Effect of Ba/Ag Ratio on the Structural, Electrical, and Thermoelectric Properties of Ba2AgSi3 Thin Films

Abstract

Ba2AgSi3 thin films were grown on Si(111) substrates using molecular beam epitaxy, and the effect of the Ba/Ag atomic ratio on the crystallinity and thermoelectric properties of the films was investigated. The results revealed that the properties changed significantly with the Ba/Ag atomic ratio. Notably, for films with a Ba/Ag ratio close to stoichiometry (Ba/Ag = 2), X-ray diffraction pattern analysis confirmed a distinct c-axis orientation, and epitaxial growth was demonstrated by reflection high-energy electron diffraction. Among the grown samples, the p-type film with Ba/Ag = 2.00 exhibited the most outstanding performance in both crystallinity and thermoelectric properties. Near room temperature (approximately 311 K), this film achieved a low thermal conductivity of 1.53 W m–1 K–1 and a high power factor of 470 μW m–1 K–2, resulting in a dimensionless figure of merit ZT of approximately 0.1. This performance is favorable for an undoped thin-film material operating near room temperature, suggesting that Ba2AgSi3 is a highly promising candidate for room-temperature thermoelectric applications.