Figure 1

(a) ${\mathrm{XeI}}_{\alpha }$-UPS spectra of as-deposited [spectrum (1)], ${\mathrm{N}}_2$-exposed [spectra (2)–(6)], ${\mathrm{O}}_2$-exposed [spectra (7)] and Ar-exposed [spectra (8)] Pn thin film (15 nm) on ${\mathrm{SiO}}_2$ substrate. Spectrum (9) includes the UPS data of as-deposited and ${\mathrm{N}}_2$-exposed $\mathrm{Pn}/\mathrm{Au}(111)$ thin film (40 nm) acquired at RT. The positions of the VL and HOMO derived bands ($H_1$ and $H_2$) are indicated by vertical (continuous) bars. The difference between the VL (HOMO) positions of the $\mathrm{Pn}/{\mathrm{SiO}}_2$ thin films in the “${\mathrm{N}}_2$” and “Ar” experiments reflects the difference between the initial ${\mathrm{SiO}}_2$ work functions. (b) DOS (log scale intensity plot) of as-deposited [closed (red) square symbols], ${\mathrm{N}}_2$-exposed [20 h, closed (magenta) circles] and ${\mathrm{O}}_2$-exposed (5 h, open circles) Pn thin film on ${\mathrm{SiO}}_2$. Continuous (black) lines are the cumulative fitting curve of the HOMO band (see Sec. III of the Supplemental Material [23]). DOS values were extracted from the UPS data, as described in Ref. 24. ${\mathrm{SiO}}_2$ data are rescaled to preserve, in the DOS scale, their relative intensity with respect to the as-deposited Pn data. Vertical arrows indicate the threshold energy position ($E_T$) where the DOS distribution deviates from the cumulative fitting curve and DOGS starts to appear. The dashed line indicates the DOGS of the Pn thin film as determined by transport measurements. Data are adapted from Ref. 12. (c) ${\mathrm{XeI}}_{\alpha }$-UPS spectra of as-deposited Pn thin film on Au(111) (40 nm) before and after ${\mathrm{N}}_2$ exposure. The Fermi edge of the Au(111) substrate is clearly visible (see also inset). No spectral change was detected upon gas exposure.Reuse & Permissions

Figure 2

Schematic representation of the gas penetration and mediated imperfections in Pn thin film on ${\mathrm{SiO}}_2$. During exposure [panel (a)], gas molecules progressively penetrate into the Pn film, where they locally alter the original intermolecular packing geometry [panel (b)]. The gas penetration proceeds through the grain boundaries of the film. Because of the weak ${\mathrm{N}}_2\mathrm{\text{−}}\mathrm{Pn}$ interaction, ${\mathrm{N}}_2$ molecules are easily removed once the film is put back in UHV. The result is a weakly disordered film [(panel (c)].Reuse & Permissions

Figure 3

(a) ${\mathrm{XeI}}_{\alpha }$-UPS data of as-deposited, ${\mathrm{N}}_2$-exposed and ${\mathrm{O}}_2$-exposed $\mathrm{Pn}/{\mathrm{SiO}}_2$ thin film in the HOMO band region. The energy scale is referred to the $H_2$ position (dotted line) where the HOMO band reaches the maximum intensity. The vertical, short bars on each plot indicate the position of the Fermi level. The ${\mathrm{SiO}}_2$ substrate signal was not removed from the as-deposited sample spectra. (b) Same as panel (a), but plotted on a log scale. The continuous (black) line indicates the position of the threshold energy ($E_T$) from which the gap state energy distribution starts to appear. (c) Spectral ratio between the data of gas-exposed film and as-deposited film (see text for details).Reuse & Permissions