Enhancing room-temperature thermoelectricity of SrTiO₃ based superlattices via epitaxial strain

Epitaxial strain is an effective way to control thermoelectricity of a thin film system. In this work, we investigate strain-dependent thermoelectricity of (SrTiO₃)₃/(SrTi_0.8Nb_0.2O₃)₃₁₀ superlattices grown on different substrates, including −0.96% on (LaAlO₃)_0.3(SrAl_0.5Ta_0.5O₃)_0.7(001) (LSAT), 0% on SrTiO₃(001) (STO), +0.99% on DyScO₃(110) (DSO) and +1.64% on GdScO₃(110) (GSO), respectively. Our results show that the highest room-temperature thermoelectricity is achieved when the STO-based superlattice is grown on the DSO substrate with +0.99% tensile strain. This is attributed to the high permittivity and low dielectric loss arising from the ferroelectric domain and electron–phonon coupling, which boost the power factor (PF) to 10.5 mW⋅m⁻¹⋅K⁻² at 300 K.