Electronic Material Properties - und Geowissenschaften ...

Recommendations

Info

synthesis and analysis of interfaces with different contact phases. The undulator beamline U49/2-PGM2 operated by our “Collaborating Research Group” BTU Cottbus- HMI-TU Darmstadt, supplies photon energies in the range from 90 eV to 1400 eV, and thus core level emissions as well as valence electronic structures can be studied in high resolution as illustrated in Figure 3. Photoelectron spectra of differently modified silicon surfaces in the valence band and the C 1s core level regions are shown. The direct bonding of the terminator group to surface Si atoms is evidenced by the characteristic emission from the Si-C bond orbital (or analogously the Si-H bond) at around 5 eV. Another characteristic feature of direct Si-C linkage (in contrast to carboxylic bonding Si-O-C) is the low binding energy component CSi at around 284.3 eV (silicon-bound carbon) in the C 1s emission. The second component CCH2 at 285.0 eV is related to C-C or C-H bonded, aliphatic species. With increasing alkyl chain length the intensity of the aliphatic component increases. For ethylated Si(111), the ratio CCH2 / CSi is about 1:1, for butylated Si 1:3 in accordance with expectations. As mentioned above, based on a careful intensity study, the CH3 termination appears as the only one to achieve 100 % surface termination. Fig. 2: LEED pattern of Si(111)-C2H5 In addition to alkylated surfaces, aryl-functionalizations of Si(111) by for example nitrobenzene or bromobenzene were studied. These systems are interesting for surface engineering because it could be shown that the molecular dipoles grafted onto the Si(111) surface affect a surface dipole layer which modifies the silicon surface potential. In our ongoing research project, the interface engineering possibilities of such alkyl-or arylmodified surfaces in contact with electrolytes and organic or inorganic semiconductors will be further investigated. C1s hn = 650 eV C x H y C CH2 C Si 288 287 286 285 284 283 binding energy (eV) Butyl-Si Ethyl-Si Methyl-Si H-Si hn = 150 eV C 2s σ Si-C σ Si-H 20 15 10 5 0 binding energy (eV) Figure 3: Photoelectron spectra of various alkylated Si(111) surfaces. The direct Si-C linkage is evidenced by the the surface state emission from the Si-C bond orbital and the low BE component in the C 1s emission (“CSi”), which is associated with silicon-bound aliphatic carbon. “CCH2” corresponds to aliphatic, only C-C and C-H coordinated carbon. - 76 -
New unconventional superconductors: Water intercalated NaxCoO2 Yoshiharu Krockenberger, Jose Kurian, Philipp Komissinskiy, Lambert Alff The observation of superconductivity in the layered transition metal oxide NaxCoO2 · y H2O (K. Takada et al., Nature (London) 422, 53 (2003)) has caused a tremendous upsurge of scientific interest due to its similarities and its differences to the copper based hightemperature superconductors. Two years after the discovery, we report the fabrication of single-phase superconducting epitaxial thin films of Na0.3CoO2 ·1.3 D2O grown by pulsed laser deposition technique. This opens additional roads for experimental research exploring the superconducting state and the phase diagram of this unconventional material. Superconductivity in NaxCoO2 · y H2O is a property of the cobalt oxide planes. Like in the case of the cuprates, the phase diagram of sodium cobaltate encompasses several competing electronic phases, and there are many indications that the superconducting state is unconventional. While in high-temperature superconductors the twodimensional character of the corresponding copper oxide planes is stabilized by the intrinsically strongly anisotropic crystal structure, in NaxCoO2 a complicated water intercalation process is needed to amplify this anisotropy and induce superconductivity. The main difficulties in fabricating highquality bulk material of NaxCoO2 · y H2O are the following: First, sodium can be inhomogeneously distributed in the entire bulk sample, resulting in an ill-defined doping level. Second, impurity Co oxides such as CoO and Co3O4 are likely to grow due to the high volatility of sodium. Third, it is difficult to avoid the formation of Na2CO3 in conventional bulk sample fabrication. As a result, high-quality single crystals or bulk samples of NaxCoO2 · y H2O are rare, and it is even more difficult to obtain clean surfaces for optical spectroscopy and tunneling experiments in this material. While highquality thin films of high-temperature superconductors have allowed a large variety of phase-sensitive experiments to explore the symmetry of the superconducting order parameter, corresponding studies have thus far not proven possible for water-intercalated sodium cobaltate, due to the lack of superconducting thin films. Thin-film deposition techniques offer major advantages in the synthesis of highquality samples, such as a welldefined vacuum and oxidizing environment. Recently, epitaxial growth of high-quality, “dry” NaxCoO2 films by pulsed laser deposition on SrTiO3 substrates has been reported. In these thin films, phase purity was established within the detection limits of x-ray diffraction in four-circle geometry, and flat surfaces are obtained. As a further milestone, we now report the fabrication of superconducting thin films of NaxCoO2 · y D2O. - 77 - Fig. 1: White light interferometric scan image of the surface of a Na0.3CoO2 ·1.3 D2O thin film on SrTiO3 (001). Within the blue regions the surface roughness is below 10 nm. The rare spikes arise from sodium carbonate. [1].
Page 1:
ANNUAL REPORT 2 0 0 6 FACULTY OF MA
Page 4 and 5:
Annual Report 2006 Faculty 11 Mater
Page 6 and 7:
Preface The year 2006 of the Depart
Page 8 and 9:
difference of numerical and analyti
Page 10 and 11:
Institute of Materials Science Phys
Page 12 and 13:
Research Projects Bulk Amorphous Al
Page 14 and 15:
el Dsoki, C.; Landersheim, V. ; Kau
Page 16 and 17:
Das, J.; Kim, K. B.; Xu, W.; Wei, B
Page 18 and 19:
Staff Members Head Prof. Dr. Jürge
Page 20 and 21:
Zhou L.; Rixecker G.; Aldinger F.;
Page 22 and 23:
concerned with the synthesis and ch
Page 24 and 25:
Publications Fleissner, A.; Schmid,
Page 26 and 27:
• Surface analysis The UHV-surfac
Page 28 and 29: T. Mayer, U. Weiler, E. Mankel and
Page 30 and 31: Thin films The Thin Film division w
Page 32 and 33: Berky, W.; Gottschalk, S.; Elliman,
Page 34 and 35: Guest Scientists Research Projects
Page 36 and 37: Hesse, S.; Zimmermann, J.; von Segg
Page 38 and 39: Structure Research The research in
Page 40 and 41: Research Projects Functional Advanc
Page 42 and 43: Dincer, I.; Elerman, Y.; Elmali, A;
Page 44 and 45: hexakis(imidazole)nickel(II)bis(for
Page 46 and 47: Chemical Analytics The chemical ana
Page 48 and 49: Collaborations The above mentioned
Page 50 and 51: Hoffmann, P.; Non-Invasive Identifi
Page 52 and 53: Ferroelectrics For this class of ma
Page 54 and 55: Materials Modelling The research ac
Page 56 and 57: Materials for Renewable Energies In
Page 58 and 59: Joint Research Laboratory Nanomater
Page 60 and 61: Collaborative Research Center (SFB)
Page 62 and 63: B7 P.I.: Prof. H. v. Seggern / Dr.
Page 64 and 65: The glass transition temperature (T
Page 66 and 67: transition allows to investigate at
Page 68 and 69: Relative density 1.00 0.95 0.90 0.8
Page 70 and 71: Fig. 2 shows the time dependencies
Page 72 and 73: Dielectric interface trap engineeri
Page 74 and 75: ∆V C q th eff 12 −2 p ( VGS = 0
Page 76 and 77: Fig. 3: Schematic of the photovolta
Page 80 and 81: Fig. 2: Resistivity vs temperature
Page 82 and 83: Fig. 2: X-ray appearance near-edge
Page 84 and 85: Capacity [mAhg -1 ] 700 600 500 400
Page 86 and 87: Texture investigations and field em
Page 88 and 89: screening effects. Gold coating of
Page 90 and 91: Figure 2 shows a selected region of
Page 92 and 93: The spectrum shows that apart from
Page 94 and 95: The effect of crystallinity on the
Page 96 and 97: Electrochemical investigation and c
Page 98 and 99: This phenomenon can be understood c
Page 100 and 101: ∆ = 0 − exhibiting dominance of
Page 102 and 103: constituents. The requirement of va
Page 104 and 105: In order to assess the influence of
Page 106 and 107: In this study, we have therefore de
Page 108 and 109: Fig. 1: Proposed models for a) Pt,
Page 110 and 111: Synthesis of oxide-polymer nanocomp
Page 112 and 113: Diploma Theses Böhme, Mario; Herst
Page 114 and 115: Sperling, Sebastian; Untersuchungen
Page 116 and 117: Institute of Applied Geosiences Phy
Page 118 and 119: Research Projects Geomorphology and
Page 120 and 121: Engineering Geology Engineering Geo
Page 122 and 123: Investigation of a Doline in NE-Hes
Page 124 and 125: Applied Sedimentology Sedimentary r
Page 126 and 127: econstruction.(Diploma thesis in co
Page 128 and 129:
Darmstadt University of Technology
Page 130 and 131:
Geomaterials Science Geomaterial Sc
Page 132 and 133:
Gregori, G.; Kleebe H.-J.; Sorarù,
Page 134 and 135:
Hessische Industriemüll GmbH). Due
Page 136 and 137:
Technical Personnel Josef Kolb, Dip
Page 138 and 139:
Research Projects Environmental sca
Page 140 and 141:
Fig. 1: Aerial photo of the Lake Li
Page 142 and 143:
Lithological Map of the Japanese Ar
Page 144 and 145:
tower stripping, and therefore much
Page 146 and 147:
Diffusion and reaction in micro- an
Page 148 and 149:
Rift dynamics, uplift and climate c
Page 150 and 151:
Geology, land use change and erosio
Page 152 and 153:
nearly half a century has been perf
Page 154 and 155:
The Effect of LiF Addition on the S
Page 156 and 157:
In case of the undoped sintered B6O
Page 158 and 159:
Microstructures in Omphacite and Ot
Page 160 and 161:
Modelling phase-assemblage diagrams
Page 162 and 163:
As an example, Fig. 2 shows the che
Page 164:
MATERIALS SCIENCE Physical Metallur
show all

Electronic Material Properties - und Geowissenschaften ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?