Electrical transport properties of Cu₃Ge thin films

Resistivity, Hall-effect, and magnetoresistance measurements have been performed in the temperature range 4.2-300 K on thin films of the ε1-Cu3Ge phase that has a long-range ordered monoclinic crystal structure. The results show that ε1-Cu 3Ge is a metal with a room-temperature resistivity of ∼6 μΩ cm. The temperature dependence of resistivity follows the Block-Grüneisen model with a Debye temperature of 240±25 K. The density of charge carriers, which are predominantly holes, is ∼8×1022/cm3 and is independent of temperature and film thickness. The Hall mobility at 4.2 K is ∼ 132 cm2/V s. The elastic mean free path is found to be ∼1200 Å, which is surprisingly large for a metallic compound film. The results show that the residual resistivity is dominated by surface scattering rather than grain-boundary scattering. An increase in Ge concentration above 25 at. % (but less than 35 at. %) is found to affect the resistivity and Hall mobility, but not the density of charge carriers.