By Dr. Jutta Schwarzkopf, Leibniz-Institut für Kristallzüchtung, Berlin

16.05.2023 1:15 pm | Bd.600, R.301 CHyN

Abstract:

A promising way to tune the ferroelectric properties of complex oxides is to deliberately
modify the crystalline structure of these materials. This can be achieved by the deposition of thin oxide
films, where lattice strain is introduced by the heteroepitaxial growth on lattice mismatched
substrates. However, a directive tuning of the functional properties of thin films requires a detailed
understanding of the correlation between lattice strain and ferroelectric phase formation as well as the
availability of oxide substrates with tailored lattice mismatch. A very suitable growth method that
permits the growth of high-quality layers for this purpose is given by the metal-organic vapor phase
epitaxy (MOVPE) technique. It offers the advantages of high oxygen partial pressure, independent
control of all constituents, growth nearby thermodynamic equilibrium and large scale-up potential. In
my talk, I will discuss the influence of lattice strain in the material system Potassium-Sodium-Niobate
(K,Na)NbO3. (K,Na)NbO3 is a lead-free, environmentally friendly material which offers as bulk material
excellent piezoelectric and electromechanical properties, high Curie temperature and good thermal
stability. However, for most applications (like memory devices, actuators, sensors or RF devices),
reproducible growth of epitaxial films is necessary, which is still challenging due to the high volatility of
Na and K. Growth of epitaxially strained (K,Na)NbO3 thin films on IKZ own oxide substrates will be
discussed with regard to the impact of lattice strain on the ferro-/piezoelectric properties of the films.
As application example, the propagation of surface acoustic waves and the use of thin films in
biosensors are addressed.

Nanowire arrays interfaced with biological cells have been demonstrated to be potent tools for advanced applications such as sensing, stimulation, or drug delivery. This study published in Advanced Materials Interfaces demonstrates the generation of functional human iPSC-derived neurons on nanowire arrays with varying geometrical specifications. The cell/nanowire interactions range from fakir-like states to nanowire-encapsulating states depending on the array characteristics. The neurons are functional with similar kinetics of the action potentials highlighting the equivalence of the nanowire arrays for neuronal differentiation.

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A press release entitled “Cell-culture microarchitectures for 3D neuronal networks” has been published by Nanoscribe GmbH referring to the work of Cornelius Fendler published in Advanced Biosystems.

 

 

 

A tech note entitled “Fabrication and Characterization of Nanofluidic Devices for DNA Optical Mapping” has been published by Carl Zeiss Microscopy GmbH, Germany and Parisa Bayat, Robert H. Blick, and Irene Fernández-Cuesta.

A joined publication entitled “Electrochemical Engineering of Nanoporous Materials for Photocatalysis: Fundamentals, Advances, and Perspectives” with the group of Dr. Abel Santos (University Adelaide) has been publishedin ACS Langmuir

Abstract: Photocatalysis comprises a variety of light-driven processes in which solar energy is converted into green chemical energy to drive reactions such as water splitting for hydrogen energy generation, degradation of environmental pollutants, CO2 reduction and NH3 production. Electrochemically engineered nanoporous materials are attractive photocatalyst platforms for a plethora of applications due to their large effective surface area, highly controllable and tuneable light-harvesting capabilities, efficient charge carrier separation and enhanced diffusion of reactive species. Such tailor-made nanoporous substrates with rational chemical and structural designs provide new exciting opportunities to develop advanced optical semiconductor structures capable of performing precise and versatile control over light–matter interactions to harness electromagnetic waves with unprecedented high efficiency and selectivity for photocatalysis. This review introduces fundamental developments and recent advances of electrochemically engineered nanoporous materials and their application as platforms for photocatalysis, with a final prospective outlook about this dynamic field.

A new publication “Low-Temperature Vapor-Solid Growth of ZnO Nanowhiskers for Electron Field Emission”  from Stefanie and Carina has been published in MDPI Coatings.

Abstract:

One-dimensional zinc oxide nanostructures have aroused interest from scientists and engineers for electron field emission applications because of their experimentally accessible high aspect ratio in combination with their low work function. A comprehensive study of the vapor-solid growth of zinc oxide (ZnO) nanowhiskers by utilizing zinc acetylacetonate hydrate and oxygen at low temperature (580 °C) is reported herein. The nanowhiskers morphology was investigated by varying different growth parameters, such as temperature, substrate type and position, gas flow, precursor amount, and growth time. According to the obtained parameter dependences, the process was optimized to achieve homogenous crystalline nanowhiskers with high aspect ratios and clearly defined surface facets and tips. We show electron field emission measurements from tailor-made ZnO nanowhiskers grown on n-doped silicon, titanium thin films, and free-standing silicon nitride membranes, revealing field emission turn-on fields significantly lower compared to a perfect flat ZnO thin film. Especially the latter devices—ZnO nanowhiskers on a free-standing membrane—might pave the way into a novel nanomembrane detector unit in proteomics, which can significantly extend the mass range of current time-of-flight mass spectrometers.

Paul defended his PhD thesis successfully on the 4th of November. Congratulations!

Jonas is going to defend his PhD thesis entitled: “Electron Spin Resonance Studies on Spin-Orbit Interactions
in Graphene” on Monday, 30.09.2019 at 1pm in CHyN (room 3.01).

Please support him and his work by showing up.