The effect of an interface dipole layer on the energy level alignment at organic-conductor interfaces is studied on a copper phthalocyanine (CuPc) monolayer/electric dipole layer/graphite system via ultraviolet photoemission spectroscopy (UPS) and metastable atom electron spectroscopy. An oriented monolayer of the OTi-phthalocyanine molecule, which has an electric dipole moment, is grown on graphite to yield a welldefined dipole layer with the vacuum side negatively charged. The CuPc monolayer is sequentially deposited on the dipole layer kept at 123 K. This weakly interacting system made of a very thin organic layer on top of a very thin dipole layer is in thermodynamic equilibrium. The UPS data from the system grown with and without the interface dipole layer show that the binding energy of the highest occupied state of the CuPc monolayer decreases when the dipole layer is inserted. The binding energy shift is in excellent agreement with the increase in vacuum level energy of the graphite substrate upon deposition of the dipole layer. The results show that the Fermi level of the CuPc shifts toward the valence states when the interface dipole layer is inserted.
Ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) films were formed without initial nucleation using a coaxial arc plasma gun. The UNCD crystallite diameters estimated from the X-ray diffraction peaks were approximately 2 nm. The Fourier transform infrared absorption spectrum exhibited an intense sp 3 -CH peak that might originate from the grain boundaries between UNCD crystallites whose dangling bonds are terminated with hydrogen atoms. A narrow sp 3 peak in the photoemission spectrum implied that the film comprises a large number of UNCD crystallites. Large optical absorption coefficients at photon energies larger than 3 eV that might be due to the grain boundaries are specific to the UNCD/a-C:H films.
For the two crystal materials, XaI(T1) and CsI(Sa), total, photoelectric and photopeak efficiencies are derived at several y-ray energies and crystal thicknesses. The effects of the stochastic variations in photomultiplier pulse production and of multiple Compton events on resolution are combined so as to give the modulation transfer function of gamma cameras without collimators. The effect of a hypothetical Compton discrimination on sensitivity and resolution is discussed.
Kr 3d ionization energies of small, variable size krypton clusters are investigated by photoelectron spectroscopy, where the size regime of clusters with an average size N< or =30 is studied. Characteristic shifts in Kr 3d ionization energies to lower binding energies are found compared to the bare atom. These are also different from those of large krypton clusters. Moreover, we find evidence for photoionization of the krypton dimer. Its 3d ionization energy is barely shifted relative to the atomic value. Results from model calculations considering different isomers and cluster sizes as well as defect sites give evidence that the experimental results can be related to photoionization from different surface sites in variable size krypton clusters. This can be related to site-specific photoemission in small Kr clusters. The results are compared to size effects in Kr 3d near-edge features of variable size Kr clusters as well as recent results on Kr 3d photoionization of large Kr clusters.
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