Showing papers on "Ion implantation published in 2019"

A Review of Recent Applications of Ion Beam Techniques on Nanomaterial Surface Modification: Design of Nanostructures and Energy Harvesting.

Abstract: Nanomaterials have gained plenty of research interest because of their excellent performance, which is derived from their small size and special structure. In practical applications, to acquire nanomaterials with high performance, many methods have been used to modulate the structure and components of materials. To date, ion beam techniques have extensively been applied for modulating the performance of various nanomaterials. Energetic ion beams can modulate the surface morphology and chemical components of nanomaterials. In addition, ion beam techniques have also been used to fabricate nanomaterials, including 2D materials, nanoparticles, and nanowires. Compared with conventional methods, ion beam techniques, including ion implantation, ion irradiation, and focused ion beam, are all pure physical processes; these processes do not introduce any impurities into the target materials. In addition, ion beam techniques exhibit high controllability and repeatability. Here, recent progress in ion beam techniques for nanomaterial surface modification is systematically summarized and existing challenges and potential solutions are presented.

Fabrication of capacitive pressure sensor using single crystal diamond cantilever beam

Abstract: Fabrication of single crystal diamond capacitive pressure sensor is presented. Firstly, the single crystal diamond cantilever beam was formed on HPHT diamond substrate by using selective high-energy ion implantation, metal patterning, ICP etching and electrochemical etching techniques. Secondly, on this diamond cantilever beam, the desired electrode patterns were processed with photolithography and metal evaporation methods. Furthermore, the displacements of cantilever beam under different pressure conditions were investigated by atomic force microscopy. The capacitance-voltage curves of single crystal diamond cantilever beam and substrate under different force loading conditions were measured by using Agilent B1505A parameter analyzer. The results show that sensitivity increases with the enlargement of electrode area of cantilever beam, and decreases with the rise of measurement frequency.

Toward wafer-scale diamond nano- and quantum technologies

Abstract: We investigate native nitrogen vacancy (NV) and silicon vacancy (SiV) color centers in a commercially available, heteroepitaxial, wafer-sized, mm thick, single-crystal diamond. We observe single, native NV centers with a density of roughly 1 NV per μm3 and moderate coherence time (T2 = 5 μs) embedded in an ensemble of SiV centers. Using low temperature luminescence of SiV centers as a probe, we prove the high crystalline quality of the diamond especially close to the growth surface, consistent with a reduced dislocation density. Using ion implantation and plasma etching, we verify the possibility to fabricate nanostructures with shallow color centers rendering our material promising for fabrication of nanoscale sensing devices. As this diamond is available in wafer-sizes up to 100 mm, it offers the opportunity to up-scale diamond-based device fabrication.

High-pressure, high-temperature molecular doping of nanodiamond

Abstract: The development of color centers in diamond as the basis for emerging quantum technologies has been limited by the need for ion implantation to create the appropriate defects. We present a versatile method to dope diamond without ion implantation by synthesis of a doped amorphous carbon precursor and transformation at high temperatures and high pressures. To explore this bottom-up method for color center generation, we rationally create silicon vacancy defects in nanodiamond and investigate them for optical pressure metrology. In addition, we show that this process can generate noble gas defects within diamond from the typically inactive argon pressure medium, which may explain the hysteresis effects observed in other high-pressure experiments and the presence of noble gases in some meteoritic nanodiamonds. Our results illustrate a general method to produce color centers in diamond and may enable the controlled generation of designer defects.

Triple nitrogen-vacancy centre fabrication by C5N4Hn ion implantation.

Abstract: Quantum information processing requires quantum registers based on coherently interacting quantum bits. The dipolar couplings between nitrogen vacancy (NV) centres with nanometre separation makes them a potential platform for room-temperature quantum registers. The fabrication of quantum registers that consist of NV centre arrays has not advanced beyond NV pairs for several years. Further scaling up of coupled NV centres by using nitrogen implantation through nanoholes has been hampered because the shortening of the separation distance is limited by the nanohole size and ion straggling. Here, we demonstrate the implantation of C5N4Hn from an adenine ion source to achieve further scaling. Because the C5N4Hn ion may be regarded as an ideal point source, the separation distance is solely determined by straggling. We successfully demonstrate the fabrication of strongly coupled triple NV centres. Our method may be extended to fabricate small quantum registers that can perform quantum information processing at room temperature. There is an extensive literature discussing the potential applications of individual nitrogen vacancy centres but some proposed developments require the use of multiple, coupled defects. Here the authors demonstrate a method to fabricate coupled nitrogen vacancy centre triplets.

Tuning the Electrical and Thermoelectric Properties of N Ion Implanted SrTiO 3 Thin Films and Their Conduction Mechanisms.

Abstract: The SrTiO3 thin films were fabricated by pulsed laser deposition. Subsequently ion implantation with 60 keV N ions at two different fluences 1 × 1016 and 5 × 1016 ions/cm2 and followed by annealing was carried out. Thin films were then characterized for electronic structure, morphology and transport properties. X-ray absorption spectroscopy reveals the local distortion of TiO6 octahedra and introduction of oxygen vacancies due to N implantation. The electrical and thermoelectric properties of these films were measured as a function of temperature to understand the conduction and scattering mechanisms. It is observed that the electrical conductivity and Seebeck coefficient (S) of these films are significantly enhanced for higher N ion fluence. The temperature dependent electrical resistivity has been analysed in the temperature range of 80–400 K, using various conduction mechanisms and fitted with band conduction, near neighbour hopping (NNH) and variable range hopping (VRH) models. It is revealed that the band conduction mechanism dominates at high temperature regime and in low temperature regime, there is a crossover between NNH and VRH. The S has been analysed using the relaxation time approximation model and dispersive transport mechanism in the temperature range of 300–400 K. Due to improvement in electrical conductivity and thermopower, the power factor is enhanced to 15 µWm−1 K−2 at 400 K at the higher ion fluence which is in the order of ten times higher as compared to the pristine films. This study suggests that ion beam can be used as an effective technique to selectively alter the electrical transport properties of oxide thermoelectric materials.

Mg implantation dose dependence of MOS channel characteristics in GaN double-implanted MOSFETs

Abstract: Lateral GaN double-implanted MOSFETs (DIMOSFETs) on Mg ion implanted GaN layers with different Mg ion implantation doses have been evaluated to investigate the impact of Mg dose on MOS channel properties. It is demonstrated that the threshold voltage (V th) and the field effect mobility (μ fe) depend on the Mg dose. A maximum μ fe of 173 cm2 V−1 s−1 has been obtained with a V th of 2.2 V on the Mg implantation layer with a dose of 4.2 × 1013 cm−2. The obtained results indicate that the channel characteristics of a GaN DIMOSFET can be designed by p-type ion implantation.

Diamond cutting of micro-structure array on brittle material assisted by multi-ion implantation

Abstract: Micro-structures have numerous applications for improving the surface functionability in various fields, such as surface mechanics, optics, and biology. However, machining micro-structures on brittle materials is difficult owing to the serious fractures that occur on the machined surface. To solve this problem, a method using ion implantation to modify the workpiece surface layer has been developed over the last seven years, but how to fabricate the modified layer efficiently is still unsolved and becomes a critical issue which blocks the application of this method in production. A modified layer that is thick enough for the machining is always preferred. This is difficult for the single-implantation approach studied before, owing to the large consumption in cost and time. In this study, diamond cutting assisted by multi-implantation is proposed to fabricate micro-structure array on silicon, a typical hard and brittle material. The novel method in this study shows distinct flexibility in the design of process parameters, as well as obvious improvement in efficiency. The result of surface modification is evaluated from aspects of crystal lattice and nanomechanics. The influence of channel effect is also discussed. Furthermore, chips with shear bands are discovered and analyzed in the cutting of modified silicon, which is extraordinary in the machining of brittle materials. And the brittle–ductile transition depth is significantly enhanced. Therefore, not only is multi-implantation capable of preparing thick modified layer, it also realizes further modification on material properties which is fundamental for improving the machinability. Finally, a micro-pillar array formed by 270 orthogonal cylindrical grooves (17956 micro-pillar units) is achieved in ductile mode by fly-cutting. It indicates that multi-implantation is a promising method for the micro-machining of brittle materials.

Realizing High Thermoelectric Performance at Ambient Temperature by Ternary Alloying in Polycrystalline Si1-x-yGexSny Thin Films with Boron Ion Implantation

Abstract: The interest in thermoelectrics (TE) for an electrical output power by converting any kind of heat has flourished in recent years, but questions about the efficiency at the ambient temperature and safety remain unanswered. With the possibility of integration in the technology of semiconductors based on silicon, highly harvested power density, abundant on earth, nontoxicity, and cost-efficiency, Si1-x-yGexSny ternary alloy film has been investigated to highlight its efficiency through ion implantation and high-temperature rapid thermal annealing (RTA) process. Significant improvement of the ambient-temperature TE performance has been achieved in a boron-implanted Si0.864Ge0.108Sn0.028 thin film after a short time RTA process at 1100 °C for 15 seconds, the power factor achieves to 11.3 μWcm−1 K−2 at room temperature. The introduction of Sn into Si1-xGex dose not only significantly improve the conductivity of Si1-xGex thermoelectric materials but also achieves a relatively high Seebeck coefficient at room temperature. This work manifests emerging opportunities for modulation Si integration thermoelectrics as wearable devices charger by body temperature.

Normally-OFF Two-Dimensional Hole Gas Diamond MOSFETs Through Nitrogen-Ion Implantation

Abstract: Diamond is a promising material for power applications owing to its excellent physical properties. Two-dimensional hole gas (2DHG) diamond metal–oxide–semiconductor field-effect transistors (MOSFETs) with hydrogen-terminated (C-H) channel have high current densities and high breakdown fields but often show normally- ON operation. From the viewpoint of safety, normally- OFF operation is required for power applications. In this letter, we used ion implantation to form a shallow and thin nitrogen-doped layer below the C-H channel region, which realized normally- OFF operation. Nitrogen-ion implanted length is fixed at 5 or 10 $\mu \text{m}$ . Nitrogen is a deep donor (1.7 eV) and the nitrogen-doped layer prevents hole accumulation near the surface. The threshold voltage was as high as −2.5 V and no obvious dependence on the threshold voltage of nitrogen-ion implanted length is observed. The breakdown field was 2.7 MV/cm at room temperature. Of 64 devices with a common gate length, 75% showed normally- OFF operation. We confirmed the threshold voltage shift by a thin and shallow nitrogen-doped layer formed by ion implantation.

Narrow Optical Line Widths in Erbium Implanted in TiO2.

Abstract: Atomic and atomlike defects in the solid state are widely explored for quantum computers, networks, and sensors. Rare earth ions are an attractive class of atomic defects that feature narrow spin and optical transitions that are isolated from the host crystal, allowing incorporation into a wide range of materials. However, the realization of long electronic spin coherence times is hampered by magnetic noise from abundant nuclear spins in the most widely studied host crystals. Here, we demonstrate that Er3+ ions can be introduced via ion implantation into TiO2, a host crystal that has not been studied extensively for rare earth ions and has a low natural abundance of nuclear spins. We observe efficient incorporation of the implanted Er3+ into the Ti4+ site (>50% yield) and measure narrow inhomogeneous spin and optical line widths (20 and 460 MHz, respectively) that are comparable to bulk-doped crystalline hosts for Er3+. This work demonstrates that ion implantation is a viable path to studying rare earth ions in new hosts and is a significant step toward realizing individually addressed rare earth ions with long spin coherence times for quantum technologies.

Magnesium ion-implantation-based gallium nitride p-i-n photodiode for visible-blind ultraviolet detection

Abstract: In this work, a GaN p-i-n diode based on Mg ion implantation for visible-blind UV detection is demonstrated With an optimized implantation and annealing process, a p-GaN layer and corresponding GaN p-i-n photodiode are achieved via Mg implantation As revealed in the UV detection characterizations, these diodes exhibit a sharp wavelength cutoff at 365 nm, high UV/visible rejection ratio of 12×104, and high photoresponsivity of 035 A/W, and are proved to be comparable with commercially available GaN p-n photodiodes Additionally, a localized states-related gain mechanism is systematically investigated, and a relevant physics model of electric-field-assisted photocarrier hopping is proposed The demonstrated Mg ion-implantation-based approach is believed to be an applicable and CMOS-process-compatible technology for GaN-based p-i-n photodiodes

Normally-off 400 °C Operation of n- and p-JFETs With a Side-Gate Structure Fabricated by Ion Implantation Into a High-Purity Semi-Insulating SiC Substrate

Abstract: We demonstrate normally-off 400 °C operation of n-channel and p-channel junction field-effect transistors (JFETs) fabricated by an ion implantation into a common high-purity semi-insulating silicon carbide (SiC) substrate. The side-gate structure proposed in this letter has good controllability of threshold voltage. The present results assure the potential of JFET-based complementary logic integrated circuits (ICs) operational at high temperature.

Investigating radiation damage in nuclear energy materials using JANNuS multiple ion beams

Abstract: Ion accelerators have been used by material scientists for decades to investigate radiation damage formation in nuclear materials and thus to emulate neutron-induced changes. The versatility of conditions in terms of particle energy, dose rate, fluence, etc., is a key asset of ion beams allowing for fully instrumented analytical studies. In addition, very short irradiation times and handling of non-radioactive samples dramatically curtail the global cost and duration as compared to in-reactor testing. Coupling of two or more beams, use of heated/cooled sample holders, and implementation of in situ characterization and microscopy pave the way to real time observation of microstructural and property evolution in various extreme radiation conditions more closely mimicking the nuclear environments. For these reasons, multiple ion beam facilities have been commissioned worldwide. In France, under the auspices of the Universite Paris-Saclay, the JANNuS platform for ‘Joint Accelerators for Nanosciences and Nuclear Simulation’ comprises five ion implanter and electrostatic accelerators with complementary performances. At CSNSM (CNRS & Univ Paris-Sud, Orsay), a 200 kV Transmission Electron Microscope is coupled to an accelerator and an implanter for in situ observation of microstructure modifications induced by ion beams in a material, making important contribution to the understanding of physical phenomena at the nanoscale. At CEA Paris-Saclay, the unique triple beam facility in Europe allows the simultaneous irradiation with heavy ions (like Fe, W) for nuclear recoil damage and implantation of a large array of ions including gasses for well-controlled modelling-oriented experiments. Several classes of materials are of interest for the nuclear industry ranging from metals and alloys, to oxides or glasses and carbides. This paper gives selected examples that illustrate the use of JANNuS ion beams in investigating the radiation resistance of structural materials for today’s and tomorrow’s nuclear reactors.

Improvement on corrosion resistance and biocompability of ZK60 magnesium alloy by carboxyl ion implantation

Abstract: Magnesium alloys have been considered to be potential biocompatible metallic materials. Further improvement on the anti-corrosion is expected to make this type of materials more suitable for biomedical applications in the fields of orthopedics, cardiovascular surgery and others. In this paper, we introduce a method of carboxyl ion (COOH+) implantation to reduce the degradation of ZK60 Mg alloy and improve its functionality in physiological environment. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) experiments show the formation of a smooth layer containing carbaxylic group, carbonate, metal oxides and hydroxides on the ion implanted alloy surface. Corrosion experiments and in vitro cytotoxicity tests demonstrate that the ion implantation treatment can both reduce the corrosion rate and improve the biocompatibility of the alloy. The promising results indicate that organic functional group ion implantation may be a practical method of improving the biological and corrosion properties of magnesium alloys.

Surface modification of Al by high-intensity low-energy Ti-ion implantation: Microstructure, mechanical and tribological properties

Abstract: A high-intensity metal ribbon ion beam was generated using plasma immersion extraction and the acceleration of the metal ions with their subsequent ballistic focusing using a cylindrical grid electrode under a repetitively pulsed bias. To generate the dense metal plasma flow, two water-cooled vacuum arc evaporators with Ti cathodes were used. The ion current density reached 43 mA/cm2 at the arc discharge current of 130 A. High-intensity ion implantation (HIII) with a low ion energy ribbon beam was used for the surface modification of the aluminium. The irradiation fluence was changed from 1.5 × 1020 ion/cm2 to 4 × 1020 ion/cm2 with a corresponding increase in the implantation temperature from 623 to 823 K. The structure and composition of the Ti-implanted aluminium were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX). The mechanical properties and wear resistance were measured using nanoindentation and “pin-on-disk” testing, respectively. It was shown that the HIII method can be used to form a deep intermetallic Al3Ti layer. It has been established that a thin (0.4 μm) modified layer with a hcp Ti(Al) structure is only formed on the surface at 623 K, while the formation of the ordered Al3Ti intermetallic phase occurs at the implantation temperatures of 723 and 823 K. Despite the significant ion sputtering of the surface, the thickness of the modified layer increases from ~1 μm to ~6 μm, and the implantation temperature rises from 723 to 823 K. It was found that the homogeneous intermetallic Al3Ti layer with a thickness of up to 5 μm was formed at 823 К. The mechanical and tribological properties of the aluminium were substantially improved after HIII. For the Ti-implanted aluminium, the hardness of the surface layer increases from 0.4 GPa (undoped Al) to 3.5–4 GPa, while the wear resistance increases by more than an order of magnitude.

Gallium, neon and helium focused ion beam milling of thin films demonstrated for polymeric materials: study of implantation artifacts

Abstract: Focused ion beam milling of ∼200 nm polymer thin films is investigated using a multibeam ion microscope equipped with a gallium liquid metal ion source and a helium/neon gas field-ionization source. The quality of gallium, neon, and helium ion milled edges in terms of ion implantation artifacts is analyzed using a combination of helium ion microscopy, transmission electron microscopy and light microscopy. Results for a synthetic polymer thin film, in the form of cryo-ultramicrotomed sections from a co-extruded polymer multilayer, and a biological polymer thin film, in the form of the base layer of a butterfly wing scale, are presented. While gallium and neon ion milling result in the implantation of ions up to tens of nanometers from the milled edge and local thinning near the edge, helium ion milling produces much sharper edges with dramatically reduced implantation. These effects can be understood in terms of the minimal lateral scatter and larger stopping distance of helium compared with the heavier ions, whereby due to the thin film geometry, most of the incident helium ions will pass straight through the material. The basic result demonstrated here for polymer thin films is also expected for thin films of hard materials such as metals and ceramics.

Surface-Modified Graphene Oxide-Based Cotton Fabric by Ion Implantation for Enhancing Antibacterial Activity

Abstract: Graphene has been a concern as a promising antibacterial material. The antibacterial activity is proved to be related to the distinctive conformation. In this study, ion implantation is used to mod...

Convergent ion beam alteration of 2D materials and metal-2D interfaces

Abstract: Tailoring the properties of two-dimensional (2D) crystals is important for both understanding the material behavior and exploring new functionality. Here we demonstrate the alteration of MoS2 and metal-MoS2 interfaces using a convergent ion beam. Different beam energies, from 60 eV to 600 eV, are shown to have distinct effects on the optical and electrical properties of MoS2. Defects and deformations created across different layers were investigated, revealing an unanticipated improvement in the Raman peak intensity of multilayer MoS2 when exposed to a 60 eV Ar+ ion beam, and attenuation of the MoS2 Raman peaks with a 200 eV ion beam. Using cross-sectional scanning transmission electron microscopy (STEM), alteration of the crystal structure after a 600 eV ion beam bombardment was observed, including generated defects and voids in the crystal. We show that the 60 eV ion beam yields improvement in the metal-MoS2 interface by decreasing the contact resistance from 17.5 kΩ · μm to 6 kΩ · μm at a carrier concentration of n2D = 5.4 × 1012 cm−2. These results advance the use of low-energy ion beams to modify 2D materials and interfaces for tuning and improving performance in applications of sensors, transistors, optoelectronics, and so forth. PAPER 2019

Prediction of ion-induced nanopattern formation using Monte Carlo simulations and comparison to experiments

Abstract: Ion induced nanopattern formation has been experimentally investigated for many different ion-target combinations and different ion irradiation conditions. Several theories and models have been developed throughout the past few years to explain the observed boundary conditions for pattern formation as well as features of the patterns like wavelengths, growth rates, shapes, and amplitudes. To compare specific experiments with the predictions of analytical theories, it is necessary to calculate the linear and non-linear coefficients of the respective equation of motion of a surface profile. Monte Carlo simulations of ion–solid interactions based on the binary collision approximation provide a very fast, rather universal, and accurate way to calculate these coefficients. The universality expresses the broad range of ion species, ion energies, and target compositions accessible by the simulations. The coefficients are obtained from the moments of calculated crater functions, describing ion erosion, mass redistribution, and ion implantation. In this contribution, we describe how most linear, non-linear, and higher order coefficients can be determined from crater function moments. We use the obtained data to compare the results of selected experimental studies with the predictions of theoretical models. We find good quantitative agreement, e.g., for irradiation of Si with Ar and Kr ions, Al2O3 with Ar and Xe ions, and amorphous carbon with Ne ions.

Cathodoluminescene study of Mg implanted GaN: the impact of dislocation on Mg diffusion

Abstract: Magnesium (Mg) ion implanted homoepitaxial GaN layers is investigated by cathodoluminescence (CL) and secondary ion mass spectrometry (SIMS). The impact of dislocations on Mg diffusion is clarified by CL monitoring the Mg-related donor-acceptor pair (DAP) emission on novel angle cutting specimen. CL results suggest that: (1) there exist high concentration of nonradiative defects in a Mg implanted layer; and (2) Mg shows pipe diffusion along threading dislocations throughout epilayer to substrate. To achieve successful Mg doping by ion implantation, it is necessary to suppress the formation of a dead region in the Mg implanted layer and the pipe diffusion along threading dislocations.

Influence of low energy ion beam implantation on Cu nanowires synthesized using scaffold-based electrodeposition

Abstract: Copper nanowires with 100 nm diameter were potentiostatically deposited in the pores of ion track etched polycarbonate membrane. Ion implantation in a colossally used technique to tailor properties of the materials. The nanowires were implanted with 1.5 MeV Ar 6 + ions in the fluence range between 1012 to 1014 ions/cm2. XRD analysis confirmed the formation of Cu nanowires and EDS result established implantation of Ar into the nanowires. The crystallite size increased from 54 nm to 59 nm due to merging of grains caused during the implantation of Ar ions. XRD patterns show that nanowires exhibit a cubic fcc structure, with increase in preferred orientation along plane (311) with increase in implantation fluence. Rietveld analysis was performed to characterize the pristine and implanted samples. The relationship between the microstructural evolution and the variation of strengthening coefficient was examined in this study. The electrical conductivity of the nanowires was observed to increase from 5.21 × 10 6 Ω −1m − 1 to 6.63 × 10 6 Ω −1m−1. The increase in conductivity is due to ion implantation induced rise in charge carriers and local heating that resulted into coalescence of grain boundaries

Realization of p-type gallium nitride by magnesium ion implantation for vertical power devices.

Abstract: Implementing selective-area p-type doping through ion implantation is the most attractive choice for the fabrication of GaN-based bipolar power and related devices. However, the low activation efficiency of magnesium (Mg) ions and the inevitable surface decomposition during high-temperature activation annealing process still limit the use of this technology for GaN-based devices. In this work, we demonstrate successful p-type doping of GaN using protective coatings during a Mg ion implantation and thermal activation process. The p-type conduction of GaN is evidenced by the positive Seebeck coefficient obtained during thermopower characterization. On this basis, a GaN p-i-n diode is fabricated, exhibiting distinct rectifying characteristics with a turn-on voltage of 3 V with an acceptable reverse breakdown voltage of 300 V. Electron beam induced current (EBIC) and electroluminescent (EL) results further confirm the formation of p-type region due to Mg ion implantation and subsequent thermal activation. This repeatable and uniform manufacturing process can be implemented in mass production of GaN devices for versatile power and optoelectronic applications.