Ultra-thin Al2O3 films grown by atomic layer deposition for corrosion protection of copper

Ultra-thin Al2O3 films with thickness in the range of 4.5-29.4 nm were prepared on a copper substrate by atomic layer deposition (ALD) at the temperature of 150 degrees C to protect the substrate from corrosion. Auger electron spectroscopy (AES) was employed to analyze the elemental components of the film surface and to detect elemental distribution in a depth direction of the film, and atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to measure the surface morphology before and after the corrosion experiment. Electrochemical impedance spectroscopy (EIS) was used to measure anti-corrosion properties of the film in a 0.1 M NaCl solution. The results demonstrate that high quality ultra-thin Al2O3 films with a uniform in-depth stoichiometry are achieved on the copper substrate and the films can efficiently decrease the corrosion of copper. A thicker Al2O3 film can provide better corrosion resistance because of its lower porosity. When the film thickness is 7.8 nm or above, the copper surface can be well protected, which is embodied by the fact that the AFM and SEM images of the surface do not show a great difference before and after corrosion.