# Sunlight Bleaching of Subporphyrazine Dye Films
## 3 Results and Discussion
### Film Morphology  
In both the \(\theta\)-2\(\theta\) geometry and the grazing incidence angle geometries, all films under study showed no noticeable peaks in the X-ray diffraction patterns, regardless of whether they were pristine or irradiated. This indicates the absence of a measurable long-range order of molecules in the vacuum-deposited SubPc/SubPz layers. Moreover, in an attempt to stimulate crystallization in the SubPzS\({}_{3}\)H\({}_{0}\) layer, the substrates were heated to 100 \({}^{\circ}\)C and above, similarly to what was performed in Ref [22] for SubPc5\({}_{0}\)H\({}_{12}\). Despite this, the SubPzS\({}_{3}\)H\({}_{0}\) layers retained their X-ray amorphous structure up to the resublimation threshold. The surface of the SubPzS\({}_{3}\)H\({}_{0}\) films was uniformly glossy to the eye, with a pinkish time typical of SubPc derivatives. The root-mean-square roughness (Sq) of the surface on a microscale was assessed by WLI with a pixel size of 1 \(\upmu\)m. Since the transparency of such films strongly reduces the reliability of WLI profiling, the film surface was decorated--see Experimental. Three random measurements on the sample surface were taken over the same scanning area; the averaged values are collected in Table 1.  
The microscale surface relief revealed periodic height differences of no more than 20 nm--Figure S2. Microscopic Sq values in the range of 5-6 nm indicate that the 80 nm thick films were relatively smooth. Sq somewhat decreased with a decrease in scanning area, which correlates with a probability of coming across some large-sized inhomogeneities, including contaminations. After the exposure to unfiltered irradiation in argon, the films became about two times smoother, most of the spherical objects decreased in size. The filtered sunlight irradiation in both air and argon increased Sq only slightly--Table 1. Consequently, the film morphology on a microscale depends on the spectrum of the incident radiation rather than on atmosphere. The combined AFM and SEM study added more detail to the surface morphology at the submicron scale--Figure 3; Table 1. The surface of the films, both in the pristine state and after irradiation, was covered with irregularly-shaped island-type objects of about 2 \(\upmu\)m in size. The lateral dimensions of such an object often exceeded the maximum area scanned with the tip, so that only its edge appeared in the AFM window--Figure 3a. The edge height was about 40 nm; these edges determined larger values of Sq derived from AFM--Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Sample** & **Pristine** & **Direct Sunlight, Ar** & **Filtered Sunlight, Ar** & **Direct Sunlight, Air** \\ \hline Scanning area & 0.9 \(\times\) 0.9 cm\({}^{2}\) (WLI) & 5.8 & 2.0 & 4.4 & 4.9 \\  & 0.3 \(\times\) 0.3 cm\({}^{2}\) (WLI) & 5.4 & 1.5 & 3.9 & 4.6 \\  & 0.1 \(\times\) 0.1 cm\({}^{2}\) (WLI) & 5.4 & 0.8 & 3.8 & 4.3 \\  & 2.25 \(\times\) 2.25 μm\({}^{2}\) (AFM) & 17.7 & 11.8 & 19.4 & 17.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Values of Sq, in nm, for the V-metallized surface of SubPzS\({}_{3}\)H\({}_{0}\) films on glass, measured over different scanning areas by WLI and AFM. The observed objects cannot have resulted from V-decoration, since they also appeared on the nonmetallized surfaces, as seen by SEM--Figure 3b. SEM images confirm that the objects were flat, grainless, and resemble patches of dried soil rather than typically fractal nano-objects formed by vacuum-deposited phthalocyanines on glass or metal surfaces [23]. According to AFM, the surface of the islands and between them consisted of fine spherical structures of up to 100 nm in size--Figure 3a. The absence of faceting, or even a well-defined granular structure, of the objects suggests very low crystallinity [23]. There were also irregular ditches whose depth is comparable with the nominal film thickness. The prevailing heights in the AFM statistics (i.e., average film thickness) lie in the range of 70 nm.