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@MASTERSTHESIS{Finck:875400,
      author       = {Finck, Dennis},
      title        = {{D}evelopment of a surface acoustic wave sensor for in situ
                      detection of molecules},
      volume       = {216},
      school       = {Universität Köln},
      type         = {Masterarbeit},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2020-02009},
      isbn         = {978-3-95806-464-5},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {63 S.},
      year         = {2020},
      note         = {Universität Köln, Masterarbeit, 2020},
      abstract     = {Surface acoustic wave sensors are highly sensitive micro
                      acoustic devices which can be used as microactuators or
                      detectors. In this work a mass detector based on surface
                      acoustic waves has been developed which is suitable for the
                      detection of molecules. The detector is based on a kind of
                      delay line and mainly measures smallest changes of its
                      resonance frequency, which is caused by the mass of
                      molecules adsorbed on the delay line. Using the conventional
                      piezoelectric material LiNbO$_{3}$ (Y cut, Z propagation
                      direction) a resolution of the optimized mass detector has
                      been achieved which is equivalent to a thickness resolution
                      of a 3-aminopropyltriethoxysilan (APTES) layer of 0.01 nm.
                      This has been achieved by optimizing the sample holder,
                      sample design and sample mounting and by investigating and
                      comparing their electronic properties via open and short
                      tests. Furthermore our standard lift-off process for the
                      electrode fabrication has been improved by an additional
                      plasma ashing which led to a removal of residual
                      contamination (most likely PMMA) underneath the electrodes
                      and improved the mechanical adhesion.In order to further
                      enhance the mass detectors’ resolution, the mass load
                      sensitivity of epitaxial grown thin film
                      K$_{0.7}$Na$_{0.3}$NbO$_{3}$ (Z propagation direction) on
                      SmScO3 (110 cut) has been investigatedand compared to the
                      conventional LiNbO$_{3}$ bulk material. At the same
                      operating frequency both materials’ sensitivities seem to
                      be identical. At low mass loads a linear frequency dependent
                      regime has been observed with the sensitivity of c$_{m}$ =
                      0.11 m$^{2}$/(MHz kg). This is in agreement with the
                      literature for LiNbO$_{3}$. At higher mass loads and/or
                      frequencies a deviation of the linearity is observed which
                      leads to a significantly increased sensitivity (factor 9).
                      This regime might not only be of interest due to its higher
                      sensitivity, it could also offer the possibility to use the
                      sensor in liquids by transforming the Rayleigh-type sensor
                      into a Love-type surface acoustic wave (SAW) via adding a
                      wave guiding layer to generate so called Love waves. In
                      addition, the SAW intensity distribution of the various
                      harmonics showed that thin film KNNO seems to be applicable
                      at higher frequencies which would lead to a further
                      improvement in sensitivity. An attempt has been made to in
                      situ monitor our molecular deposition and removal process of
                      APTES with the developed SAW mass detector. The change of
                      the detectors resonance frequency can monitor both
                      processes. After the deposition the layer thickness of APTES
                      has been determined to 0.35 nm assuming a molecular density
                      equivalent to the liquid state. The frequency recording of
                      the detector shows additional features when opening and
                      closing the molecular source, which could provide further
                      insights into the underlying physics of the deposition
                      process itself. In conclusion, the optimized SAW mass
                      detector is suitable for molecular detection, and its
                      thickness resolution of 0.01 nm (with respect to the liquid
                      state of APTES) could most likely be improved by thin film
                      KNNO and/or by adding an wave guiding layer on the detector,
                      which could also make it suitable for detection in liquids.},
      cin          = {ICS-8},
      cid          = {I:(DE-Juel1)ICS-8-20110106},
      pnm          = {899 - ohne Topic (POF3-899)},
      pid          = {G:(DE-HGF)POF3-899},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)19},
      urn          = {urn:nbn:de:0001-2020060518},
      url          = {https://juser.fz-juelich.de/record/875400},
}