An investigation using atomic force microscopy and X-ray photoelectron spectroscopy of the modification of the surface of mica with an argon RF-plasma discharge

Atomic force microscopy (AFM), together with X-ray photoelectron spectroscopy (XPS), has been used to investigate the topography and composition of air-cleaved mica surfaces modified by an argon RF-plasma discharge run at various power levels. At low power, the plasma-treated surfaces of the mica were formed to show more or less uniformly distributed dome-shaped topographical features. The RMS roughness and the mean lateral size of the main protrusions on the surfaces are relatively small. With increasing plasma power, the rounded features change both in shape and size and the surfaces become more disordered. The XPS data demonstrate that the mica surfaces, following argon RF-plasma treatment at high power levels, show a build-up of the aluminium and silicon present while the attendant oxygen is decreased significantly. All of the phenomena observed are attributed to a disorganization of the mica surfaces during sputtering, followed by re-deposition of the component elements with loss of oxygen becoming apparent as the RF-plasma power used is increased.