title: Ultra-low thermal conductivities in large-area Si-Ge nanomeshes for thermoelectric applications.
abstract: In this work, we measure the thermal and thermoelectric properties of large-area Si0.8Ge0.2 nano-meshed films fabricated by DC sputtering of Si0.8Ge0.2 on highly ordered porous alumina matrices. The Si0.8Ge0.2 film replicated the porous alumina structure resulting in nano-meshed films. Very good control of the nanomesh geometrical features (pore diameter, pitch, neck) was achieved through the alumina template, with pore diameters ranging from 294 ± 5nm down to 31 ± 4 nm. The method we developed is able to provide large areas of nano-meshes in a simple and reproducible way, being easily scalable for industrial applications. Most importantly, the thermal conductivity of the films was reduced as the diameter of the porous became smaller to values that varied from κ = 1.54 ± 0.27 W K(-1)m(-1), down to the ultra-low κ = 0.55 ± 0.10 W K(-1)m(-1) value. The latter is well below the amorphous limit, while the Seebeck coefficient and electrical conductivity of the material were retained. These properties, together with our large area fabrication approach, can provide an important route towards achieving high conversion efficiency, large area, and high scalable thermoelectric materials.
authors.affiliation: Instituto de Microelectrónica de Madrid (IMM-CSIC), Calle de Isaac Newton 8, Tres Cantos, 28760 Madrid, Spain.
authors.forename: Jaime Andres
authors.initials: JA
authors.lastname: Perez-Taborda
authors.affiliation: Instituto de Microelectrónica de Madrid (IMM-CSIC), Calle de Isaac Newton 8, Tres Cantos, 28760 Madrid, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Muñoz Rojo
authors.affiliation: Instituto de Microelectrónica de Madrid (IMM-CSIC), Calle de Isaac Newton 8, Tres Cantos, 28760 Madrid, Spain.
authors.forename: Jon
authors.initials: J
authors.lastname: Maiz
authors.affiliation: School of Engineering, University of Warwick, Coventry, CV4 7AL, UK.
authors.forename: Neophytos
authors.initials: N
authors.lastname: Neophytou
authors.affiliation: Instituto de Microelectrónica de Madrid (IMM-CSIC), Calle de Isaac Newton 8, Tres Cantos, 28760 Madrid, Spain.
authors.forename: Marisol
authors.initials: M
authors.lastname: Martin-Gonzalez