% 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{vonWitzleben:828265,
author = {von Witzleben, Moritz Alexander},
othercontributors = {Waser, Rainer and Negra, Renato},
title = {{S}witching kinetics of valence change memory devices on a
sub-100 ps timescale},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2021-09047},
pages = {1 Online-Ressource : Illustrationen, Diagramme},
year = {2021},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, Rheinisch-Westfälische Technische
Hochschule Aachen, 2021},
abstract = {The further development of today's memory technologies
faces several technological barriers, which yields the
demand for new approaches. One emerging memory type that has
the potential to overcome these barriers is the valence
change memory (VCM), which may also be usable for
neuromorphic applications or in-memory computations. In VCM
devices, the information is stored within different
resistive states, namely a high resistive state (HRS) and a
low resistive state (LRS), which can be programmed with
electrical stimuli. The transition from the HRS to the LRS
is referred to as SET and the opposite transition as RESET.
In this thesis, the SET and RESET times of TaOx-, ZrOx-, and
HfOx/TiOx-based VCM devices were studied in the time regime
from 50 ps to 100 ns. Signals in this time regime contain
high frequency components in the gigahertz regime. The
signals require proper impedance matching up to the VCM
device, which are, therefore, integrated into coplanar
waveguide (CPW) structures. Nevertheless, an integrated VCM
device constitutes a parallel plate capacitor with a
considerable electrical charging time, which delays the
measured SET and RESET times. To estimate the electrical
charging time, an experimental approach was used, with which
the time-dependent effective voltage at the VCM device could
be determined. This approach used the Fourier transformation
of the applied voltage pulse and the VCM device's scattering
parameters. From the resulting effective voltage at the VCM
device, the electrical charging time of all tested VCM
devices was determined. The results indicate that conducted
optimizations of the CPW structure decreased the electrical
charging time significantly and allowed fast measurements on
a sub-100 ps time scale. By employing dedicated hardware and
integrating this hardware into a software, the measurements
could be automated. This allowed collecting comprehensive
data sets on the SET and RESET kinetics of the tested VCM
devices and, thereby, allowed resolving their transient
resistance on a picosecond time scale. The measured SET
kinetics revealed that all studied devices can switch within
50 ps from the HRS to the LRS. To the author's knowledge,
this is the fastest switching time reported for VCM devices.
By comparing the SET kinetics of differently sized
TaOx-based VCM devices and using the determined electrical
charging times, it could be shown that the SET kinetics of
VCM devices in the subnanosecond regime are mainly limited
by the electrical charging time. The migration of mobile
donors (e.g. oxygen vacancies), which limits the SET
kinetics on slower time scales, and the heating time of the
VCM device have only a minor influence. Achieving similar
fast RESET times proved to be more difficult. In all studied
VCM devices, the coexistence of a unipolar switching mode
could be shown. This unipolar switching mode is triggered at
higher voltages, which would be required for faster RESET
times. Nevertheless, on some HfOx/TiOx-based VCM devices 50
ps fast RESET times could be measured repeatedly. From these
kinetics measurements, RESET programming windows could be
determined and, finally, approaches were derived to achieve
faster RESET times.},
cin = {611610},
ddc = {621.3},
cid = {$I:(DE-82)611610_20140620$},
pnm = {DFG project 167917811 - SFB 917: Resistiv schaltende
Chalkogenide für zukünftige Elektronikanwendungen:
Struktur, Kinetik und Bauelementskalierung "Nanoswitches"
(167917811) / BMBF-16ES1134 - Verbundprojekt:
Neuro-inspirierte Technologien der künstlichen Intelligenz
für die Elektronik der Zukunft - NEUROTEC -
(BMBF-16ES1134)},
pid = {G:(GEPRIS)167917811 / G:(DE-82)BMBF-16ES1134},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2021-09047},
url = {https://publications.rwth-aachen.de/record/828265},
}
guest ::