Oxidation of Metallic Substrates

In the case of the oxidation of a metallic substrate the anodization depends strongly on the humidity of the adsorbed water molecules which is the working electrolyte. The anodization process is carried out in conventional configuration with the tip as the counter electrode and the metal substrate as the working electrode. The anodization takes place when the metallic substrate is biased positively with respect to the tip, which as mentioned before can be either the STM tip or the tip of a conducting AFM. 

In this context of proximal probe induced oxidation it is worthwhile to point out an interesting observation where a high current passing through a metal film leads to its oxidation [67]. This process can be coupled to the SPM-based anodic oxidation to form patterns at the nanometer level. The planar oxidation was carried out with a current density of J 10 A cm. The oxide growth rate was found to vary oc/ where n 4. 

It is expected that with more control of the anodic oxidation process, the local oxidation of metals will become a viable tool to create sub-100 nm patterns. However, there is a need to understand the process and the underlying factors that control the resolution somewhat quantitatively to enable more control of the process. 

One of the first reports of single tip SPM-based oxidation of passivated Si (111) was made in 1990 [69]. This was followed by reports of oxidation of GaAs and other 

The threshold time for oxide formation was found to be arormd 10 to 10 s. The pattern was transferred to the Si substrate below using wet etching with KOH. The oxide grown by the SPM method is stoichiometric Si02, as has been shown by recent spectroscopic studies on such oxides [71]. 

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Rusting Oxidation of metallic substrates, such as iron or steel, when film permits moisture-or chemicals to attack substrates... 

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