摘要:

The structures of point defect clusters of both interstitial and vacancy type were examined by computer simulation using molecular dynamics and molecular statics with the DYNAMO code (Daw, Foiles and Baskes [6]). The code implements an isotropic potential of embedded atom method (EAM) developed by Daw and Baskes [5]. Interstitial clusters relax to either the immobile mixture of <100> dumbbell and bcc interstitials or a mobile platelet of parallel <110> interstitials. The latter cluster moves along <110> directions. A tri-vacancy relaxes to an un-collapsed stacking fault tetrahedron (sft) of Damask-Dienes type (3v-sft) containing a central atom that vibrates with a large amplitude. A hexa-vacancy relaxes to a stacking fault tetrahedron the structure of which fluctuates between a sft and void. Larger vacancy clusters are stable as a combination of sft and 3v-sft. In these vacancy clusters, atoms show significant vibration with large amplitude. Voids form only with the inclusion of gas-atoms into vacancy clusters.

ISSN:1042-0150    

DOI:10.1080/10420159408219806

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

One of the main problems while developing analytical multilayer models for ion implantation is how to make them ‘physical'. Satisfactory agreement between results obtained with existing multilayer models and the Monte Carlo prediction cannot always be expected, since mostly none of the important physical effects is accounted for. Extensive Monte Carlo study has been performed in order to extract some guiding principles for the construction of a more physically based multilayer model. Ion reflection accross the interfaces has a very strong impact on the final shape of a multilayer profile. First attempts to include this phenomenon in a multilayer model have been made. In this paper, a simple approach for light ion reflection at an interface is presented and the incorporation into a multilayer model is discussed.

ISSN:1042-0150    

DOI:10.1080/10420159408219807

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Research into displacement cascade processes in alloy systems has received little attention, yet is potentially of interest because issues such as the effect of solutes on the displacement threshold and the defect distribution and movement in cascades are important. As part of a wider study, we have initially considered the minor substitutional solute Au in a Cu matrix, and have used molecular dynamics to investigate the properties of point defects, the threshold displacement energy Ed, and temporal and spatial distribution of defects in low-energy (≤500 eV) displacement cascades. The results show that the influence of the solute on the properties of defects is important and that Edis dramatically different from its form in pure copper. In comparison with pure copper, the recoil of the Au solute gives rise to a higher peak at longer times in the number of displaced atoms in the generation of a displacement cascade. The influence of this on defect density in the cascade and the final number and arrangement of defects has been investigated.

ISSN:1042-0150    

DOI:10.1080/10420159408219808

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The computer program IMPETUS calculates sputter depth profiles by solving Fokker-Plank type equations for mixing. In the standard model, the effective volume of the mixing constituents is taken to be constant throughout the mixing regardless of the composition of their atomic environment. Experimentally measured values for atomic densities of materials and compounds indicate that this assumption is not correct and that non-constant atomic volumes need to be considered. Although the way in which the variation of the volumes take place is not known, the present work is aimed at developing the treatment of Fokker-Plank type equations such that composition dependent effective atomic volumes can be included. The complexity of the equations and a method for solution together with its application for a simple case are explained in this paper

ISSN:1042-0150    

DOI:10.1080/10420159408219809

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The experimental SIMS profiles of Si30/Si28multilayers depth profiled using 2–10 KeV Ne+, Ar+and Xe+(K. Wittmaack and D. B. Poker, Nucl. Instr. Meth. B47 (1990) 224) have been simulated using a diffusion approximation to ion mixing. Both the leading and trailing edges of peaks in the depth profiles could be fitted for all ion energies by mixing efficiencies of 25, 40 and 65 Å5eV−1respectively. These values are larger than the estimates of 5, 11 and 15 Å5eV−1from ballistic mixing. The additional contributions to the mixing, 20, 29 and 50 Å eV−1, scale with cascade energy density, suggesting that stimulated motion in thermal spikes is important. A simple spike model in which cascade defects are trapped at fixed sinks agrees with the experimental mixing efficiencies.

ISSN:1042-0150    

DOI:10.1080/10420159408219810

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In a previous paper a revised version of the Projected Range ALgorithm (PRAL) was presented. These new equations, called the Kent Range ALgorithm (KRAL), consider fully the motion of the ion in three dimensions. In the current paper we review a simple derivation of the KRAL equations starting from the standard LSS integral equations for moments of the range distribution. The resulting 2ndorder ordinary differential equations are difficult to solve using classical numerical techniques. We present a modified set of equations called the Kent Optimised Range ALgorithm (KORAL) which is designed for iterative solution. Finally, we compare results from KORAL and 1stand 2ndorder PRAL codes with Monte Carlo data from a TRIM code modified to treat targets of infinite extent. Comparisons are performed using consistent nuclear and electronic energy loss models.

ISSN:1042-0150    

DOI:10.1080/10420159408219811

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:1042-0150    

DOI:10.1080/10420159408219812

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor