Chemistry and electronic properties of ferromagnetic metal‐organic semiconductor interfaces: Fe on CuPc

Abstract

The chemistry and electronic properties of the interfaces formed between the ferromagnetic metal (Fe) and the model organic semiconductor copper phthalocyanine are investigated in ultra-high vacuum conditions for the case of metal deposition onto the organic molecular thin film. The studies were performed by means of core-level and valence-band high-resolution photoemission electron spectroscopy (PES) as well as near-edge X-ray absorption fine structure using synchrotron radiation. Metal overlayer formation on the top of the organic semiconductor was observed without substantial penetration of deposited metal species into the organic film. At the thin interface layer the ferromagnetic metal shows strong chemical interaction with the nitrogen and carbon of the organic films. Moreover, our results infer that, as a consequence of Fe deposition onto CuPc, central copper atoms of the organic molecules at the interface are reduced from Cu(II) to Cu(I), while Fe atoms are oxidized and/or the ferromagnetic metal replaces this central Cu atom. Further optimization of such an interface is thus required to allow and/or facilitate the injection of spin-polarized carriers into organic semiconductors

Fluorination-Guided Li-Anchoring Behaviors on Phthalocyanines

“…The peak at 285.8 eV belongs to the pyrrole carbon linked to nitrogen (NC−N, denoted as C N ), and the peak at 284.5 eV originates from the aromatic carbon of the benzene rings (C−C(H), denoted as C B ). 44,45 Additional peaks are observed at binding energies of 286.8 and 287.8 eV, which are associated with π−π* satellite features from the aromatic carbon and the pyrrole carbon, respectively. 46−49 The N 1s core-level spectrum of CuPc shows a single peak at 398.8 eV, indicating that the outer aza bridge nitrogen (CN, denoted as N a ) and the pyrrolic nitrogen coordinated with the Cu(II) ion (C−N−Cu, denoted as N p ) are in a similar chemical bonding environment (N c ).…”

“…In the XPS spectra of CuPc (Figure ), the C 1s region mainly consists of two carbon peaks. The peak at 285.8 eV belongs to the pyrrole carbon linked to nitrogen (NC–N, denoted as C N ), and the peak at 284.5 eV originates from the aromatic carbon of the benzene rings (C–C­(H), denoted as C B ). , Additional peaks are observed at binding energies of 286.8 and 287.8 eV, which are associated with π–π* satellite features from the aromatic carbon and the pyrrole carbon, respectively. − The N 1s core-level spectrum of CuPc shows a single peak at 398.8 eV, indicating that the outer aza bridge nitrogen (CN, denoted as N a ) and the pyrrolic nitrogen coordinated with the Cu­(II) ion (C–N–Cu, denoted as N p ) are in a similar chemical bonding environment (N c ). ,, An extra peak at 400.6 eV is added to fit the N 1s region, which results from the π–π* shakeup satellites of N. − The Cu 2p region of CuPc possesses two peaks originating from the spin–orbit split doublets, with the Cu 2p 3/2 peak located at 935.5 eV. , It should be noted that shakeup satellites can be observed at the higher binding energy side for both the Cu 2p 3/2 and the Cu 2p 1/2 peaks, which is a well known characteristic of Cu­(II) species. ,,− The core-level spectra of F 16 CuPc are similar to those of CuPc except for the F 1s peak at 687.9 eV with a π–π* satellite feature and a strong C 1s peak at the highest binding energy of 287.4 eV (C F ) due to the fluorination on the outer carbon atoms of the benzene rings, ,, as illustrated in the molecular structure of F 16 CuPc in Figure . The C 1s, N 1s, and Cu 2p peaks of F 16 CuPc show higher binding energies compared with those of CuPc, which is mainly attributed to the strong electronegativity of the outer F atoms.…”

“…46−49 The N 1s core-level spectrum of CuPc shows a single peak at 398.8 eV, indicating that the outer aza bridge nitrogen (CN, denoted as N a ) and the pyrrolic nitrogen coordinated with the Cu(II) ion (C−N−Cu, denoted as N p ) are in a similar chemical bonding environment (N c ). 44,46,50 An extra peak at 400.6 eV is added to fit the N 1s region, which results from the π−π* shakeup satellites of N. 46−49 The Cu 2p region of CuPc possesses two peaks originating from the spin−orbit split doublets, with the Cu 2p 3/2 peak located at 935.5 eV. 37,46 It should be noted that shakeup satellites can be observed at the higher binding energy side for both the Cu 2p 3/2 and the Cu 2p 1/2 peaks, which is a well known characteristic of Cu(II) species.…”

Morphology and properties of a hybrid organic-inorganic system: Al nanoparticles embedded into CuPc thin film

“…The occurrence of such copper atom behavior would parallel the effects of Li, Fe, and Co deposition onto CuPc. [32][33][34] However, the C 1 s and N 1 s core level data shown in Figs. 4(b) and 4(d) proof that this conception is too simple and that the phthalocyanine molecule entirely is affected by the interface reactions.…”

Metal-Diffusion-Induced Interface Dipole: Correlating Metal Oxide–Organic Chemical Interaction and Interface Electronic States

“…12 An X-ray absorption study showed that a ferromagnetic metal, Fe, deposited on CuPc makes a chemical reaction and charge carrier traps into CuPc molecules. 13 However, these results cannot explain the effect of metal diffusion on the change of the interface dipole (ID) and the charge carrier injection barrier (CIB). The ID has an important influence on charge injection properties and device performance in terms of low operation voltage, high quantum efficiency, high stability, and so on.…”