method and electrochemical test. The results guided that for a higher dose of ion implantation, the corrosion resistance increased and loss of mass of exposed surface of specimens decreased, which reflect the enhancement of corrosion resistance.

Two-dimensional waveguides in magneto-optical glasses fabricated by carbon ion implantation and femtosecond laser ablation

The exploration of 2D waveguide structures on optoelectronic materials is important for applications in integrated optics devices. In this work, 2D waveguides on the magneto-optical glass were fabricated via combining the carbon ion implantation and the femtosecond laser ablation. Firstly, the 1D waveguide was formed by the double energy (6.0+5.5) MeV carbon ion implantation with fluences of (8.0+4.0)×1013 ions/cm2. Subsequently, the femtosecond laser ablation with 800-nm central wavelength and 1.0-kHz repetition rate was conducted on the 1D waveguide surface to manufacture 2D guiding structures. The end-facet images were captured by an optical microscope. The near-field modal profiles of the 2D waveguides were recorded by an end-face coupling system at near-infrared (976 nm) and visible (532 nm) bands. The research results provide the feasibility and the experimental basis for the preparation of a magneto-optical waveguide isolator.

Regularities of PLA mechanical property modification under ion implantation conditions

The investigations of the surface physicochemical properties of polylactic acid (PLA) modified by argon, carbon and silver ion implantation to fluences of 1∙1014, 1∙1015 and 1∙1016 cm−2 and energies of 20 keV, 20 keV and 42 keV respectively are described. The projected ion ranges in the polymer matrix are estimated by the computer simulation with the TRIDYN code, as well as energies of electron and nuclear stopping are assessed according to the SRIM modelling. The microhardness and elastic modulus are established to be dependent on the degree of crystallinity of the material. It was found that the microdistortions and strains of the PLA crystal lattice increase after ion implantation due to the structural alteration and defect formation. Long-range effect expressed as bigger depth of modified surface layer than the ion range in the material is suggested as a result of the radiation-stimulated diffusion and thermal restructuring of the material.

Enhanced Raman intensity in ZnS planar and channel waveguide structures via carbon ion implantation

Planar and channel waveguides in ZnS single crystal are fabricated by 6.0 MeV C ion implantation with fluences of 5 × 1014 and 1 × 1015 ion/cm2 at room temperature. The optical modes for the planar waveguides are measured by using a prism coupler by the well-known m-line method. The near-field light intensity profiles for the planar and channel waveguides are measured by the end-face coupling setup at 633 nm and 1539 nm. The reflectivity calculation method and the finite difference beam propagation method are used to reconstruct the refractive index profile of the planar waveguides and near-field intensity distribution of planar and channel waveguides. Raman images obtained with a 532-nm laser are collected to evaluate the damage to the ZnS crystal and waveguide layers.

(Invited) SnS2 Thin Film and Powder for Artificial Photosynthesis

Solar photoreduction of CO2 to produce value added hydrocarbons is highly desirable to tackle environmental and energy issues. [1-2] Despite the great improvement in the efficiency and cost of solar cells, the efficiency in artificial photosynthesis is much lower than the >15% of solar cells. Recent progress in 2D chalcogenides with tunable bandgap and layer numbers offers great opportunity for the investigation in this field. In this work, thin film and powder SnS2 have been synthesized for the study. Hydrothermal synthesis of carbon-containing SnS2 exhibits a highly active photocatalytic conversion of CO2 to selective hydrocarbons under visible-light irradiation. Overall, the carbon doping in the SnS2 nanostructure plays a key role and significantly enhance the visible light photocatalytic activity with a photochemical quantum efficiency above 0.7%. [3-4] Meanwhile, Thin film SnS2 has been grown for the mechanism study. By carbon-ion implantation of the thin film, we observed enhanced CO2 reduction under solar illumination. Other FTIR, Raman, NMR, BET, SECM, and synchrotron based facilities including APXPS and XAS have been used to investigate this issue.1. Shown, H.C. Hsu, Y.C. Chang, C.H. Lin, P.K. Roy, A. Ganguly, C.H. Wang, J.K. Chang, C.I. Wu, L.C. Chen, K.H. Chen, Nano Letters 14, 6097-6103 (2014).2. Billo, F.Y. Fu, P. Raghunath, I. Shown, W.F. Chen, H.T. Lien, T.H. Shen, J.F. Lee, M. C. Lin, J.S. Hwang, C.H. Lee, L.C. Chen, and K.H. Chen, Small 14, 1702928 (2018).3. Shown, S. Samireddi, Y.C. Chang, R. Putikam, P.H. Chang, A. Sabbah, F.Y. Fu, W.F. Chen, C.I. Wu, T.Y. Yu, P.W. Chung, M.C. Lin, L.C. Chen, and K.H. Chen, Nature Comm. 9, 169 (2018).4. T. Billo, I. Shown, A.K. Anbalagan, T.A. Effendi, A. Sabbah, F.Y. Fu, C.M. Chu, W.Y. Woon, R.S. Chen, C.H. Lee, K.H. Chen, L.C. Chen, Nano Energy 72, 104717 (2020).

Direct Graphene Synthesis on Lithium Niobate Substrate by Carbon Ion Implantation

A dozen-micron-scale 4-7 layers of graphene was synthesized directly on Lithium Niobate (LiNbO3, LN) by carbon implantation in nickel covered LiNbO3 film. The 1.52E16 ions·cm-2 carbon ions of 80KeV were implanted to the nickel film with the implantation depth of 100nm, which is close to the interface between the nickel film and LiNbO3. The implanted carbon atoms dissolved in nickel at an elevated temperature and diffused towards to the interface between nickel film and LiNbO3 during annealing. After the nickel film fell off, the graphene material was found by Raman spectroscopy and confirmed by the Atomic Force Microscope (AFM) topographic image. Implantation combined with patterned metal film suggests the possibility to engineer two-dimensional graphene with special confinement. It also provides a valuable and novel way for integrating graphene-wafer structure for other available substrate wafer in microelectronics and photonics devices.

Depth Profile Analysis of Deep Level Defects in 4H-SiC Introduced by Radiation

Deep level defects created by implantation of light-helium and medium heavy carbon ions in the single ion regime and neutron irradiation in n-type 4H-SiC are characterized by the DLTS technique. Two deep levels with energies 0.4 eV (EH1) and 0.7 eV (EH3) below the conduction band minimum are created in either ion implanted and neutron irradiated material beside carbon vacancies (Z1/2). In our study, we analyze components of EH1 and EH3 deep levels based on their concentration depth profiles, in addition to (−3/=) and (=/−) transition levels of silicon vacancy. A higher EH3 deep level concentration compared to the EH1 deep level concentration and a slight shift of the EH3 concentration depth profile to larger depths indicate that an additional deep level contributes to the DLTS signal of the EH3 deep level, most probably the defect complex involving interstitials. We report on the introduction of metastable M-center by light/medium heavy ion implantation and neutron irradiation, previously reported in cases of proton and electron irradiation. Contribution of M-center to the EH1 concentration profile is presented.

Raman Light Scattering in Silicon with the Crystal Structure Damaged by Implantation of Carbon Ions

Raman scattering spectra from silicon whose crystal lattice is damaged by implantation of carbon ions with an energy of 40 keV and dose 5 × 1016 cm–2 have been recorded. The parameters of the Raman spectral line of the implanted samples have been measured after their thermal annealing in the temperature range 600–1150°C. As a result of these measurements, the fraction of the crystalline phase was determined in relation to the annealing temperature. Two thermodynamic processes have been revealed that describe the kinetics of restoration of the crystal lattice during annealing. It has been shown that a silicon layer with a damaged crystal lattice does not restore its crystallinity during thermal annealing simultaneously in the entire volume, but in the form of clusters that become larger with increasing annealing temperature. The sizes of crystalline clusters are estimated for different annealing temperatures. The performed calculations take into account the complex dependence of the light absorption coefficient of a partially damaged crystal lattice on the fraction of the crystalline phase arising in it during thermal annealing.

Corrosion Behavior and Mechanism of Carbon Ion-Implanted Magnesium Alloy

Carbon ion implantation was conducted on an AM60 magnesium alloy with fluences between 1 × 1016 and 6 × 1016 ions/cm2 and an energy of 35 keV. The microstructure and electrochemical properties of the samples were systematically characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Raman scattering, scanning electron microscopy, transmission electron microscopy, and electrochemical methods. These studies reveal that a 250 nm-thick C-rich layer is formed on the surface and the Mg2C3 phase embeds in the ion-implanted region. The crystal structure of the Mg2C3 was constructed, and an electronic density map was calculated by density-functional theory calculation. The large peak in the density of states (DOS) shows two atomic p orbitals for Mg2C3. The main electron energy is concentrated between −50 and −40 eV, and the electron energy mainly comes from Mg (p) and Mg (s). The electrochemical experiments reveal that the Ecorr is −1.35 V and Icorr is 20.1 μA/cm2 for the sample implanted with the optimal fluence of 6 × 1016 ions/cm2. The sample from C ion implantation gives rise to better corrosion resistance.

The investigation of mechanical and thermal properties of super-hydrophobic nitinol surfaces fabricated by hybrid methods of laser irradiation and carbon ion implantation

Comparing with laser irradiation only, the laser ablation combined with chemical modification process is a widely used technique to obtain bio-inspired super-hydrophobic surface. However, the as-prepared surfaces may be polluted by toxic substance during chemical modification such as fluoroalkyl silane and stearic acid. The side effect of polluted functional surface on organisms and environment limited its application value. In this paper, a green and environmental-friendly super-hydrophobic surface was quickly fabricated on nitinol substrates through hybrid of nanosecond laser ablation and carbon ion implantation. The time that turning from super-hydrophilicity to super-hydrophobicity was only 16 h exhibiting high efficiency compared with pure laser processing. Surface morphology and chemical component were systematically investigated to reveal the formation mechanism of super-hydrophobicity in such short time. The mechanical abrasion tests implied that the mechanical properties of surface microstructure could be heightened after carbon ion implantation, showing the superior structure stability. It is noted that chemical modified super-hydrophobicity could be hardly destroyed under high temperature, and the thermal stability of this ion implanted super-hydrophobic surface was on a par with it. This hybrid method of laser irradiation and carbon ion implantation paves a green way for rapid fabrication super-hydrophobic surface on nitinol, which would have great application value in biomedicine and industry.

Effect of copper surface modification applied by combined modification of metal vapor vacuum arc ion implantation and laser texturing on anti-frosting property

Heat transfer deterioration due to frost accumulation on metallic surfaces provided motivation for development of protective barriers that could effectively repel water in many forms. Currently, extensive attention has focused on superhydrophobic surfaces which have been found to be effective in reducing droplets condensation and frost accumulation. The combined modification using nanosecond laser and metal vapor vacuum arc (MEVVA) ion implantation of carbon is applied to the copper surface. The results revealed that the increased proportion of carbon content contribute to the increase of surface hydrophobicity, the contact angle of the combined surface was 152.1° ± 1° and the rolling angle was 6.7° ± 1°, which exhibited a superhydrophobic character, without thermal conductivity deterioration. The processes of droplet condensation, freezing and the frosting of three kinds of surfaces (rough #1, combined surface modification #2, silanization coating #3) have been examined. The combined surface can delay the freezing process to some extent. Compared with rough copper surface, combined surface had sparse frost structure and the growth of frost could be delayed by 43% when the frost thickness was 1.5 mm. Thus, the method of combined surface shows a great advantage of frost inhibition applicability.

Critical behavior and magnetocaloric effect in C-implanted Fe93Zr7 amorphous films

We report on the effect of carbon ion-implantation on the critical behavior of Fe93Zr7 amorphous films. Both the as-grown and carbon-implanted Fe93Zr7 samples exhibit a second order ferromagnetic to paramagnetic transition. The critical exponents were investigated through different techniques such as modified-Arrott plot, the critical isotherm analysis and the Windom scaling relation. Analysis of the critical behavior was presented in terms of the magnetocaloric effect around TC. While there is a significant increase of the magnetization and TC upon C-implantation, the critical exponents were only slightly affected by implantation and were in line with those of the 3D-Heisenberg model.

BEOL-compatible synthesis of multi-layer graphene by carbon ion implantation on cobalt thin films

We present a study on the synthesis of multi-layer graphene using carbon ion implantation on thin cobalt (Co) films. Carbon ions were bombarded at 20 keV and doses of 4 × 1015 cm−2 and 8 × 1015 cm−2 onto the surface of a Co/SiO2/Si substrate. This process was followed by heat treatment (500–900 °C) to form graphene on Co film. The effects of the heating conditions were systematically investigated by micro-Raman spectroscopy and transmission electron microscopy. The result proved that multi-layer graphene with high coverage, even at moderate temperature and with a relatively short period of time, was synthesized on the cobalt film when the amount of carbon source inside the cobalt was sufficient. A phase transition of Co film from hcp to fcc turned out to be deeply related to graphene formation at moderate temperatures. The phase transition induces synthesis of graphene on cobalt film at 450–500 °C, although it causes some defects in the graphene. Our results indicate that moderate temperature synthesis of graphene on Co film using carbon ion implantation provides a facile and direct route for integrating graphene with Si microelectronics.

Effect of Carbon-Ion Implantation on the Surface Physical and Chemical Properties of Polylactic Acid, Hydroxyapatite and a Composite Based on Them

The results of investigation of the surface physical and chemical properties of polylactic acid, hydroxyapatite and a composite material based on them taken in the ratio of components 80/20, modified by carbon ions with exposure doses of 1 × 1015 and 1 × 1016 ion/cm2 at an accelerating voltage of 20 kV are presented. The surface chemical composition of the samples is studied by Fourier transform infrared spectroscopy. The elemental composition of the surface is studied by X-ray photoelectron spectroscopy. According to the obtained results, the simultaneous processes of destruction and cross linking of polylactic acid and polymer macromolecules are established. To assess the wettability of the untreated and modified surface of materials, contact-angle measurements and surface energy calculations are performed. It is established that carbon-ion implantation leads to improvement in the hydrophobic properties of materials; this process is accompanied by a decrease in the free surface energy.