Element-specific local structure of crystalline and amorphous CuI-based alloys

• Applicant: Professorin Dr. Claudia Sarah Schnohr
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 403159832

Copper iodide (CuI) is clearly one of the most promising materials for realizing a high-performance transparent p-type semiconductor required for novel fully transparent electronic devices. Doping or alloying CuI with a third element offers the potential to tailor the electrical and optical properties according to the needs of a specific application. The resulting ternary compounds can be of crystalline or amorphous nature. In both cases, the local atomic arrangements significantly affect important material properties and hence the device performance. Therefore, it is the aim of this project to study the element-specific local structure of CuI-based ternary alloys using X-ray absorption spectroscopy. In the first funding period, we have already analysed Cu-Sn-I-O and CuBrxI1-x thin films and powders, revealing the coordination of the different elements in the material and determining the element-specific local structural parameters such as coordination numbers, bond lengths and bond length variations (disorder). In the second funding period, we will extend these studies to novel ternary alloys investigated by the Research Unit, including crystalline alloys realized by either isovalent or aliovalent cation substitution (AgxCu1-xI, RbxCu1-xI or CuI:Se, CuI:Ni, respectively) and amorphous alloys stabilized by incorporation of suitable aliovalent elements such as In or Mo. The element-specific local structure determined with X-ray absorption spectroscopy provides important feedback for the optimization of the growth procedures, especially for amorphous alloys, where standard diffraction techniques are no longer adequate. Furthermore, the local structural parameters can serve as benchmark for theoretical calculations and they will help to interpret and understand the results from electrical and optical measurements. In this way, our study strongly contributes to a comprehensive understanding of the correlations between growth conditions, structure and important material properties, which is a prerequisite to advance CuI-based materials on their way to practical application in future transparent electronic devices.

• DFG Programme: Research Units
• Subproject of: FOR 2857: Copper Iodide as Multifunctional Semiconductor