Gas Ion Implantation Research Articles

Tailored conductivity in ion implanted polyetheretherketone

Ion implantation can be used to confer electrical conductivity upon conventional insulating polymers such as polyetheretherketone (PEEK). We have implanted PEEK films using three different types of ion implantation: conventional inert gas and metal ion implantation, and ion beam mixing. We have applied a number of analytical techniques to compare the chemical, structural and electrical properties of these films. The most effective means of increasing electrical conductivity appears to be via ion beam mixing of metals into the polymer, followed by metal ion implantation and finally, inert gas ion implantation. Our results suggest that in all cases, the conducting region corresponds to the implanted layer in the near surface to a depth of ∼750 Å (ion beam mixed) to ∼5000 Å (metal ion). This latter value is significantly higher than would be expected from a purely ballistic standpoint, and can only be attributed to thermal inter-diffusion. Our data also indicates that graphitic carbon is formed within the implant region by chain scission and subsequent cross-linking. All ion implanted samples retained their bulk mechanical properties, i.e. they remained flexible. The implant layers showed no signs of de-lamination. We believe this to be the first comparative study between different implantation techniques, and our results support the proposition that soft electronic circuitry and devices can be created by conductivity engineering with ion beams.

From plasma immersion ion implantation to deposition: a historical perspective on principles and trends

Plasma immersion techniques of surface modification are known under a myriad of names. The family of techniques reaches from pure plasma ion implantation, to ion implantation and deposition hybrid modes, to modes that are essentially plasma film deposition with substrate bias. In the most general sense, all plasma immersion techniques have in common that the surface of a substrate (target) is exposed to plasma and that relatively high substrate bias is applied. The bias is usually pulsed. In this review, the roots of immersion techniques are explored, some going back to the 1800s, followed by a discussion of the groundbreaking works of Adler and Conrad in the 1980s. In the 1990s, plasma immersion techniques matured in theoretical understanding, scaling, and the range of applications. First commercial facilities are now operational. Various immersion concepts are compiled and explained in this review. While gas (often nitrogen) ion implantation dominated the early years, film-forming immersion techniques and semiconductor processing gained importance. In the 1980s and 1990s we have seen exponential growth of the field but signs of slowdown are clear since 1998. Nevertheless, plasma immersion techniques have found, and will continue to have, an important place among surface modification techniques.

Functional voids by gas ion implantation for applications in semiconductor processing

AbstractThe recent work in the field is reviewed and some new applications are reported. In particular we review some aspects where new contributions have been added. The mechanism of bubble formation when He is implanted into silicon is described till the supersaturation of vacancies (void formation). The void evolution has been described considering direct coalescence or Ostwald ripening. Applications such as gettering, lifetime control, and more recently nanosensors for interstitials are critically discussed.

Effects of crystal defects on the stopping powers for channeled ions in ion implanted single crystals

The ion beam channeling method is used in the study of impurity distribution and implantation damage in crystalline materials. This technique requires knowledge of the stopping power of a channeled ion. Although the stopping powers for non-channeled ions are well established, the energy loss of channeled ions has been studied only in perfect crystals. The energy-loss measurements have been made for 2.2 MeV protons in different damaged Si crystals. The defects were created by multiple energy implantation of noble gas ions (He and Xe). The total implantation dose was varied to produce different types and concentrations of defects. The average ratio of channeled and non-channeled energy loss of ions has been measured by resonance backscattering. These data have a precision of 3%. The influence of the beam alignment from crystal axis on stopping power ratio has been investigated.

Efficient production of silicon-on-insulator films by co-implantation of He+ with H+

We have investigated the process of thin film separation by gas ion implantation and wafer bonding, as well as the more basic phenomenon of blistering, on which the technique is based. We show that when H and He gas implants are combined they produce a synergistic effect which enables thin-film separation at a much lower total implantation dose than that required for either H or He alone. By varying the H and He implantation doses we have been able to isolate the physical and chemical contributions of the gases to the blistering processes. We find that the essential role of H is to interact chemically with the implantation damage and create H-stabilized platelet-like defects, or microvoids. The efficiency of H in this action is linked to its effective lowering of the silicon internal surface energy. The second key component of the process is physical; it consists of diffusion of gas into the microvoids and gas expansion during annealing, which drives growth and the eventual intersection of the microvoids to form two continuous separable surfaces. He is more efficient than H for this process since He does not become chemically trapped at broken bonds and thus segregates into microvoids more readily. In particular, we have demonstrated that a 1×1016 cm−2 He dose in combination with a 7.5×1015 cm−2 H dose are sufficient to shear and transfer a thin silicon film onto a handle wafer after bonding the two wafers together.

In-situ studies of phase formation and transformation in carbon ion implanted iron: Investigation of electrical resistivity

High fluence carbon ion implantation into pure iron has been performed at temperatures of −70°C. In situ measurements of electrical resistivity were done during ion bombardment to fluences of up to 1.2 × 10 18 C +/cm 2. Several models are tested to estimate the transformed volume fraction from the experimentally determined values for resistivity. The transformation kinetics are compared to formal theories for isothermal reactions. The Avrami exponents have been determined to be smaller than 1. In addition resistivity during implantation of noble gas ions was measured. Clear differences between the implantation of light respectively heavy ions were found.

On the residual stress profile developed in titanium nitride by ion implantation

The effect of gas and metal ion implantation on the residual stress and the strain distribution has been studied using glancing incidence parallel beam X-ray diffraction. Monolithic TiN coatings were chosen with very low residual stress as made by chemical vapor deposition onto cemented carbide. Implants of nitrogen, NiTi dual and Y were made at different doses and acceleration energies. The results showed that the residual stress in the implanted zone was in the range 0.5 GPa tensile down to −2 GPa compressive, with very large distributions of strain corresponding to high dislocation densities or grain comminution. With one exception, the residual stress below the implanted zone became tensile up to 1 GPa down to depths of about 2 μm with some increase in strain distribution. In the sample implanted with Y at high dose and energy the residual stress is highly compressive (−4 GPa), with a very high degree of strain broadening corresponding to a high degree of disorder. Below this zone a tensile stress is developed associated with moderate dislocation densities corresponding to a hardening of the material. At high implantation doses and energies, the high compressive stress and high dislocation density may correspond to a condition of over-implantation causing mechanical damage to the lattice.

Surface modification of superalloys and heat resistant steels by irradiation of low and high energy ion beams

The effect of ion beam treatment (IBT) using low and high energy ion beams, on surface topography, chemical composition and structure of surface layer and service properties of nickel based superalloys, heat resistant steels and pure Ni was studied. It was shown that low energy high current IBT ( E ≈ 10 −1 to 10 ° keV, j ≈ 10 −1 to 10 mA cm −2) enabled: (1) to form a surface of irradiated samples with a roughness varying over a wide range; (2) to carry out radiation-enhanced relaxation of residual stress, formed during pretreatment; (3) to clean the surface layers of the sample from contamination by C, O and S; (4) to detect the cast superalloy macrostructure. The results of gas and metal ion implantation investigation indicate that at the traditional regimes of implantation ( E ≈ 10 keV, < j> ≈ 10 μA cm −2, D ≈ 10 17 ions cm −2), the depth of ion penetration is 10 −2 to 10 −1 μm and the thickness of the modified structure layer is h M ≈ 10 −1 μm. One can increase the h m considerably by high current ion implantation (j≥10 3 μA cm −2) and high power pulse IBT ( N p≥10 7 W cm −2, τ p ≈ 10 1 to 10 2 ns). The irradiation by high energy ion beams allows to change the service properties of the materials (wear resistance, oxidation resistance, fatigue strength) over a wide temperature range. Plausible reasons of these changes are discussed.

New broad beam gas ion source for industrial application

A source delivering a broad, high current ion beam compatible with both chemically active and inert gases has been developed which gives reliable, long term, maintenance-free operation. It uses a glow discharge with a cold cathode in a magnetic field where a dense uniform plasma is generated in large volumes at low gas pressures. Optimal selection of the electrode configuration and magnetic field ensures operation at pressures lower than 0.1 Pa in pulse–periodic mode (1–10 A discharge current, 1 ms pulse length, 25–50 Hz frequency), and continuous mode (discharge current up to 2 A). The current density of a 15-cm-diam beam can reach 10 mA cm−2 in the former, and 1 mAcm−2 in the latter. Tests with a 50-cm-diam discharge chamber show the uniformity of the ion emission current to be better than ±10%, confirming that the technology is scaleable, and that beams of up to 2000 cm2 cross-sectional area can be obtained without loss of beam uniformity through appropriate design of the extraction system. The source is completely reactive gas-compatible, generating ion beams from oxygen, nitrogen, argon or ionized CH radicals (e.g., using C3H8). Mass-charge beam analysis shows the beams generated to be of high purity (≳99%). Applications include low energy (1–3 keV) ion beam cleaning of glass, ceramic and metal surfaces prior to the deposition of protective and decorative coatings such as TiN and diamondlike carbon, ion beam assisted deposition, and high energy gas ion implantation using, e.g., pulse–periodic beams of ions with energies up to 50 keV.

Plasma and Ion Beam Tools for Enhanced Battery Electrode Performance

AbstractPlasma and ion beam methods such as gas and metal ion implantation, plasma immersion ion implantation (PIII), and metal plasma immersion ion implantation and deposition (MePIIID) are introduced as powerful tools to modify the properties of battery electrodes. Three kinds of rechargeable electrochemical cells have been investigated: the lead-acid cell, the nickel alkaline-electrolyte cell, and the lithium cell. It was experimentally shown that (i) metal ion implantation of Ti, V, Cr, Ni, and W into lead and lead-antimony electrodes reduced the corrosion current by more than one order of magnitude, (ii) cobalt ion implantation into nickel electrodes enhanced the interconversion of Ni(OH)2 to NiOOH and the associated cycle life, (iii) nitrogen-PIII resulted in the formation of a nitrided lithium layer on lithium which stabilized the surface against corrosion, (iv) MePIIID with a tungsten plasma reduced the pitting corrosion of aluminum, a current collector for a lithium battery.

Colour centres, dislocations and colloids in ion-implanted LiF and LiF(Mg)

Pure and magnesium-doped LiF crystals have been implanted with mainly magnesium and argon ions of 100 keV energy. Fluences were in the range of 6*1015-1*1017 ions cm-2. Changes in optical absorption during thermal annealing are reported. The magnesium colloid band at 280 nm and the lithium colloid band at 520 nm are identified. Some cases of anomalous colloid growth are observed. Hidden structural factors such as dislocations are thought to produce this anomalous annealing behaviour. Magnesium colloids develop in doped crystals after the implantation of rare gas ions. The responsible mechanism is thought to involve the interaction of F centres with impurity-vacancy (IV) dipoles. We find that the dopant has little effect on the concentration of F and F2 colour centres or on their thermal stability in ion-implanted samples.

The equipment for and process of metal ion beam enhanced deposition

Abstract The equipment for metal ion beam enhanced deposition is introduced. This is composed of an all-element gas-solid ion source and low energy ion sputtering source, and thus can be used for simple gas ion or metal ion implantation, simultaneous implantation of gas and metal ions, as well as gas ion or (and) metal ion beam enhanced deposition. The process of metal ion beam enhanced deposition and multi-ion beam enhanced deposition was investigated. As an example of optical films, pure Ag films and Al films were prepared by metal ion beam enhanced deposition. The results show that the adhesion of the films to substrates is high and there is a mixed interface between the films and substrates. As an example of corrosion resistant films, (Ti, Mo)N films were prepared on YG8 hard alloy by multi-ion beam enhanced deposition. The corrosion resistance of the (Ti, Mo)N film is much higher than that of TiN film and the YG8 hard alloy substrate.

Ion bombardment effects in conducting polymers

The modification of properties of conducting polymers by ion bombardment offers interesting possibilities for their application in the field of muelectronics and electrochemistry. Therefore foils of intrinsically conducting polymers (polypyrrole and polythiophene) were modified by noble gas ion implantation. By ion bombardment the resistivity can be increased by several orders of magnitude. This effect depends on the species, energy and ion fluence. Cyclovoltammetric experiments show the same electrochemical features for the modified foils as the untreated polymers, but the observed currents are smaller by two orders of magnitude. The conductivity of the virgin foil (σ = 100 S/cm) is sufficient for galvanic metal deposition. The bombardment induced change of resistivity causes an inhibition of electrochemical deposition. By using masks lateral structures in the range of several μm can be produced. During implantation the black colour of the untreated foil changes to brown depending on the implanted dose. The associated changes of the chemical structures, investigated by XPS, are discussed.

Phase transformations in Mo under simultaneous implantation of metal and gas ions

Phase transformations of molybdenum under ion implantation with metal and gas ions have been studied by means of transmission electron microscopy. It is shown that, as a result of ion mixing of the surface-adsorbed gas elements of the ion source, thin (⩽ 100 nm) solid layers of the interstitial phases may be formed in the ion-implanted layers. The mechanisms of formation of the structure found are discussed by investigating the crystallographic details of phase transformations.

Deuterium interaction with impurities in tungsten studied with TDS

The deuterium-tungsten system was studied using thermal desorption spectrometry (TDS). Impurities (oxygen and helium) were introduced by gas exposure and ion implantation. Auger electron spectroscopy was used to monitor surface coverage with impurities. The release of deuterium from subsurface defects including surface recombination to D2 has been modelled. It was shown that for deuterium dissociation enthalpies lower than 1.3 eV surface recombination is the rate determining step. By fitting of the experimental data a deuterium vacancy dissociation enthalpy of 1.43 ± 0.02 eV and an attempt frequency of 1 × 1013 s−1 was found. Though oxygen and nitrogen coverage of the surface inhibited surface trapping of deuterium from the vacuum no indication was found of an oxygen induced enthalpy barrier for deuterium detrapping from the surface. Ion induced defects varying from monovacancies to helium bubbles give rise to deuterium detrapping with activation enthalpies varying from 1.2 to 1.8 eV.

Implantation and diffusion of noble gas atoms during ion-beam etching of silicon

The excessive damage and high defect density generated during ion-beam etching of crystalline Si is characterized by Rutherford backscattering, photoluminescence, and transmission electron microscopy. In samples etched at room temperature, a highly damaged surface layer (d≊5 nm) with a large concentration of noble gas atoms is detected and analyzed using Rutherford backscattering in axial channeling geometry. Point defects due to the low-energy noble gas ion implantation are produced within a depth of 100 nm and deeper, and are monitored by their characteristic photoluminescence. The intensity of the noble-gas-defect photoluminescence is studied for different ion-beam energies (200–2000 eV) and crystal orientations. A threshold to produce the defects can then be determined, leading to an estimate of the number of vacancies contained in the noble gas defect. Annealing of etched samples at 650 °C causes the formation of different new photoluminescent centers. Although little is known about the structure of these defects, it is observed that the defects effectively getter copper. Further annealing of the Ar-etched samples at 1050 °C causes the formation of Ar bubbles with an average diameter of about 5 nm.

Large-aperture, axially symmetric ion-optical lens systems using new types of electrostatic and magnetic elements

We have developed new types of ion-optical systems having larger solid angles (i.e., collecting power) and flexibility than many existing designs. They use relatively simple axially symmetric elements, namely solenoids, axial magnetic dipoles, and radial electric field lenses. The systems can focus, with good optical properties, energetic ions in the range of tens of keV up to tens of MeV kinetic energy and are capable of operating in nondispersive, achromatic modes. The key elements for the latter are new types of defocusing magnetic and electrostatic correction lenses. The lens systems have applications in any existing devices used to collect and focus energetic ions (including electrons). Typical devices are: mass spectrometers, leak detectors and gas analyzers, ion sources, accelerators and ion implantation systems, nuclear particle spectrometers, electron microscopes, ion microprobes, and ion-beam lenses for cancer therapy.

Formation of silicon carbide layers by the ion beam technique and their electrical properties

β-type SiC layers were fabricated by high dose implantation of carbon ions into silicon with subsequent annealing. The effect of implanting energetic Si or P ions following the carbon ion implantation on the ß-SiC formation behaviour was studied by means of infrared absorption spectroscopy. The results were compared with those obtained by implantation of Ar or Ne noble gas ions which caused a reduction in the ß-SiC formation temperature. The electrical properties of the ß-SiC layers formed by this ion beam technique were also evaluated.

ステンレス鋼における照射誘起相変態 ＩＩ 金属イオン注入効果

In a previous paper, we have shown that noble gas ion implantation to austenitic stainless steels has induced γ→α (martensitic) transformation, and we have discussed a mechanism for this phase transformation. In the present paper, phase transformations in austenitic stainless steels implanted with metal ion have been investigated by conversion electron Mössbauer spectroscopy (CEMS) and X-ray diffraction. Observation by CEMS and X-ray diffraction, showed clearly that different metal ion species make different contributions to ion-induced γ→α transformation. It was confirmed that γ→α transformation in 17/7 steels implanted with Fe ion and Ni ion occured by both the effect of compositional change (the alloying effect) and that of damage-induced stress (the stress effect). In case of Snion-implanted 17/7 steel, on the other hand, it seems that only the stress effect is a driving force for γ→α transformation.

ステンレス鋼における照射誘起相変態 Ｉ 希ガスイオンの照射効果

In a previous paper, we have shown that noble gas ion implantation to austenitic stainless steels has induced γ→α (martensitic) transformation, and we have discussed a mechanism for this phase transformation. In the present paper, phase transformations in austenitic stainless steels implanted with metal ion have been investigated by conversion electron Mossbauer spectroscopy (CEMS) and X-ray diffraction. Observation by CEMS and X-ray diffraction, showed clearly that different metal ion species make different contributions to ion-induced γ→α transformation. It was confirmed that γ→α transformation in 17/7 steels implanted with Fe ion and Ni ion occured by both the effect of compositional change (the alloying effect) and that of damage-induced stress (the stress effect). In case of Snion-implanted 17/7 steel, on the other hand, it seems that only the stress effect is a driving force for γ→α transformation.