Erbium films of varying thickness (5-1.5 mu m) were deposited on a-C substrates at different substrate temperatures. Microstructures of films are obtained by transmission electron microscopy and scanning electron microscopy while the selected area diffraction patterns of films are analysed using an image analyser. A phenomenological description of film growth and its morphological changes based on nucleation, mobility of clusters and a liquid-like mode of coalescence is given.