Match!
Uwe Hartmann
Saarland University
PhysicsMagnetic force microscopeMaterials scienceNuclear magnetic resonanceSuperconductivity
108Publications
11H-index
571Citations
What is this?
Publications 113
Newest
#1Xian Lin Zeng (Saarland University)H-Index: 4
#2Michael Rudolf Koblischka (Saarland University)H-Index: 23
Last. Uwe Hartmann (Saarland University)H-Index: 11
view all 4 authors...
Abstract We prepared La 1.85 Sr 0.15 CuO 4 / La 0.7 Sr 0.3 MnO 3 nanowire network hybrid systems by means of electrospinning. From observation by scanning electron microscopy, the average diameter of the nanowires is around 220 nm and the average length can reach over 50 μ m. The randomly aligned La 1.85 Sr 0.15 CuO 4 and La 0.7 Sr 0.3 MnO 3 nanowires exhibit numerous interconnects among each other and form a complicated, non woven hybrid network system. The nanowires are polycrystalline with a ...
1 CitationsSource
#1Thomas Karwoth (Saarland University)H-Index: 3
#2Xian Lin Zeng (Saarland University)H-Index: 4
Last. Jian Min Li (ZJU: Zhejiang University)H-Index: 1
view all 7 authors...
Abstract Nonwoven nanowire network fabrics of the material class La 1− x Sr x MnO 3 (LSMO) with x = 0.2 were fabricated employing a sol-gel-process via electrospinning and a subsequent thermal treatment process based on thermal gravity analysis results. Investigations by means of scanning electron microscopy revealed an average diameter of the resulting nanowires of around 230 nm and a length of more than 100 μm. The chemical phases of the samples have been confirmed via X-Ray diffraction. The n...
1 CitationsSource
#1Xian Lin ZengH-Index: 4
#2Thomas KarwothH-Index: 3
Last. Thomas HauetH-Index: 16
view all 7 authors...
Source
#1Thomas Karwoth (Saarland University)H-Index: 3
#2K Furutani (Saarland University)H-Index: 1
Last. Uwe Hartmann (Saarland University)H-Index: 11
view all 8 authors...
The superconducting properties of bulk, polycrystalline FeSe samples were characterized through magnetic and electric transport measurements. In order to improve the superconducting properties, the sintering temperature was varied up to 900 °C and to improve the grain connectivity, silver was added (0 to 7 wt.-%). Electric properties of the samples were investigated by the four point probe method (R-T measurements and V-I characteristics). Generally, the sample with 4 wt.-% Ag-addition showed th...
1 CitationsSource
#1Anjela Dimitrova Koblischka-Veneva (Saarland University)H-Index: 11
#2Michael Rudolf Koblischka (Saarland University)H-Index: 23
Last. Uwe Hartmann (Saarland University)H-Index: 11
view all 5 authors...
Electrospun, superconducting nanowires are characterized concerning the grain orientation, their texture and the respective grain boundary misorientations by means of electron backscatter diffraction (EBSD) analysis. The individual nanowires in such electrospun, nonwoven nanowire networks of Bi2Sr2CaCu2O x (Bi-2212) are polycrystalline, have average diameters up to 250 nm and their grains are in the 20-50 nm range. This requires a high spatial resolution for the analysis in the scanning electron...
4 CitationsSource
#1Xian-Lin Zeng (Saarland University)H-Index: 1
#2Michael Rudolf Koblischka (Saarland University)H-Index: 23
Last. Oliver Eibl (University of Tübingen)H-Index: 30
view all 9 authors...
Bi2Sr2CaCu2O8+δ (Bi-2212) nanowires were fabricated employing electrospinning. A subsequent thermal treatment based on thermal gravity analysis is required to obtain the final crystal structure and superconductivity; however, if this preparation temperature is too high, the nanowire structure may completely collapse during the treatment, which is even more pronounced when aligning the nanowires. Therefore, Li acetate was added in various amounts to the starting composition, which enabled to prod...
1 CitationsSource
#1Anne Holtsch (Saarland University)H-Index: 1
#2Tobias Euwens (Saarland University)H-Index: 1
Last. Uwe Hartmann (Saarland University)H-Index: 11
view all 6 authors...
Abstract In scanning tunneling microscopy the lattice mismatch between graphene and Rh(1 1 1) is observed as an additional superstructure. This superstructure is called Moire pattern. Various symmetry sites occur in a Moire pattern. These are distinguished by the arrangement of the graphene lattice over the Rh(1 1 1) lattice. The symmetry sites of the Moire unit cell are investigated by scanning tunneling microscopy and spectroscopy. The observed additional corrugation of the graphene sheet with...
1 CitationsSource
#1Bernd Uder (Saarland University)H-Index: 1
#2Hai-Bin Gao (Saarland University)H-Index: 4
Last. Uwe Hartmann (Saarland University)H-Index: 11
view all 5 authors...
Two-dimensional atomically flat sheets with a high mechanical flexibility are very attractive as ultrathin membranes but are also inherently challenging for microscopic investigations. We report on a method using Scanning Tunneling Microscopy (STM) under ultra-high vacuum conditions for non-indenting low-force spectroscopy on micrometer-sized freestanding graphene membranes. The method is based on applying quasi-static voltage ramps with active feedback at low tunneling currents and ultimately r...
5 CitationsSource
#2Bernd UderH-Index: 1
Last. Uwe HartmannH-Index: 11
view all 3 authors...
Crystalline Moire patterns have gained new interest with the discovery of two-dimensional atomically thin layers. Graphene, the most prominent example of this class of materials, is well suited to study fundamental aspects due to its inertness under ambient conditions, its well-established production and handling methods, and because of an adequate theoretical understanding of its properties. Bonding scenarios for graphene on any substrate can reach from covalent bonding to van der Waals interac...
1 CitationsSource
#1Michael Rudolf Koblischka (Saarland University)H-Index: 23
#2Xian Lin Zeng (Saarland University)H-Index: 4
Last. Uwe Hartmann (Saarland University)H-Index: 11
view all 3 authors...
12345678910