Thin Sb2Te films with a thickness gradient were studied via transmission electron microscopy. The processes of forced crystallization were examined with thermal annealing and an electron beam. The crystallization’s general tendencies, including competitive nucleation and growth crystallization, were revealed. As the thickness of the sample increases, the size of the crystals growing in the film enlarges. As the temperature increases, the number of crystals in the film grows. Crystallization under the action of an electron beam occurs mainly by nucleation mechanism.