% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@PHDTHESIS{Morgan:141552,
      author       = {Morgan, Caitlin},
      title        = {{M}agnetoresistance and transport in carbon nanotube-based
                      devices},
      volume       = {78},
      school       = {Universität Duisburg},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2013-06719},
      isbn         = {978-3-89336-926-3},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / key technologies},
      pages        = {VIII, 131 S.},
      year         = {2013},
      note         = {Dissertation, Universität Duisburg, 2013},
      abstract     = {In addition to exhibiting ballistic transport, the low
                      atomic number and low abundance of $^{13}$C spin nuclei in
                      CNTs lead to low spin orbit coupling [1, 2] and hyperfine
                      interaction, indicating a long spin dephasing length. This
                      makes CNTs a material of interest in spintronics, where
                      injecting a spin-polarized current from a ferromagnetic lead
                      into a nonmagnetic channel presents an ongoing challenge. As
                      typical ferromagnetic materials form unreliable contact to
                      CNTs [3, 4, 5], we investigate a novel contact material, the
                      alloy CoPd. We thus combine the stable ohmic contact Pd
                      forms to CNTs [6] and the high polarization of Co and
                      Co-based alloys [7]. This work begins with a
                      characterization of the material CoPd to find the optimal
                      alloy composition. When grown on an SiO$_{2}$ surface, CoPd
                      is shown to have both surface and interfacial roughness of
                      less than 0.5 nm. Magnetically, extended films of CoPd
                      exhibit a complicated behavior with a large out-of-plane
                      component manifesting itself in bubble and stripe domains.
                      However, arrays of fabricated nanostructures of CoPd show a
                      clear in-plane easy axis with little or no out-of-plane
                      component and a high saturation magnetization. Lastly,
                      electrical measurements performed in CoPd-contacted CNTs
                      indicate the formation of highly transparent ohmic contacts.
                      The best performance was found with the alloy
                      Co$_{50}$Pd$_{50}$. Local magnetoresistance (MR)
                      measurements show a dependence on the contact geometry,
                      temperature, and the electronic structure of the CNT.
                      Devices with nanostructured contacts resulted in precise,
                      reliable switching. The magnitude of local MR was shown to
                      increase with lower temperatures and in devices where a
                      stronger tunnel barrier was present. CNTs intrinsically form
                      tunnel barriers at low temperatures, and the strength
                      depends on the contact interface, although it may be
                      suppressed and enhanced via tuning of the bias and gate
                      voltages. Finally, nonlocal three-terminal measurements were
                      performed. While the signal in local measurements may be
                      enhanced by effects such as anisotropic magnetoresistance
                      (AMR), Hall efects, and various local ohmic effects,
                      nonlocal measurements probe only the pure spin current, and
                      are proof that spin injection and detection occur in
                      CNT-based devices with CoPd contacts. Furthermore, Hanle
                      measurements showed a clear spin precession, with a spin
                      lifetime $\tau_{s}$ = 1.1 ns. In conclusion, we have
                      successfully demonstrated the occurrance of spin injection
                      and detection in CNTs contacted by CoPd. The system has all
                      the requirements of a spin valve device: highly polarized
                      leads, intrinsic tunnel barriers, and transparent contact
                      resulting in efficient injection, a nanotube channel that
                      allows for a long spin lifetime, and reliable spin
                      detection, and can therefore provide much useful information
                      for the field of spintronics.},
      keywords     = {Dissertation (GND)},
      cin          = {PGI-6},
      cid          = {I:(DE-Juel1)PGI-6-20110106},
      pnm          = {422 - Spin-based and quantum information (POF2-422)},
      pid          = {G:(DE-HGF)POF2-422},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/141552},
}