Topology and electronic structure of flexible (Nb,Ru)O₂thermoelectrics

Abstract

Using combinatorial reactive sputtering, we have synthesised Nb-Ru-O thin films on Kapton (polyimide) with the Ru/Nb ratio from 0.5 to 1.1 in a dioxide type of environment. Based on correlative analysis, including synchrotron diffraction experiments and density functional theory, the topology of these amorphous samples is characterised by short metal-oxygen bonds and very pronounced metal-metal interactions within the second coordination shell. We suggest that the role of Nb is within bond length reduction and promotion of quantum confinement, giving rise to an increase in the Seebeck coefficient. Furthermore, these Nb-Ru-O thin films are mechanically flexible as there are no crack formation and delamination upon bending or rolling. This may be rationalised as follows. Nb-Ru-O appears ductile due to low topological connectivity and forms strong bonds with Kapton.

Temperature independent Seebeck coefficient through quantum confinement modulation in amorphous Nb-O/Ni-Ta-O multilayers

“…5shows the structure of such a multilayer configuration. Nb is bonded to O having the bond length of 2.07 Å, which is comparable to the corresponding bond length in cubic NbO of 2.10 Å[1] and consistent with amorphous Nb-Ru-O[54] and our XPS observations above. Unlike Nb, Ni exhibits two distinctive classes of the short-range ordering.…”

Experimental and theoretical exploration of mechanical stability of Pt/NbO2interfaces for thermoelectric applications

“…Based on the XRD data shown in figure 1, NbO 2 grown without intentional heating is xray amorphous. According to a previous synergic work using synchrotron analysis and density functional theory [53], NbO 2 alloyed with Ru is amor phous. As NbO 2 is synthesised here under similar growth conditions, it is likely that a broad XRD hump at about 25° detected for NbO 2 is not a fingerprint of nanocrystallinity.…”

“…Amorphous NbO 2 cells, obtained in a previous work by melting and quenching [6], were applied to form an inter face with Pt(1 0 0). The strategy to describe amorphous Nb oxides was critically evaluated by comparison with synchro tron data [53]. The whole Pt/NbO 2 slab system had 204-210 atoms, depending on the interfacial composition.…”