Optical Coefficients of Nanoscale Copper Films in the Range of 9–11 GHz

The reflectance, transmittance, and absorption coefficient of ultrathin copper films on a quartz substrate have been measured in a waveguide at frequencies of 9–11 GHz. Films less than 5 nm thick are oxidized almost completely and transparent to microwave radiation. A conducting layer is formed at a film thickness above 5 nm; however, the reflectance increases with thickness in the range of 5–15 nm more slowly than is yielded by calculations using the model conductivity of a continuous film. These results can be explained by the film morphology.