The anisotropic optical constants of vacuum deposited films of H2TMPP, CuTMPP, and NiTMPP (TMPP=5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin) in the thickness range of 50 to 150nm were obtained by ...spectroscopic ellipsometry measurements and subsequent modelling. The angle of the planar molecular backbone with respect to the substrate plane was determined from the degree of optical anisotropy of the optical constants. The resulting angles were compared to those of near edge X-ray absorption fine structure (NEXAFS) spectroscopy on 2 to 5nm thick films. Gold and natively oxidised silicon were used as substrates. The molecular tilt angle on Si (~38°) was found to be slightly smaller than on gold (~41°) for the thick films. This trend was confirmed by NEXAFS. Magneto-optical Kerr effect spectroscopy was applied in order to obtain the off-diagonal elements of the dielectric tensor under a magnetic field. These results were then used to calculate magnetic circular dichroism spectra for comparison with literature results and the assignment of Faraday terms to the particular absorption features.
•Tetramethoxyphenylporphyrins were thermally evaporated in vacuum to grow thin films.•Their anisotropic optical constants were determined by spectroscopic ellipsometry.•The molecular orientation in the films was estimated from the optical anisotropy.•MOKE spectroscopy results are related to the nature of the optical transitions.•Methoxy side groups modify the magneto-optical behavior of H2-tetraphenylporphyrin.
The semiconducting properties of a bithiophene-naphthalene diimide copolymer (PNDIT2) prepared by Ni-catalyzed chain-growth polycondensation (P1) and commercially available N2200 synthesized by ...Pd-catalyzed step-growth polycondensation were compared. Both polymers show similar electron mobility of ∼0.2 cm 2 V −1 s −1 , as measured in top-gate OFETs with Au source/drain electrodes. It is noteworthy that the new synthesis has several technological advantages compared to traditional Stille polycondensation, as it proceeds rapidly at room temperature and does not involve toxic tin-based monomers. Furthermore, a step forward to fully printed polymeric devices was achieved. To this end, transistors with PEDOT:PSS source/drain electrodes were fabricated on plastic foils by means of mass printing technologies in a roll-to-roll printing press. Surface treatment of the printed electrodes with PEIE, which reduces the work function of PEDOT:PSS, was essential to lower the threshold voltage and achieve high electron mobility. Fully polymeric P1 and N2200-based OFETs achieved average linear and saturation FET mobilities of >0.08 cm 2 V −1 s −1 . Hence, the performance of n-type, plastic OFET devices prepared in ambient laboratory conditions approaches those achieved by more sophisticated and expensive technologies, utilizing gold electrodes and time/energy consuming thermal annealing and lithographic steps.
The interface formation between manganese phthalocyanine (MnPc) and cobalt was investigated combining ultraviolet photoelectron spectroscopy and inverse photoelectron spectroscopy. The transport band ...gap of the MnPc increases with the film thickness up to a value of (1.2 ± 0.3) eV while the optical band gap as determined from spectroscopic ellipsometry amounts to 0.5 eV. The gap values are smaller compared to other phthalocyanines due to metallic Mn 3d states close to the Fermi level. The transport band gap was found to open upon air exposure as a result of the disappearance of the occupied 3d electronic states.
The changes of the optical properties of several organic thin films induced by potassium doping were monitored using in situ spectroscopic ellipsometry. The samples were prepared in a high vacuum ...chamber by organic molecular deposition. Then, potassium (K) was evaporated by passing current through K getters. The three different organic molecules used, show very distinct and different spectral behaviour upon doping. While for Tris-(8-hydroxyquinoline)-aluminium(III) and N,N′-Di-(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine only small shifts of the spectral features were noticed, Manganese Phthalocyanine revealed significant changes of the optical properties induced by the K doping. This work indicates that the K doping process can have a dramatic effect on the electronic and the optical properties of the organic molecules, but the effect on the optical spectra remains specific for each organic molecule used, and cannot be easily predicted.
•Monitoring organic film growth and doping with in situ spectroscopic ellipsometry•K doped organic thin films•Optical properties of organic thin films change by K doping.•The changes in the optical spectra remain specific for each organic molecule used.
The phenomenon of `first sharp diffraction peaks' (FSDP) present in the diffractograms of certain amorphous solid or liquid systems below the so-called main diffraction peak is studied by the use of ...Fourier transforms remaining within the diffraction theory of non-crystalline systems. Performing the inverse transformation of the reduced radial distribution functions (RDFs) in separate parts enables us to trace the origin of an FSDP – or any other features of the diffraction pattern – to real space. This means that all pieces of information on the (disordered) structure contained by the structure factors are comprised of the pair distribution functions too. The input of extraneous distances, layers, etc. is unnecessary and therefore misleading.
In this work, an approach for copper atomic layer deposition (ALD) via reduction of Cu x O films was investigated regarding applications in ULSI interconnects, like Cu seed layers directly grown on ...diffusion barriers (e. g. TaN) or possible liner materials (e. g. Ru or Ni) as well as non-ferromagnetic spacer layers between ferromagnetic films in GMR sensor elements, like Ni or Co. The thermal Cu x O ALD process is based on the Cu (I) β-diketonate precursor ( n Bu 3 P) 2 Cu(acac) and a mixture of water vapor and oxygen ("wet O 2 ") as co-reactant at temperatures between 100 and 130°C. Highly efficient conversions of the Cu x O to metallic Cu films are realized by a vapor phase treatment with formic acid (HCOOH), especially on Ru substrates. Electrochemical deposition (ECD) experiments on Cu ALD seed/Ru liner stacks in typical interconnect patterns are showing nearly perfectly filling behavior. For improving the HCOOH reduction on arbitrary substrates, a catalytic amount of Ru was successful introduced into the Cu x O films during the ALD with a precursor mixture of the Cu (I) β-diketonate and an organometallic Ru precursor. Furthermore, molecular and atomic hydrogen were studied as promising alternative reducing agents.
The semiconducting properties of a bithiophene-naphthalene diimide copolymer (PNDIT2) prepared by Ni-catalyzed chain-growth polycondensation (P1) and commercially available N2200 synthesized by ...Pd-catalyzed step-growth polycondensation were compared. Both polymers show similar electron mobility of similar0.2 cm2 V−1 s−1, as measured in top-gate OFETs with Au source/drain electrodes. It is noteworthy that the new synthesis has several technological advantages compared to traditional Stille polycondensation, as it proceeds rapidly at room temperature and does not involve toxic tin-based monomers. Furthermore, a step forward to fully printed polymeric devices was achieved. To this end, transistors with PEDOT:PSS source/drain electrodes were fabricated on plastic foils by means of mass printing technologies in a roll-to-roll printing press. Surface treatment of the printed electrodes with PEIE, which reduces the work function of PEDOT:PSS, was essential to lower the threshold voltage and achieve high electron mobility. Fully polymeric P1 and N2200-based OFETs achieved average linear and saturation FET mobilities of >0.08 cm2 V−1 s−1. Hence, the performance of n-type, plastic OFET devices prepared in ambient laboratory conditions approaches those achieved by more sophisticated and expensive technologies, utilizing gold electrodes and time/energy consuming thermal annealing and lithographic steps.
Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
The semiconducting properties of a bithiophene-naphthalene diimide copolymer (PNDIT2) prepared by Ni-catalyzed chain-growth polycondensation (P1) and commercially available N2200 synthesized by ...Pd-catalyzed step-growth polycondensation were compared. Both polymers show similar electron mobility of similar0.2 cm2 V−1 s−1, as measured in top-gate OFETs with Au source/drain electrodes. It is noteworthy that the new synthesis has several technological advantages compared to traditional Stille polycondensation, as it proceeds rapidly at room temperature and does not involve toxic tin-based monomers. Furthermore, a step forward to fully printed polymeric devices was achieved. To this end, transistors with PEDOT:PSS source/drain electrodes were fabricated on plastic foils by means of mass printing technologies in a roll-to-roll printing press. Surface treatment of the printed electrodes with PEIE, which reduces the work function of PEDOT:PSS, was essential to lower the threshold voltage and achieve high electron mobility. Fully polymeric P1 and N2200-based OFETs achieved average linear and saturation FET mobilities of >0.08 cm2 V−1 s−1. Hence, the performance of n-type, plastic OFET devices prepared in ambient laboratory conditions approaches those achieved by more sophisticated and expensive technologies, utilizing gold electrodes and time/energy consuming thermal annealing and lithographic steps.
Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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