We explore the effects of curvature-dependent surface tension on the elastic behavior
of a line edge dislocation embedded in a free-standing thin film. The dislocation
line is assumed to be parallel to the surface of the film, while the entire
system is confined to plane strain deformations. The total surface tension
is treated as the sum of a constant initial part arising from the originally
flat surface of the film and a configuration-dependent part proportional to
the curvature of the deformed surface of the film. We employ the complex
variable formalism of elasticity and develop a series-based solution procedure to
determine the dislocation-induced stress field in the film subjected to the
nonclassical boundary conditions related to the curvature-dependent surface
tension. The image force, describing the mobility of the dislocation, is also
represented in terms of the obtained coefficients of the series. By setting the
curvature-dependence parameter of surface tension to zero, our procedure
recovers accurately the known analytic results in the literature for an edge
dislocation in an elastic half-plane with constant surface tension. Numerical
examples are presented for illustrating the influence of the curvature-dependence
parameter of surface tension on the local stress field near the surface of the film
and the image force. It is shown that as the thickness of the film decreases
to a few nanometers, the curvature dependence of surface tension always
contributes significantly to the determination of the stress concentration
around the surface of the film irrespective of the direction of the Burgers
vector of the dislocation. In contrast, however, it is found that even for a
few-nanometer-thickness film the influence of the curvature dependence of
surface tension on the image force becomes notable only when the Burgers
vector is at a large angle to the surface of the film (for example, more than
) and
simultaneously the distances from the dislocation to the two surfaces of the film differ
significantly (for example, by a factor of three or more).
Keywords
thin film, surface tension, curvature dependence, edge
dislocation, image force