Front propagation in a phase field model with phase-dependent heat absorption

Abstract

We present a model for the spatio-temporal behaviour of films exposed to radiative heating, where the film can change reversibly between amorphous (glassy) and crystalline states. Such phase change materials are used extensively in read-write optical disk technology.In cases where the heat absorption of the crystal phase is less than that in the amorphous state we find that there is a bi-stability of the phases. We investigate the spatial behaviours that are a consequence of this property and use a phase field model for the spatio-temporal dynamics in which the phase variable is coupled to a suitable temperature field. It is shown that travelling wave solutions of the system are possible and, depending on the precise system parameters, these waves can take a range of forms and velocities. Some examples of possible dynamical behaviours are discussed and we show, in particular, that the waves may collide and annihilate. The longitudinal and transverse stability of the travelling waves are examined using an Evans function method which suggests that the fronts are stable structures.

Threshold switching via electric field induced crystallization in phase-change memory devices

“…Our phase-transformation model uses a Gillespie cellular automata (GCA) approach that combines thermodynamic features of rate-equation approaches 15 with elements from probabilistic cellular automata (PCA) models 16,17 and phasefield models; 18,19 in addition, it uses the Gillespie algorithm 20 for efficient time-stepping. Our GCA model has been previously described in detail 21 and in summary considers a homogeneous, isotropic material in a square lattice where the state of the material is described through a set of points in the lattice that can be either crystalline or amorphous.…”