Thermodynamical properties of ultrathin layered structures

Thermodynamical properties of ultrathin films were analysed using Green's function method. Mean-square of the molecular displacements, mean-square of the velocities and the phonon contribution to the specific heat of the thin films were calculated. A comparison with crystal bulk has shown that thermodynamical properties of thin films are strongly influenced both by the sample dimensions and boundary conditions. The results of the specific heat analyses make the validity of free surface model doubtful, because the specific heat calculated in this model becomes negative at very low temperature.