Epitaxial Growth of Complex Metal Oxides

14.6. Conclusions and outlook

Thin films of cobaltates are promising as thermoelectric materials and their properties can be engineered in several ways. By engineering the average grain size in Na_xCoO₂ thin films, a doubling of the thermoelectric power factor was obtained (Brinks, Kuiper, et al., 2014). Furthermore, size effects of these thin films result in preservation of the electronic properties in ultrathin Na_xCoO₂ films (Brinks, Rijnders, et al., 2014). Although the thermal conductivity of thin films of Na_xCoO₂ is significantly lower than that of single crystals (Brinks, Kuiper, et al., 2014), it can be even more reduced by enhanced phonon scattering. This can be obtained in superlattice structures, where the interfaces act as phonon scatterers. ...