Partial oxidation of copper and cobalt-iron thin films: Microstructural mechanisms
Oxygen-containing copper thin films deposited in an ion beam sputtering system show sharply increased resistivity with decreasing thickness for films around 5.0 nm or less, while bulk resistivity values prevail for thicknesses of 10.0 nm and greater. Oxygen concentration in the range of 6 to 10% reduced Cu resistivity for these thin films. Copper films, measured by atomic force microscopy and x-ray reflectivity, have significantly smoother surfaces in the range of 6 to 10% oxygen. This suggests increased specular scattering of electrons at smoother copper interfaces and surfaces in this thickness regime. X-ray and electron diffraction data show a mixed phase film composed of fine cuprous oxide in the Cu film. Nanoscale cuprous oxide particles, in the copper grain boundaries, effectively obstruct copper grain growth, refining the copper grains and smoothing the surface.
Oxygen sputtering of Co-Fe10 saw no interface smoothing nor was a second phase detected.