Laser-induced transverse voltage effect and thermopower anisotropy of c-axis inclined Ca_3Co_4O_9 thin film

摘要

Ca_3Co_4O_(9+δ) thin films were prepared on 5° vicinal cut LaAlO_3 (001) substrates by pulsed laser deposition and subsequently annealed at various temperatures. Under the irradiation energy density of 8 mJ cm~(-2), a large laser-induced transverse voltage (LITV) signal with 6.4 V peak voltage and 33 ns rising edge was obtained in the 800 ℃ annealed film, which was nearly 11 times larger and 2 times faster than that in the as-grown film without annealing (0.54 V, 100 ns). The results suggested that the significant enhancement of LITV by annealing was mainly owing to the improved crystallization and electrical transport property. Based on the LITV results and heat flow model, a nearly intrinsic Seebeck coefficient anisotropy ∆S = |S_(ab)-S_c| ≈ 33.4 μV K~(-1) was obtained, demonstrating the c-axis inclined Ca_3Co_4O_(9+δ) thin film with large thermopower anisotropy has great application potentials in high sensitive and fast response thermoelectric detectors.