Large deviation from Matthiessen’s rule in chemical vapour deposited copper films and its correlation with nanostructure

The resistivity $(\rho)$ of copper films grown by varying the pressure, and hence the growth rate, in metalorganic chemical vapour deposition has been studied in the temperature range 4.2 K–300 K. The films exhibit a fairly high $\rho$(300 K) of 8–20 $\mu \Omega$ cm. Analysis of the temperature variation of $\rho$ shows that the high $\rho$ values are not just caused by elastic scattering from the impurities but the temperature dependence of $\rho$ is also very high, resulting in a large deviation from Matthiessen’s rule (DMR) in these films. This strong dependence on temperature and DMR has been explained in a semi-quantitative manner as arising from grain boundary (GB) and surface scattering (SS). This is corroborated by STM studies on the films which show that films having a smooth surface and well connected grains have a lower $\rho$ as opposed to films with poor connectivity