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.