The transition metal ions Fe, Mn, Ni, Ti, and Cr as well as the group III-A ion Ga were implanted in a random direction close to the c-axis of α-Al2O3 single crystals. These were subsequently annealed in flowing oxygen at temperatures between 600 and 1500°C. The impurity and damage distributions were determined by He backscattering and channeling techniques. The normally trivalent ions, Fe, Ga, and Cr show strong tendency to become incorporated into substitutional sites, whereas the normally divalent ions, Cu and Mn show no such tendency, even at high temperatures. Most of the impurities tend to move toward the surface with only Fe, Ga, and Cr showing tendency towards bulk diffusion. In all cases the Al sublattice recovers at lower temperatures than the oxygen sublattice.

Cleaved {100} MgO single crystal surfaces have been implanted with 300keV Ti+and Cr+ ions to doses in the range 10 16 −1018 ions cm−2. Localised plasticity and fracture behaviour has been investigated using microhardness indentation tests at loads of between 10gf and 500gf.Significant surface hardening has been observed at lower doses with amorphisation related softening occurring at higher doses. Post-implantation heat treatments produce precipitation reactions with associated hardness changes.

An Analytical Electron Microscopy (AEM) investigation of polycrystalline TiB2 implanted with 1 MeV Ni+ to 1 × 1021 ions/m2 has shown that the implanted region remained crystalline and showed no evidence of precipitation. A region containing tangled dislocations extended from the implanted surface to ∼500 nm. Between ∼500 and 750 nm, the microstructure was more complicated and could be indicative of a high density of 5 to 10 nm diam defects. The maximum nickel concentration determined by energy dispersive spectroscopy (EDS) occurred at ∼450 nm, slightly deeper than the calculated depth of 390 nm. Observations after in situ annealing revealed cavities and nickel-rich precipitates. Radiation damage models are invoked to explain the microstructures observed.

Ion implantation provides a mechanism for radically modifying the electronic and transport properties of a variety of polymers that are normally insulating. By using masks and tailoring the implanted species and ion energies, conducting paths in an insulating medium can be fabricated between specific reference points, an application of obvious relevance to the microelectronics industry. Specific results are reported for modification of the structure, electrical conductivity, thermoelectric-power, optical transmission and electron spin resonance for several polymers under a variety of implantation conditions. The temperature and frequency dependence of the conductivity suggest a onedimensional variable range hopping mechanism for conduction along the polymer chains. Comparison is made between implantation in the 200 keV and 2 MeV energy ranges.

Ion implantation causes an increase by ~14 orders of magnitude in the electricalconductivity of normally insulating polymers such as polyacrylonitrile (PAN), poly(2,6 dimethyl phenylene-oxide) (PPO), and poly (pphenylene sulfide) (PPS), after ion implantation with Br at fluences of 3 × 1015 ions/cm2. The temperature dependence of the dc conductivity was measured in the range 23 〈 T 〈 293 K and results show an exponential law σ ~ exp(−To/T)a) for PAN, PPO and PPS with α =1/2, suggesting a one-dimensional hopping mechanism. The temperature dependence of the thermoelectric power (TEP) identifies the sign of the dominant carrier type. The TEP exhibits linear metallic behavior, with small magnitudes (~3μV/K), and shows Br implantation to yield p-type material in PPS and n-type material in PAN with extremely low values of mobility (〈 10−3 cm2/V sec) and correspondingly very high values of the carrier concentration estimated to be 5 × 1022 cm-3. Results are also reported for the frequency dependence of the AC conductivity and of similarly implanted PPS and PAN samples.

Multiple analytical techniques including FABMS, XPS/Auger, magnetic susceptibility,and conductivity are used to probe the effects of transition-metal implantation on the structural and physical properties of covalent polymers and HOPG. Post-implantation chemistry and solid-state interactions between the implanted atoms and the polymer are investigated.

Ion implantation of selected polymer films leads to the formation of semiconductive (σ ~ 10−4 S/cm) derivatives, which are presumably partially carbonacėous products derived from gross structural rearrangements. In support of this contention we find that Br-implanted polyacrylonitrile, PAN, exhibits a narrow ESR signal with a g-value of 2.0033, consistent with the presence of free radicals delocalized within a П-electron system. Thermopower measurements reveal that the sign of the majority carrier is dependent upon the molecular structure of the parent polymer.For example, implantation of PAN with Br+ affords n-type derivatives while under similar conditions poly(p-phenylene sulfide), PPS, and poly(2,6-dimethylphenylene-oxide), PPO, yield p-type semiconductors. It is suggested that the majority carriers arethe ions (carbenium ions or carbanions) which are best stabilized by the parent polymerstructure, remnants of which presumably exist after implantation. Resonance and/or inductive effects are invoked to explain the data. For example, the rather electron-rich backbone of PPQ is expected to stabilize holes more effectively than electrons, and the observed p-type behavior is consistent with this prediction.

We propcoe a novel technique to convert polymer films into useful inorganic films by ion beam irradiation. Along the track of an ion the polymer is dissociated into smaller fragments. volatile fragments diffuse through the film and escape. Any element which is not removed in the form of volatile species is subsequently enriched with respect to the other elements. We demonstrate this effect in a polymer poly(dimethylsilylene-co-methylphenylsilylene), which initially has a C:Si ratio of 45:1. Upon irradiation with 2 MeV Ar+ ions at a dose of 1015 ions/cm2 the C:Si ratio changes to 3.4:1 as verified by Rutherford backscattering spectrometry. We believe that the effect of the ion beam irradiation is to produce more Si-C bonds at the expeme of the C-H and Si-Si bonds, with ≲10% of the original hydrogen being present in the film at high doses. The loss of the H atoms is further confirmed by a nuclear reaction technique. The IR spectra of the film as a function of the irradiation dose shows a progressive loss of fine molecular features with significant increase of the refractive index. The IR spectrum at the high doses appears to be due to a mixture of various Si and C bonds. However, the irradiated films are very hard and scratch resistant (knoop value ≳1300) suggesting an increase in the number of silicon carbide bonds

We have measured the magnetic properties of highly oriented pyrolytic graphite (HOPG), polyethylene (PE), and polyvinylidine fluoride (PVF2), implanted with fluences of 25 keV iron atoms ranging from 1016 to 1017 atoms/cm2 . The lowest fluence specimens were paramagnetic down to 2 K, with evidence for clusters of only a few spins, while the highest fluence specimens were clearly ferromagnetic, with magnetization curves resembling those of a set of randomly oriented soft magnetic planes. The critical fluence for formation of a ferromagnetic state appears to be between 1 and 3 × 1016 atoms/cm2 at 25 keV. Theseresults can be qualitatively understood based on the critical density for percolation of near neighbor exchange interactions.

The electrical properties of pyrolyzed polymers have been studied recently.1,2 It has been shown that organic, polymeric3 and non-polymeric4 films can be made conductive (ρ ~ 10−3Ωcm) by ion beam irradiation. Common to all of the films was the presence of carbon as a constituent element and both pyrolysis and ion beam irradiation3 was shown to increase the relative carbon content of the films. The ion beam irradiated organic films 3,4 exhibited a temperature dependence of their resistivity of the form ρ(T) = ρ∞e−(TЛ)*, where ρ is the ion-induced resistivity, ρ∞ and T0 are constants and T is the temperature. At very high doses of irradiation (1017cm−2Ar+@ 2MeV) the film resistivity was temperature independent. Very similar transport properties were observed in the pyrolyzed polymers1 as well, though the lowest resistivities achieved were higher than the resistivity values observed in the ion irradiated3 polymer films. In both the pyrolysis and ion-irradiation experiments the temperature dependence has been explained by a model due to Sheng and Abeles,5 which involves charge transport by hopping between conducting islands embedded in an insulating matrix. Such striking similarities between two distinctly different modes of energy deposition in the films, prompted us to compare the effects of pyrolysis and ion irradiation in different carbon containing films. We compared both a polymer (HPR-204°) and a film of electron beam evaporated carbon film. While in the former case one would observe chemical degradation as well as structural modification, by studying pure carbon films the physical nature of the processes could be clarified. We report metallic carrier densities in both films and evidence for significant structural rearrangement. We conclude that pyrolysis and ion beam irradiation have similar effects on both polymer and carbon films.

Depth profiling of hydrogen in polymeric materials poses special problems. Backscattering methods are ruled out because of kinematics. Nuclear reaction methods are undesirable because small reaction cross sections necessitate large fluences of high mass projectiles and result in unacceptable levels of radiation damage. We have used a helium-induced proton-recoil technique with 3 MeV 4He particles to measure the hydrogen distribution in pristine and ion-implanted polyvinylidene fluoride (PVDF) films. The incident 4He particles stopped in the 25 micron PVDF films while the recoiling protons were detected after passing through the polymer film. Large changes in the hydrogen content of PVDF films implanted with modest fluences of 6 MeV carbon, oxygen and nickel ions were observed.

Post implantation annealing of ion-damaged, highly oriented pyrolytic graphite (HOPG) has been studied by Raman spectroscopy, the ion channeling technique and Transmission Electron Microscopy. Complementary information obtained by these methods provides confirmation for the completion of the first step of graphitization of iondamaged graphite at annealing temperatures of ~2300°C. This is manifested by the formation of carbon planes with two dimensional ordering but no correlation in the third (c-axis) dimension.

The crystallization of disordered surface layers on highly oriented pyrolytic graphite (HOPG) have been studied by Rutherford backscattering spectrometry (RBS) and channeling techniques. Disordered layers (~1000–3000Å thick) are produced on the surface of HOPG by the implantation of various ions. The disordered layers are regrown by thermal annealing of the samples in an inert environment. Isochronal anneals reveal two distinct regrowth processes: one, a rapid process of low activation energy (Ea ~ 0.15 eV) which is observed primarily in regions where the disorder is sufficient to prevent the channeling of the ions but insufficient to totally destroy the graphitic structure. This low activation energy may indicate annealing of the damage by migration of interstitials where the interstitials are the knock-on carbon atoms produced by the primary ions. A regrowth process with higher activation energy (Ea ~ 2.0 eV) occurs primarily in regions where the disorder is close to the saturation-disorder produced by ion implantation. Both the regrowth processes are epitaxial in nature and the epitaxial nature of the process may explain the much lower activation energy for 3D AB stacking as measured in ion implanted graphite when compared with results on the bulk graphitization of pyrocarbons.

In previous studies it was found that when highly oriented pyrolytic graphite (HOPG) is implanted at room temperature, the damage caused by the implantation could be completely annealed by heating the sample to temperatures higher than ∼ 2500°C. However at these high temperatures, the implanted species was found to diffuse out of the sample, as evidenced by the disappearance of the impurity peak in the Rutherford backscattering (RBS) spectrum. If, on the other hand, the HOPG crystal was held at a high temperature (≥ 600°C) during the implantation, partial annealing could be observed. The present work further shows that it is possible to anneal the radiation damage and simultaneously to retain the implants in the graphite lattice by means of high temperature implantation (Ti ≥ 450°C) followed by annealing at 2300°C.

Rutherford backscattering spectrometry (RBS) is used to characterize the stoichiometry of graphite intercalation compounds (GIC). Specific application is made to several stages of different donor and acceptor compounds and to commensurate and incommensurate intercalants. A deviation from the theoretical stoichiometry is measured for most of the compounds using this non-destructive method. Within experimental error, the RBS results agree with those obtained from analysis of the (00ℓ) x-ray diffractograms and weight uptake measurements on the same samples.

Graphite fibers with high structural perfection and small diameters (∼1 μm) provide a sensitive medium to study the effect of ion implantation on the transport properties of graphite and to observe the defect structure associated with the implantation process. Graphite fibers prepared from the thermal decomposition of benzene and subsequent heat treatment to high temperatures (∼2900°C) have been shown to achieve the high structural perfection necessary to carry out such experiments. Implantation-induced changes in the fiber resistivity are reported and are found to be larger at low temperature, as expected on the basis of residual resistance arguments. Using the lattice fringe imaging technique of high resolution electron microscopy, the implantation-induced defect structure can be observed directly. The results show local expansion of the interlayer graphite planes, with an interlayer separation ranging up to 3.9 Å in the implanted region, compared with ∼3.4 Å for the well-ordered layers beyond the ion penetration depth.

The use of a hot stage (T ∼ 600°C) for ion implantation into graphite permits the introduction of foreign species into the host material while eliminating most of the lattice damage associated with ion implantation at room temperature. This permits the use of the magnetoreflection technique for examination of changes in the electronic band structure induced by implantation Samples of graphite implanted with 31P and 11B at various energies and fluences are examined, and the in-plane and c-axis disorder are characterized using Raman spectroscopy and Rutherford Backscattering Spectrometer (RBS) techniques. Implantation-induced changes in the electronic band structure are interpreted in terms of the Slonczewski-Weiss- McClure band model. Small changes are found relative to the band parameters that describe pristine graphite.

In the Ionized-Cluster Beam (ICB) technique, deposition by macroaggregates consisting of 500 to 2000 atoms loosely coupled together involves low ratios of charge to mass. Consequently, high mass density beams at low equivalent energy per atom in an optimum range for film formation can be transported without problems due to space charge repulsion forces and deposition onto insulating substrates is easily possible due to low accumulation of ion charge. The presence of ionic charge has great influence upon film formation mechanisms in spite of low content of ions in the total flux. Also, because of the kinetics of cluster breakup upon impact, enhancement of migration of adatoms upon a substrate surface can be achieved by increasing the acceleration voltage. It is possible to control the mechanical, crystallographic, optical and magnetic properties of films over three dimensions by variation of acceleration voltage or ion content in the total flux. Films of many materials have been formed at low temperatures with well-controlled characteristics. Among examples of interest are included metal and semiconductor material films for functional devices and VLSI applications, intermetallic compound films for magnetic or thermoelectric uses and organic material films. Results suggest that ICB offers exceptional potential for applications involving formation of new materials.

In Dynamic Recoil Mixing (DRM) a film of constant thickness is sputtered on to a substrate by using a broad low energy (lkeV) ion beam and is subsequently bombarded by a high energy (10 key) ion beam. During the bombardment process a dynamic balance is maintained between the backsputtering and the deposition of the film, thus providing an ‘unlimited’ source of the dopant material. In this way very high surface dopant concentrations may be achieved which otherwise cannot be reached by more conventional ion beam mixing techniques. Furthermore, by choosing reactive ion species, films of novel chemical compositions may be produced. This technique has been employed to produce silicon nitride films on polished commercial mild steel samples. Measurements of knoop hardness of these films indicate an increase of over 200% whilst the wear and friction properties have shown considerable improvement. Conventionally sputtered silicon films of similar thickness, recoil mixed silicon using argon, or implantation of 10 keV argon and nitrogen to similar doses, indicate only a modest change in tribological characteristic compared to the reactive mixed films.

We describe the structure of Al-N films deposited with N/Al ratios varying from 0 to 1. A dual ion beam system supplies the Al flux by inert ion sputtering, and the N flux by low energy (100–500 eV) N2+ ion bombardment of the growing film. For N/Al < 1, a cermet structure forms with large Al grains mixed with AlN. Above the composition N/Al = 1, excess N is rejected from the AlN. The AlN films show a pronounced change in preferred orientation from c-axis perpendicular to the film surface, to c-axis parallel to the film surface with increasing N2+ energy