DEPARTMENT OF MATERIAL PHYSICS

Anionic amidinate ligands of the type [RC(NR')₂]^- have become indispensable tools in the coordination chemistry of virtually every metallic element in the Periodic Table. They enable the synthesis of new homogeneous catalysts as well as the design of volatile orecusors for ALD and CVD processes in materials science (e.g. phase-change and semiconductor materials). The main goal of the current research project is the investigation of alkynylamidinate ligands in the coordination chemistry of transition metals.

View project in the research portal

Major goal of this project is the synthesis and full characterization (IR, Raman, NMR, elemental analysis, X-ray structure determination) of polysulfide anions and their metal complexes.

View project in the research portal

Binary metal oxides and their alloys (In,Ga,Al)₂O₃ are among the materials with the greatest adjustability of physical properties. They include insulators, semiconductors and conductors, they are used in magnetic and ferroelectric layers and thus allow the development of a new generation of electronic components. The production of oxide structures with the highest material quality and the understanding of the fundamental physical properties are of fundamental importance for the development of application-oriented technologies. This is the subject of the Leibniz ScienceCampus Growth and fundamentals of oxides for electronic applications - GraFOx . The focus of the work in the Materials Physics department is on the determination of the dielectric function from the mid-infrared to the vacuum-ultraviolet spectral range (also using synchrotron radiation), the determination of fundamental band structure properties and the analysis of multi-particle effects in highly doped transparent conductive oxides (TCOs).
This text was translated with DeepL

View project in the research portal

Binary metal oxides and their alloys (In,Ga,Al)₂O₃ are among the materials with the greatest adjustability of physical properties. They include insulators, semiconductors and conductors, they are used in magnetic and ferroelectric layers and thus allow the development of a new generation of electronic components. The production of oxide structures with the highest material quality and the understanding of the fundamental physical properties are of fundamental importance for the development of application-oriented technologies. This is the subject of the Leibniz ScienceCampus Growth and fundamentals of oxides for electronic applications - GraFOx . The focus of the work in the Materials Physics department is on the determination of the dielectric function from the mid-infrared to the vacuum-ultraviolet spectral range (also using synchrotron radiation), the determination of fundamental band structure properties and the analysis of multi-particle effects in highly doped transparent conductive oxides (TCOs).
This text was translated with DeepL

View project in the research portal

Binary metal oxides and their alloys (In,Ga,Al)₂O₃ are among the materials with the greatest adjustability of physical properties. They include insulators, semiconductors and conductors, they are used in magnetic and ferroelectric layers and thus allow the development of a new generation of electronic components. The production of oxide structures with the highest material quality and the understanding of the fundamental physical properties are of fundamental importance for the development of application-oriented technologies. This is the subject of the Leibniz ScienceCampus Growth and fundamentals of oxides for electronic applications - GraFOx . The focus of the work in the Materials Physics department is on the determination of the dielectric function from the mid-infrared to the vacuum-ultraviolet spectral range (also using synchrotron radiation), the determination of fundamental band structure properties and the analysis of multi-particle effects in highly doped transparent conductive oxides (TCOs).
This text was translated with DeepL

View project in the research portal

Various metal oxide compounds can be used as conductive transparent contact materials, some of which are already in technological use. In this project, the basic band structure properties are being investigated primarily for the semiconductors In2O3, SnO2 and Ga2O3, which have only recently become available in crystalline quality. Both single crystals and epitaxial thin films are being investigated, with the samples exhibiting conductivities ranging from semi-insulating to metallic. Exemplary results of the investigations include, for example, the determination of the components of the dielectric tensor from the infrared to the ultraviolet spectral range, the analysis of this data to determine the effective masses of the charge carriers, the fundamental absorption edges and the influence of high charge carrier densities on the band structure (multi-particle effects) and thus on the optical properties.
This text was translated with DeepL

View project in the research portal

The aim is to evaluate the potential of group III nitride semiconductors for photo-electrochemical water splitting, i.e. to comprehensively investigate and optimize the conditions for generating hydrogen at the semiconductor/electrolyte interface. Within the project, investigations on epitaxially deposited layers are realized by means of (i) spectral ellipsometry to determine the absorption properties as a function of the layer composition, (ii) photoluminescence and electrical methods to determine the defect properties, (iii) photo-electrochemical methods to determine the hydrogen generation.
This text was translated with DeepL

View project in the research portal

AlN-Voulmen crystals and epitaxial Al-rich AlGaN alloys with wurtzite structure are investigated by synchrotron-based spectroscopic ellipsometry in the energy range from 4 to 20 eV at low temperatures. The data analysis provides the ordinary and extraordinary components of the dielectric tensor for light polarization perpendicular and parallel to the optical axis. The high-resolution investigations (resolution 0.5 meV) in the region of the fundamental absorption edge (~6 eV) provide the excitonic transition energies involving the three highest valence bands in the center of the Brillouin zone. Taking into account the optical selection rules, the symmetries of the excitons can also be determined, and their splitting provides spin-exchange energy. The use of epitaxial layers with different strain states answers the question of the sign of the exchange energy, which is controversially discussed in the literature.
This text was translated with DeepL

View project in the research portal

Applying synchrotron-based spectroscopic ellipsometry, we will determine the complex dielectric functions of tin oxide as well as copper oxides of different stoichiometry up to 20 (30) eV. The studies of SnO2 will reveal in addition the strong optical anisotropy at high energies. Samples with various electron/hole concentrations (influence of screening on electron-hole interaction) are investigated as a function of temperature. The experimental data will be compared to the available theory results. It serves as a test for the accuracy of various exchange/correlation potentials and quasi-particles schemes used for the calculations.

View project in the research portal

Theoretical and experimental studies will be combined in order to get a better understanding of the structural, band structure and optical properties of group-III nitrides in the hexagonal and cubic crystal structure. The project focuses on the ternary and quaternary alloy systems. Ellipsometry by the group of Magdeburg provides the dielectric functions from the near infrared into the ultraviolet spectral region obtained by ellipsometry for various compositions, characteristic transition energies related to critical points of the band structure as well as the valence band density of states extracted from photoelectron spectroscopy measurements. The theory results needed for the interpretation will be provided by the group of India. Density functional theory in the Engel-Vosko’s corrected generalized gradient approximation for exchange and correlation combined with GW perturbation calculations yields the lattice parameters, excited states band structure, density of state, and the quasi-independent dielectric function. The inclusion of electron-hole interaction leads finally to the excitonic DF to be compared with the experimental data and allowing critical point assignment. The increase of the supercell to 64-atom allows to enhance the reliability of the theory results.

View project in the research portal

Indium nitride is a new narrow gap semiconductor (<0.7 eV), which, alloyed with GaN (3.5 eV) and AlN (6.2 eV), will allow the spectral range from telecom to hard UV wavelengths to be covered. This narrow band gap makes InN an exciting material from which to develop the highest efficiency solar cells. Moreover, due to an electron mobility of around 4000 cm2/Vs and very high saturation velocities, InN is an ideal material for the development of high electron mobility devices capable of operating in the Terahertz range. To ensure the production of reliable commercial devices, rigorous fundamental research is required to understand the layer growth mechanisms and optimize material properties. In the RAINBOW academic and industrial consortium, the theoretical work will encompass modelling of the atomic structure and properties of the material from empirical potentials to ab initio techniques. Experiments will provide correlated structural, electronic, optical and chemical information from the nano to the macroscopic scale. In a closely concerted effort, we will determine the best conditions for the growth of highest quality InN and In rich (In,Ga,Al)N alloys by the main growth techniques (MOVPE, PAMBE, and HVPE). Under the supervision of world leading experts, numerous ER/ESRs will directly benefit from this interdisciplinary and multisectorial research and training effort. The ER/ESRs involved in this programme will also learn to manage research and industrial projects.

View project in the research portal