Measurement of thermal conductance of La0.7Sr0.3MnO3 thin films deposited on SrTiO3 and MgO substrates

We present measurements of the thermal conductance of thin-film-on-substrate structures that could serve as thin film uncooled bolometers. Studied samples were 75 nm thick epitaxial La 0.7 Sr 0.3 MnO 3 thin films deposited on SrTiO 3 (0 0 1) and MgO (0 0 1) substrates patterned in square geometries of areas ranging from 50 µm × 50 µm to 200 µm × 200 µm. The model allows estimating thermal boundary con-ductance values at the interface between film and substrate of 0.28 ± 0.08 × 10 6 W K −1 m −2 for LSMO/STO (0 0 1) and 5.8 ± 3.0 × 10 6 W K −1 m −2 for LSMO/MgO (0 0 1) from measurements performed in the static regime. Analytical expressions of thermal conductance and thermal capacitance versus modulation fre-quency are compared to measurements of the elevation temperature due to absorbed incoming optical power. The overall good agreement found between measurements and model finally provides the pos-sibility to calculate the bolometric response of thin film bolometers, thus predicting their frequency response for various geometries.