The effects of film morphology (mosaic- or bamboo-like grain structures) and of He bubbles on the redistribution of Cu, as well as on the formation of Al-Cu precipitates in 200 nm thick Al/SiO2 films similar to microelectronic device interconnects, are investigated using Rutherford backscattering spectrometry, elastic recoil detection analysis and transmission electron microscopy. As-deposited and pre-annealed Al films were implanted with Cu and/or He ions forming concentration profiles located 100 nm below the surface and with peak concentrations of about 3 at.%. It is shown that grain boundaries and/or He bubbles can affect the vacancy fluxes inside the grains and reduce or even inhibit the Cu redistribution as well as the nucleation and growth of θ and θ′ Al-Cu precipitates during post-implantation annealings at temperatures from 473 to 553 K. It is also shown that mosaic-like grain structures allow the control of grain size distribution within the 25 to 1500 nm size range, thus providing an additional microstructure engineering tool to improve device reliability against electromigration failures.

The deposition of a thin film on a substrate surface can be achieved with a wide variety of techniques. Deposition using low energy ion beams is not a common technique, but it yields promising features, due to the hyperthermal nature of the deposited ions. With low energy ion deposition, it is possible to grow films with good characteristics at significantly lower temperatures compared to thermal deposition. The quality of these films critically depends on the energy of the impinging ions. We investigated the influence of the energy on the surface morphology for the deposition of Co onto Si(111). The roughness of this surface decreases significantly when the ion energy is increased, until it reaches a minimum at 25 eV. When the ion energy is further increased, the surface roughness increases again. This behavior can be explained by taking into account the interplay between the beneficial and detrimental effects due to the ion energy. Beneficial effects such as enhanced mobility and improved layer-by-layer growth cause a decrease in surface roughness when the deposition energy is increased from thermal to 25 eV. For energies above that value, undesirable effects such as defect creation and pileup dominate, leading to an increase in surface roughness. This study shows that low energy ion deposition can be used to improve the surface quality of a thin film by choosing the optimal deposition energy.

A magnetic nanocomposite material has been obtained by dispersing ball milled magnetic nanoparticles of barium ferrite within a styrene- isoprene- styrene block copolymer, sonicating the solution, and spin coating it onto a quartz crystal. Ferromagnetic resonance spectra of pristine and irradiated magnetic nanocomposites are reported. Although the flux of incoming protons was not large, modifications in the ferromagnetic resonance spectra were noticed. This suggests that the future ultra high-density media would present an enhanced sensitivity to the radiation component of the space environment.

The nuclear microprobe facility of the Italian National Laboratories of Legnaro was used for an Ion Beam Induced Charge Collection (IBIC or IBICC) experiment which measured the charge collection of a 4H-SiC Schottky diode irradiated with 2 MeV He+ at increasing doses. The experiment was arranged so as to obtain a statistics of about 1400 events per each He+ ion from the 1st to the 500th one on the ion microprobe spot (1.5 × 1.5 μm2). These figures correspond to He+ fluence values in the range 107−1011 ions/cm2. The charge collection of the diode was almost constant from the 1st to the 10th He+ ion, i.e. up to a fluence of 109 ions/cm2, and then monotonically decreased for the subsequent ions. The SiC device collection efficiency was modelled by representing the electrical effects of the damage produced by ions as a planar interface region of given carrier recombination velocity at the depth of the damage peak. Experimental and computed data scale one to the other assuming that the interface recombination velocity and He+ fluence are linearly related.

We have demonstrated position controlled GaN nano structures with a combination of surface treatments and nucleation sites control assisted by low energy focused ion beam. Ga ions in the range of 100 eV - 10 keV were irradiated onto the surface of the As-terminated Si (100) to create the nucleation sites. The deposited Ga atoms migrated on the surface and were trapped at the nucleation sites to form Ga droplets. Subsequently an excited atomic nitrogen source was supplied to the surface. By SEM observation, the GaN microcrystals of diameter about 800 nm were found to be allocated every 2 μm periodically on the substrates, and cathodoluminescence peaks from GaN nano structures were observed.

A size-selected gas cluster ion beam (GCIB) system has been developed to study the size effects of energetic large cluster ion bombardments on a solid surface for the first time. This system equipped a permanent magnet with a magnetic flux density of 1.2 T. There is a sliding detector and sample holder on a guiding rail perpendicular to the incoming cluster beam axis. By locating a sample at a certain position, particular size of cluster ion can be irradiated continuously with affordable ion current density. When the total acceleration energy of Ar-GCIB was 5keV, both amorphous and oxide thickness on Si substrate increased with decreasing cluster size. This result showed good agreement with that obtained from molecular dynamics simulations.

TiNi shape memory alloy samples were irradiated within R-phase by 1.7 MeV electrons with different doses. The martensitic transformation temperatures were measured by Differential Scanning Calorimeter (DSC). The results indicated that the temperature M s of the onset of R-phase-to-martensite transformation decreased with increasing the dose. The electron irradiation had a slight effect on the other transformation temperatures. The second lifetime of positrons determined by Positron Annihilation Technology were lowered with an increment of the irradiated dose. Relaxation of the elastic stress fields around the Ti3Ni4 precipitates was the cause of the observed change of the transformation characteristics because of the migration and accumulation of electron irradiation-induced point defects.

Focused Ion Beam (FIB) systems employ a finely focussed beam of positively charged ions to process materials. Ion induced charging effects in non-conductive materials have been confirmed using Scanning Surface Potential Microscopy (SSPM). Significant localized residual charging is observed within the ion implanted micro-volumes of non-conductive materials both prior to and following the onset of sputtering. Characteristic observed surface potentials associated with the resultant charging have been modelled, giving insight into the charging processes during implantation and sputtering. The results of this work have implications for the processing and microanalysis of non-conductive materials in FIB systems.

Positron lifetime spectroscopy was employed to study the as-electron-irradiated (10 MeV, 1×1018 cm-2) n-type 6H silicon carbide sample in the measuring temperature range of 15 K to 294 K. Isochronal annealing studies were also performed up to the temperature of 1373 K by carrying out the room temperature positron lifetime measurement. Negatively charged carbon vacancies and VCVSi divacancy were identified as the major vacancy type defects induced by the electron irradiation process. The concentration of the VCVSi divacancy was found to decrease dramatically after the 1973 K annealing.

The effects of helium implantation parameters and heating schemes on the formation of surface porosity have been studied. Confinement of the implanted helium by a coating on the metal leads to a prolonged development of the bubble structure. Finally, delamination and blistering occurs and rather open surface structures remain.

Electron beam co-irradiation graft polymerization has been carried out up to an absorbed dose of 30 kGy in air at room temperature between methyl methacrylate (MMA) monomer and γ- Al2O3 nanoparticles and micronparticles, respectively. The results showed that the percent graft of nano-Al2O3 and micron-Al2O3 is 6.4% and 0.9%, respectively. In the FT-IR spectra of irradiated nanoparticles, there was a new absorption peak at 1725 cm-1 that was attributed to carbonyl stretching vibration and Al-O-C bonds forming on the surface of nanoparitcle. But in the spectra of micron-Al2O3, the absorption peak at 1725 cm-1 was very weak. X-ray photoelectron spectroscopy (XPS) measurements confirmed the existence of carbonyl. The UV absorption intensities of two γ- Al2O3 powders strengthened after irradiation graft polymerization. These results showed that MMA has been successfully grafted onto nano-Al2O3 surface at the dose of 30 kGy. However, there were few new chemical bonds on micron-Al2O3 surface. It could be deduced that irradiation graft polymerization of γ- Al2O3 nanoparticles was easier than that of micronparticles.

The results of high-resolution solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) indicate the bond angles of Al-O-Si decrease with the increase of neutronirradiation dose, but there are only minor changes for Si-O-Si bond angles in the current dose range studied. This suggests that zeolite with higher Si/Al ratio is more resistant to neutron irradiation damage. It is also found that [AlO6] formed at higher dose range. The ratio of Si/Al changed from 2.57 before neutron irradiation to 2.76 when the dose reached 2.25×1019 n/cm2, which shows that mild dealumination occurred during neutron irradiation. The strontium ion exchange experiments have been conducted for neutron irradiated, thermally treated and original zeolite samples, respectively. It is found that the ion-exchange ability of neutron-irradiated zeolite-NaY is between those of original and heat-treated zeolite samples. The distortion of the framework under neutron irradiation by the decrease of Al-O-Si bond angles and the formation of [AlO6] is partially responsible for the ion-exchange variability variation of zeolite-NaY.

Crystalline damage created by ion-implantation of dopant impurities in ZnO (0001) substrates was characterized as a function of atomic mass of implanted species using triple-axis (2θ-ω/ω) x-ray diffraction and Rutherford backscattering (RBS). The former revealed the presence of implantation-induced strain through the broadening of the isometric and asymmetric 2θ-ω reflections. However, RBS indicated that the damage introduced during implantation of these ions was insufficient to transform the crystalline lattice into a completely amorphous state. Additional XRD characterization as a function of annealing temperature of the implanted materials showed a reduction in the broadening of the isometric reflections, indicating that structural recovery of implanted ZnO crystals can be achieved.

Scalability and performance of current flash memories can be improved substantially by novel devices based on Multi-Dot Floating Gate MOSFETs. The multi-dot layer in the very thin gate oxide can be fabricated CMOS-compatibly by ion beam synthesis (IBS). Here, we present both experimental and theoretical studies on IBS of multi-dot layers consisting of Si nanocrystals (NCs). The NCs are produced by ultra low energy Si+ ion implantation, which causes a high Si supersaturation in the shallow implantation region. During post-implantation annealing, this supersaturation leads to phase separation of the excess Si from the SiO2. Till now, the study of this phase separation suffered from the weak z contrast between Si and SiO2 phases in Transmission Electron Microscopy (TEM). Here, this imaging problem is solved by Energy Filtered Scanning Transmission Electron Microscopy (EFSTEM). Additionally, kinetic lattice Monte Carlo simulations of Si phase separation have been performed and compared with EFSTEM images. It has been predicted theoretically that the morphology of the multi-dot Si floating gate changes with increasing ion fluence from isolated, spherical NCs to percolated spinodal Si pattern. These patterns agree remarkably with EFSTEM images. However, the predicted fluence for spinodal pattern is lower than the experimental one. Because oxidants of the ambient atmosphere penetrate into the as-implanted SiO2, a substantial fraction of the implanted Si is lost due to oxidation.

Diffuse elastic scattering of electrons by single nanometer-sized defects in ion irradiated Au has been measured quantitatively. Results are given for two dislocation loops and compared with published calculations to establish the loop geometry and interstitial or vacancy nature. Defect images using only diffuse scatttering are achieved with high sensitivity and good resolution by a hollow-cone dark-field method.

We developed a new scheme, namely ion beam manipulation, i.e. interface-assisted ion beam mixing, for fabricating amorphous alloys and artificial solid-state microstructures in metal-metal multilayers, in which the individual layer thickness is down to about 2 nm, differing significantly from the typical thickness of 5–8 nm in conventional ion beam mixing. Employing the scheme, some interesting results were obtained in three highly immiscible systems. In the Ag-W system, which has the largest positive heat of formation among the transition metal alloys, amorphous alloys were obtained, for the first time, through a two-step structural transition, i.e. the initial polycrystalline Ag and W transformed into an intermediate bcc phase, which later transformed into an amorphous state. In the Ru-Pd system, the initial polycrystalline Pd and Ru first transformed into a single crystalline FCC phase, and then turned into a well-ordered structure, which showed an apparent tendency to transform back to the FCC phase upon over-irradiation. In the Ag-Co system, an ordered layered structure was observed and identified to consist of two overlapped FCC lattices, corresponding to a new magnetic state of Co atom with an average magnetic moment measured to be 2.84 μB, which was about twice the equilibrium datum and was the largest value ever observed. We present, in this paper, a brief review concerning the scheme of ion beam manipulation in fabricating the metastable alloys, the structural evolution upon ion irradiation and the associated magnetic properties of some ordered structures obtained by the scheme.

The effects of electron irradiation on the defects associated electronic levels in Schottky diodes on 4H silicon carbide epilayers grown by chemical vapour deposition were investigated by Deep Level Transient Spectroscopy (DLTS) and Capacitance-Voltage (C-V) characteristics. These investigations were performed before and after irradiation with 8.6 MeV electrons at different doses. After irradiation four new traps with enthalpies equal to (Ec-0.23 eV), (Ec-0.39 eV), (Ec-0.63 eV) and (Ec-0.75 eV) were detected. Their thermal stability, a key point to determine their structure on the basis of recent theoretical and experimental results, was carefully investigated since it was earlier observed that during DLTS temperature runs up to 500 K a slight but significant recovery of a few irradiation-induced levels occurs. This effect was previously observed in literature for the level (Ec-0.70 eV) after thermal treatment at 500 °C [1], but the present results indicate that it involves more than a single level and is also effective at lower temperature. DLTS analyses were also performed from room temperature to liquid nitrogen temperature and vice versa up to 500 K.The annealing kinetics is reported and a few conclusions on the structure of the defects involved in the recovery are drawn. The correlation with the diode charge collection efficiency is also reported.

Experimental and computational results on ion-beam-induced defect production, damage accumulation, and thermal recovery in SiC are reviewed. The accumulation and recovery of disorder on the Si and C sublattices have been determined experimentally by ion-channeling methods. Atomic-level simulations are used to determine defect production, cascade-overlap effects, and defect migration energies. Energetic Si and C collision cascades, with energies up to 50 keV, primarily produce single interstitials, mono-vacancies, antisite defects, and small defect clusters. Overlapping of Si and C cascades results in the interaction of defects and clusters that stimulates cluster growth and produces long-range structural disorder. For energetic Au cascades, nanoscale amorphous clusters are produced directly within about 25% of the Au cascades, along with point defects and smaller clusters. The disordering behavior and the changes in volume and elastic modulus obtained experimentally and from molecular dynamics simulations are in good agreement, thus providing atomic-level interpretation of experimentally observed features. Simulations of close-pair production and recombination in SiC indicate that the activation energies for recombination of most close pairs range from 0.24 to 0.38 eV. Multiaxial channeling measurements indicate annealing below 300 K results in relaxation of some interstitials to lower-energy configurations. Long-range migration energies for interstitials and vacancies have likewise been determined by computational methods.

Using a focused ion beam (FIB), secondary electron (SE) imaging of n-wells under oxide from the backside of thinned integrated circuits without electrical bias was accomplished. From the backside, the n-wells were initially observed at a remaining silicon thickness ∼4.5μm, which correlates to the actual implant depth where n and p carrier concentrations are equal. When the wells were FIB imaged, contrast appeared dark relative to the p substrate. During deposition of the oxide film, the n-well brightness changed from dark relative to the p-substrate, to bright. It appears that initially during this deposition step the interaction volume of the beam reached the silicon/oxide interface to create tunneling electrons. This phenomenon dominated the capacitive effect. Then as the film thickness increased the capacitive effect prevailed. The imaging structure is analogous to a Metal-Oxide-Semiconductor (MOS) capacitor. The n- and p-MOS capacitive properties yielded a permanent imaging contrast. At an optimized oxide thickness (130nm), the n-wells appear white relative to the p-substrate with a contrast up to 85% {(Ip-substrate − In-wells)/(Ipsubstrate + In-wells)}.

A new method for the acceleration of MD (molecular dynamics) simulation of ion implantation into crystalline targets is presented, named REACE (Rare Event Algorithm with Cascade Effect). This method can speed up the MD simulation of ion implantation with cascade processes. As a result, the time required to perform a simulation with high precision and dose effect is drastically reduced. And many details producing statistical noise in the simulation are simulated in the REACE and help it to be more reasonable and reliable.