Self-organized pattern formation in the oxidation of supported iron thin films. I. An experimental study - art. no. 035408

The evolution of patterned morphology during thermal oxidation of a support ed metal thin film is examined as a case of strained reaction-diffusion sys tem; the strain originates from the large density difference between the ox ide and the metal. In the moderate temperature regime, where bulk diffusion is weak, the pattern reflects the length scale of the original metal film grain structure, with local features characteristic of self-organized chemi cal microreactors, as well as large scale polygonal surface undulations pre sumably caused by stress accommodation. At higher temperature, where bulk d iffusion is brisk, the process of Ostwald ripening strongly reforms the mor phology formed at lower temperature, and leads to distributed spiral-type c onfigurations. These observations and analysis are supported by a simulatio n study reported in the accompanying paper II by Abhijit S. Ogale.