**3.1. Thin film specimens**

A pair of platinum-titanium (Pt-Ti) coated silicon (Si) thin film specimens is used in the present experiments. The Si substrate is cut along the [1 0 0] plane and 750 μm in thickness. The Ti layer is coated on the Si substrate and the Pt is coated over the Ti layer. The thickness of the Pt and Ti layers are 100 nm and 10 nm, respectively. In one specimen (the treated specimen) of the pair, the Ti layer is coated after the substrate surface is treated with oxygen-plasma bombardment. This treatment makes the Si surface hydrophilic, and therefore strengthens the Ti-Si bond. In the other specimen (the untreated specimen), the Ti layer is coated without a surface treatment.
