The neutron irradiation effect of polycrystalline Si1-xMnx semiconductor thin films has been studied. The Si1-xMnx semiconductor thin films were grown on SiO2/(100) Si substrate at 400 degrees C by using a MBE. The as-grown specimens are irradiated by the fast neutrons of 0.82 MeV in a neutron research reactor at KAERI. After neutron irradiation, the electrical resistivities of neutron-irradiated specimens increase with the irradiation amount, while the saturation magnetizations decrease. Hall analysis reveals that the mobility of neutron-irradiated specimen decreases remarkably. The XRD and TEM analyses show that the phase transformation is not induced by the neutron irradiation. (c) 2005 Elsevier B.V. All rights reserved.