News

SFB-TR 87

Lukas Mai and colleagues on new chemistry for ultra-thin gas sensors 

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A Bochum team has developed a new process for zinc oxide coatings that can be used in nitrogen oxide sensors and as protective coatings on plastics.
The application of zinc oxide coatings in industry is manifold and ranges from the protection of perishable goods from air to the detection of toxic nitrogen oxides. Such layers can be produced by means of atomic layer deposition (ALD), which normally uses precursor chemicals, so-called precursors, which ignite immediately in air. An interdisciplinary research team at the Ruhr-Universität Bochum (RUB) has now established a new production process based on non-self-igniting precursors that takes place at such low temperatures that plastics can also be coated. The team reported in the magazine "Small", which selected the article for its title in the issue of 4 June 2020.

Applying ultra-thin coatings

To produce a sensor for nitrogen dioxide (NO2), a thin layer of nanostructured zinc oxide (ZnO) must be applied to a sensor substrate and then integrated into an electrical component. Prof. Dr. Anjana Devi's team used ALD to apply ultra-thin ZnO layers to such sensor substrates.

In general, ALD processes are used in industry to miniaturize electrical components by means of ultra-thin layers, some of which are only a few atomic layers thick, while at the same time increasing the efficiency. This requires precursors that react on a surface in the ALD process to form a thin layer. "The chemistry behind ALD processes is therefore essential and has a great influence on the resulting layers," emphasizes Anjana Devi.

Safe handling and highest quality

In industry, ZnO coatings have so far been produced with an extremely reactive zinc precursor that ignites immediately in air, experts call it pyrophoric. "The key to developing a safe ALD process was to research a new, non-pyrophoric precursor that can be handled safely and is capable of producing ZnO coatings of the highest quality," said Lukas Mai, lead author of the study. "The challenge was to find an alternative chemistry capable of replacing pyrophoric, industrially used compounds".
The special feature of the new process is that it is even possible at low temperatures, which makes it possible to coat plastics. Thus, the new process is not only suitable for the production of gas sensors, but also for gas barrier layers. These are applied to plastic in industry and are used to protect sensitive goods such as food and medicines from air.

This was made possible by the interdisciplinary cooperation of natural scientists and engineers. The team included the working groups Chemistry of Inorganic Materials headed by Anjana Devi and General Electrical Engineering and Plasma Technology headed by Prof. Dr. Peter Awakowicz, researchers from Heinrich Heine University Düsseldorf and the company Paragon.

The work was funded by the European Fund for Regional Development (EFRE) in the Funald project and by the German Research Foundation in the framework of the Collaborative Research Centre/Transregional TR87. Lukas Mai was supported by the Stiftung der Deutschen Wirtschaft.

adapted from Meike Drießen, RUB
Eickhoff prize

Dr.-Ing. Schmidt is awarded for his outstanding dissertation

Technical plasmas are among the things that have a significant influence on the world around us, without many people knowing about it. "You can, for example, process surfaces with plasmas; but they are crucial in the production of modern computer chips, which are built into almost all modern technical devices - from cars to smart phones," explains Frederik Schmidt. "A better understanding of this technology leads to innovations that make our lives easier, network people and shape our future.

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In his dissertation, he investigated how the energy gets into a plasma. The path from the power socket to nanometer-sized semiconductor tracks is being investigated by various specialists and is in part well understood. Frederik Schmidt has brought together two of these specialist areas: the electrical network between the power socket and the plasma on the one hand, and detailed plasma simulations on the other. This makes it possible to investigate the relationship between the two. "For example, I have looked at the paths along which energy flows and how much is lost on its way into the plasma. That is sometimes quite a lot," says the researcher. The results help to make systems and superstructures more efficient and thus more economical and ecological. In addition, he has developed his own electrical network that can be implemented for certain applications with considerably less effort and losses than before. "I was able to show theoretically that this works. Colleagues in France were then able to prove in experiments that it is also practically possible to build something like this," says Schmidt.

adapted from Meike Drießen, RUB
Successful collaboration with INP Greifswald

Research data management as central aspect within the collaborative research centres

Research data is a central output of science. They expand the scientific knowledge and are the basis for future research projects. The documentation of research data should follow subject-specific standards. The long-term archiving of research data is important for the quality assurance of any scientific work, but is also a fundamental prerequisite to allow the reusability of research results.

Researcher from the INP Greifswald enrolled a BMBF funded project with the title Quality assurance and networking of research data in plasma technology - QPTDat. This project aims to develop and test processes and methods for a quality assured and interdisciplinary reuse of research data from plasma technology.

QPTDat cooperation

A collaboration between INP and the CRC 1316 started in 2018 and now the Research Department Plasmas with Complex Interactions, and also the SFB-TR 87 join the activities on research data management. A workshop organized by INP Greifswald in January 2020 was the starting point for further active implementations in the field of research data management in the plasma community in the CRCs as well as in the Research Department.

First measures at EP2

As a first measure, an initiative at the research group EP2 at RUB results in an improved data storage on the local server of the institute. The storage volume has a regular backup and granting access to the complete group or to individual persons is possible. Beside measurement data, all further analysis steps are documented including meta data from all process steps. The members of the research group used a file name scheme, so that files can be found easily by other researchers.

Research data repository

Finally, published research data can be stored and published for the open public on the repository at

Scheme of publish process of data within the repository.

The idea of such a repository is the full documentation of measurement conditions (measurement data in a readable file format including meta data). First research groups from the CRCs have access to this repository and upload research data of published papers.

The concept of the repository is based on a multi-level system for publishing records. Users can put data online for review, which are then published by group moderators. The standards for publishing records must be defined by the group. In addition, meta data standards are currently being developed within the CRCs and together with INP Greifswald, so that data entry will be clearer and more uniform in future.

NFDI4Phys

Recently, the Research Department Plasmas with Complex Interactions has started to join the collaboration of different scientific institutions within the so-called
NFDI4Phys consortium. It aims to create structures and tools to simplify and unify the exchange of (mainly) numerical factual data in all areas of physics, with related disciplines and with the industry. The consortium is applying to the DFG for funding within the National Research Data Infrastructure (NFDI) project.

Within the framework of the NFDI4Phys consortium, the CRCs developing meta data standards for research questions in plasma science. Further goals are to contribute to the definition of basic and interdisciplinary standards and to develop methods to make research data from different sources generally accessible and interpretable.

Education

International School on Low Temperature Plasma Physics 2020

Due to the situation with Covid-19, the Plasma School will be an online course lasting over two weeks (October 5th until October 16th, 2020). Unfortunately, the Master Class “Spectroscopy” has to be cancelled for 2020. However, this Master Class will take place during the next school in 2021.


Since all teachers of the school confirmed their participation also in an online format, we changed the schedule, so that the intensity of the courses will be comfortable for the participants. Some of the courses will be online in advance, so that you can decide when to watch the videos. Other teachers prefer to do their courses live, so there will be a defined time slot to watch the lectures. However, all teacher of the corresponding day will be available online for Q & A discussions in the afternoon. The school will be free of charge for all participants.


In order to guarantee an optimal interaction between teachers and students, we limit the access to the school. Therefore, a registration on the school webpage is necessary with an appropriate motivation text. Please, register until July 15th if you would like to attend the online format of the school. After this date, the organization team will decide about the participants. All previously registered students will of course also be considered for the school's online format.

 

Research success in the SFB-TR 87

Zanders et al. generate an unusual cobalt compound 

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A research team from Ruhr-Universität Bochum (RUB) and Carleton University in Ottawa has developed a novel, highly versatile cobalt compound. The molecules of the compound are stable, extremely compact and have a low molecular weight so that they can be evaporated for the production of thin films. Accordingly, they are of interest for applications such as battery or accumulator production. Because of their special geometry, the compound also has a very unusual spin configuration of ½. A cobalt compound like that was last described in 1972. The team published their report in the journal Angewandte Chemie International Edition from 5 May 2020.

The geometry makes the difference

“The few known cobalt(IV) compounds exhibit high thermal instability and are very sensitive towards air and moisture exposure. This impedes their implementation as model systems for broad reactivity studies or as precursors in material synthesis,” explains lead author David Zanders from the Inorganic Materials Chemistry research group in Bochum, headed by Professor Anjana Devi. In his ongoing binational PhD project, which has been agreed upon by Ruhr University and Carleton University by a Cotutelle agreement, David Zanders and his Canadian colleagues Professor Seán Barry and Goran Bačić discovered a cobalt(IV) compound that does not only possess the aforementioned properties but also exhibits an unusually high stability.

Based on theoretical studies, the researchers demonstrated that a nearly orthogonal embedding of the central cobalt atom in a tetrahedrally arranged environment of connected atoms – so-called ligands – is the key to stabilising the compound. This specific geometric arrangement within the molecules of the new compound also enforces the unusual electron spin of the central cobalt atom. “Under these extraordinary circumstances, the spin can only be ½,” points out David Zanders. A cobalt compound with this spin state and similar geometry has not been described for almost 50 years.

Following a series of experiments, the team also showed that the compound has a high volatility and can be evaporated at temperatures of up to 200 degrees Celsius with virtually no decomposition, which is unusual for cobalt(IV).

Promising candidate for ultra-thin layers

Individual molecules of the compound dock onto surfaces in a controllable manner after evaporation. “Thus, the most fundamental requirement of a potential precursor for atomic layer deposition has been fulfilled,” asserts Seán Barry. “This technique has increasingly gained in importance in industrial material and device manufacturing, and our cobalt(IV) compound is the first of its kind that is fit for this purpose.” “Our discovery is even more exciting as the high-valent oxides and sulfides of cobalt are considered to have great potential for modern battery systems or microelectronics,” adds Anjana Devi. Following frequent charging and discharging, electrodes in rechargeable batteries become more and more unstable, which is why researchers are looking for more stable and, consequently, more durable materials for them. At the same time, they also focus on using new manufacturing techniques.

“This binational collaboration, which was initiated by David Zanders, has pooled the creativity and complementary expertise of chemical engineers from Bochum and Ottawa. All this has produced unexpected results and was certainly the key to success,” concludes Anjana Devi.

written by Meike Drießen, RUB