Self-diffusion of the constituent elements in LaAlO3

• Applicant: Dr. Peter Fielitz
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 511609623

Lanthanum aluminum oxide (LaAlO3) occupies a prominent role in fundamental research directly related to the semiconductor industry: one of the most challenging tasks in the field of semiconductor industry is the continuous downsizing of CMOS structures. To achieve this goal, the use of new materials with high permittivity is required. With a high dielectric constant, and low lattice mismatch with silicon, LaAlO3 is a very promising gate dielectric. In addition, LaAlO3 is also a very interesting material from a fundamental point of view: at the interface with SrTiO3, a two-dimensional electron gas is formed, which is currently the subject of fundamental research. This interface effect forms the physical basis for novel electronic components (e.g. oxide field-effect transistors).Considering this prominent role of LaAlO3, the lack of experimental self-diffusion data in single crystals and thin films is particularly disadvantageous. Computer simulations of the mobility of the constituents of a material are very powerful nowadays - but experimental reference data are still necessary to verify/evaluate the results. Such reference data are to be obtained in this project under experimental conditions that are as well characterized as possible (defined structure of the material and chemical analysis of the impurities).The main goal of this project is therefore to provide the missing diffusion reference data for LaAlO3 by performing tracer diffusion measurements of all constituent elements in single crystalline LaAlO3 and thin LaAlO3 films. The measurement of interdiffusion in the SrTiO3/LaAlO3 heterostructure will supply experimental information (diffusion profiles) which will be the basis for modelling the coupling of the cation mobilities in this special case. Furthermore, a correlation between the mobility of the cations and the microstructure of the heterostructure will be shown. This also provides the relevant information on the atomic transport of the constituents for LaAlO3, which already exists for SrTiO3 and which is crucial for understanding the behaviour of the heterosystem at higher process temperatures. This understanding is not only important in manufacturing but also for predictions on the long-term stability of the heterostructures.

• DFG Programme: Research Grants