Change of electrical properties of Co-doped and Cr-doped FeSi2 thin films during amorphous-to-crystalline transformation

The annealing temperature dependences of the XRD pattern, Seebeck coefficient and electrical resistivity for Cr-doped and Co-doped FeSi2 thin films were studied. The films were deposited by rf-sputtering method. Below 380°C, the films were amorphous and their Seebeck coefficient and electrical resistivity were relatively low. The crystallization of FeSi2 occurred at 400° to 460°C. The Seebeck coefficient (in absolute value) and electrical resistivity steeply increased with increasing amount of FeSi2 crystals in the amorphous matrix. Above 460°C, the electrical resistivity of the films gradually decreased with rising annealing temperature. The results of activation energy measurement explained the observed decrease of the electrical resistivity in Cr-doped thin films as due to both the increase of the carrier density and to the decrease of the activation energy.