Tuning microstructure and light-induced transverse thermoelectric effect of inclined La1−xCaxMnO3 films by modulating Ca ratio in A-site

Abstract

Inclined epitaxial La1−xCaxMnO3 films based on the light-induced transverse thermoelectric (LITT) effect have attracted significant attention in fast light/thermal detection. In this work, a series of inclined La1−xCaxMnO3 (0.1≤x≤0.8) films are fabricated based on a home-designed MOCVD system by adjusting the ratio of La/Ca sources. The composition-induced microstructure for La1−xCaxMnO3 films is revealed. La1−xCaxMnO3 tends to form a single orientation under a small lattice mismatch with the substrate, while with a multi-domain structure under an obvious mismatch, significant lattice distortions are observed in the films. With increasing Ca content, the electrical conductivity gradually increases, which is responsible for enhanced response voltage from 5.5 V for Ca10 to 25.5 V for Ca40. However, with a further increase in conductivity, the response voltage gradually decreases, which may be attributed to the deteriorated anisotropic Seebeck coefficient. Benefitting from enhanced conductivity, the response time decreases from 2984 ns for Ca10 to 58 ns for Ca60, which increases to 80 ns for Ca80 due to enhanced phonon scattering originating from the lattice distortions. This work may serve as a reference for modulating the LITT effect based on electron/phonon transport for other material systems applied in fast light/thermal detection.