The resistivity and Hall coefficient of CoGe and CoGe2thin films

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Abstract
This is a report of measurements of the electrical resistivity and of the Hall coefficient of CoGe and CoGe2 films between 80 and 520 K. Both germanides behave as metallic conductors with resistivities increasing linearly with increasing T over the whole temperature range. There is a slight deviation from linearity for CoGe2 which is attributed to the fact that the mean free path of the carriers becomes comparable with the lattice dimensions at high temperatures. The Hall coefficient is negative for CoGe, giving an apparent carrier concentration of (0.86+or-0.01)*1028 m-3 and a Hall mobility of (11.0+or-0.1)*10-4 m2V-1s-1 at room temperature. On the other hand, p-type conduction is revealed for CoGe2 with apparent carrier concentration and Hall mobility equal to (1.93+or-0.01)*1028 m-3 and (2.2+or-0.1)*10-4 m2V-1s-1, respectively, at 300 K. For a quantitative explanation of the resistivity and Hall behaviour of germanides, detailed information about the energy band structure near the Fermi level is required. At this information is lacking, the rough approximation of the two-band model is the only way to obtain insight into the electrical properties of germanides.