Scanning tunneling microscopy characterization of the surface morphology of copper films grown on mica and quartz

The morphology of copper films grown on quartz, mica, and Ti/quartz has been investigated by means of scanning tunneling microscopy (STM). Films grown on quartz, both bare and pre-plated with titanium, are characterized by self-affine fractal scaling behavior over the length scale of 10∼500 nm, while films grown on mica are not. Annealing of the films to 340 °C reduces the root-mean-square (RMS) roughness values, despite the overall scaling behavior remains the same. Films grown on bare quartz have significantly larger RMS roughness than those grown on mica, or quartz pre-plated with titanium. For the latter two cases, the RMS roughness is very low, 1-4 nm for the length scale of L = 500 nm. The overall dependence of copper film morphology on various substrates were discussed in terms of interfacial reaction, lattice mismatch, and surface energy difference of interface surfaces.