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The elongation of metallic nanoparticles (NPs) embedded in a dielectric matrix after irradiation with swift heavy ions is a phenomenon that has been known for several years. However, the precise mechanism behind this deformation process is still not fully understood, primarily due to the dearth of information during intermediate stages of deformation. In this study, we report the continuation of our previous work [Peña-Rodríguez et al., Sci. Rep. 7(1), 922 (2017)], exploiting the strong dependence of the localized surface plasmon resonance on the aspect ratio of elongated metal NPs to study the elongation kinetics in situ. In situ optical absorption spectra were measured using a polarizing beam splitter to separate the longitudinal and transverse plasmon modes of the anisotropic NPs. Then, the detailed geometrical and compositional parameters were determined from a fit of these spectra. The use of linearly polarized light allowed for a more accurate analysis of the elongation kinetics, particularly useful in the first stages, where longitudinal and transverse modes overlap. [ABSTRACT FROM AUTHOR]

The present paper reports the multifunctional properties of lead‐free BiFeO3–La (BFO–La) thin films. The structural, microstructural, and optical properties have been investigated as a function of the lanthanum doping concentration. The structural properties at room temperature showed the formation of the perovskite structure, thus suggesting the high quality of the obtained thin film compositions. Raman spectroscopy analysis revealed a slight variation in both the peak position and absolute intensity for the Raman active modes, as lanthanum content increases in BiFeO3–La. Crystallized thin films with well‐defined grains as well as crack‐free surfaces have been obtained, for all the studied compositions, as inferred from atomic force microscopy images. The optical properties have been measured, and the values for the direct bandgap was significantly lower than those reported for other BFO‐based systems, being the lowest ∼1.87 eV for the Bi0.90La0.10FeO3 composition. Results revealed a noteworthy effect of the defect concentrations induced by the lanthanum doping on the long‐range crystallinity and directly affecting the polarizability of the A–O bond as well as the Fe–O and Fe–O–Fe bond lengths in the perovskite structure. The enhanced optical absorption properties registered for the Bi1–xLaxFeO3 (x = 0–20) compositions make these perovskite multiferroic thin films as a potential candidate material for the high‐performance photovoltaic device applications. [ABSTRACT FROM AUTHOR]