Chair of Nanoelectronics

News

Dr. habil. Martin Ziegler from the Chair of Nanoelectronics accepted an appointment for a W3 Professorship at the TU Ilmenau

Jun 08, 2018

Dr. habil. Martin Ziegler from the Chair of Nanoelectronics of the Faculty of Engineering (Kiel University) has been appointed for a W3 professorship for “Micro and nanoelectronics Systems” at the TU Ilmenau. Dr. Martin Ziegler recently accepted the offered professorship and will start his new position on July 1st 2018. His colleagues at the Institute for Electrical Engineering and Information Technology and the Institute of Material Science congratulate Dr. Martin Ziegler for this remarkable achievement. Although Dr. Martin Ziegler will leave Kiel University his fruitful scientific contribution within the DFG research Group entitled “Memristive Devices for Neural Systems” will continue and it is planned to tighten the ties between the TU Ilmenau and Kiel University in the future further.

Memristive device based on a depletion-type SONOS field effect transistor

Jun 07, 2017

State-of-the-art SONOS (silicon-oxide-nitride-oxide-polysilicon) field effect transistors were operated in a memristive switching mode. The circuit design is a variation of the MemFlash concept and the particular properties of depletion type SONOS-transistors were taken into account. The transistor was externally wired with a resistively shunted pn-diode. The underlying memristive mechanism is purely electronic, which eliminates an initial forming step of the as-fabricated cells. This fact, together with reasonable design flexibility, in particular to adjust the maximum RON/ROFF ratio, makes these cells attractive for neuromorphic applications.
 

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In situ hard x-ray photoemission spectroscopy of barrier-height control at metal/PMN-PT interfaces

Jul 07, 2016

With an ever-decreasing device sizes, it becomes fundamental to investigate the interfaces thoroughly in order to understand fully and manipulate the device functionalities. Here, we report the structural and electronic properties of metal/ferroelectric, Au(SRO)/PMN-PT, interfaces under in-situ bias voltage using hard x-ray photoelectron spectroscopy (HAXPES). The paper is highlighted as an editors`suggestion in Physical Review B.

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Polarity-tunable spin transport in all-oxide multiferroic tunnel junctions

May 26, 2016

Multiferroic tunnel junctions (MFTJs) are the next generation non-volatile memory devices that offer multinary memory states in response to electric- and magnetic-fields, referring to tunneling electroresistance (TER) and tunneling magnetoresistance (TMR), respectively. In the article recently published in Nanoscale, our results on nominally symmetric epitaxial LSMO/PZT/LSMO MFTJs revealed that the inherent asymmetry in the MFTJ (arising from the microstructural and chemical asymmetry at the interfaces) likely suffices to drive the intertwined TER and TMR.

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Pattern recognition with TiOx-based memristive devices

Aug 10, 2015

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In a recent publication the development of TiO2-x-based memristive devices for bio-inspired neuromorphic systems is reported. A physical-based equivalent circuit model is employed to analyze the obtained switching characteristics in some more detail and to provide a realistic device model for network level simulations. As an example for a neural network application of the developed devices, a pattern recognition system was investigated by using the well accepted MNIST Database benchmark system. The recognition model system compromises memristive devices with gradual (homogenous) I-V characteristics, a cross-bar array with a feed-forward neural network, leaky-integrate-and-fire neurons including a winner-take it all strategy.

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Hebbian plasticity model for memristive devices

May 07, 2015

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 In a recent publication we discuss the requirements of individual memristive devices for the emulation of Hebbian plasticity in neuromorphic applications. The paper presents a plasticity model suitable for memristive devices based on advanced novel learning rules, which provide Hebbian plasticity in accordance to the Bienenstock-Cooper-Munro (BCM) rule.

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Observation of 0–π transition in SIsFS Josephson junctions

Feb 02, 2015

The 0-π transition in Superconductor-Insulator-superconductor-Ferromagnet-Superconductor (SIsFS) Josephson junctions (JJs) was investigated experimentally. As predicted by theory, an s-layer inserted into a ferromagnetic SIFS junction can enhance the critical current density up to the value of an SIS tunnel junction. We fabricated Nb'|AlOx|Nb|Ni60Cu40|Nb JJs with wedge-like s (Nb) and F (Ni60Cu40) layers and studied the Josephson effect as a function of the s- and F-layer thickness, ds and dF, respectively. For ds = 11 nm, π-JJs with SIFS-type jc(dF) and critical current densities up to jc = 60 A/cm²  were obtained at 4.2 K. Thicker ds led to a drastic increase of the critical current decay length, accompanied by the unexpected disappearance of the 0-π transition dip in the jc(dF) dependence. Our results are relevant for superconducting memories, rapid single flux quantum logic circuits and solid state qubits.

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Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions

Feb 02, 2015

In recent years, tunneling electroresistance effect in ferroelectric tunnel junctions (FTJs) has evoked great interest within the scientific community as a potential candidate for future non-volatile memory, logic and neuromorphic computing applications.

In the article recently published in Nature Communications, we study theoretically and experimentally the ferroelectric/metal electrode interface role in determining the ferroelectric driven tunneling electroresistance (TER) effect. We believe our findings would impact significantly on optimization of FTJs in terms of electrode materials design.

Reference:  Rohit Soni, Adrian Petraru, Paul Meuffels, Ondrej Vavra, Martin Ziegler, Seong Keun Kim,
Doo Seok Jeong, Nikolay A. Pertsev & Hermann Kohlstedt, Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions. Nat. Commun. 5:5414 doi: 10.1038/ncomms6414 (2014).

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Strain effects on the transition temperature in vanadium dioxide thin films

Feb 02, 2015

The metal–insulator transition (MIT) in VO2 is accompanied by an abrupt change in the conductivity and optical properties, raising a large interest for theoretical studies as well for potential application in sensing and switching.

Controlling the transition temperature of these materials in a wide range is of particularly high interest. This can be achieved by doping or by strain in thin films.
We investigate the effect of strain in epitaxially grown vanadium dioxide films on various crystalline substrates. Moreover, by growing these films on piezoelectric substrates with huge piezoelectric coefficients like PMN-PT, we are able control the strain in a continuous way by simply applying an external bias to the substrate.

Electrostatic surface charge, photon irradiation or current excitation are recently investigated as key parameters for external control of the metal - insulator transition.

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Binary thin films with thickness and composition gradients

Sep 03, 2014

We present a versatile sputter deposition technique to produce alloy layer libraries. Colloidal particles embedded in a matrix can serve as active layers for various structures e.g. in the fields of superconducting electronics and resistive switching. The free choice of materials and the controlled deposition with layer gradients of thickness and composition over the wafer facilitates systematic investigations.

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Visiting scientist in our group

Sep 03, 2014

Dr. Ing. Doo Seok Jeong
Korea Institute of Science and Technology (KIST)

Doo Seok received his BSc and MSc in materials science from Seoul National University in 2002 and 2005, respectively. He received his PhD degree in materials science from RWTH Aachen University, Germany, in 2008. Since 2008, he has worked for KIST.

His research interests are developments of artificial synapses and neurons by means of nanoionic systems and understanding of nanoionic behaviour. In the Figure the potentiation behavior of different memresitive devices are shown. [H. Lim et al. Nanotechnology  24, 384005 (2013).]



Strain effects on the transition temperature in vanadium dioxide thin films

Sep 03, 2014

The metal–insulator transition (MIT) in VO2 is accompanied by an abrupt change in the conductivity and optical properties, raising a large interest for theoretical studies as well for potential application in sensing and switching.

Controlling the transition temperature of these materials in a wide range is of particularly high interest. This can be achieved by doping or by strain in thin films.
We investigate the effect of strain in epitaxially grown vanadium oxide films on various crystalline substrates.

Electrostatic surface charge, photon irradiation or current excitation are recently investigated as key parameters for external control the metal - insulator transition.

Taylored pi shifters for RSFQ logic

Sep 03, 2014

Rapid single flux quantum logic (RSFQ) is a superconducting, inherently digital circuit design. The information is represented and transmitted by single flux quanta h/2e (elementary charge e and Planck’s constant h) that are stored in superconducting loops.

Josephson junctions represent the active elements of the circuit. To enhance the robustness and design of the circuit a "complementary" Josephson junction, called Pi Junction, is desireable. They exist but suffer from poor operation parameters. We fabricated Pi junctions that show potential to drastically increase the critical current density of previous concepts.

An electronic implementation of amoeba anticipation is highlighted by Advances in Engineering

Sep 03, 2014

Anticipation in biological systems is the process of speculation of the probable future based on the memory of past events. In nature, anticipation can be already observed in unicellular organisms like amoebas...

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