h1

% 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{Jekat:985425,
      author       = {Jekat, Felix Michael},
      othercontributors = {Morgenstern, Markus and Schäpers, Thomas},
      title        = {{D}evelopment of a charge sensor in {III}-{V} semiconductor
                      nanowires for scanning tunneling microscopy},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2024-04614},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2024},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University; Dissertation, RWTH Aachen University, 2024},
      abstract     = {This thesis presents key achievements needed to realize a
                      single electron scanning tunneling microscope (SE-STM). A
                      SE-STM combines the spatial resolution of a STM and the
                      statistical information gained by counting single electrons.
                      The design of the charge detector features two gate-
                      controlled nanowire quantum dots (QD) in series. A third
                      nanowire quantum dot or nanowire quantum point contact (QPC)
                      acts as the sensor QD/QPC. The sensor QD/QPC is coupled to
                      the double quantum dot by a floating gate. As soon as
                      electrons tunnel through the double quantum dot, charges on
                      the floating gate are set in motion. Due to the sensitivity
                      of the QD/QPC current to the surrounding charge
                      distribution, the charge state of the double quantum dot can
                      be read out by analyzing the current changes of the sensor
                      QD/QPC. With a SE-STM the full counting statistics of
                      tunneling electrons can be analyzed down to the atomic
                      length scale. Electrostatic simulations were carried out to
                      optimize the floating gate design. The simulation reveals
                      that the Si backgate and the finger gates adjacent to the
                      floating gate are the biggest contributing factors to the
                      cross capacitance of the floating gate, as they contribute
                      $\approx 50$ \% to the total floating gate capacitance. The
                      usage of the nanowire's natural oxide decouples the floating
                      gate from the most relevant cross- capacitances and thus
                      improves the charge coupling of the quantum dots. In order
                      to verify the design in practice, low temperature transport
                      measurements were carried out. Samples were fabricated by
                      the novel combination of two fabrication methods. The
                      nanowires were placed under an optical microscope with an In
                      tip and then stamped onto the prepared finger gate
                      structure, resulting in a placement precision of $\approx1$
                      µm even when using very long $\approx 20$ µm stemless InSb
                      nanowires. Multiple gate controllable quantum dots in an
                      InSb nanowire, with charging energies
                      $E_\mathrm{C}=2\text{--}3$ meV were analyzed in 300 mK
                      transport studies. The charge stability diagram reveals
                      excited states with an energy of $\Delta=0.6\text{--}1.1$
                      meV. Magnetic field measurements reveal an intrinsic
                      parasitic quantum dot in an InSb nanowire coupled to the
                      main quantum dot. The resulting pattern looks qualitatively
                      similar to the measurement result of 2e to e transitions
                      observed in superconductor induced InSb nanowires. The
                      parasitic quantum dot is likely in a dead end configuration
                      with the main dot. The size of the parasitic dot is
                      estimated at $\approx 30 $nm. Employing exfoliated h-BN as
                      the finger gate dielectric, the potential fluctuation noise
                      of $\sqrt{S_\mathrm{pot}(1\,\mathrm{Hz})}=1$
                      µeV$/\mathrm{\sqrt{Hz}}$ at $T=300$ mK in InSb nanowire
                      quantum dots is competitive to the current state of the art
                      quantum dot spin qubit materials which have a potential
                      fluctuation noise of
                      $\sqrt{S_\mathrm{pot}(1\,\mathrm{Hz})}=1\text{--}5$
                      µeV$/\mathrm{\sqrt{Hz}}$ at $T=300$ mK. The nanowire gate
                      hysteresis is improved by exfoliated h-BN. The sample
                      reveals a $\Delta V_\mathrm{hyst}\approx 2$ mV with a sweep
                      rate of 25 mV/s. The ratio of gate hysteresis to the gate
                      voltage range was improved by one order of magnitude in
                      comparison to InAs or InSb nanowires on other gate
                      dielectrics. A SE-STM utilizing all the discoveries reported
                      in this thesis, should be able to count single electrons
                      with a 50 kHz time resolution and also function as a STM.},
      cin          = {132310 / 130000},
      ddc          = {530},
      cid          = {$I:(DE-82)132310_20140620$ / $I:(DE-82)130000_20140620$},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2024-04614},
      url          = {https://publications.rwth-aachen.de/record/985425},
}