@article{ShanjiaXinzhangGreineretal.1992,
  author    = {Shanjia, Xu and Xinzhang, Wu and Greiner, P. and Becker, Charles R. and Geick, R.},
  title     = {Microwave transmission and reflection of stratified lossy dielectric segments partially filled waveguide},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37958},
  year      = {1992},
  abstract  = {The microwave transmission and reßection is evaluated for stratified lossy dielectric segments partially filling the rectangular waveguide by the method which combines the multimode network theory with the rigorous mode matching procedure. As an example, we investigate in detail the microwave scattering properties of II-VI-epitaxial layer on a lossy dielectric substrate inserted in the rectangular waveguide. The experimental data verify the accuracy and the effectiveness of the present method. Extensive numerical results are presented to establish useful guidelines for the contactless microwave measurement of the conductivity of the epitaxiallayer.},
  language  = {en}
}
@article{ShanjiaXinzhangBoegeetal.1993,
  author    = {Shanjia, Xu and Xinzhang, Wu and Boege, P. and Sch{\"a}fer, H. and Becker, Charles R. and Geick, R.},
  title     = {Scattering characteristics of 3-D discontinuity consisting of semiconductor sample filled in waveguide with gaps},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37964},
  year      = {1993},
  abstract  = {No abstract available},
  language  = {en}
}
@article{HeBeckerBicknellTassiusetal.1993,
  author    = {He, L. and Becker, Charles R. and Bicknell-Tassius, R. N. and Scholl, S. and Landwehr, G.},
  title     = {Molecular beam epitaxial growth and evaluation of intrinsic and extrinsically doped (100) Hg\(_{0.8}\)Cd\(_{0.2}\)Te on (100) Cd\(_{0.96}\)Zn\(_{0.04}\)Te},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37885},
  year      = {1993},
  abstract  = {No abstract available.},
  language  = {en}
}
@article{SchikoraHausleitnerEinfeldtetal.1994,
  author    = {Schikora, D. and Hausleitner, H. and Einfeldt, S. and Becker, Charles R. and Widmer, T. and Giftige, C. and Lischka, K. and von Ortenburg, M. and Landwehr, G.},
  title     = {Epitaxial overgrowth of II-VI compounds on patterned substrates},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37985},
  year      = {1994},
  abstract  = {The selected area epitaxial overgrowth of narrow gap HgTe as well as wide gap CdTe and ZnTe on CdTe/GaAs substrates, which had been structured by dry etching techniques, has been investigated. A plasma etching process using a barrel reactor with CH\(_4\)-CH\(_2\) gases has been employed to prepare stripes with a width of about 1 μm with anisotropic as well as isotropic etching profiles. It has been found, that the selected area HgTe overgrowth takes place with a high local selectivity to the low index planes of the patterned surface. In contrast, the selected area overgrowth of the wide gap CdTe and ZnTe is controlled by anisotropic growth kinetics provided that the substrate temperature is not lower than 220°C and the starting surface consists of well developed low index crystallographic planes.},
  language  = {en}
}
@article{EinfeldtHeinkeBehringeretal.1994,
  author    = {Einfeldt, S. and Heinke, H. and Behringer, M. and Becker, Charles R. and Kurtz, E. and Hommel, D. and Landwehr, G.},
  title     = {The growth of HgSe by molecular beam epitaxy for ohmic contacts to p-ZnSe},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38001},
  year      = {1994},
  abstract  = {The structural properties of HgSe grown by molecular beam epitaxy (MBE) are investigated for different lattice mismatches to the substrate and various growth conditions. The growth rate is shown to depend strongly on the growth temperature above lOO°C as well as on the Hg/Se flux ratio. It has been found that the crystalline perfection and the electrical properties are mainly determined by the layer thickness, especially for the growth on highly lattice mismatched substrates. Changes in the surface morphology are related to growth parameters. Differences between the electrical behavior of MBE-grown and bulk HgSe are discussed. The electrical properties of HgSe contacts on p-ZnSe are investigated as a function of different annealing procedures.},
  language  = {en}
}
@article{WuBeckerWaagetal.1993,
  author    = {Wu, Y. S. and Becker, Charles R. and Waag, A. and Bicknell-Tassius, R. N. and Landwehr, G.},
  title     = {Removal of oxygen and reduction of carbon contamination on (100) Cd\(_{0.96}\)Zn\(_{0.04}\)Te},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38014},
  year      = {1993},
  abstract  = {No abstract available},
  language  = {en}
}
@article{ZhangBeckerZhangetal.1994,
  author    = {Zhang, X. F. and Becker, Charles R. and Zhang, H. and He, L. and Landwehr, G.},
  title     = {Investigation of a short period (001) HgTe-Hg\(_{0.6}\)Cd\(_{0.4}\)Te superlattice by transmission electron microscopy},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38029},
  year      = {1994},
  abstract  = {No abstract available},
  language  = {en}
}
@article{BeckerMartin1972,
  author    = {Becker, Charles R. and Martin, T. P.},
  title     = {Infrared absorption by Impurity-pair resonant modes in NaCl:F},
  isbn      = {1098-0121},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37840},
  year      = {1972},
  abstract  = {New resonant-mode infrared absorption lines have been observed in NaCl with high concentrations of fluorine impurities. The quadratic concentration dependence of the strength of these lines indicates that they are due to pairs of fluorine impurities. At the resonant frequencies, the motion of some host ions appears to be as important as the motion of the impurities themselves.},
  subject      = {Festk{\"o}rperphysik},
  language  = {en}
}
@article{BeckerNath1970,
  author    = {Becker, Charles R. and Nath, G.},
  title     = {Optical properties of LiIO\(_3\) in the far infrared},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37905},
  year      = {1970},
  abstract  = {No abstract available},
  language  = {en}
}
@article{TackeSchuberthBeckeretal.1982,
  author    = {Tacke, M. and Schuberth, W. and Becker, Charles R. and Haas, L. D.},
  title     = {The dielectric constant of PbTe at 4.2 K and \(\tilde ν\)=84.15 cm\(^{-1}\), 96.97 cm\(^{-1}\), 103.60 cm\(^{-1}\)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30821},
  year      = {1982},
  abstract  = {The dielectric constant of a PbTe epitaxial layer has been measured by surface wave spectroscopy using an optically pumped far-infrared laser and the technique of attenuated total reflection.},
  language  = {en}
}
@article{GeisGeickBeckeretal.1977,
  author    = {Geis, G. and Geick, R. and Becker, Charles R. and Wagner, V.},
  title     = {Antiferromagnetic resonance in CoO/NiO mixed crystals},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31239},
  year      = {1977},
  abstract  = {We have studied the lowest magnetic excitation of Ni\(_{1-x}\)Co\(_x\)O mixed crystals for 0.94 \(\leq\) x \(\leq\) 1. Together with previous results for 0.02 \(\leq\) x \(\leq\) 0.07 and neutron data for x = 0.14 and x = 0.30, the results are discussed by means of a model, especially the variation of AFMR frequency and preferred spin direction with Co concentration x.},
  language  = {en}
}
@misc{IshigamaBeckerMartinetal.1972,
  author    = {Ishigama, M. and Becker, Charles R. and Martin, T. P. and Prettl, W.},
  title     = {Impurity-pair mode in NaCl:KF},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31255},
  year      = {1972},
  abstract  = {No abstract available},
  language  = {en}
}
@article{Becker1970,
  author    = {Becker, Charles R.},
  title     = {Impurity-induced absorption in or near the phonon gap of KI},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30757},
  year      = {1970},
  abstract  = {In or near the phonon gap of KI a single weak line due to OW (OD\(^-\)) at 69.7 (69.3) cm\(^{-1}\) has been observed. A second and much stronger line at 94.1 cm\(^{-1}\) was shown not to be related to OH\(^-\), but instead is thought to be due to CO\(_3\).},
  language  = {en}
}
@misc{KoehlerBecker1976,
  author    = {K{\"o}hler, H. and Becker, Charles R.},
  title     = {Infrared-active lattice vibrations in SnSe\(_2\)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30838},
  year      = {1976},
  abstract  = {No abstract available},
  language  = {en}
}
@misc{UnkelbachBeckerKoehleretal.1973,
  author    = {Unkelbach, K. H. and Becker, Charles R. and K{\"o}hler, H. and Middendorff, A. V.},
  title     = {Optical Phonons of Bi\(_2\)Te\(_3\)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30809},
  year      = {1973},
  abstract  = {No abstract available},
  language  = {en}
}
@article{KoehlerBecker1974,
  author    = {K{\"o}hler, H. and Becker, Charles R.},
  title     = {Optically active lattice vibrations in Bi\(_2\)Se\(_3\)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31296},
  year      = {1974},
  abstract  = {The preparation of Bi2Sea single crystals with low free carrier densities allowed an investigation of the lattice vibrations to be carried out from the reflectivity of cleavage planes at nearly normal incidence of the radiation (E ~ c). The experimental results ean be explained with two classical oscillators, whose eigenfrequencies oceur at 92 and 69.5 cm-I. The static dielectric constant was determined to be 100 ± 10 for E ~ c.},
  language  = {en}
}
@article{KlitzingBecker1976,
  author    = {Klitzing, K. von and Becker, Charles R.},
  title     = {Far infrared photoconductivity of residual acceptors in pure tellurium},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-31278},
  year      = {1976},
  abstract  = {The photoconductivity of both undeformed and deformed Te samples has been investigated at liquid He temperature by means of a Fourier spectrometer. Three peaks were usually found in the spectra of undeformed samples at 11, 24 and 46 cm\(^{-1}\). These are shown to be due to three different chemical impurities. The deformed samples are characterized by additional structure at higher frequencies.},
  language  = {en}
}
@article{Becker1971,
  author    = {Becker, Charles R.},
  title     = {Evidence for a quasi-phonon gap in CsCl},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30767},
  year      = {1971},
  abstract  = {The observed impurity induced far-infrared absorption in CsCl : Rb\(^+\) and CsCl : K\(^+\) is compared with a calculated density of acoustic phonon states in CsCl. The absorption due to CsCl : Rb\(^+\) displays a minimum between the acoustic and optic phonon bands. A narrow line is observed in CsCl: K\(^+\) at 85.8 cm\(^{-1}\) which falls in this quasi-phonon gap.},
  language  = {en}
}
@article{SchubertKrausKenkliesetal.1992,
  author    = {Schubert, D.W. and Kraus, M.M and Kenklies, R. and Becker, Charles R. and Bicknell-Tassius, R.N.},
  title     = {Composition and wavelength dependence of the refractive index in Cd\(_{1-x}\)Mn\(_x\)Te epitaxial layers},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37716},
  year      = {1992},
  abstract  = {We have investigated Cd\(_{1-x}\)Mn\(_x\)Te thin films with Mn concentrations of x=0.12, 0.18, 0.30, 0.52, and 0.70. These single crystal layers were grown by molecular beam epitaxy on [001] CdTe substrates. The real part of the refractive index, n, was determined below the band-gap Eo in the range of 0.5-2.5 eV at T=300 K. The parallel reOectivity was measured near the Brewster angle at the YAG laser wavelength of 1.064 J.Lm (hv= 1.165 eV). Combining these results with the optical pathlength results (nd) of reOection measurements in a Fourier spectrometer we have determined n(x,v) over a wide spectral range by utilizing a three parameter fit. The accuracy of these results for n should improve waveguide designs based on this material.},
  language  = {en}
}
@phdthesis{Fuchs2009,
  author    = {Fuchs, Oliver},
  title     = {Soft x-ray spectroscopy of organic molecules and liquids},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37055},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2009},
  abstract  = {In this thesis, soft x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) studies of the electronic structure of selected organic molecules and liquids were carried out. The first part focuses on the used experimental techniques and the development of the instrumentation necessary for these studies, namely a soft x-ray spectrometer, and a temperature-controlled flow-through liquid cell. The former was optimized by a special analytical ray tracing method developed exclusively for this purpose. Due to its high transmission, the spectrometer facilitates a novel experimental approach of recording comprehensive 'RIXS maps', which are 2-dimensional plots of x-ray scattering intensities as a function of both, excitation and emission photon energy. The liquid cell extends these possibilities to the study of liquids, especially the interaction of molecules in liquids and their chemical reactions under well-controlled conditions. Organic molecules have attracted considerable attention in the last decade. The intense research activities related to these materials have two main motivations: on the one hand, organic molecules have a technological application as building blocks of organic semiconductors, while, on the other hand, organic molecules are the functional elements in biological systems. In order to cost-effectively produce optimized organic electronic devices, a fundamental knowledge of the electronic properties of the organic molecules interface is necessary. Therefore, many studies of the electronic structure of potential candidates for organic electronics exist. Two of these candidates, namely C60 and well-ordered multilayers PTCDA on a Ag(111) surface are investigated in this thesis. For the study of C60 molecules, a comprehensive 'RIXS map' was recorded and analyzed. The RIXS map taken in only 25 minutes allows a quantitative analysis of energy losses, yielding for example the HOMO-LUMO distance. It also identifies a core-excitonic state and facilitates a quantitative comparison of its binding energy with that of valence excitons in C60. Furthermore, decay channel-selective partial fluorescence yield XAS spectra can be extracted from the RIXS map, yielding information on the population of the core-excitonic state as a function of excitation energy. As a second model system of organic molecules relevant for organic electronics, PTCDA was chosen. The complex electronic structure of the occupied states of a highly ordered, flat-lying PTCDA multilayer on a Ag(111) surface was investigated by symmetry-resolved resonant x-ray emission spectroscopy. The rapidly occurring beam damage effects were characterized on the basis of irradiation-time dependent series of C and O x-ray emission spectra. Upon varying the excitation energy and emission geometry, atom- and symmetry-specific carbon K emission spectra with negligible beam damage effects were obtained that allow to distinguish between electronic states with sigma and pi symmetry. A density functional theory calculation of the PTCDA molecule reproduces the energy positions of the most prominent emission features remarkably well. In addition, the energy positions of the sigma and pi emissions agree well with the calculated energies of the respective orbitals. In order to shed light on the second aspect of organic molecules, namely their role in biological systems, first a detailed investigation of the electronic structure and proton dynamics of liquid water as the medium of most chemical and biochemical reactions was carried out. Therefore, a comprehensive oxygen K RIXS map of liquid water was recorded and analyzed in great detail. A temperature-dependent comparison with XAS and RIXS data of D2O, NaOH, and NaOD leads to the conclusion, that ultra-fast dissociation takes place in liquid water on the timescale of the oxygen 1s core hole lifetime, resulting in a characteristic spectral contribution in the RIXS spectra. The dissociation is promoted by intact hydrogen bonds with neighboring molecules. In consequence, the rate of dissociation directly depends on the initial hydrogen bond configuration. In the next step towards biologically relevant systems, the nitrogen K edges of the amino acids glycine and histidine were investigated in powderous form as well as in their native environment, namely in aqueous solution. X-ray absorption and emission spectra of the aqueous solutions were analyzed at pH-values of 6 and for glycine also at pH 12 and compared to the spectra of powders. A pH-value of 12 causes deprotonation of the amino group, leading to significant changes in the nitrogen spectra as compared to pH 6. The results from these four examples demonstrate that a wealth of novel information can be obtained by using the new experimental tools developed in this thesis, namely a highly sensitive x-ray spectrometer and a flow-through liquid cell.},
  subject      = {Organisches Molek{\"u}l},
  language  = {en}
}