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Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - Novel Materials


Metal and semiconductor nanostructures and their hybrids are investigated by transport measurements. The nanostructures are made by bottom-up and top-down fabrication techniques. Electrical contacts to single nanostructures such as nanowires are made by micro- and nanolithography. We study size effects of the conductivity, magnetoresistance, thermopower and thermal conductance with respect to varying electrical fields, low- and high-magnetic fields  and  temperature. We are particularly interested in determining thermal transport properties at the nanoscale and in developing the required measurement techniques. Materials presently under investigation are metal-based (Ag, Ni, Co...), Si-based, and Bi2-based (Bi2Se3, Bi2Te3,...) nanostructures.


Selected Publications


Absolute Seebeck coefficient of thin platinum films
M. Kockert, R. Mitdank, A. Zykov, S. Kowarik, and S. F. Fischer 
Journal of Applied Physics 126, 105106 (2019).

Perfect quintuple layer Bi2Te3 nanowires: Growth and thermoelectric properties
P. Schönherr, D. Kojda, V. Srot, S. F. Fischer, P. A. van Aken, and T. Hesjedal
APL. Mat. 5, 086110 (2017).
Short abstract

Free-standing millimetre-long Bi2Te3 sub-micron belts catalyzed by TiO2 nanoparticles
P. Schönherr, F. Zhang, D. Kojda, R. Mitdank, M. Albrecht, S. F. Fischer, and T. Hesjedal
Nanoscale Res Lett 11: 308 (2016).
Short abstract

Surface effects on thermoelectric properties of metallic and semiconducting nanowires
D. Kojda, R. Mitdank, S. Weidemann, A. Mogilatenko, Z. Wang, J. Ruhhammer, M. Kroener, W. Töllner, P. Woias, K. Nielsch, and S. F. Fischer
Phys. Status Solidi A 213, No. 3, 557–570 (2016).
Short abstract
Feature Article

Temperature-dependent thermoelectric properties of individual silver nanowires
D. Kojda, R. Mitdank, M. Handwerg, A. Mogilatenko, M. Albrecht, Z. Wang, J. Ruhhammer, M. Kroener, P. Woias, and S. F. Fischer
Phys. Rev. B 91, 024302 (2015).
DOI: 10.1103/PhysRevB.91.024302
Short abstract

Dielectrophoretic investigation of Bi2Te3 nanowires — a microfabricated thermoelectric characterization platform for measuring the thermoelectric and structural properties of single nanowires
Z. Wang, D. Kojda, N. Peranio, M. Kröner, R. Mitdank, K. Nielsch, W. Töllner, S. F. Fischer, S. Gutsch, M. Zacharias, O. Eibl, and P. Woias
Nanotechnology 26, 125707 (2015).
DOI: 10.1088/0957-4484/26/12/125707
Short abstract

The Effect of a Distinct Diameter Variation on the Thermoelectric Properties of Individual Bi0.39Te0.61 Nanowires
D. Kojda, R. Mitdank, A. Mogilatenko, W. Töllner, Z. Wang, M. Kröner, P. Woias, K. Nielsch, and S. F. Fischer
Semicond. Sci. Technol. 29, Special Issue, 124006 (2014).
DOI: 10.1088/0268-1242/29/12/124006
Short abstract
2014 - Highlight Article

Thermoelectric Properties Investigation of Single Nanowires by Utilizing a Thermoelectric Nanowire Characterization Platform
Z. Wang, J. Ruhhammer, S. Adhikari, R. Rostek, D. Moser, O. Paul, D. Kojda, R. Mitdank, S. F. Fischer, W. Toellner, K. Nielsch, M. Kroener, and P. Woias
Proc. IEEE NEMS 2013, 738-741 (2013).
DOI: 10.1109/NEMS.2013.6559834

Electrical conductivity and Seebeck coefficient measurements of single nanowires by utilizing a microfabricated thermoelectric nanowire characterization platform
Z. Wang, S. S. Adhikari, M. Kroener, D. Kojda, R. Mitdank, S. F. Fischer, W. Toellner, K. Nielsch, and P. Woias
IEEE 26th International Conference on Micro Electro Mechanical Systems (MEMS), 508-511, (20.-24. Jan. 2013).
DOI: 10.1109/MEMSYS.2013.6474290

Porous Nanostructures and Thermoelectric Power Measurement of Electro-Less Etched Black Silicon
G.D. Yuan, R. Mitdank, A. Mogilatenko, and S. F. Fischer
J. Phys. Chem. C 116, 13767−13773 (2012).
DOI: 10.1021/jp212427g

Thermoelectric power factor of a 70 nm Ni-nanowire in a magnetic field
R. Mitdank, M. Handwerg, C. Steinweg, W. Töllner, M. Daub, K. Nielsch, and S. F. Fischer
J. Appl. Phys. 111, 104320 (2012).
arXiv:1111.1873 [cond-mat.mes-hall]

Coherent spin dynamics in Permalloy-GaAs hybrids at room-temperature
P. E. Hohage, J. Nannen, S. Halm and G. Bacher, M. Wahle, S. F. Fischer, U. Kunze D. Reuter, and A. D. Wieck
Appl. Phys. Lett. 92, 241920 (2008).
DOI: 10.1063/1.2943279

Aging phenomena in nanopatterned permalloy wires
T. Last, M. Wahle, S. Hacia, S. F. Fischer, and U. Kunze
Physica B
384, 9-11 (2006).
DOI: 10.1016/j.physb.2006.05.022

Magnetotransport study of nanoscale Permalloy-Si tunnelling structures in lateral spin-valve geometry
S. Hacia, T. Last, S. F. Fischer, and U. Kunze
J. Phys. D: Applied Physics
37 (9), 1310-1315 (2004).
DOI: 10.1088/0022-3727/37/9/002

Optimization of nanostructured permalloy electrodes for a lateral hybrid spin-valve structure
T. Last, S. Hacia, S. F. Fischer, and U. Kunze
J. Appl. Phys.
96, 6706-6711 (2004).
DOI: 10.1063/1.1810197

Study of spin-valve operation in Permalloy-SiO2-Silicon nanostructures
S. Hacia, T. Last, S. F. Fischer, and U. Kunze
J. Supercond.: Incorperating Novel Magnetism 16 (1), 187-190 (2003).
DOI: 10.1023/A:1023242330715

Hexagonally ordered 100 nm period nickel nanowire arrays
K. Nielsch, R.B. Wehrspohn, J. Barthel, J. Kirschner, and U. Gösele, S. F. Fischer, and H. Kronmüller
Appl. Phys. Lett. 79 (9), 1360-1362 (2001).
DOI: 10.1063/1.1399006