ISSN:1042-0150    

DOI:10.1080/10420159408219766

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The binary collision approximation (BCA) has long been used in computer simulations of the interactions of energetic atoms with solid targets, as well as being the basis of most analytical theory in this area. While mainly a high-energy approximation, the BCA retains qualitative significance at low energies and, with proper formulation, gives useful quantitative information as well. Moreover, computer simulations based on the BCA can achieve good statistics in many situations where those based on full classical dynamical models require the most advanced computer hardware or are even impracticable.

ISSN:1042-0150    

DOI:10.1080/10420159408219767

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The simulation of point defect production in crystal lattices by irradiation presents many difficult problems in computational geometry. Shapes such as lobes, ‘starbursts', and chains are common at many scales of measure. With the exception of molecular dynamics methods, simulation techniques use simple, distance based models to detect the interaction of these complex objects. A constructive procedure based on recursive space partitioning and a data structure called ak-dBSP tree has been developed and applied to simulating the spontaneous recombination of unstable Frenkel pairs. Frenkel pair distributions were obtained for BCC iron from displacement cascades simulated using the binary collision approximation. Approximately 57% of the Frenkel pairs generated by these displacement cascades were found to be unstable.

ISSN:1042-0150    

DOI:10.1080/10420159408219768

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We review recent results on the mechanisms of atomic mixing, radiation-induced disordering, and defect production and clustering induced by displacement cascades in Cu, Ag, Cu3Au and Ni3Al. We employ molecular dynamics computer simulation (MD) methods with isotropic many body potentials and recoil energies near the subcascade formation regime (up to 30 keV). Atomic mixing is shown to be dominated by diffusion in the locally molten cascade core in both the pure metals and the intermetallic compounds. Disordering of the intermetallics was found to take place in the core of the cascades. However, because of the short lifetime of the displacement cascade, chemical short range order is preserved in the molten zone. Our results reveal the appearance of very large vacancy and interstitial type defect clusters at high recoil energy and cascade energy density. Vacancies agglomerate and collapse into Frank dislocation loops as the result of the quenching of the cascade molten core. Large interstitial clusters are directly produced in cascades and form prismatic dislocation loops. The fraction of defects in clusters for low temperature cascades increases with recoil energy and approaches ∼70% and 60% for interstitials and vacancies, respectively, at recoil energies near the threshold for subcascade formation. In the case of intermetallic (A3B) compounds, the large energy required to produce and transport a superdislocation appears to inhibit the interstitial prismatic loop punching process and interstitials appear as isolated (100) dumbbells formed by pairs of majority-type atoms.

ISSN:1042-0150    

DOI:10.1080/10420159408219769

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Ion-beam processes are still at the developmental stage, except for the use of wide-area beams for ion implantation which has led to a continued miniaturization of semiconductor devices, resulting in an increase in speed as well as in device complexity. However, ionized beams are also highly suitable for material modification by sputter-deposition, ion milling, lithography, ion microscopy and materials analysis. Evaluation of the optimum physical parameters in these ion-beam processes would significantly improve the utilization of ion beams.

ISSN:1042-0150    

DOI:10.1080/10420159408219770

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The energy loss of low energy (<1 keV) B ions traversing a very thin <100>Si crystal is calculated using a Monte Carlo (MC) and a Molecular Dynamics (MD) computer code, respectively. The MC simulation is based on a modified binary collision model where large range interactions are treated separately within the momentum approximation. Because of the small thickness of the Si crystal the MD calculations are performed for the whole crystal considered, using the Stillinger-Weber many-body potential for silicon. For the B-Si interatomic interaction in both codes the same numerically calculated potential is used. By comparison of the MC and MD results the validity of the binary collision model is discussed.

ISSN:1042-0150    

DOI:10.1080/10420159408219771

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:1042-0150    

DOI:10.1080/10420159408219772

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In this contribution we deal with the influence of plural and multiple scattering of high energy projectiles in two characteristic applications: Rutherford backscattering spectroscopy (RBS) and the response of particle implanted and passivated silicon detectors (PIPS) to monoenergetic MeV alpha particles.

ISSN:1042-0150    

DOI:10.1080/10420159408219773

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The formalism for the binary collision code Crystal-TRIM which simulates ion implantation effects in crystalline solids is presented. The treatment of binary collisions, the kinematics and the crystal description are elucidated in detail. The nuclear scattering is described by the ‘universal’ potential. The scattering angles are calculated by semianalytical and analytical formulae. We employ a semiempirical model to describe the electronic stopping of the ions. Thermal vibrations of lattice atoms, the radiation-induced production of vacancies and interstitials and their accumulation, the generation of static lattice disorder due to electronic energy deposition and the influence of a thin amorphous surface layer are considered in the simulation model. The program Crystal-TRIM is applied to calculate range profiles for P+and B+implantation into Si at energies between 500 keV and 1 MeV, at ion incidence into axial and planar channels and into ‘random’ directions, and at ion doses between 1013and 1014cm−2. A relatively good agreement with experimental data is found if the effects of radiation damage, static lattice disorder and the influence of an amorphous surface layer are taken into account simultaneously. We study dechanneling processes during ion implantation. The dechanneled fraction of the ion beam is calculated in dependence on the depth. Furthermore, we illustrate the motion of individual projectiles within the crystalline solid.

ISSN:1042-0150    

DOI:10.1080/10420159408219774

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Ion channeling along the c-axis of YBaCuO single crystals revealed anomalies at Tc, which were attributed to a different dynamical behaviour of the Cu atoms in the normal and the superconducting state.1,2Using the O16(α/α)O16resonant scattering at 3.05 MeV we observed additional anomalies in the O-sublattice.3The latter experiments were performed on c-axis oriented single crystals and on a- and c-axis oriented thin YBaCuO films. The experimentally observed dependences of the angular yield curves on the temperature and on the tilt plane could be well reproduced by Monte-Carlo (MC) simulation calculations. Several displacement models have been used to simulate the structural distortions in the Cu- and O-sublattices at Tc. The most probable model is the assumption of structural distortions in the Cu- and O-sublattice above Tc, which relax below Tc. The change in the total displacement amplitudes is about 0.4 pm for the Cu- and about 2 pm for the O-sublattice.

ISSN:1042-0150    

DOI:10.1080/10420159408219775

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor