Materials Science and Engineering, A164 (1993) 433-437 433 Misfit dislocations and other defects in thin films M. Yu. Gutkin Institute of Machine Science Problems, Russian Academy of Sciences, Bolshoj 61, Vas. Ostrov, St. Petersburg, 199178 (Russian Federation) A. L. Kolesnikova State Technical University, Polytechnicheskaya 29, St. Petersburg, 195251 (Russian Federation) A. E. Romanov* Max-Planck-Institut fiir Metallforschung, Institut ~ r Physik, Heisenbergstrasse 1, 7000 Stuttgart 80 (Germany) (Received August 30, 1992; in revised form November 30, 1992) Abstract The methods and the results of calculations of the elastic properties of misfit and lattice dislocations and disclinations in thin films are considered. For one-phase films the following problems are solved: a straight edge dislocation perpendicular to the film surfaces; wedge disclinations parallel or perpendicular to the surfaces. In the case of a film on a substrate, the critical thickness for the appearance of misfit dislocations is determined in the continuum model. For multilayer films (superlattices) the effect of a reduction in the grown-in dislocation density is analysed. The behaviour of dislocations in two-phase films is also briefly reviewed. 1. Introduction The physical properties (mechanical, electrical, optical etc.) of thin films depend on the presence of structural defects in them, in particular dislocations and disclinations. The production of thin film systems is usually accompanied by the formation of a character- istic dislocation structure, the basis elements of which are misfit dislocations (MDs) and grown-in threading dislocations (TDs)[1-5]. MDs compensate atomic misfit in two contacted phases and are localized in and/or near phase boundaries [2, 4]. TDs propagate through the entire bulk of the films and lead much more strongly than MDs to degradation of various electrical and optical characteristics of semiconductor devices [3, 5]. The mechanisms of the formation of dislocation structure during film growth are connected with the stress concentration on the film surface, existing dis- locations, and the elastic field of misfit. All the above factors have specific features in thin films where the *Permanent address: A. F. Ioffe Physico-Technical Insti- tute, Polytechnicheskaya 26, St. Petersburg, 194021, Russian Federation. effects of free surface screening on elastic fields and energies of defects must be taken into account. There are now a score of publications concerning the solution of boundary value problems of the theory of elasticity for dislocations and disclinations. Reviews of these solutions have been presented in refs. 6-8. Some of the results may be used to analyse the peculiarities of defect behaviour in the simplest thin film systems (as will be shown below), but new solutions are also needed for more complex thin film structures. The aim of the present work is to analyse the behaviour of MDs, TDs and disclinations for three kinds of thin film systems: one-phase films, films on a semi-infinite substrate, and two-phase films. 2. The method of virtual defects (MVD) One of the most useful methods for solving the boundary value problems of the theory of elasticity for straight dislocations is the method of surface virtual dislocations (MSVD), first formulated by Louat [9] and developed in general form by Marcinkowski [10]. It has been further generalized for surface disclinations, flux lines in type-II superconductors, and circular disloca- tion-disclination loops, for a review see ref. 7. A more recent application of this technique by Hecker and 0921-5093/93/$6.00 © 1993 - Elsevier Sequoia. All rights reserved