Heiko B. Weber’s research while affiliated with Friedrich-Alexander-University Erlangen-Nürnberg and other places

When annealing a 4H silicon carbide (SiC) crystal, a sequence of optically active defect centers occurs among which the TS center is a prominent example. Here, we present low-temperature photoluminescence analyses on the single defect level. They reveal that the three occurring spectral signatures TS1, TS2 and TS3 originate from one single defect. Their polarization dependences expose three different crystallographic orientations in the basal plane, which relate to the projections of the nearest neighbor directions. Accordingly, we find a three-fold level-splitting in ensemble studies, when applying mechanical strain. This dependency is quantitatively calibrated. A complementary electrical measurement, deep level transient spectroscopy, reveals a charge transition level of the TS defect at 0.6 eV above the valence band. For a future identification, this accurate characterization of its optical and electronic properties along with their response to mechanical strain is a milestone.

Silicon Carbide (SiC) is an outstanding material, not only for electronic applications, but also for projected functionalities in the realm of spin-based quantum technologies, nano-mechanical resonators and photonics-on-a-chip. For shaping 3D structures out of SiC wafers, predominantly dry-etching techniques are used. SiC is nearly inert with respect to wet etching, occasionally photoelectrochemical etching strategies have been applied. Here, we propose an electrochemical etching strategy that solely relies on defining etchable volumina by implantation of p-dopants. Together with the inertness of the n-doped regions, very sharp etching contrasts can be achieved. We present devices as different as monolithic cantilevers, disk-shaped optical resonators and membranes etched out of a single crystal wafer. The high quality of the resulting surfaces can even be enhanced by thermal treatment, with shape-stable devices up to and even beyond 1550°C. The versatility of our approach paves the way for new functionalities on SiC as high-performance multi-functional wafer platform.

FAIRmat develops concepts for paving the way to enable FAIR research data in solid-state physics. For selected theoretical data in this field, the NOMAD portal has developed mature concepts and technological solutions for storing data according to the FAIR principles. Extending this approach to experimental data is challenging due to their diversity and missing standards. In this paper we present our comprehensive approach to establish FAIR data in the field of experimental solid-state physics despite its heterogeneity. The concept includes elaboration of standards, community building and methods that facilitate the community’s transition to FAIR standards.

Scientific research is becoming increasingly data centric, which requires more effort to manage, share, and publish data.NOMAD is a web-based platform that provides research data management (RDM) for materials-science data. In addition to core RDM functions like uploading and sharing files, NOMAD automatically extracts structured data from supported file formats, normalizes, and converts data from these formats. NOMAD provides an extendable framework for managing not just files, but structured machine-actionable harmonized and inter-operable data. This is the basis for a faceted search with domain-specific filters, a comprehensive API, structured data entry via customizable ELNs, integrated data-analysis and machine-learning tools. NOMAD is run as a free public service and can additionally be operated by research institutes. Connecting NOMAD installations through the public services will allow a federated data infrastructure to share data between research institutes and further harmonize RDM within a large research domain such as materials science.

Research data management is becoming an increasingly important topic due to the growing amounts of types, formats, and sizes of data produced by scientific research. In addition, a growing demand to make data accessible and comprehensible requires standardizing, managing, and planning the data life-cycle. For this reason, many funding agencies now require a data management plan (DMP) as part of submitted research proposals. While some of them and other scientific bodies offer DMP templates, there is no one-size-fits-all solution, due to the heterogeneity of data generated by different scientific disciplines. Here, we present as an example FAIRmat’s effort in enhancing data literacy on the topic of DMP aiming to guide physicists and materials scientists to writing DMPs that comply with the requirements of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG).

Silicon Carbide (SiC) is an outstanding material, not only for electronic applications, but also for projected functionalities in the realm of photonic quantum technologies, nano-mechanical resonators and photonics on-a-chip. For shaping 3D structures out of SiC wafers, predominantly dry-etching techniques are used. SiC is nearly inert with respect to wet-etching, occasionally photoelectrochemical etching strategies have been applied. Here, we propose an electrochemical etching strategy that solely relies on defining etchable volumina by implantation of p-dopands. Together with the inertness of the n-doped regions, very sharp etching contrasts can be achieved. We present devices as different as monolithic cantilevers, disk-shaped optical resonators and membranes etched out of a single crystal wafer. The high quality of the resulting surfaces can even be enhanced by thermal treatment, with shape-stable devices up to and even beyond 1550{\deg}C. The versatility of our approach paves the way for new functionalities on SiC as high-performance multi-functional wafer platform.

The TS center is a promising temperature-stable photoluminescence center in 4H SiC. Here we investigate the carbon di-vacancy-antisite complex inthe framework of ab initio theory as a tentative model for the TS center. We identify optical transitionsof the basal complexes with the TS lines based on excitation energies, Stark shifts, and radiative char acteristics. Charge-state-control of the TS center in p- and n-type Schottky contacts is demonstrated. Our experimental findings are consistent with the positively charged complex.