Vacuum oxidation of freshly deposited iron nanofilms

Abstract

The interaction between freshly deposited iron films and oxygen at different evacuation degrees (from 10−5 to 760 mmHg) and room temperature is studied with the use of gravimetry (weighing with quartz nanobalance) and atomic force microscopy. According to data of atomic force microscopy, upon deposition of the metal on a glass substrate and during its subsequent oxidation, a metal-oxide composite film composed of metal-oxide nanoparticles with sizes of 20–30 nm where a metal core is covered with an oxide shell is formed. The reaction between freshly deposited iron and oxygen is shown to proceed quickly already at a pressure of 10−5 mmHg. An increase in the pressure is found to result in an increase in the bulk oxidation degree of the film. The growth kinetics of the film is two-stage. The initial oxidation stage can approximately be described with a linear-logarithmic dependence. The thinner the deposited iron nanolayer, the higher the bulk oxidation degree. The large value of the rate of initial oxidation of freshly deposited layer at a pressure of 10−5 mmHg, can be related to redox processes at the magnetite-hematite interfaces of multilayer nanoparticles that constitute the deposited nanocomposite layer. Upon passivation of the layer, the inherent nanoporosity makes the metal-oxide nanocomposite an adsorbent that can accumulate and store the adsorbed components of the environment (air).