Nanoscale Enhancement of the Local Optical Conductivity near Cracks in Metallic SrRuO3 Film

Cracking has been recognized as a major obstacle degrading material properties, including structural stability, electrical conductivity, and thermal conductivity. Recently, there have been several reports on the nanosized cracks (nanocracks), particularly in the insulating oxides. In this work, we comprehensively investigate how nanocracks affect the physical properties of metallic SrRuO3 (SRO) thin films. We grow SRO/SrTiO3 (STO) bilayers on KTaO3 (KTO) (001) substrates, which provide +1.7% tensile strain if the SRO layer is grown epitaxially. However, the SRO/STO bilayers suffer from the generation and propagation of nanocracks, and then, the strain becomes inhomogeneously relaxed. As the thickness increases, the nanocracks in the SRO layer become percolated, and its dc conductivity approaches zero. Notably, we observe an enhancement of the local optical conductivity near the nanocrack region using scanning-type near-field optical microscopy. This enhancement is attributed to the strain relaxation near the nanocracks. Our work indicates that nanocracks can be utilized as promising platforms for investigating local emergent phenomena related to strain effects.

Automated summary

Cracks have a significant impact on the physical properties of materials, including structural stability, electrical conductivity, and thermal conductivity. This study comprehensively investigates the effect of nanocracks on the physical properties of metallic SrRuO3 (SRO) thin films. It is found that the presence of nanocracks leads to inhomogeneous relaxation of strain in the SRO layer, resulting in its dc conductivity approaching zero. Additionally, an enhancement of the local optical conductivity near the nanocrack region is observed, which is attributed to the strain relaxation near the nanocracks. This research suggests that nanocracks can be utilized as promising platforms for investigating local emergent phenomena related to strain effects.