Use Of Ion Implantation Research Articles

Miniature Mesa Extension for a Planar Submicron AlGaN/GaN HEMT Gate Formation.

In this letter, a novel approach is presented to overcome issues in AlGaN/GaN high electron mobility transistors (HEMTs), such as metal discontinuity of the gate stemmed from conventional mesa isolation. This usually requires a careful mesa etch process to procure an anisotropic mesa-wall profile. An alternative technique is the use of ion implantation for device isolation instead of conventional mesa for a planar device formation. However, ion implantation is a costly process and not always easily accessible. In this work, the proposed method is to simply extend the mesa below the gate just enough to accommodate the gatefeed, thereby ensuring the entire gate is planar in structure up to the gatefeed. The newly developed device exhibited no compromise to the DC (direct current) and RF (radio frequency) performance. Conversely, it produced a planar gate configuration with an enhanced DC transconductance (approximately 20% increase is observed) and a lower gate leakage while the etch process is considerably simplified. Similarly, the RF transconductance of proposed device (device B) increased by 80% leading to considerable improvements in RF performance.

Erbium-implanted materials for quantum communication applications

Erbium-doped materials can serve as spin-photon interfaces with optical transitions in the telecom $C$ band, making them an exciting class of materials for long-distance quantum communication. However, the spin and optical coherence times of ${\mathrm{Er}}^{3+}$ ions are limited by currently available host materials, motivating the development of new ${\mathrm{Er}}^{3+}$-containing materials. Here we demonstrate the use of ion implantation to efficiently screen prospective host candidates, and show that disorder introduced by ion implantation can be mitigated through post-implantation thermal processing to achieve inhomogeneous linewidths comparable to bulk linewidths in as-grown samples. We present optical spectroscopy data for each host material, which allows us to determine the level structure of each site, allowing us to compare the environments of ${\mathrm{Er}}^{3+}$ introduced via implantation and via doping during growth. We demonstrate that implantation can generate a range of local environments for ${\mathrm{Er}}^{3+}$, including those observed in bulk-doped materials, and that the populations of these sites can be controlled with thermal processing.

Experimental evidence of auxeticity in ion implanted single crystal calcite

We report initial experimental evidence of auxeticity in calcite by ion implanting (1010) oriented single crystalline calcite with Ar+ at room temperature using an ion energy of 400 keV and a dose of 1 × 1014 cm−2. Lattice compression normal to the substrate surface was observed, which is an atypical result for ion implanted materials. The auxetic behavior is consistent with predictions that indicate auxeticity had been predicted along two crystallographic directions including [1010]. Materials with a positive Poisson’s ratio experience lattice expansion normal to the substrate surface when ion implanted, whereas lattice contraction normal to the surface is evidence of auxetic behavior. Triple-axis X-ray diffraction measurements confirmed the auxetic strain state of the implanted calcite substrates. Reciprocal space maps for the symmetric 3030 and asymmetric 1450 reflections revealed that the implanted region was fully strained (pseudomorphic) to the bulk of the substrate, as is typical with implanted single crystals. A symmetric (3030) ω:2θ line scan was used with X-ray dynamical diffraction simulations to model the strain profile and extract the variation of compressive strain as a function of depth normal to the substrate surface. SRIM calculations were performed to obtain a displacement-per-atom profile and implanted Ar+ concentration profile. It was found that the strain profile matches the displacement-per-atom profile. This study demonstrated the use of ion implantation and X-ray diffraction methods to probe mechanical properties of materials and to test predictions such as the auxeticity.

Ion implantation synthesis of long-term stable high-entropy metallic glass nanoparticles

High-entropy metallic glass nanoparticles (HEMG-NPs) have shown great potential in the development of sustainable energy. Discovering new nanomaterials for electrocatalysis and maintaining their long-term stability is an effective way. The presence of nanoparticles in an independent transparent substrate material provides a unique way for its stability and maximum performance. This special composite structure is very beneficial to the study of the fine structure of a single specific particle. Here, we propose a general synthesis strategy, in which alloy targets are implanted into the substrate by ion implantation and annealed to grow into NPs. The disordered arrangement of ions into the substrate and the subsequent slow dynamics, disordered microscopic microstructure. Calculating the similarity of the depth range of simulated metal ion implantation provides a theoretical basis for the successful formation of HEMG-NPs. Electrocatalytic water splitting shows that CuCoNiFeZn HEMG-NPs is a non-precious single nano-microcatalyst suitable for multifunctional (HER and OER) electrocatalysis, highlighting its application in sustainable energy conversion. The use of ion implantation aims to synthesize HEMG-NPs with long-term stable storage and minimized denaturation. In further research, the formation of fine structure corresponds to the law of electrocatalytic activity. Develop high-efficiency electrocatalytic HEMG-NPs materials based on the original microstructure.

Ion implantation in β-Ga2O3: Physics and technology

Gallium oxide, and in particular its thermodynamically stable β-Ga2O3 phase, is within the most exciting materials in research and technology nowadays due to its unique properties. The very high breakdown electric field and the figure of merit rivaled only by diamond have tremendous potential for the next generation “green” electronics enabling efficient distribution, use, and conversion of electrical energy. Ion implantation is a traditional technological method used in these fields, and its well-known advantages can contribute greatly to the rapid development of physics and technology of Ga2O3-based materials and devices. Here, the status of ion implantation in β-Ga2O3 nowadays is reviewed. Attention is mainly paid to the results of experimental study of damage under ion irradiation and the properties of Ga2O3 layers doped by ion implantation. The results of ab initio theoretical calculations of the impurities and defect parameters are briefly presented, and the physical principles of a number of analytical methods used to study implanted gallium oxide layers are highlighted. The use of ion implantation in the development of Ga2O3-based devices, such as metal oxide field-effect transistors, Schottky barrier diodes, and solar-blind UV detectors, is described together with systematical analysis of the achieved values of their characteristics. Finally, the most important challenges to be overcome in this field of science and technology are discussed.

Investigation of Factors Affecting the Radiation Intensity of Quantum Wells

We study the possibilities of increasing the light-emission intensity of quantum wells. We describe the influence of the quantum-well width and the effective mass of charge carriers on the radiation intensity. Since the formation of negatively charged layers near the quantum well can increase the photon emission, we propose to form the charged layers with the use of ion implantation. The results of the study can be implemented in the field of quantum-size light-emitting structures and sensors.

THE INFLUENCE OF ION IMPLANTATION ON THE PROPERTIES OF Ti6Al4V TITANIUM ALLOY IN BIOTRIBOLOGICAL SYSTEMS

The article is devoted to the assessment of the geometrical structure of the surface as well as the mechanical and tribological properties of the surface layers obtained in the process of ion implantation. The titanium alloy Ti6Al4V used in biotribological systems was implanted with nitrogen and argon ions. Investigations of the geometrical structure of the surface before and after the tribological tests were carried out using confocal microscopy. The hardness of the tested materials was determined by the instrumental indentation method using a Vickers indenter. A nanotribometer was used for tribological tests. The tests were carried out in a reciprocating motion under conditions of technically dry friction and friction with the lubrication of Ringer's solution. SEM scanning microscopy was used to determine the width of the wear pattern and the wear mechanism. The conducted research showed that the hardness of the tested materials increased as a result of ion implantation. The tribological tests showed that the use of ion implantation improves the tribological properties, and the dominant wear mechanism was abrasive wear.

Design of Ion-Implanted Junction Termination Extension for Vertical GaN Pin Rectifiers

In recent years, GaN bipolar switches have attracted much research interests for the implementation of high-power and high-voltage applications that laterally-scaled GaN-based power field-effect transistors were not optimally implemented. In the context of vertical power device design, a proper electric field engineering would be of crucial importance to exploit the device performance that could potentially reach the theoretical power switching limit for a given material system. In this report, we studied the effectiveness of the floating guard ring design of a vertical GaN p-i-n (PIN) rectifiers for kV-range applications using a planar device fabrication that involves the use of ion-implantation as a mean of device isolation and the formation of floating guard rings. We found the gap between floating guard ring has major impact on the electric field distribution in vertical PIN rectifiers. As a result, 1 kV of blocking voltage was achieved by 6 floating guard ring design using nitrogen-ion implanted isolation.

ENHANCEMENT OF MECHANICAL PROPERTIES OF UHMWPE POLYMER BY NITROGEN ION IMPLANTATION

The use of ion implantation as a surface treatment technology has been conquered by its applications to prevent wear and oxidation in metal alloys, even though some early works already pointed out that ion implantation could also be effective as a surface treatment for other materials, including polymers. Further research has shown that low dose implantation of energetic light ions could be very effective for improving properties such as wear resistance and hardness in many different polymers. Cross linking of polymeric chains due to ionization energy provided by the stopping process is the main mechanism to explain the changes in mechanical properties. According to this model the lighter the ion is, the stronger is the effect. This thesis presents the results obtained by nitrogen implantation in ultra-high molecular weight polyethylene (UHMWPE). N+ ions were implanted at 80 keV, 100 keV and 120 keV energy levels which are maintained at a fluencies or dose of 5×1015 ions/cm2 . Wear resistance was measured using pin-on-disc wear testing machine at a constant load of 18 kg or 177N with a sliding speed of 2 m/s for about 1000m sliding distance. The results clearly show a lower weight and volume loses for samples implanted with nitrogen, in comparison to those implanted with untreated samples. Hence from the results of weight and volume loses of the treated or implanted samples with nitrogen ion, gives very good wear resistance than untreated samples.

(Invited) Ion Implantation and Activation of n- and p-Type Dopants in GaN

GaN-based power switching devices are of significant interest for high efficiency power conversion circuits in medium voltage applications. However, there are still significant challenges preventing mass production and widespread adoption. Recently, GaN-based vertical and lateral power devices have attracted significant interest due to promising device results coupled with progress in native substrate, epitaxial growth, and processing technology developments. However, there are two significant limiting factors for vertical GaN power devices at present. The first issue is substrate and epitaxial layer uniformity and reliability, and the second is the lack of a planar selective-area doping process. While p-type epitaxial growth capability and the ability to stack layers are quite mature from the LED industry, power devices require planar selective-area doping, which is a routine step by ion implantation in the Si and SiC device industry. The ability to implant and activate dopants, particularly p-type dopants, in GaN still remains a challenge as implant activation typically requires annealing at temperatures ~ 2/3 of the melting point, which is a region where the GaN crystal is unstable and readily decomposes to Ga + N2 at atmospheric pressure. The NRL-developed symmetric multicycle rapid thermal annealing (SMTRA) technique has been the most successful, demonstrating electrical activation of up to ~10% of the implanted Mg dopant atoms using a combination of a temporary, thermally stable capping layer, annealing in a moderate nitrogen overpressure, and performing a well-optimized annealing temperature profile including multiple spike anneals. Advances in the SMRTA process development, including optimization of capping processes, implantation profile, and processing steps such as metallization and surface treatments will be reviewed here. In addition, the evaluation of components of the SMRTA process, such as the cap and overpressure anneal, have been applied to Si implantation for n-type doping and will be presented here. This is a critical step to reduce contact resistance in lateral GaN structures as well as form the source regions of vertical devices that is typically accomplished by selective area regrowth. The use of ion implantation and activation utilizes fewer process steps and avoids impurity incorporation at sidewalls compared to the selective area regrowth process, and has been shown to yield lower contact resistance as well. This presentation will review advances in both Mg and Si ion implantation and assess the viability of this process for practical device fabrication.

Plasma‐immersion ion implantation: A path to lower the annealing temperature of implanted boron emitters and simplify PERT solar cell processing

AbstractIon implantation is a suitable and promising solution for the massive industrialization of boron doping, which is a crucial process step for most next‐generation solar cells based on crystalline silicon (c‐Si). However, the use of ion implantation for boron doping is limited by the high temperature (in the 1050°C range) of the subsequent activation anneal, which is essential to dissolve the boron clusters and reach a high‐emitter quality. In this work, we propose the use of plasma‐immersion ion implantation (PIII) from B2H6 gas precursor instead of the standard beamline ion implantation (BLII) technique to decrease this temperature down to 950°C. PIII and BLII boron emitters were compared with annealing temperatures ranging from 950°C to 1050°C. Contrary to BLII, no degradation of the emitter quality was observed with PIII implants annealed at 950°C along with a full activation of the dopants in the emitter. At 1000°C, emitter saturation current densities (J0e) below 21 fA/cm2 were obtained using the PIII technique regardless of the tested implantation doses for sheet resistances between 110 and 160 Ω/sq. After metallization steps, the metal/emitter contact resistances were assessed, indicating that these emitters were compatible with a conventional metallization by screen‐printing/firing. The PIII boron emitters' performances were further tested with their integration in n‐type passivated emitter rear totally diffused (PERT) solar cells fully doped by PIII. Promising results already show a conversion efficiency of 20.8% using a lower annealing temperature than with BLII and a reduced production cost.

Compensating film stress in thin silicon substrates using ion implantation.

Future space telescopes, especially X-ray telescopes, will require thin mirrors to achieve high optical throughput. Thin mirrors are more difficult to fabricate than thick mirrors, but recent advances have made accurate fabrication of thin mirrors possible. However, mirrors must have a reflective coating, which typically has non-repeatable and non-uniform intrinsic stress that deforms a thin mirror. Reducing coating stress by controlling deposition parameters typically reduces reflectivity. Non-uniform integrated stress compensation (NISC) methods, in which spatially controlled stress is applied to the mirror substrate backside to balance the frontside coating stress, decouple the film stress from the reflectivity. Ion implantation is one NISC method, where high-energy ions are implanted into a glass or silicon substrate to generate stress near the substrate surface. In this paper, we demonstrate the use of ion implantation for stress compensation of 30 nm thick chromium films applied to the front of five silicon wafers. The reflective films have mean integrated stress between -8 and -35 N/m, which cause deformations between 400 and 1600 nm RMS. We demonstrate that these wafers can be restored to the pre-coating shape to within 60 nm RMS, in most cases within 1/20th of the coating deformation.

Quantification of organic materials by ion implantation

Secondary ion mass spectrometry was initially considered to be a semiquantitative technique because of as much as 5 orders of magnitude variation in secondary ion yields over the periodic table for oxygen and cesium bombardment. The use of ion implantation to create standards has made it possible to accurately quantify elements and isotopes in a wide range of inorganic materials. The development of new ion sources has extended depth profiling to organic materials. It is of interest to explore ion implantation to quantify elements and molecular species in organic substrates. It is unrealistic to ion implant an organic molecule. Even if the molecular species was formed into a charged beam, the species will disintegrate upon impact with the substrate. However, if the species of interest contains an element not present in the substrate, then it should be possible to implant that element into the substrate and make a quantitative determination. In recent work, the authors demonstrated quantification of the insecticides permethrin and deltamethrin in mosquito netting, which is high density polyethylene, by ion implantation of chlorine and bromine, respectively [C. Zhou, F. A. Stevie, and S. C. Smith, J. Vac. Sci. Technol., B 34, 03H107 (2016) and C. Zhou, F. A. Stevie, and S. C. Smith, J. Vac. Sci. Technol., B 35, 031802 (2017)]. The authors have now explored extension of this method to a nitrogen containing an insect growth regulator, pyriproxyfen, by ion implantation of nitrogen. The species 12C14N− was monitored because of high secondary ion yield as opposed to negligible yield for N−. Initial results show that nitrogen can be quantified, but the detection limit is insufficient to monitor this compound. The ion implantation approach may be applicable to other materials, and the use of minor abundance isotopes, such as 15N and 18O, should also be considered.

ToF-SIMS analysis of ion implanted standard to quantify insecticide in mosquito netting with cesium and argon gas cluster sputtering beams

Ion implantation has been investigated for quantification of species in organic materials. Quantitative analysis of two insecticides in mosquito netting was recently achieved by ion implantation and time-of-flight secondary ion mass spectroscopy analysis with a Cs+ sputtering beam [Zhou et al., J. Vac. Sci. Technol., B 34, 03H107 (2016) and Zhou et al., J. Vac. Sci. Technol., B 35, 031802 (2017)]. Gas cluster ion beams (GCIBs) are of increasing utility in depth profiling of organic materials, and it was of interest to try the ion implantation approach with argon GCIB. The study was conducted on permethrin treated mosquito netting and on the substrate material [high density polyethylene (HDPE)] which was ion implanted with chlorine. The negative ion mass spectrum of permethrin is dominated by Cl−. Analysis of the ion implanted HDPE with Cs+ provided the expected Gaussian distribution, but analysis with argon GCIB shows a very sharp change in matrix species intensity at the penetration depth of the ion implant. This is presumably due to the degradation of the polymer structure by the implant. Even with reduced chlorine implant dose, the ability to use the analysis of the standard to quantify chlorine in insecticide treated fiber with GCIB was limited because of secondary ion yield variations. Analysis of netting which was no longer effective against mosquitoes showed significantly less chlorine at the surface than fresh netting, similar to the results obtained with the Cs+ sputtering beam. The results are useful to understand the effectiveness of insecticide treated nets and have implications for the analysis of other organic materials with the use of ion implantation for quantification.

Ultra-low specific contact resistivity (1.4 × 10−9 Ω·cm2) for metal contacts on in-situ Ga-doped Ge0.95Sn0.05 film

A heavily Ga-doped Ge0.95Sn0.05 layer was grown on the Ge (100) substrate by molecular beam epitaxy (MBE), achieving an active doping concentration of 1.6 × 1020 cm−3 without the use of ion implantation and high temperature annealing that could cause Sn precipitation or surface segregation. An advanced nano-scale transfer length method was used to extract the specific contact resistivity ρc between the metal and the heavily doped p-Ge0.95Sn0.05 layer. By incorporating Sn into Ge and in-situ Ga doping during the MBE growth, an ultra-low ρc of 1.4 × 10−9 Ω·cm2 was achieved, which is 50% lower than the ρc of p+-Ge control and is also the lowest value obtained for metal/p-type semiconductor contacts.

Accelerator-Based Nuclear Techniques for Processing and Characterization of Oxide Semiconductors for Solar Energy Conversion

Accelerator-based nuclear techniques are an important tool for the modification and characterization of surfaces in general, down to a depth of around one micrometer. For oxide semiconductors used in solar energy conversion, the surface plays a critical role in facilitating the use of solar photon energy to obtain hydrogen via spontaneous water oxidation. For such a process, the required surface properties are complex and include specific chemical composition, as well as the defect composition, and both of these characteristics may be augmented using accelerator-based nuclear techniques. The targeted modification of surfaces makes use of ion implantation for changing the chemical composition, and ion irradiation for changing the defect structure. The defect formation is a very complex process, and in this work we placed more emphasis on this aspect. We attempted to present the defect formation under the irradiation of ion beams at the two extremes: formation of extensive and large-scale cluster defects; and formation of small-scale point defects. In addition, we review the main characterization techniques based on ion beams, with examples from work carried out on semiconductors and oxide semiconductors.

Defect evolution and dopant activation in laser annealed Si and Ge

Defect evolution and dopant activation are intimately related to the use of ion implantation and annealing, traditionally used to dope semiconductors during device fabrication. Ultra-fast laser thermal annealing (LTA) is one of the most promising solutions for the achievement of abrupt and highly doped junctions. In this paper, we report some recent investigations focused on this annealing method, with particular emphasis on the investigation of the formation and evolution of implant/anneal induced defects and their impact on dopant activation. In the case of laser annealed Silicon, we show that laser anneal favours the formation of “unconventional” (001) loops that, following non-melt anneals, act as carrier scattering centres, leading to carrier mobility degradation. In contrast, in the case of melt anneals, the molten region itself is of excellent crystalline quality, defect-free and with very high activation rates. As for laser annealed Germanium, we studied in detail the amorphous to crystalline Ge phase transition as a function of the increasing LTA energy density and we found that using LTA, very high carrier concentrations (above 1020cm−3) were achieved in As doped regions, which are unachievable with conventional rapid thermal annealing (RTA) processes.

Changes of tribological properties of Inconel 600 after ion implantation process

Abstract Commercial Inconel 600 nickel-chromium alloy was implanted with nitrogen, titanium, chromium, copper with tin (as bronze components) and yttrium ions to doses ranging from 1.6e17 to 3.5e17 cm−2. The aim of this research was to investigate the properties of the modified alloy in the context of its application in foil bearings. The virgin and the treated samples were tribologically tested and examined by Scanning Electron Microscopy, Glow Discharge Mass Spectrometry and Energy Dispersive Spectroscopy. The technological studies were preceded by modelling of concentration values of the introduced elements. The results obtained with the use of ion implantation are discussed. There are two advantages which should be highlighted: good agreement in modelling and experimental results of depth profiles of implanted ions, wear resistance improvement of Inconel 600 surface by implantation of copper and tin ions. The tribological tests indicate that abrasion and corrosion are the predominant mechanisms of surface wear.

Back-junction back-contact n-type silicon solar cell with diffused boron emitter locally blocked by implanted phosphorus

The highest energy conversion efficiencies in the field of silicon-based photovoltaics have been achieved with back-junction back-contact (BJBC) silicon solar cells by several companies and research groups. One of the most complex parts of this cell structure is the fabrication of the locally doped p- and n-type regions, both on the back side of the solar cell. In this work, we introduce a process sequence based on a synergistic use of ion implantation and furnace diffusion. This sequence enables the formation of all doped regions for a BJBC silicon solar cell in only three processing steps. We observed that implanted phosphorus can block the diffusion of boron atoms into the silicon substrate by nearly three orders of magnitude. Thus, locally implanted phosphorus can be used as an in-situ mask for a subsequent boron diffusion which simultaneously anneals the implanted phosphorus and forms the boron emitter. BJBC silicon solar cells produced with such an easy-to-fabricate process achieved conversion efficiencies of up to 21.7%. An open-circuit voltage of 674 mV and a fill factor of 80.6% prove that there is no significant recombination at the sharp transition between the highly doped emitter and the highly doped back surface field at the device level.

SIMS analysis of zinc oxide LED structures: quantification and analysis issues

Zinc oxide (ZnO) is a wide band gap semiconductor that shows great promise for development of light emitting diode structures. Interest in this technology has increased significantly, but even though controlled n‐type doping can be readily achieved, p‐type doping has been difficult. Numerous potential p‐type dopants were investigated in this SIMS study using a CAMECA IMS‐6F. The dopants and other elements of interest were quantified by use of ion implantation into ZnO substrates. Relative sensitivity factor values were obtained for H, Li, N, F, Na, Mg, Al, Si, K, Ga, As, Se, Ag, Cd, Te. Sample charging was encountered for some specimens, and adjacent electron neutralization procedures were employed. ZnO structures were prepared and subsequently analyzed with both O2+ and Cs+ primary beams. Depth profiles exposed a number of analysis issues. Because of the large number of elements, especially those at low atomic number, that were present in the structures, many mass interferences were encountered. Ag in particular was very difficult to monitor. Matrix effects were also noted, especially when high Mg doping was used. The need to monitor Al, Na, and K in the near surface region required analysis without conductive Au coating to reduce contamination. With careful choice of secondary ion species, it was possible to monitor the elements of primary interest using O2+ primary beam. SIMS demonstrated the ability to characterize the layers in the ZnO structure, including quantum wells, and to determine dopant and contaminant levels. Copyright © 2012 John Wiley & Sons, Ltd.