전이금속 SrRuO3 산화박막의 엑스선 분광 연구

Abstract

The investigation of itinerant 4d transition metal epitaxial oxide thin films, particularly SrRuO3, has been a subject of intensive research over the past50 years. These films exhibit noninteger magnetic moments, which are rare instances of itinerant ferromagnetism in oxides. In this dissertation, ferromagnetic thin films of 4d transition metal oxides were synthesized using the pulsed laser deposition (PLD) technique. X-ray magnetic circular dichroism (XMCD), a well-established method at the L2,3-edge or M2,3-edge, was employed to investigate the ferromagnetic properties of the thin films. Fully strained epitaxial SrRuO3 thin films were fabricated on SrTiO3 (001) substrates, exhibiting a two-dimensional growth mode and an atomically flat surface. The crystal structure of the films was confirmed using various x-ray scattering spectroscopy techniques, including XRD, XRR, and RHEED. The chemical composition of the SrRuO3 thin films was examined through element-sensitive in-situ x-ray photoemission spectroscopy (XPS). Optimized growth conditions were identified to produce defect-free and stoichiometric thin films within the thickness range of several monolayers to 70nm. Moreover, large compressively strained SrRuO3 epitaxial thin films on SrTiO3 (111) substrates were grown using the PLD system. The magnetic moments of the SrRuO3 (111) thin films were investigated as a function of film thickness using Ru M2,3-edge XMCD sum rule analysis. Notably, the z-components of the orbital magnetic moment were found to increase with increasing film thickness. A 2D percolated array of metallic microparticles (MPs) has been successfully fabricated on a flexible PDMS substrate. The current was examined by applying a tip-sample bias using conductive atomic force microscopy (AFM). Notably, under low elongation strain conditions where contact resistance dominates, the current flow exhibited a highly sensitive response. This significant finding holds potential for the development of stretchable strain sensors, including precision pulse sensors.