Computer simulation is a major tool for studying the interactions of swift ions with solids which underlie processes such as particle backscattering, ion implantation, radiation damage, and sputtering. Numerical models are classed as molecular dynamics or binary collision models, along with some intermediate types. Binary collision models are divided into those for crystalline targets and those for structureless ones. The foundations of such models are reviewed, including interatomic potentials, electron excitations, and relationships among the various types of codes. Some topics of current interest are summarized.

The interaction of small energetic clusters of Cu atoms with Cu surfaces has been investigated by molecular dynamics computer simulations. The simulations are fully dynamical and three dimensional; they employ embedded atom method potentials. The simulations described here are an extension of our past work on cluster solid interactions [1]. In this work, the effects of the angle of incidence, energy, size and temperature of the cluster are examined. In addition, soft landings of Cu clusters on Cu are simulated.

Our binary collision code Crystal-TRIM is applied to simulate 1 MeV P+ implantation into single-crystalline silicon at ion incidence into the [100] axial channel direction and doses between 2 × 1013 cm−2 and 6.7 × 1014 cm−2. The maximum penetration depth of the ions is determined by the electronic stopping of the well-channeled particles. The shape of the range distributions depends on (i) the thin amorphous surface layer on silicon, (ii) the radiation-induced production of vacancies and interstitials, and (iii) the static atomic disorder due to electronic energy deposition. The comparison of experimental data with results of computer simulations shows that at low doses at least the influence of the first two factors has to be considered. At higher doses the radiation damage due to nuclear energy deposition dominates the other effects.

Dynamic ion beam mixing (simultaneous deposition and ion beam irradiation) was simulated for the first time. Standard Monte Carlo (MC) programs do not account for the steady change of target geometry caused by the layer growth during the process. Therefore a time-step strategy was realized by integrating a MC simulator in a system together with a geometry update module. A comparison between simulation results and XPS and TEM measurements shows reasonable agreement between simulation and measurements.

The paper concerns the computer simulation of heat flow induced on matter by laser irradiation in presence of heat sources or sinks. The model is 3D analytical and accounts for the dependence of thermal properties of matter on temperature. The results describe in particular the effect of a heat source due to a local phase change or solid state reaction releasing energy in a point of the laser affected zone. The purpose of the paper is to evidence how this additional energy affects the thermal field and then the heating and cooling rates. PACS 47.25.-Qv

LPE-grown YBCO single crystal films were irradiated with oxygen ion beam up to a fluence level of 8 × 1019 cm−2 Irradiation parameters were as follows: , beam energy 0.8 keV, current density 0.4 mA/cm2. Ultimate vacuum was not less than 5 × 10−6 Torr, operating vacuum was 2 × 10−4 Torr. Tc = 53K and transition width ΔT> 10 K characterized the starting state of the films. After irradiation Tc was found to increase up to 94 K and Δ to decrease down to 0.5 K. Proceeding from transition character one can conclude that the irradiated film composition was changing into a single phase one. Half widths of the characteristic peaks of x-ray spectra were decreasing with the increase in fluence. The best results were obtained upon the irradiation of cooled samples. Upon heating the samples up to 600° C it was impossible to obtain Tc = 86 k and ΔT = 2 K.

This paper will give a rapid overview of the main experimental results concerning the effects of high electronic energy deposition in metallic targets and present a tentative model based on the Coulomb explosion mechanism. More detailed reviews have been made recently concerning both the experiments [1–3] and the theoretical model [4].

High levels of localized energy deposition in electronic excitation are easily obtained using GeV heavy ions which during their slowing-down typically transfer a few keV/Å to the electronic system of the target and a few eV/Å in elastic collisions with target nuclei. In insulators and organic materials, it is well-known that both slowing-down processes contribute to damage creation, whereas in metals it has been claimed for a long time that the sole nuclear collisions are involved in damage processes. Although this last assertion remains true for some metals such as Cu, Ag, W, Cu3Au …[2], high levels of electronic excitation can induce a partial annealing of the defects resulting from nuclear collisions in Fe, Ni, Nb, Pt…. lead to additional defect creation in Fe, Co, Zr, Ti… [2] or even to phase transformations in NiZr2 [5], Ni3B[6], NiTi [7], Ti [8]… In the following, we shall only focuss on the last two effects.

The ordered intermetallic Ll2 alloy Zr3Al was irradiated with 2 MeV protons at -124 °C to fluences up to 2 × 1015 H+/mm2 and at 250 °C to fluences up to 1 × 1015 H+/mm2. Defects with spherically symmetric strain fields were produced at both irradiation temperatures. They are of interstitial character at -124 °C and vacancy character at 250 °C. Disordering is induced at -124 °C, whereas irradiating at 250 °C initially lowers, then slightly raises, the degree of long-range order above its unirradiated value. Additional defects that appear as black spots were imaged using superlattice reflections in dark field. For the low-temperature irradiations they were seen at all doses, but were present at only the lowest close for the high-temperature irradiations. They are probably disordered zones, although some of the zones may be amorphous at the higher doses in the low-temperature irradiations.

Results are presented of an in-situ study of 1-MeV electron irradiation induced {113}-defect generation in silicon with boron, phosphorus or arsenic doped surface layers. By 1-MeV electron irradiation in a high voltage transmission electron microscope, {113}-defects are dorni-nandy formed in areas with a well defined dopant concentration range which depends on the tjpe of dopant atom, the irradiation temperature and fluence and the sample thickness. The observations for samples with boron and phosphorus concentration profiles are compared with published data on electron irradiation induced ( 113}-defect formation in uniformly doped silicon. In the present paper first results on heavily arsenic doped silicon are presented. It is shown that ihe observed dopant dependence of the {113}-defect generation can be understood on the basis of known point defect reactions. A few irradiation experiments are also performed on a local isolation structure illustrating for the first time the influence of localised tensile and compressive strain fields on {113} -defect nucleation.

Highly oriented pyrolytic graphite was irradiated at room temperature with 300-keV electrons. High resolution transmission electron microscopy and electron energy loss spectroscopy were employed to study the structure of electron-irradiated graphite. All the results obtained here consistently indicated die absence of long-range order periodicity in the basal plane and the loose retention of the c-axis periodicity. The structure was modeled based on a mixture of sixfold and non-sixfold atom rings. The formation of non-sixfold atom rings was related to the observed buckling and discontinuity of the original graphite basal plane.

In order to understand the properties of intrinsic point defects and their interactions at high defect concentrations GaAs wafers were irradiated at 4.5 K with 3 MeV electrons up to a dose of 4.1019 e-/cm2. The irradiated samples were investigated by X-ray Diffraction and optical absorption spectrocopy. The defect production increases linearly with irradiation dose and characteristic differences are observed for the two sublattices. The Ga-Frenkel pairs are strongly correlated and are characterized by much larger lattice relaxations (Vrel=2–3 atomic volumes) as compared to the As-Frenkel pairs (Vrel ≈ 1 at.voL). The dominating annealing stage around 300 K is attributed to the mobility of the Ga interstitial atoms whereas the As-interstitial atoms can recombine with their vacancies only around 500 K. These results are compared to those for InP, ZnSe and Ge. Implications for the understanding of the damage after ion irradiation and implantation are discussed.

Two-dimensional electron gas 60–120-nm deep from the surface was irradiated with 10-keV Ar ions (projected range = 8.8 nm) and resulting change in the mobility was analyzed. Defect distribution thus obtained is exponential in depth with the larger penetration length for the lower irradiation temperature. In-situ Hall measurements revealed that the mobility decreases simultaneously with the irradiation at 90 K. Consequently, the deep penetration of defects is concluded to be mainly due to the ion channeling. Results of iso-chronal annealing indicate that thermal diffusion of the defect that affects the mobility takes place at around 340–400 K, whereas the mobility starts to recover at ∼120 K.

The results are presented of a fundamental study of electrically active damage introduced in silicon diodes by irradiation with the fission products resulting from the decay of a 252Cf source and with high energy protons. The influence of the oxygen content of the silicon substrate and the irradiation type on the damage formation is investigated using deep level transient spectroscopy. A radiation hardening effect by interstitial oxygen is observed. Bom types of irradiation create the same dominant defect levels but with different relative densities. The identification of the induced deep levels are confirmed by isochronal annealing results.

We have investigated the effects of electron beam (EB) irradiation on the optical and electrical properties of GaAs/AlGaAs heterostructures in the energy range between 5 and 25 keV. By using 10 keV-EB irradiation, the photoluminescence from quantum wells is shown to be degraded at doses higher than 1×1019 electrons/cm2, further, the two-dimensional-electron-gas mobility is degraded at doses more than 5xl020 electrons/cm2. EB irradiation of 5 and 25 keV, on the other hand, produces no degradation of both properties even at these dose levels. Such an energy dependence of EB-induced damage can be interpreted in terms of the EB energy dependence of the electron penetration and energy-loss-rate. Electrons with an incident energy of 5 keV do not penetrate sufficiently deep into the active region, and 25 keV electrons have an energy-loss-rate that is too low to cause damage.

The concept of using internal cavities in semiconductors for surface studies is presented. The microstructures of He-implanted (001) Si are characterized with [110] cross-section TEM, which shows that internal areas 5–7 times that of the specimen front surface are achieved with 1×1017 He/cm2 implanted at 30 keV and annealed at 700 or 800°C. Examples using internal cavities to determine surface bond strengths of other elements adsorbed on Si are indicated. Facets on the cavities are used to examine the equilibrium crystal shape of Si and to measure the ratios of the surface free energies of the observed planes. The {111} planes have the lowest energy, and those of {001} and {110} are 1.09(7) and 1.07(3) times higher, respectively. We also find cavities in He-implanted Ge after annealing that can be used for similar studies.

A buried (Fe1−xCox) Si2 (x < 0.2) layer was formed by two step high dose implantation of Fe and Co into {100}-Si with as well as without intermediate annealing between the implantations. The suicide layer remains semiconducting if the temperature of the post implantation annealing is lower than 850°C. The depth distribution of Fe and Co, the phase composition as well as the microstructure of the layer system was investigated.

The influence of an electric field on the formation of radiation-induced defects in silicon irradiated respectively with γ-ray, electrons and neutrons has been investigated using the DLTS method. It is found that the application of an electric field across the p-n junction during irradiation can reduce the formation efficiency of A-centers, divacancies and E3(Ec-0.37 eV) defects, and that the concentration of radiation defects in the junction depletion region is lower than that in the quasineutral bulk. The formation characteristics of radiation defects in the depletion region could be related mainly to the transformation of the charge states of the defects caused by the electric field.

The study of ESR splitting effects induced by fluorine implantation into a-Si:H and a-C:H films has been performed. The implanted fluorine concentration Cp ranges from 1 × 1017 to 6 × 1021 cm−3. It is found that for both a-Si:H and a-C:H after fluorine implantation, in addition to the g1 resonances due to dangling bonds in the respective materials, there is a g2 resonance of g value close to 2.003 in both materials. This g2 resonance is further observed to be closely related to some doping effect of the implanted fluorine atoms in both materials. For a-C:H, it is also found that there is anisotropie hyperflne splitting (HFS) induced by the implanted fluorine atoms. These HFS signals exhibit unexpected peculiar CF dependence and do not show up at some intermediate CF values. A model based on the spin polarization effect has been proposed to attribute the HFS signals to be arisen from interaction between the π electrons of the carbon atoms and the 2p orbitals of the fluorine atoms.

Thin Ge specimens have been irradiated with Kr ions of different energies, and the dose required for complete amorphization determined by in situ transmission electron microscopy. Because Ge is directly amorphized by a single energetic Kr ion, onset of amorphization was detected after the lowesi ion doses. The Kr dose required for complete amorphization was found to increase linearly with ion energy over the range 0.5 MeV to 3.5 MeV. With the assumption that the defect density required for amorphization is independent of ion energy, the number of defects produced in a thin specimen by each ion decreases with increasing energy as the reciprocal of the incident ion energy. TRIM calculations indicate that there is a slight decrease in the amount of damage required with increasingion energy.

The author observed that both high-current-ion-beam and low-accelerationvoltage arsenic-implanted polycrystalline silicon-film surfaces are resistant to radical-fluorine-gas-etching. If we accept the simple assumption that a depth profile of concentration distribution of the implanted high-dose As atoms in polycrystalline Si film can be expressed with a standardized distribution function in the previous report of S. Furukawa, H. matsumura, and H. Ishiwara [Jpn. J. Appl. Phys. 11, 134 (1972)], we can take the premise that the chemical bonding reaction itself between radical-fluorine atoms and silicon atoms is prevented rather than that the covering of an arsenic- metal thin layer like amorphous state prevents the chemical bonding- reaction. We present a model of the prevention Si-F bond formation by high-dose arsenic implantation at low acceleration voltage. The model seems to be related to potential barrier increase and lattice vibration suppression for electromagnetic force-phonon interaction.