Transmission Electron Microscopy Probing Electronic Structure and Strain at Low Temperatures

Objective

The TEMPEST project - Transmission Electron Microscopy Probing Electronic Structure and Strain at Low Temperatures - addresses a critical challenge in quantum device engineering: understanding how device morphology, especially metallic gate configurations, governs local strain in active layers and thus impacts electronic band structure and quantum transport. TEMPEST focuses on the understanding of Si/Ge-based qubits, which mostly operate as spin qubits and as superconducting qubits. To unlock this previously inaccessible knowledge, TEMPEST will advance the (Scanning) Transmission Electron Microscopy ((S)TEM)-based characterisation of materials. The project will first measure local nanoscale strain in quantum devices at cryogenic temperatures around 5 K, which replicate the materials structural properties expected at the mK conditions of their typical operating regimes as functional devices. Second, to correlate strain and other structural parameters with band structure measurements, the project will push beyond current momentum-resolved electron energy loss spectroscopy (EELS) techniques by developing a methodology capable of spatially mapping band structure by optimising the triple limit of spatial-momentum-energy resolution. As part of this, TEMPEST will establish a comprehensive theoretical framework to interpret momentum-resolved EELS data by integrating experimental results from the main host, FZJ/ER-C (Germany), with corresponding theoretical calculations performed at the secondment host, ICFO (Spain). These groundbreaking insights will be integrated to create digital twins that optimise a heuristic, physics-informed research cycle, enabling a faster and more efficient development of next-generation quantum devices with reduced time and resource demands. Although demonstrated on Si/Ge quantum devices, TEMPEST’s approach is designed to be broadly applicable across materials science, including major academic and industrial sectors such as semiconductors.