Formation of the conduction band electronic structure during deposition of ultrathin dicarboximide-substituted perylene films on the oxidized silicon surface

The results of the investigation of the conduction band electronic structure and the interfacial potential barrier during deposition of ultrathin dicarboximide-substituted perylene films (PTCBI-C$_8$) on the oxidized silicon surface have been presented. The measurements have been performed using the very low energy electron diffraction (VLEED) technique implemented in the total current spectroscopy (TCS) mode with a variation in the incident electron energy from 0 to 25 eV. Changes in the intensities of the maxima from the deposited PTCBI-C$_8$ film and from the substrate with an increase in the organic coating thickness to 7 nm have been analyzed using TCS measurements. A comparison of the structure of the maxima of PTCBI-C$_8$ and perylene-tetracarboxylic-dianhydride (PTCDA) films has made it possible to distinguish the energy range (8–13 eV above $E_{\mathrm{F}}$) in which distinct differences in the structures of maxima for PTCDA and PTCBI-C$_8$ films are observed. This energy range corresponds to low-lying $\sigma^*$-states of the conduction band of the films studied. The formation of the interfacial region of the PTCBI-C$_8$ film and (SiO$_2$)$_n$-Si substrate is accompanied by an increase in the surface work function by 0.6 eV, which corresponds to the electron density charge transfer from the (SiO$_2$)$_n$-Si substrate to the PTCBI-C$_8$ film.