Surface Plasmon Resonance Sensing Characteristics of Thin Aluminum Films in Aqueous Solution

Detection of Initial Stage of Aluminum Corrosion in NaCl Solution Utilizing Surface Plasmon Resonance

“…Although the effect of such pits cannot be taken into account, a simple flat multilayer model has been used to describe the SPR measurement of Al films successfully [11], [23]. Such a simplification may be allowed for the very initial stage of the corrosion, in which the roughening of the surface by pitting corrosion is not severe and each layer can be modeled as a flat layer with an effective thickness and the refractive index of the original material.…”

“…As for the oxide layer, we need to consider the distension in aqueous solution [11], [26]. In air, the oxide layer can be regarded as Al 2 O 3 [12, p. 230] and the thickness is 2.7 nm in our sample as mentioned above.…”

“…Bussjager and Macleod have demonstrated that the deposition of a thin copper layer of approximately 1 nm thickness improves the corrosion resistance of Ag to laboratory air, air with a relative humidity of 94% in a test chamber, and aqueous H 2 O [10]. From the viewpoint of biosensing applications, Oliveira et al [11] have evaluated the corrosion resistance of an Al film in an aqueous solution. They reported that a hydrous form likely coexists with the Al oxide film and remains stable in a deionized water solution.…”

“…The thickness of the natural oxide in a dry form was estimated to be about 2.7 nm by angleresolved X-ray photoelectron spectroscopy (XPS) [19]- [22]. Here, the natural oxide is likely to be amorphous [11], [12, p. 235], [13, p. 144], [14], [17, pp. 102-105].…”

“…102-105]. As mentioned later, the oxide film thickness may increase upon contact with the aqueous solution [11]. The samples used in the TEM and XPS measurements were fabricated by the same procedure as the samples used in the SPR measurement.…”