Ion-beam irradiation can be used as a processing tool to synthesize metastable materials. A particular case is the preparation of solid solutions from immiscible alloys, which have been achieved for a whole range of systems. In this process, enhanced solute concentration is obtained through the local mixing induced by each irradiation event, which if occurring at a high enough frequency, can outweigh demixing by thermal diffusion. The resulting microstructure forms in far from equilibrium conditions, and theoretical results for these kind of driven alloys have shown that novel microstructures exhibiting self-organization can develop. To test these predictions, we prepare Ag-Cu multilayered thin films that we subject to 1 MeV Kr+-ion irradiation at temperatures ranging from room temperature to 225 °C, and characterize the specimens by x-ray diffraction, TEM and STEM. We observe two different phenomena occurring at different length scales: On the one hand, regardless of the irradiation temperature, grains grow under irradiation until reaching a size limited by film thickness (~200 nm). On the other hand, the distribution of species inside the grains is greatly affected by the irradiation temperature. At intermediate temperatures, a semi-coherent decomposition is observed at a nanometer scale. This nanometer-scale decomposition phenomenon appears as an evidence of patterning, and thus confirms on the possibility of using ion-beam irradiation as a route to synthesize nanostructured materials with novel magnetic and optical properties.

The strain and damage produced on Si substrates by high-dose ion implantation of Si and C is investigated after thermal treatments by double and triple crystal X-ray diffraction, high ressolution transmission electron microscopy (HRTEM) and Secondary Ion Mass Spectrometry (SIMS). Si implantation (180 keV, 5×1015 Si at cm−2) at liquid nitrogen temperature forms a buried amorphous layer. Annealing at temperatures close to 650°C results in epitaxial films with significant defect recovery. X-ray rocking curves show the existence of interference fringes on the left hand side of the 004 Si peak indicating the presence of tensile strained Si layers due to the generation of Si interstitials during the implantation process. C implantation, at 60 keV, 7×1015 cm−2 and 450°C, in the preamorphized Si wafers results in the growth of Si1-yCy epitaxial films with a low amount of substitutional carbon (y≍ 0.1%). Rapid thermal annealing at 750°C results in highly defective epitaxial films with a maximum carbon content close to 0.4%.The high density of defects is responsible for the partial strain relaxation observed in those layers. The amount of substitutional Si also decreases drastically with increasing temperature. Profile fitting of rocking curves using dynamical X-ray theory is used to estimate the C concentration and the strain and disorder profiles of the heterostructures.

The microstructure evolution of aluminum implanted with nickel at 5 MeV and at 100 K to a local concentration of 25 at. % is described. Transmission Electron Microscopy (TEM) observa- tions and Rutherford Backscattering Spectrometry (RBS) experiments are conducted to deter-mine the Ni profile and the microstructure of the implanted samples. For lower Ni concentration, it has been previously observed that Al0.75Ni0.25 amorphous precipitates are formed together with a high dislocation density. When the Ni concentration reaches 25 at. %, a new crystalline multi-layered microstructure is observed: the TEM observations reveal the presence of well-defined crystalline layers separated by sharp interfaces. To our knowledge, it is the first time that such a structure is observed without further annealing of the implanted sample. A series of mechanisms describing the formation of the crystalline multilayer are briefly discussed. It is argued that its formation is the result of a recrystallization front produced by the exothermal amorphous to crystal transformation.

Ion implantation has become a versatile and powerful technique for synthesizing nanometer-scale clusters and crystals embedded in the near-surface region of a variety of hosts. The resulting nanocomposite materials often show unique optical, magnetic, and electronic properties. Here we review some of the principal features of this nanophase materials synthesis technique and discuss the outstanding experimental difficulties that currently hamper the development of devices based on the many unique properties of these nanocomposite materials. Possible solutions to these problems and future research directions are discussed.

200 keV iodine and 400 keV strontium ions have been implanted into YSZ in order to study the effects of fission product incorporation in YSZ as an inert fuel matrix. The ion implantation was conducted at room temperature. The ion fluences reached 1×1021 ions/m2 which gives peak displacement damage levels of ~ 290 dpa for I ion implantation and ~ 200 dpa for Sr ion implantation. The peak concentration reaches ~26 at. % for implanted I ions and ~11.6 at.% for Sr ions. Cross-sectional transmission electron microscopy (TEM) was completed to investigate the microstructure changes caused by the implantation. No evidence of amorphization was detected in both samples although a high density of defect clusters was observed by TEM. Cross-sectional TEM revealed formation of iodine containing voids in I- implanted samples and crystalline precipitates of a few tens of nanometers in Sr-implanted samples after annealing of the implanted sample at 1000°C for 0.5 to 2 hours. The void size increased with increasing annealing time. The nano-crystalline precipitates in Sr-implanted YSZ are isometric SrZrO3 (a≅0.41 nm). The orientation relation between the matrix and precipitates, as determined by selected area diffraction pattern, was: [011]YSZ// [111]SrZrO3 and [200]YSZ// [110]SrZrO3.

Carbon nitride (C-N) thin films were prepared on several substrates by ion-beam-assisted deposition technique. In this experiment, carbon was evaporated by electron beam. Nitrogen and argon ion beams were bombarded simultaneously. Aluminum alloy (7075), high-carbon chrome bearing steel (SUJ2), pure titanium plates (99.5%) and Si(100) wafer were used as substrates. Here, mechanical properties, such as hardness, adhesion, friction coefficient and wear resistance were investigated. These results show the adhesion between the films and substrates were improved by formation of the carbon layer. The microstructure of the carbon nitride films were investigated by cross sectional high-resolution transmission electron microscopy (HRTEM).

Thin layers of metal clusters in silica glass were formed by high dose ion implantation of Ag, Ni and Cu using a metal vapor vacuum arc (MEVVA) ion source. Characterization of the implanted layers was performed using Rutherford backscattering spectroscopy, transmission electron microscopy, x-ray diffraction, and optical measurements. The nonlinear optical properties of the implanted samples were studied by the z-scan method, using a self mode-locked Ti: sapphire laser delivering linearly polarized pulses of 130fs long at a wavelength of 790nm at 76MHz. The variation of the intensity-dependent refractive index n2 with the ion species and the implantation conditions were studied. An n2 value of about 0.6 cm2/GW was measured for one of the Cu and Ni co-implanted samples. The correlation between n2 and the cluster size was also analyzed. Ellipsometry spectra of the samples were measured in the visible range from 0.4 to 0.7 [.proportional]m and in the near infrared range from 0.9 to 1.6 [.proportional]m. Preliminary results are reported on our attempt to deduce the effective complex refractive indices of the implanted layers by fitting of the ellipsometry spectra using a simple single uniform layer on substrate model and the Maxwell-Garnett effective medium approximation.

In this work we investigate the ion beam synthesis of Sn and Sb clusters in thin oxides. 80 keV (fluences of 0.1-1 × 1016 cm−2) Sn implantation in 85 nm thick SiO2, followed by annealing (800-1000°C for 30-300 sec under Ar or N 2 dry ambient) in a rapid thermal processing (RTP) system, leads to the formation of two cluster bands, near the middle of the SiO2 layer and the Si/SiO2 interface. In addition, big isolated clusters are randomly distributed between the two bands. Cluster-size distribution and cluster-crystallinity are related to implantation fluence and annealing time. Low energy (10-12 keV) Sb and Sn implantation (fluences 2-5 × 1015 cm−2) leads to the formation of very uniform cluster-size distribution. Under specific process conditions, only an interface cluster band is observed.

Dynamic Monte Carlo simulations with the binary collision approximation have been applied to the synthesis of hydrogenated amorphous carbon (a-C:H) films by plasma based ion implantation (PBII). We take as representative carbon carriers energetic CH3+ ions and CH3 radicals. The direct chemical incorporation of the radicals, like CH3 reacting with a diamond surface, is too low for the deposition of DLC films, so that the other reaction mechanisms should be responsible. We assumed (a) complete dissociation of CH3+ ions into one C atom and three H atoms with identical velocities upon bombarding the surface, (b) a unity and only one mono-layer sticking of CH3 radicals on the surface, (c) incorporation (stitching) of H and C atoms under the surface induced by binary collisions with energetic CH3+ ions, (d) release of H atoms by the dissociation of CH3 radicals on the surface, and (e) release of a part of displaced H atom after the subsequent collision cascade. We also assumed only the stitched carbon atoms form sp3 states and all other carbon atoms form sp2 states. The effect of the target voltage on the ion dose was also included. The effects of ion/neutral arrival ratio and ion energy on the growth rate, the mixing layer thickness, the hydrogen content, and the sp3/sp2 ratio in the deposited film are presented.

In this study we present the results of Positron Beam Annihilation (PBA) experiments on the gettering of copper in Cz-Si implanted with 33 keV He+ ions with doses ranging from 0.5 to 3× 1016cm−2 followed by an anneal treatment at 1100 K under N2 ambient. For the higher doses this yields a sub-surface layer containing nanometer sized cavities. Copper is introduced into these cavities by diffusing from the backside of the wafer at 1000 K, again under N2 ambient. Mapping of the S and W Doppler broadening parameters, with the implantation dose as running parameter, shows the formation of cavities. After the Cu in-diffusion the change in the values of the characteristic S-W cluster points clearly demonstrates the arrival of Cu at the internal surface of the cavities.

Dilute III-Nx-V1-x alloys were successfully synthesized by nitrogen implantation in GaAs and InP. The fundamental band gap energy for the ion beam synthesized III-Nx-V1-x alloys was found to decrease with increasing N implantation dose in a manner similar to that commonly observed in epitaxially grown GaNxAs1-x and InNxP1-xthin films. The fraction of N occupying anion sites ("active" N) in the GaNxAs1-x layers formed by N implantation was thermally unstable and decreased with increasing annealing temperature. In contrast, thermally stable InNxP1-x alloys with N mole fraction as high as 0.012 were synthesized by N implantation in InP. Moreover, the N activation efficiency in InP was at least a factor of two higher than in GaAs under similar processing conditions. The low N activation efficiency (<20%) in GaAs can be improved by co-implanting Ga and N in GaAs.

Samarium ion implantation was conducted to synthesize Sm-disilicide films on silicon wafers, using a metal vapor vacuum arc ion source and the continuous SmSi2 films were directly obtained with neither external heating during implantation nor post-annealing. Diffraction and surface morphology analysis confirmed the formed Sm-disilicilde films were of a fine crystalline structure under appropriate experimental conditions. Besides, the formation mechanism of the SmSi2phase is also discussed in terms of the temperature rise caused by ion beam heating and the effect of ion dose on the properties of the SmSi2films.

H+-implantation is the basis for an ion-cut process, which combines hydrophilic wafer bonding, to produce heterostructures over a wide range of materials. This process has been successfully applied in Si to produce a commercial silicon-on-insulator material. The efficacy of implantation to produce thin-film separation was studied by investigation of H+-induced exfoliation in Si and SiC. Experiments were done to isolate the effects of the hydrogen chemistry from that of implant damage. Damage is manipulated independently of H+ dosage by a variety of techniques ranging from elevated temperature irradiation to a two-step implantation scheme in Si, and the use of channeled-ion implantation in SiC. The results will demonstrate that such schemes can significantly reduce the critical dose for exfoliation.

Efficient infra-red and visible electroluminescence(EL) has been obtained from implanted rare earth ions in the SiO2 of a silicon-metal-oxide-semiconductor (MOS) diode structure at room temperature. The rare earth ions are excited by the direct impact of hot electrons tunneling through the oxide at electric fields larger than 6 MV/cm. The internal quantum efficiencies of Er and Tb implanted MOS diodes are estimated to be 10 % and 3 %, respectively. The hgh quantum efficiency is due to the high impact excitation cross-section of more than 10− 15cm2. These observations on MOS structures are an experimental proof for efficient light generation by hot electron impact.

The electrical and optical properties of hydrogenated amorphous silicon-carbide alloy films (a-Si1-xCx:H), modified by Fe+ ion implantation (D = 1×1016 - 1×1017 cm-2), have been investigated. Optical transmission spectra have been measured in the visible range (400-900 nm) and considerable absorption edge shift to the longer wavelength region has been registered, together with well-defined decrease of transmittance in the whole measured range. These effects are increased with the dose and are similar for samples with different carbon content (x1=0.08 and x2=0.15). Room temperature (RT) surface electrical conductivity is also increased by Fe+ implantation and the effect is most pronounced for the highest doses (D ~ 1017cm-2). The temperature dependence of the conductivity was measured in the temperature range from RT to 250 oC. The activation energy is considerably reduced and the effect is again strongest for the highest doses. From the above results we conclude that high doses Fe+ implantation in a-Si1-xCx:H affects both the localised states deep in the gap and the shallow states in the band tails.

Aluminum nitride (AlN) thin films were prepared by ion-beam assisted deposition method, and the influence of the nitrogen ion beam energy on their microstructure and mechanical properties was studied by changing the ion beam energy from 0.1 to 1.5 keV. Films prepared with a low-energy ion beam show a columnar structure, while films prepared with a high-energy ion beam show a granular structure. The film hardness is found to decrease with increasing nitrogen ion beam energy. It is also found that the film hardness does not change drastically after annealing in nitrogen atmosphere at 500 °C, yielding the residual stress relaxation. It is proposed that the film hardness is dependent on the film microstructure, which can be controlled with the nitrogen ion beam energy, rather than the residual stress in the films.

Most studies of Si nanocrystals ion beam synthesized in SiO2 have shown that a link exists between the observed physical properties and the characteristics of the « populations » of nanoparticles (size-distribution, density, volume fraction). Nevertheless, the direct measurement of these parameters by Transmission Electron Microscopy (TEM) is very difficult and predictive simulations are essential to make the kinetic study complete. This paper presents atomistic simulations aimed at predicting the kinetic evolution of the Si nanoparticles during annealing, taking into account eventual interaction effects. The theoretical results are compared to TEM measurements of the size-distributions observed after high temperature annealing. Experimentally, the growth of these nanoparticles is very slow but their size significantly increases when increasing the initial Si excess. Simulations are in agreement with these experimental results only when taking into account possible interactions between neighboring particles for initial supersaturations larger than 10 at. %.

We present recent results using ions such as C., O, Si, Fe, Zn, and Au at energies between 100 keV to 10 MeV to increase the roughness and porosity of the partially and fully cured precursor phenolic resins. The fully cured phenolic resin is called Glassy Polymeric Carbon (GPC). GPC is chemically inert, biocompatible and useful for medical applications, such as heart valves and other prosthetic devices. Ion implantation enhances biological cell/tissue growth on, and tissue adhesion to, prosthetic devices made from GPC. We have previously shown that increased porosity of GPC is also useful for drug delivery devices. The porosity of the ion implanted partially and fully cured precursor phenolic resins was measured by introducing lithium from a molten LiCl salt into each sample. By using Li(p,2α) nuclear reaction analysis (NRA) we measured the concentration of Li retention in the pre- and post-implanted samples. The surface roughness was measured using optical microscopy. The curing process was monitored using micro-Raman microscopy. We have correlated the NRA measurements of increased pore availability with the observations of increased surface roughness.

Physical properties of multiple-energy B-ion implanted C60 thin films were investigated for various doses. Fourier Transform Infra-red Spectroscopy (FTIR) results indicate the structural transformation of C60 to amorphous carbon phase during implantation. The conductivity type of the implanted films is found to be p-type and the conductivity measurements reveal a dramatic increase in the conductivity with ion implantation. Temperature dependent conductivity shows the semiconducting nature of the B-ion implanted films. The optical absorption coefficient and optical gap of the implanted films have been observed as a function of B-ion dose. Measurements on implanted films subjected to thermal annealing indicate the removal of the defects caused during the implantation. Ion implantation-induced defects are found to partially annihilate with the annealing temperature. Electrical conductivity and optical gap are determined in the post-implanted films. The observation of the systematic increase in the conductivity of the annealed films is due to the removal of the defects and the formation of defect free boron impurity acceptor.

Plasma based ion implantation (PBII) with bipolar high voltage pulses has been proposed to improve a dose uniformity in an ion implantation on a three-dimensional target. A pulsed glow discharge plasma is produced around the target by a positive high-voltage pulse, and then ions are implanted into the target from all sides by the subsequent negative high-voltage pulse. A time resolved plasma density and the spatial profiles of the pulsed glow discharge plasma are measured by a Langmuir probe in a boxcar mode, and diamond like carbon (DLC) films are deposited under optimal conditions of the pulsed plasma. It is shown that the PBII with bipolar pulses is a useful method in depositing DLC films on the three-dimensional target. A carbon ion implantation procedure results in the enhanced adherence of DLC coating to the target, and the enhanced adhesion is due to a graded carbon interface produced by carbon implantation.