We report the results of our studies of ruthenium layer structures adsorbed on GaN(0001). Ruthenium was evaporated at room temperature under ultrahigh vacuum conditions onto n-type GaN substrates epitaxially grown on sapphire. When X-ray photoelectron spectroscopy confirmed the presence of Ru bonds in the deposited adlayer, the ultraviolet photoelectron spectroscopy shown a peak at the Fermi level as well as lines originating from ruthenium. The height of the Schottky barrier was calculated based on the data measured by X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy and amounts to 1.5 eV. The work function of Ru adlayer is 4.4 eV, while the electron affinity of n-GaN(0001) substrate equals 3.4 eV.

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The electronic structures of Alq3/Si(111) and Alq3/LiBr/Si(111) interfaces are presented in this report. The studies were carried out in situ in ultrahigh vacuum by ultraviolet photoelectron spectroscopy. Alq3 and LiBr layers were vapour deposited onto a single crystal of n-type Si(111). The energy level diagrams were prepared for the structures. The formation of the LiBr interfacial layer results in a decrease of the energy barrier at the interface.

PTCDI-C8 molecules are vapor-deposited onto reconstructed Si(100)—(2 × 1) surface under ultra-high vacuum. X-ray photoelectron spectra reveal a bond formation between oxygen atoms of the molecules’ carboxylic groups and Si dangling bonds of the substrate. Following PTCDI—C8 film growth, ultraviolet photoelectron spectra show a drop in the HOMO level with respect to the Fermi level from 1.8 eV to 2.0 eV and a monotonic work function increase from 2.5 eV up to 3.3 eV. For a film thickness of 6.0 nm, a difference of 1.5 eV between the HOMO level of the film and the valence band maximum of the substrate is accomplished.