General aspects of the growth of cobalt nanofilms during heat treatment

Transformations of cobalt nanofilms have been studied by optical spectroscopy, optical microscopy, and gravimetry at film thicknesses d = 2–35 nm and heat treatment temperatures T = 473–873 K. Kinetic curves of the degree of conversion in the films are adequately represented by a linear, inverse logarithmic, cubic, or logarithmic rate law. We have measured the contact potential difference across the Co and Co2O3 films and the photovoltage across the interface and constructed the energy band diagram of the Co and Co2O3 films. A model has been proposed for the thermal transformation of Co films which includes oxygen adsorption, carrier redistribution in the Co-Co2O3 interfacial field, and cobalt(III) oxide formation.