Thin foils of Zircaloy-4 were irradiated with 350 KeV 40Ar ions in the dual ion beam/HVEM facility at Argonne National Laboratory at 300 – 650 K. The irradiation-induced araorphization of the intermetallic precipitates Zr (Cr, Fe)2 and Zr2 (Ni, Fe) was studied in situ. For Zr (Cr,Fe)2 precipitates the dose-to-amorphization was found to increase exponentially with temperature, with a critical temperature of about 650 K. The amorphization morphology was shown to be homogeneous, with no preferential site for nucleation, in contrast to neutron-irradiation amorphization which started at the precipitate-matrix interface. For Zr2 (Ni,Fe) precipitates it was found that amorphization occurred at 550 K and 600 K, whereas in neutron irradiation no amorphization has been observed at those temperatures. The results are discussed in the context of the previous experimental results of neutron and electron irradiation and likely amorphization mechanisms are proposed.

Single crystals of Ca2La8(SiO4)6O2 were irradiated with 1.5 MeV Xe+, 1.5 MeV Kr+, 1.0 MeV Ar+ and 0.8 MeV Ne+ ions to investigate the effects of recoil-energy spectrum, temperature, and crystallographic orientation on irradiation-induced amorphization. The irradiations were carried out using the HVEM-Tandem Facility at Argonne National Laboratory. The structural changes and the ion fluence for complete amorphization in the electron transparent thickness of the specimens were determined by in situ transmission electron microscopy. The displacement dose determined for complete amorphization was approximately 0.6 dpa for the Xe+, Kr+, and Ar+ ion irradiations but increased to 1.4 dpa for the Ne+ ion irradiations, which may reflect an effect of lower recoil energies. The ion fluence for complete amorphization increased exponentially with temperature over the range from 25 to 400°C. Amorphization was not observed at 500°C. The activation energy associated with this simultaneous annealing process was estimated to be 0.13 eV, and the critical amorphization temperature was estimated to be 438°C for the 1.5 MeV Kr+ irradiations.

We have studied by XTEM the kinetics of Si amorphization by light ion implantation (He) as a function of substrate temperature. The analysis of these kinetics has been performed within the framework of the “Critical Damage Energy Density” model which is shown to apply for temperatures up to 250 K. There is a drastic change in the efficiency of the amorphization process at about 175 K. These results are discussed and explained by considering the different types of defects (I, V, I2, V2, complexes…) that can be stabilized in c-Si depending on the temperature. Above 150 K, the amorphization proceeds through the accumulation of interstitials and vacancies while at higher temperature it proceeds through the accumulation of di-interstitials and di-vacancies left in the network after annihilation and recombination of the Frenkel pairs created by the bombardment.

Si (001) wafers were implanted at room temperature with 50-keV Fe ions to different doses and subsequently crystallized either by rapid thermal annealing (RTA) (900°C, 120 s) or by Si+ irradiation (500 keV, 320 °C). Transmission electron microscopy, as well as Rutherford backscattering and channeling, were used to study the phase formation of FeSi2 in Si. Depending on the implantation dose and the crystallization process, three phases of FeSi2 were produced. While RTA results in the formation of β-FeSi2, ion irradiation promotes the growth of either cubic FeSi2 phase for low implantation doses (< = 4 at.% Fe) or a-FeSi2 for high implantation doses (≈18 at.% Fe). All these phases of FeSi2 were found to grow epitaxially in the Si matrix and their orientation relationships relative to Si have been determined. The interfacial energy between FeSi2 and Si appears to be an important factor in determining the final structure of FeSi2.

The effects of Si and Kr ion implantation on the crystallization kinetics of amorphous COSi2 have been investigated by differential scanning calorimetry and in situ sheet resistance measurement. Without ion implantation, the crystallization of coevaporated COSi2 is characterized by three dimensional growth from preexisting nuclei. When the as-deposited COSi2 is implanted with Si or Kr ions at liquid nitrogen temperature, the kinetics of the subsequent crystallization is significantly altered. A 180 keV 5×1015 cm−2Si ion implantation increases the crystallization temperature by 34°C. When the Si dose is below 1×1015 cm−2, ion implantation causes a sharp decrease in the crystallization kinetic parameter defined by the Avrami equation. The amount of decrease is shown to scale with the deposited nuclear energy. At higher doses, the kinetic parameter continues to decrease with increasing dose but at a much reduced rate.

By first growing NiSi2 precipitates in a-Si and then irradiating with a 150 keV Si beam, we have studied ion beam induced epitaxial crystallization (IBIEC) of Si initiated at a-Si/NiSi2 precipitate interfaces. The growth shape and its temperature dependence are studied in-beam via in situ transmission electron microscopy. Interface roughening is evidenced. Preliminary results for the Co-Si system are also reported.

The crystallization of Sn-implanted amorphous silicon was studied as a function of tin implant dose and annealing conditions by transmission electron microscopy. The films were implanted at an energy of 110 keV with a dose in the range of 5 × 1014 to 5×1016 cm−2 and were annealed at a temperature in the range of 450°C to 550°C. An enhanced rate of crystallization in amorphous Si-Sn films compared to the non-implanted amorphous silicon films during thermal annealing was observed. The crystallization process of Si films implanted with tin at a dose of 2.5×1016 cm−2 or less is very similar to unimplanted silicon films except higher nucleation rates and shorter crystallization time were observed with increasing tin dose. Films implanted with tin at a dose of 2.5×1016 cm−2 or more display extremely rapid crystallization (3 hours at 450°C) and very fine grain structure (10 nm); no substantial grain growth has been observed during lurther annealing, but some single crystal-like areas were formed. In-situ annealing of silicon implanted to 5×1016 cm−2 showed that the crystallization process is enhanced by the formation of the liquid tin phase.

Single crystals of Pb2P2O7 (beam stable under 200 kV TEM electrons to a fluence > 1027 e/m2 and an ionizing dose > 1014 Gy) were rendered metamict (amorphized) with ion-implantation (100 kV P+ ions with several fluences. Pb2P2O7 and PbO·P2O5 glasses were also ion implanted at identical fluences. Radial distribution functions of metamict and glassy phosphates are being generated using energy filtered electron diffraction (EFED) data collected on 100 kV field emission STEM (VG HB-5). Ion-implanted lead phosphate glasses exhibit a significant difference in their FSDP as compared to the non-irradiated ones. XTEM results also show that ion-beam damage layer was around 200 nm deep. XTEM-HREM structure images of ion-implanted single crystals, along with their optical diffraction analysis will be presented and briefly discussed.

We have recently demonstrated the ability to focus a 50-keV Ga+ beam to an 8-nm-diameter spot diameter. This ultra-high resolution probe has been used to study the resolution limits of conventional resists for focused-ion-beam lithography. Lines and dots in poly (methylmethacrylate) resist as small as 7–8 nm have been formed with high throughput. In addition, no proximity effects have been observed for 25 to 30-nm size features on high-z substrates. However, for the smallest geometries obtainable, the pattern fidelity and resolution are most likely limited by ion scattering effects and statistical dose fluctuations. The use of lighter ions (such as He, Li, or Be) with lower sensitivity resists should, in principle, allow focused-ion-beam lithography to be extended to the sub-5 nm regime.

Focused ion beam (FIB) techniques have many advantages which stem from being maskless and have attracted much interest for various applications including in situ processing. However, reduction of damage and improvement of throughput are problems awaiting solution. For reduction of damage, low energy FIB is promising and for improvement of throughput, understanding of the basic processes and optimization of process parameters based on this understanding is crucial. This paper discusses characteristics of low energy FIB system, ion beam assisted etching and ion implantation, and effect of damage with putting emphasize on in situ fabrication. Low energy (0.05–25keV) FIB system being developed forms -lOOnm diameter ion beams and is connected with molecular beam epitaxy system. Many results indicate that low damage, maskless ion beam assisted etching is feasible using low energy beams. Recently it was also shown that for ion beam assisted etching of GaAs, pulse irradiation yields very high etching rate of 500/ion. This indicates that the optimization of the relative ratio of ion irradiation and reactant gas supply as important to achieve high etching rate. Low energy FIB is also important for selective doping for high electron mobility heterostructures of GaAs/GaAlAs, because high mobility is significantly degraded by a slight damage.

In-situ processing requires totally dry approaches to pattern generation to be developed. Of particular interest are beam driven reactions that can be localised without prior masking. This paper considers the adsorption - desorption characteristics of chlorine, dichloroethane and sulphuryl chloride on GaAs(lOO). The surface reactivity in these systems is seen to vary considerably. The implications of this are considered with regard to their use as chemically assisted ion beam and laser photochemical etching gases.

Tungsten is emerging as the absorber material of choice for x-ray masks due to recent advances in the deposition of low stress films. For a practical technology, the masks must be free from defects. These defects may be in the form of excess or missing absorber. Finely focused ion beams have been used for defect repair on x-ray masks, both for removal of excess absorber material by physical sputtering and for addition of absorber material by ion-induced deposition. The eifect of ion channeling in polycrystalline tungsten films is spatially nonuniform material removal during sputtering. Different grains will have significantly different sputtering yields, depending on their orientation with respect to the direction of the ion beam. The repaired features then suffer from roughness on the bottoms and sidewalls of the sputter craters. We have investigated the use of XeF2 assisted sputtering with a 20 keV Ga+ focused ion beam to reduce this roughness. The chemical etching component of the material removal lessens the directional dependence and therefore the roughness during defect repair. It was also found that chromium etch rate was reduced in the presence of XeF2 gas while the etch rate of W was enhanced so that the removal rate of Cr is much less than that of W. We can take advantage of this etch selectivity by using a thin Cr layer under the W absorber as an etch stop layer to eliminate the roughness at the bottom of the features and a thin layer of Cr on top of the W as an etch mask for reducing the sidewall roughness.

We report the realization of free standing 3D structures as tall as ∼ 7μm with nano-scale thickness in Si using the technique of Ga focused ion beam implantation and sputtering followed by wet chemical etching. Some of the previously investigated subjects such as anisotropie etching behavior of crystalline Si and etch stop effect of Ga+implanted Si etched in certain anisotropie chemical etchants have been further explored with the emphasis on exploiting them in realizing free standing structures. The design and fabrication considerations in achieving such free standing structures are discussed and some typical structures fabricated by this technique are shown.

Nano-scale Ga dots are deposited through the decomposition of triethylgallium (TEGa) adsorbed on HF-treated Si(111) surfaces using a scanning tunneling microscope (STM). The deposition of Ga dots of 2–13 nm in diameter is achieved by applying a negative voltage pulse to the sample, while no deposition is observed when a positive voltage pulse is applied. The conditions for Ga deposition are systematically investigated by varying the gap conductance, pulse height, and pulse width. A tentative model for the mechanism of Ga deposition is proposed, in which TEGa molecules are decomposed by the electric field between the tip and the sample.

In earlier low-energy ion scattering experiments of 6 keV Ne ions on Cu(100), Cu adatoms were observed to appear on the surface. The number of produced adatoms per incoming ion was found to decrease to 50% of its initial value of 3.5 after prolonged irradiation. In this paper we present calculations of the adatom production as a function of irradiation dose. From a comparison with the experimental data, the trapping radius of a vacancy was determined to be 5.4 ± 0.9 Å, in agreement with values reported in the literature.

XPS analysis was used to characterise GaAs, Al0.4Ga0.6As and Al0.8Ga0.2As targets bombarded with an O2+ beam ranging from 1 keV to 5 keV. The bombardments were carried out at different angles of incidence from 0° to 60°. In all cases a strong preferential sputtering of arsenic gives rise to an As-depleted altered layer, formed by a mixture of gallium, arsenic and aluminium oxides with metallic gallium and arsenic. Aluminium and gallium are preferentially oxidized, a fact that correlates with the corresponding heat of formation of the oxides, whereas the arsenic oxidation requires a minimum incorporation of oxygen into the matrix. For all experimental conditions a considerably lower oxidation level has been observed in every case as compared to the IBO of silicon.

Fluoroboron (BF2+) ion implantation into silicon is frequently used for fabrication of shallow junctions. For scaling down of the junction dimensions, one of the efficient approaches is to lower the implantation energy. This work reports fluoroboron ion interactions with (100) oriented silicon at 10 to 500 eV ion energy. Ion bombardment was carried out using a mass-separated BF2+ ion beam in an ultrahigh vacuum low energy ion beam system. The temperature of the silicon crystal during bombardment was kept either at room temperature or 500°C. The reactions (both etching and incorporation) were characterized by x-ray photoemission spectroscopy (XPS), Rutherford backscattering (RBS) and Raman scattering. The results show that BF2+ ions dissociated on the silicon surface at an energy as low as 10 eV and most of fluorine segregated to the surface and desorbed. Both the physical and chemical etching rate of the beam were energy dependent but much lower than the accumulation rate. For beam fluences higher than 1 × 1018/cm2, continuous amorphous boron films were deposited on silicon.

The diffusivity of Au in sputter-deposited amorphous Pd80Si20 has been measured by Rutherford backscattering spectrometry (RBS) between 275°C and 380°C. A new method based on scaling of the evolution of the variance of the concentration profile was used to analyze the data. The diffusivity was found to be independent of the Au concentration below 3 at.%. Structural relaxation causes a time dependence that is evident at short times. The kinetics of this relaxation can be described by the bimolecular relaxation model used in the analysis of viscous flow.

Photo-assisted epitaxy is a versatile growth technique which allows in situ modification of surface chemical reactions. Under appropriate growth conditions the surface stoichiometry can be tuned by selectively desorbing surface species, or by decomposing particular molecular species, or by affecting the reaction rate constant of a chemical process. A potential application of laser-assisted growth rate enhancement or growth rate retardation is in the area of maskless selective area epitaxy. We have investigated the effect of photons on the growth of ZnSe by solid and gaseous source molecular beam epitaxy using various combination of sources. Significant growth rate enhancement (up to 20x), as well as growth rate suppression (as much as 70%), have been observed depending on the sources employed. In all cases, the laser power density remained low (∼200 mW/cm2), and the creation of photo-generated carriers was found to be required. An electron beam incident to the surface has a similar effect and increased the growth rate.

i-CxSiyOzHw films were formed by thermal evaporation of a tetraphenyl-tetramethyl-trisiloxane diffusion pump oil onto silicon and steel substrates with simultaneous bombardment of the growing film with 40 keV Ar+ ions to decompose the (C6H5)4(CH3)4Si3O2 molecules. Both the current density of the ion beam and the oil arrival rate were varied to produce hard, adhesive films on room temperature substrates, with densities ranging from 1.4 to 2.3 g/cm3 and Knoop microhardness values (at 15 g load) from 1000 to 2100. Unlubricated friction coefficients against a 440C steel ball with a 50 g load ranged from 0.03 to 0.40, depending on deposition conditions, and all films were more wear-resistant than the substrate materials. The films were examined with RBS, hydrogen forward recoil scattering, SEM, TEM, photon tunneling microscopy, electron diffraction, and ellipsometry to ascertain and correlate their chemical compositions and microstructures with their mechanical/chemical properties (microhardness, adhesion, friction and wear).