PbTiO3 강유전체 나노튜브의 STXM 연구 = STXM study of ferroelectric PbTiO3 nanotube

다국어 초록 (Multilingual Abstract)

We investigated the thickness-dependent local structures of Ti in PbTiO₃ (PTO) nanotubes by performing Scanning Transmission X-ray Microscopy(STXM) and Ti L₂,₃-edge XAS at the PLS-II 10A1 beamline in Pohang Light Source. Two samples with the same outer diameter (~400 nm) but different wall thicknesses (~32.5 nm and ~50 nm) were examined by comparing spectra at multiple positions (top, bottom, left, right) under linearly polarized X-rays (E ∥ x and E ∥ y). No significant spectral differences with respect to position or polarization were observed, signifying that the in-plane Ti displacement is effectively isotropic. Ti L-edge signals detected at positions of the Al2O3 template and nominally hollow tube centers reveal incomplete removal of PTO, suggesting that the etching and sample preparation procedures require optimization. Comparison with reference spectra shows that the thinner sample exhibits an anatase-like Ti–O coordination, whereas the thicker sample resembles SrTiO₃ with a perovskite-like TiO₆ environment, implying that below a certain wall thickness the local structure of PTO nanotubes deviates from bulk PTO toward a more asymmetric, anatase-like configuration.

목차 (Table of Contents)

• 목차 5
• Abstract 6
• List of figures 7
• 1. 서론 8
• 1.1. 연구 배경 8
• 1.2. 시료 9
• 2. 이론 11
• 2.1. STXM 11
• 2.2. XAS 14
• 2.2.1. Ti L2,3-edge XAS 14
• 2.2.2. 2p-3d 전이와 선택 규칙 14
• 2.2.3. 2p core-hole과 최종 상태 다체 상호작용 15
• 2.2.4. 결정장 분리와 국소 대칭성 16
• 2.2.5. Ti 3d-리간드 p 혼성화와 전하 이동 18
• 2.2.6. 편광 의존성 및 x, y 방향 비등방성 18
• 3. 실험 방법 20
• 4. 실험 결과 21
• 5. 결론 34
• 참고
• 문헌 35
• Publication list 37