  The impact of epitaxial strain on the structural, electronic, and
thermoelectric properties of p-type transparent Sr-doped LaCrO3 thin films has
been investigated. For this purpose, high-quality fully strained
La0.75Sr0.25CrO3 (LSCO) epitaxial thin films were grown by molecular beam
epitaxy on three different (pseudo)cubic (001)-oriented perovskite oxide
substrates: LaAlO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, and DyScO3. The lattice mismatch
between the LSCO films and the substrates induces in-plane strain ranging from
-2.06% (compressive) to +1.75% (tensile). The electric conductivity can be
controlled over 2 orders of magnitude, ranging from 0.5 S/cm (tensile strain)
to 35 S/cm (compressive strain). Consistently, the Seebeck coefficient S can be
finely tuned by a factor of almost 2 from 127 microV/K (compressive strain) to
208 microV/K (tensile strain). Interestingly, we show that the thermoelectric
power factor can consequently be tuned by almost 2 orders of magnitude. The
compressive strain yields a remarkable enhancement by a factor of 3 for 2%
compressive strain with respect to almost relaxed films. These results
demonstrate that epitaxial strain is a powerful lever to control the electric
properties of LSCO and enhance its thermoelectric properties, which is of high
interest for various devices and key applications such as thermal energy
harvesters, coolers, transparent conductors, photocatalyzers, and spintronic
memories.
