Electronic structure of a vapor-deposited metal-free phthalocyanine thin film

Abstract

The electronic structure of a vapor-sublimated thin film of metal-free phthalocyanine (H2Pc) is studied experimentally and theoretically. An atom-specific picture of the occupied and unoccupied electronic states is obtained using x-ray-absorption spectroscopy (XAS), core- and valence-level x-ray photoelectron spectroscopy (XPS), and density-functional theory (DFT) calculations. The DFT calculations allow for an identification of the contributions from individual nitrogen atoms to the experimental N1s XAS and valence XPS spectra. This comprehensive study of metal-free phthalocyanine is relevant for the application of such molecules in molecular electronics and provides a solid foundation for identifying modifications in the electronic structure induced by various substituent groups.

Potassium-intercalated H2Pc films: Alkali-induced electronic and geometrical modifications

“…1), and a feature at higher BE (at about 400 eV), due to ionization of the N1 atoms. 6 After the first K deposition, the whole spectrum is seen to shift by about 0.4 eV towards higher BE and to slightly broaden. For the next intercalation step (x = 0.6), the main feature of the N1s spectrum is shifted back with about 0.15 eV (towards lower BE), and the line-shape is considerably modified, showing a pronounced asymmetry of the main feature.…”

“…3,4 Their chemical and thermal stability has permitted studies in ultra high vacuum (UHV) environments resulting in many spectroscopic investigations. [5][6][7][8][9][10][11][12][13][14][15][16][17][18] The possibility to modify the electronic structure of the molecular film allows the tuning of specific properties and this is clearly highly desired to further improve the performance of Pc-based devices. For this reason, the interesting results reported by Craciun et al 19 and already predicted by a theoretical study by Tosatti et al 20 about the observation of an insulator-to-metal transition of Pc films upon alkali intercalation (between 0 and 4 K atoms per molecule) have inspired a number of studies.…”

When the Grafting of Double Decker Phthalocyanines on Si(100)-2 × 1 Partly Affects the Molecular Electronic Structure

“…The average ∆ BE between benzene type carbons (C ben ) and pyrrole type carbons (C pyr ) is 1.2 eV for a single molecule and 1.1 eV for C atoms of the top Pc ring of the adsorbed molecule, which is consistent with previous studies of similar systems. 34 For the bottom Pc of the adsorbed molecule, the BE positions are rather different, having a maximum spread in the BE of 0.48 eV for the C pyr and 0.78 eV for the C ben atoms. Even though the ∆ BE between the C ben and C pyr is 1.4 eV in the case of non-bonded C atoms and 0.95 eV for chemically bonded C atoms, the average ∆ BE remains similar to the "gas-phase" single molecule calculations with ∆ BE of 1.2 eV between the C ben and C pyr contributions.…”

Study by XPS and UV−Visible and DRIFT Spectroscopies of Electropolymerized Films of Substituted Ni(II)-p-Phenylporphyrins and -Phthalocyanines

“…Finally, the minor peak at 401.5 eV (12%) could be due to high BE nitrogen species, usually observed at 401.5-403.0 eV in the N 1s XP spectra of porphyrins 27-29 and associated with shakeup satellites. 30 The N 1s spectrum of the polyNiTSPP film ( Figure 7B) shows only two components: a major one of the pyrrolic nitrogen and a minor one of the NH groups ( Figure 7B). The intensity of the NH component is 38%, much higher than that of 11% in the spectrum of the monomer, demonstrating that polymerization increases the proportion of NH groups.…”

“…The main one at 398.8 eV (60%) corresponds to the pyrrolic nitrogen bonded to Ni(II) in the porphyrin structure, while the contribution at 400.0-400.2 eV (30%) is associated with the NH 2 groups. Other minor components at higher BEs are due to shakeup satellites (402.1 eV, 3%) and inelastic scattering 30 (405.7 eV, 7%) (see also Table 5). The N 1s spectrum of the unactivated NiTAPP film ( Figure 7D) is similar to that of the monomer, but for a small increase of the shakeup satellite and a slight decrease of the NH 2 component (see Table 5), this decrease suggesting that polymerization involves the NH 2 groups.…”