Overlayer energetics from thermal desorption on Si.

Growth mechanisms of evaporated thin films are usually determined by topological techniques. This paper demonstrates that isothermal desorption measurements of film/substrate systems yield characteristic energies which allow for a closer insight into the thermodynamical driving forces which determine the film morphology. We demonstrate Stranski-Krastanov growth for the Sn on Si system and Volmer- Weber growth for the Ga on Si system by comparing the activation energies for desorption from the last layer in contact with the substrate to the pure metal values obtained from desorption of the islands. The preexponential factors for desorption are discussed in terms of the entropy associated with the surface mobility of the adatoms.