Thin films of Si with Mn concentrations up to 20 at.% were prepared by conventional radio frequency sputtering. After deposition, the films were submitted to thermal annealing treatments and their properties were investigated by composition analysis, Raman scattering, microscopic techniques, optical transmission, and electrical transport. The experimental results show that all as-deposited films are amorphous, with the Mn atoms being effective and controllably incorporated into the Si matrix. Moreover, thermal annealing at increasing temperatures induces the crystallization of the films as well as the growth of the MnSi1.7 suicide phase in the Mn-containing samples. Along with sample crystallization, some films become covered by small structures that are randomly distributed all over their surfaces. These structures are essentially Mn-containing Si crystals with typical sizes in the (sub-) micrometer range and, as the thermal annealing advances, the density of structures increases at the expense of their individual average dimension. The development and characteristics of the observed superficial structures are discussed in view of the main structural and morphological properties of the samples. (C) 2011 Elsevier B.V. All rights reserved.