Project Details
Projekt
Exploring the upper limits of piezoelectric polarization in ternary metal nitrides (Acronym: Piezo-Explorer)
Subject Area
Synthesis and Properties of Functional Materials
Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
Term
since 2025
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 562499410
The working hypothesis of the “Piezo-Explorer” project is: The maximum achievable piezoelectric polarization per strain as well as maximum coupling coefficients can be achieved by the highest possible alloy between binary metal nitrides AlN, GaN, InN and ScN, YN, LaN, whose wurtzite lattices are not yet show any indication for the structural transition into the rock salt (or layered hexagonal) lattice. The “Piezo-Explorer” project aims to theoretically and experimentally research the maximum achievable piezoelectric polarization per strain and the maximum coupling coefficient of ternary metal nitrides with wurtzite lattices. The focus is on ternary alloys of semiconducting, binary metal nitrides whose metal atoms have no or only one unpaired d-electron in the ground state. Building on extensive preliminary work on wurtzite-ScAlN, alloys of AlN, GaN and InN (metal atom has no unpaired d-electron) with ScN, YN and LaN (metal atom has an unpaired d-electron) are produced in the form of thin layers using molecular beam epitaxy and magnetron sputtering and are experimentally characterized and simulated with regard to their structural, elastic, dielectric, electrical and piezoelectric properties. The systematic variation of the ternary alloys and the determination of alloy-induced structural transitions are important focuses of the work program. The data obtained are used to determine the piezoelectric polarization per strain achievable by uniaxial, biaxial or hydrostatic pressure, to predict the achievable maximum strain achieved by an electric field and to calculate the maximum coupling coefficient. Based on these findings, the potential of the alloys for improved micromechanical actuators or the optimization of piezo-acoustic resonators is evaluated. In order to achieve the scientific and application-related goal of “Piezo-Explorer”, the project team will answer the following questions: At which alloy composition does the structural transition from the hexagonal wurtzite lattice to the cubic rock salt lattice take place when AlN is alloyed with YN or LaN rather than ScN? How do the structural, elastic, electrical and dielectric properties of ternary crystals develop depending on their alloy? Can larger values of the piezoelectric coefficients and polarization be achieved with the help of the new ternary nitrides compared to ScAlN? What maximum coupling coefficients and piezoelectric expansions can be achieved with ternary metal nitrides? What potential do novel ternary metal nitrides have for applications in micro-resonators and actuators?
DFG Programme
Priority Programmes
