Abstract
Tuning of the Fermi level (EF) near Weyl points is one of the promising approaches to realize the large anomalous Nernst effect (ANE). In this work, we introduce an efficient approach to tune EF for the Co2MnAl Weyl semimetal through a layer-by-layer combinatorial deposition of the Co2MnAl1−xSix (CMAS) thin film. A single-crystalline composition-spread film with x varied from 0 to 1 was fabricated. The structural characterization reveals the formation of a single-phase CMAS alloy throughout the composition range with a gradual improvement of L21 order with x similar to the co-sputtered single layered film, which validates the present fabrication technique. Hard x-ray photoemission spectroscopy for the CMAS composition-spread film directly confirmed the rigid band-like EF shift of ∼0.40 eV toward the composition gradient direction from x = 0 to 1. The anomalous Ettingshausen effect (AEE), the reciprocal of the ANE, has been measured for the whole x range using a single strip along the composition gradient using the lock-in thermography technique. The similarity of the x dependence of observed AEE and ANE signals clearly demonstrates that AEE measurement on the composition-spread film is an effective approach to investigate the composition dependence of the ANE of Weyl semimetal thin films and realize the highest performance without fabricating several films, which will accelerate the research on ANE-based energy harvesting.
Highlights
A thermoelectric generator (TEG) using the Seebeck effect (SE) is one of the promising energy harvesting technologies that can generate electricity from everyday waste heat
The a almost linearly decreases with increasing Si content following Vegard’s law, indicating that Al atoms were substituted into the Si sites without phase separation and that the single-phase CMAS alloy film was formed in the whole composition range
The XRD characterization confirmed the formation of a single phase throughout the composition range with linear variation of the lattice constant, showing the almost linear composition gradient over the film
Summary
A thermoelectric generator (TEG) using the Seebeck effect (SE) is one of the promising energy harvesting technologies that can generate electricity from everyday waste heat. We fabricated a CMAS composition-spread thin film using the combinatorial deposition technique and experimentally demonstrated the systematic tuning of EF and other transport and thermoelectric properties with composition.
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