Abstract
Thin films (33 nm to 1.4 μm) of iron oxides were deposited onto roughened silver substrates by laser ablation of 
and 
targets. Surface enhanced Raman (SER) spectra from the 33 to 37 nm thick films, both in air and in aqueous borate buffer (pH 8.4), were identical to SER spectra of the passive film formed on iron in the same solution; that is, all were characterized by a strong broad peak centered at approximately 530 to 
. The 33 to 37 nm thick films were potentiodynamically reduced in borate buffer. Electrochemical reduction of the ablated iron oxide films initiated at a more cathodic potential than that found for the passive film on iron. Thicker 178 nm films formed by laser ablation of 
exhibited spectra partially resembling the iron passive film and partially resembling the normal Raman spectrum of bulk 
. The 153 nm and 1.4 μm thick films formed from 
and 1.3 μm thick films formed from 
gave very weak Raman spectra that were characteristic of the bulk oxides, and did not resemble the iron passive film. The observation that the SER spectra from passive films on iron, as measured in this and previous studies, are identical to the SER spectra from thin films laser ablated from targets of 
and 
(in both cases, resulting in iron oxides most probably hydrated and of small particle size) permits the more accurate assignment of spectral features in future as well as past SERS studies.