## 2 Materials and Methods
### XPS(X-ray Photoelectron Spectroscopy)  
The results of the standard XPS measurements were previously reported for the samples scratched in different environments [6]. In the present study, we pay much attention to the data itself obtained in the XPS measurements. The sample for the XPS measurement was prepared after the PE measurement during the wavelength scan from 300 to 200 nm at 25 \({}^{\circ}\)C and after cooling to 25 \({}^{\circ}\)C following the PE measurement during the wavelength scan from 300 to 200 nm at 200 and 339 \({}^{\circ}\)C. A sample was cut to \(3\times 3\) mm\({}^{2}\) in size, in which the spot area exposed to the incident light was included, and then the cut sample was rapidly transported to the measuring chamber of the XPS apparatus. The sample surface was exposed to ambient room air for a short time during transporting. During this procedure, the sample surface was successively exposed to Q gas, ambient room air, and vacuum before the commencement of the XPS measurements. Therefore, we have to consider the effect of the moisture in the room air on the sample surface. It is noted that, in our measurement room, the XPS apparatus was placed closely to the TAPE apparatus. The temperature and relative humidity of the room air were 23-26 \({}^{\circ}\)C and 21%-31%, respectively. Therefore, judging from the low humidity of the air and the presence of the hydroxyl groups on the real surface, which was presumed to reduce the activity to moisture, the effect of moisture from the ambient room air may be considered to be little and, even if it occurs, the moisture will be removed under vacuum in the XPS measurement. Of the core-level spectra measured using a Shimadzu ESCA 750 spectrometer (Shimadzu, Kyoto, Japan) with an Mg K\(\alpha\) X-ray source (8 kV and 30 mA), Fe 2\(p\), Fe 3\(p\), O 1\(s\), and C 1\(s\) spectra were taken in the present study. The energy range and sensitivity factors of these spectra were as follows: Fe 2\(p\) (725-700 eV, 10.5); O 1\(s\) (540-528 eV, 2.9); C 1\(s\) (300-280 eV, 1.0); Fe 3\(p\) (65-45 eV, 1.54). Here, the energy range of 66-48 eV for Fe 3\(p\) reported previously [13] was changed to 65-45 eV. It is noted that the main peak in the C 1\(s\) spectrum appeared at the binding energy of 285 eV. In the present study, the number of electrons counted in the XPS measurement of each core spectrum, called XPS intensity for the core spectrum, was used to represent the XPS characteristics of the environments, but it was not divided by the sensitivity factor of the spectrum. The XPS intensity was calculated from the difference between the maximum and minimum values--meaning background subtraction--obtained by the Shimadzu ESCAPAC 760 data system attached to a Shimadzu ESCA 750 spectrometer. The resolution of the O 1\(s\) spectrum was performed by curve-fitting using the Gaussian and Lorentzian functions, into three components. The components were assigned to the lattice oxide ion (O\({}^{2-}\)), the lattice hydroxyl group (OH\({}^{-}\) and OH\({}^{8-}\)), and adsorbed water (H\({}_{2}\)O), according to Reference [14]. In addition, the XPS intensity for the three O 1\(s\) components was obtained by distributing the XPS O 1\(s\) intensity to the components. An example of the curve resolution of the O 1\(s\) spectrum for acetone is shown later. The chemical structure of the overlayer for the environments was judged based on the comparison of the shape of Fe 2\(p\) spectrum with that for the spectra reported in the literatures cited below.