Title Page
Abstract
Contents
Chapter 1. Spectroscopic Imaging Scanning Tunneling Microscopy 10
1.1. Electron Tunneling 11
1.2. STM Measurement 13
1.3. Topography 14
1.4. Spectroscopy 16
1.5. STM Head 18
Chapter 2. SI-STM Laboratory 21
2.1. Ultra-Low Vibration Laboratory 21
2.2. Gas Handling System (GHS) 23
2.3. Cryostat 24
2.4. 14 Tesla Superconducting Magnet System 26
2.5. Dilution Refrigerator 29
2.6. DR and Superconducting Magnet - Operations 33
2.7. Summary 45
1. Preparation 45
2. Day I 45
3. Day II 45
4. Operation of magnet 46
Chapter 3. Cuprate Superconductors 48
3.1. Brief History of Superconductivity 49
3.2. Cuprate Superconductors 51
3.3. Bi2Sr2CaCu2O8+x[이미지참조] 52
Chapter 4. Spectroscopic Imaging Scanning Tunneling Microscopy at 25 mK 55
4.1. Scanning Tunneling Microscopy at 4.2 K 55
4.2. Scanning Tunneling Microscopy at 25 mK 56
4.3. SIS Tunneling Microscopy 58
Chapter 5. Single Electron Tunneling Spectroscopy at 25 mK 60
5.1. Coulomb Blockade and Single Electron Tunneling 60
5.2. Single Electron Tunneling (SET) Spectroscopy 61
5.3. SET Spectroscopic Measurement I 63
5.4. Vortex Charge 63
5.5. SET Spectroscopic Measurement II 65
5.6. Inhomogeneous Bias Offset 67
5.7. Bias Offset Map 69
5.8. Summary 71
Chapter 6. Conclusion 72
Bibliography 74
국문 초록 80
Figure 1.1. Schematic of the electron tunneling between tip and sample. 11
Figure 1.2. Schematic diagram of STM measurement. 14
Figure 1.3. Schematic of topographic measurement. 14
Figure 1.4. Topographic image of Bi2Sr2CaCu2O8+x[이미지참조] 15
Figure 1.5. Schematic of spectroscopic measurement. 16
Figure 1.6. The 3D drawings of the DR-STM head. 18
Figure 1.7. The DR-STM head. 19
Figure 1.8. The scanner of STM head 20
Figure 2.1. The 3D drawing of ultra-low vibration laboratory for STM measurement. 22
Figure 2.2. Gas handling system (GHS). 23
Figure 2.3. The liquid helium Dewar for DR-STM. 24
Figure 2.4. He bath flanges. 25
Figure 2.5. The real 14T superconducting magnet for DR-STM. 26
Figure 2.6. Drive mode. 27
Figure 2.7. Persistent mode. 28
Figure 2.8. Turning off persistent mode. 29
Figure 2.9. The schematic of the dilution refrigerator. 30
Figure 2.10. The cryostat with DR unit. 32
Figure 2.11. The manual valve for the OVC, the manual valves V10-V12, and the user interface by Oxford inst. 33
Figure 2.12. The still turbo pump, the cold traps, and the user interface. 34
Figure 2.13. The gate valve on the still line, the manual valve on the condensing line, and the user interface. 35
Figure 2.14. The user interface, the cold traps inside the LN₂ vessel, and the compressor. 36
Figure 2.15. The storage tank for the mixture gas, the fore pump, and the user interface. 37
Figure 2.16. The display of the magnet controller 39
Figure 2.17. The manual valve for the IVC 40
Figure 2.18. The temperature display of each stage of the DR unit. 41
Figure 2.19. The DR user interface by Oxford Inst. 42
Figure 2.20. The manget lead cables and the magnet user interface. 43
Figure 2.21. The keyholes for the sample transfer rod. 44
Figure 3.1. The comparison of normal metal and superconductor 48
Figure 3.2. Meissner effect 49
Figure 3.3. The history of supercoductors 50
Figure 3.4. Crystal structures of the cuprate superconductors 51
Figure 3.5. Schematic phase diagram of high-Tc cuprates 52
Figure 3.6. Crystal structures of Bi2Sr2CaCu2O8+x[이미지참조] 53
Figure 3.7. Cleaved Bi2Sr2CaCu2O8+x sample[이미지참조] 54
Figure 4.1. Topographic image of Bi2Sr2CaCu2O8+x at 4.2 K[이미지참조] 55
Figure 4.2. Point spectra of Bi2Sr2CaCu2O8+x[이미지참조] 56
Figure 4.3. Topographic image of Bi2Sr2CaCu2O8+x at 25 mK[이미지참조] 57
Figure 4.4. Spectroscopic measurements of Bi2Sr2CaCu2O8+x at 25 mK[이미지참조] 58
Figure 4.5. Topographic image of Bi2Sr2CaCu2O8+x by SIS tunneling[이미지참조] 59
Figure 4.6. Comparison of topographic images of Bi2Sr2CaCu2O8+x by SIN tunneling and SIS tunneling.[이미지참조] 59
Figure 5.1. Coulomb blockade tip and single electron tunneling. 60
Figure 5.2. Comparison of spectroscopic measurements using normal metal tip and Coulomb blockade tip 62
Figure 5.3. Spectroscopic measurement of Bi2Sr2CaCu2O8+x from -5 meV to -3.5 meV at 25 mK and 13 T[이미지참조] 63
Figure 5.4. Schematic of electron density redistribution at vortex core 64
Figure 5.5. Spectroscopic measurement of Bi2Sr2CaCu2O8+x from -0.2 meV to 0.2 meV at 25 mK and 13 T.[이미지참조] 65
Figure 5.6. Spectroscopic measurement of Bi2Sr2CaCu2O8+x from -10 μeV to 10 μeV at 25 mK and 13 T.[이미지참조] 67
Figure 5.7. Energy diagram of STM measurement with Coulomb blockade tip and their point spectra. 68
Figure 5.8. I-V point spectra from spectroscopic measurement 69
Figure 5.9. Bias-Offset Measurement 70