Unusually low resistivity of copper germanide thin films formed at low temperatures

We report a first observation of the remarkably low electrical resistivity of copper germanide thin films formed at temperatures below 200°C. At these low temperatures, the ε-Cu3Ge phase with a monoclinic crystal structure is formed, with room-temperature resistivity which can be as low as 5.5 μΩ cm. The films are electrically stable up to at least 600°C, and, unlike pure copper, are also stable against oxygen and air exposure.