Stabilisation of the amorphous state of a thin layer sandwiched between two crystals

It has been experimentally proven that thinning an amorphous layer, sandwiched between two crystals, up to the nanometer scale, leads to a higher crystallization temperature. The present work is an attempt to explain such behaviour on the basis of thermodynamical arguments. The approach assumes that a nanometric amorphous layer is submitted to the crystal field leading to a gradient of atomic density across the glassy layer. It is shown that the stabilisation of the glassy layer is expected when approaching a thickness of few nanometers. This study is closely related to the concerns of the phase change optical storage because such a technology involves both the use of very thin films and fast structural transitions between the two states (amorphous and crystalline) of the active material