Thermal oxidation of ultra thin palladium (Pd) foils at room conditions

The formation and growth of Palladium Oxide (PdO) onto ultra thin Pd foil by thermal oxidation (TO) is discussed. TO is a flexible method to study the theory of volumetric Pd oxidation, considering the interfaces O₂-PdO and PdO-Pd phenomena. The kinetic of the PdO growth on ultra thin Pd foil, clearly shows that oxidation process is governed by a parabolic law, which is directly related to temperature and oxidation time parameters. Oxide thickness in the range of 30 nm to 60 μm were development by TO. The XRD analysis on samples with different oxide thickness have shown a preferential growth at 2 = 33.6° explained by the highest surface energy for this plane. The peak located at 2 = 33.9° corresponding to (101) PdO direction, is the responsible of 2 allowed Raman modes reported for PdO, where the oxygen-phonon has a parallel motion to x and c axis. Ellipsometric measurement (EM) was a useful technique to study the early oxidation stage in a Pd foil. A theoretical study was done considering an existent 1 nm PdO layer. Hall measurements demonstrate the degenerated semiconductor behavior of PdO, because of the ultra short band gap in PdO, of around 0.8 eV.