The first paragraph of the above mentioned article was accidentally deleted during preparation of the final version. The omitted first paragraph is shown here: Organic electronics has reached the market in a very short period of time, since the first organic light emitting device has been demonstrated. [1] Growth of organic thin films has been the focus of intensive investigations that in the recent years have gained knowledge about the involved mechanisms: substrate-molecule interaction versus molecule-molecule interaction, preparation parameters, substrate morphology (i.e., roughness, local defects, steps), and post growth treatment. [2-6] Here we investigate thin films of diindenoperylene deposited on Au(111) single crystals by using photoelectron emission microscopy (PEEM). We also discuss the effect of the growth on the film structure using the molecular orientation (i.e., the angle between the molecular axis and the substrate). The publisher apologizes for any inconvenience caused.
Heteroepitaxially grown bilayers of ferromagnetic La0.7Ca0.3MnO3 (LCMO) on top of superconducting YBa2Cu3O7 (YBCO) thin films were investigated by focusing on electric transport properties as well as on magnetism and orbital occupation at the interface. Transport measurements on YBCO single layers and on YBCO/LCMO bilayers, with different YBCO thickness dY and constant LCMO thickness dL = 50 nm, show a significant reduction of the superconducting transition temperature Tc only for dY < 10 nm,with only a slightly stronger Tc suppression in the bilayers, as compared to the single layers. X-ray magnetic circular dichroism (XMCD) measurements confirm recently published data of an induced magnetic moment on the interfacial Cu by the ferromagnetically ordered Mn ions, with antiparallel alignment between Cu and Mn moments. However, we observe a significantely larger Cu moment than previously reported, indicating stronger coupling between Cu and Mn at the interface. This in turn could result in an interface with lower transparency, and hence smaller spin diffusion length, that would explain our electric transport data, i.e. smaller Tc suppression. Moreover, linear dichroism measurements did not show any evidence for orbital reconstruction at the interface, indicating that a large change in orbital occupancies through hybridization is not necessary to induce a measurable ferromagnetic moment on the Cu atoms.
Cerium-doped manganite thin films were grown epitaxially by pulsed laser deposition at 720 • C and oxygen pressure pO 2 = 1 − 25 Pa and were subjected to different annealing steps. According to x-ray diffraction (XRD) data, the formation of CeO2 as a secondary phase could be avoided for pO 2 ≥ 8 Pa. However, transmission electron microscopy shows the presence of CeO2 nanoclusters, even in those films which appear to be single phase in XRD. With O2 annealing, the metal-toinsulator transition temperature increases, while the saturation magnetization decreases and stays well below the theoretical value for electron-doped La0.7Ce0.3MnO3 with mixed Mn 3+ /Mn 2+ valences. The same trend is observed with decreasing film thickness from 100 to 20 nm, indicating a higher oxygen content for thinner films. Hall measurements on a film which shows a metal-toinsulator transition clearly reveal holes as dominating charge carriers. Combining data from x-ray photoemission spectroscopy, for determination of the oxygen content, and x-ray absorption spectroscopy (XAS), for determination of the hole concentration and cation valences, we find that with increasing oxygen content the hole concentration increases and Mn valences are shifted from 2+ to 4+. The dominating Mn valences in the films are Mn 3+ and Mn 4+ , and only a small amount of Mn 2+ ions can be observed by XAS. Mn 2+ and Ce 4+ XAS signals obtained in surface-sensitive total electron yield mode are strongly reduced in the bulk-sensitive fluorescence mode, which indicates hole-doping in the bulk for those films which do show a metal-to-insulator transition.
Knowledge of the electron sampling depth and related saturation effects is important for quantitative analysis of X-ray absorption spectroscopy data, yet for oxides with the perovskite structure no quantitative values are so far available. Here we study absorption saturation in films of two of the moststudied perovskites, La 0.7 Ca 0.3 MnO 3 (LCMO) and YBa 2 Cu 3 O 7 (YBCO), at the L 2,3 edge of Mn and Cu, respectively. By measuring the electron-yield intensity as a function of photon incidence angle and film thickness, the sampling depth d, photon attenuation length λ and the ratio λ/d have been independently determined between 50 and 300 K. The extracted sampling depth d LCMO ≈ 3 nm for LCMO at high temperatures in its polaronic insulator state (150 -300 K) is not much larger than values reported for pure transition metals (d Co or Ni ≈ 2 -2.5 nm) at room temperature, but is smaller than d YBCO ≈ 3.9 nm for metallic YBCO that is in turn smaller than the value reported for Fe 3 O 4 (d Fe3O4 ≈ 4.5 nm). The measured d LCMO increases to 4.5 nm when LCMO is in the metallic state at low temperatures. These results indicate that a universal rule of thumb for the sampling depth in oxides cannot be assumed, and that it can be measurably influenced by electronic phase transitions that derive from strong correlations.
We find that island shapes and aggregation in diindenoperylene deposited on Au(100), Au(110), and Au(111) single crystals are steered by the anisotropy due to the lattice geometry of the substrate. This phenomenon may be exploited as a tool for molecular patterning of surfaces.
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