Misfit dislocations in wire composite solids

Abstract

Abstract. A theoretical model is suggested, which describes generation of misfit dislocations in film/substrate composites of wire form. In the framework of the model, the ranges of the geometric parameters (wire radius, film thickness, misfit parameter) of a wire composite are calculated at which the generation of misfit dislocations is energetically favourable. The specific features of generation of misfit dislocations in wire composites are discussed and compared with those in conventional platelike composites.

Misfit dislocation loops in composite nanowires

“…Although we are as yet unaware of any experimental observations of misfit dislocations in nanowires, we suppose that such dislocations may form in composite nanowires much as they are generated in flat thin films and quantum dots (for example Fitzgerald (1991), Jain et al (1997), Liu et al (2000), and Ovid'ko and Sheinerman (2002)). In the paper by Gutkin et al (2000), conventional straight misfit dislocations in two-phase composite solids having the wire form (nanowires in 'shells') have been theoretically examined. The main aim of this paper is to suggest a theoretical model describing misfit dislocation configurations of the new type in two-phase composite nanowires, namely the misfit dislocation loops in nanowires embedded in 'shells' (figure 1).…”

“…In most cases, a partial relaxation of the misfit stresses is realized via generation of various defects (for example Fitzgerald (1991), Jain et al (1997), Mu¨llner et al (1997) and Gao et al (1999)). The conditions at which isolated misfit dislocations (MDs), misfit disclinations and their configurations (dipoles, rows and walls) are generated in wire composite solids have been analysed by Gutkin et al (2000) and Sheinerman and Gutkin (2001). In this paper we elaborate a theoretical model describing the formation of prismatic MD loops (figure 2), MD configurations of the new type in composite nanowires, whose stress fields can induce modulation of the chemical composition of the nanowires.…”

“…where f zz is the zz component of the misfit stress field, calculated by the formula (Gutkin et al 2000) f…”

“…(Note that the formula for f zz in the paper by Gutkin et al (2000) contains a misprint corrected here.) Here YðtÞ is the Heaviside function, equal to 1, for t > 0, and to 0, for t < 0.…”

“…For comparison, the dependences of the critical misfit parameter f d c for the formation of straight misfit dislocations (calculated by Gutkin et al (2000)) are shown, too. For clarity, curve 1 in figure 6 (a) is also presented in figure 6 (b) on a larger scale.…”