Title Page
Contents
ABSTRACT 11
1. Introduction 14
1.1. Metal-Insulator Transition 14
1.2. Vanadium Dioxide Thin Film 17
1.2.1. Vanadium Dioxide (VO₂) 17
1.2.2. VO₂ Film with Tungsten-Doping Gradation 21
2. Experimental Methods 24
2.1. Film Deposition 24
2.2. Energy-Dispersive X-ray Spectroscopy 28
2.3. Atomic Force Microscopy 30
2.4. Raman Spectroscopy 32
2.5. X-ray Diffractometry 34
2.6. Electrical Characterization 36
2.6.1. Resistance Vs. Temperature (R-T) Curve 36
2.6.2. Multi-channel Current-Voltage (I-V) Measurement System 38
3. Result & Discussion 40
3.1. Chemical Composition Assessment of WₓV₁₋ₓO₂ Thin Films 40
3.1.1. Energy-Dispersive X-ray Spectroscopy 40
3.1.2. Atomic Force Microscopy 42
3.2. Structural Characterization of WₓV₁₋ₓO₂ Thin Films 45
3.2.1. Raman Spectroscopy 45
3.2.2. X-ray Diffractometry 47
3.3. Electrical Characteristics of WₓV₁₋ₓO₂ Thin Films 49
4. Conclusion 54
References 55
Abstract In Korean 58
Table 1. Lattice parameters of VO₂ in M1 and R phases 20
Figure 1. Metal-insulator transition temperature (TMIT) of selected oxides with temperature-induced MIT[이미지참조] 16
Figure 2. Schematic illustrating the VO₂ MIT from the M1 phase to the R phase and several modulation methods 18
Figure 3. Lattice structure of VO₂ in (a) R phase and (b) M1 phase and band structure of VO₂ in (c) R phase and (d) M1 phase 19
Figure 4. Changing rate of TMIT with dopant atomic fraction for cation substitutional doped VO₂[이미지참조] 23
Figure 5. (a) Schematic diagram of the sputtering chamber(b) deposited film with W-doping gradation 25
Figure 6. Illustration of (a) LGW film on SiOx/Si substrate, (b) film deposited from W-V.arget on c-plane Al₂O₃ substrate and (c) film... 27
Figure 7. EDX spectra for families of X-ray lines (a) zinc, (b) niobium,(c) lanthanum and (d) platinum 29
Figure 8. (a) Schematic diagram of a typical AFM system consisting of a tip-attached cantilever, laser source and quadrant photodetector (b)... 31
Figure 9. (a) Jablonski diagram of Rayleigh (elastic) scattering and two types of Raman (inelastic) scattering[25] (b) Raman spectrum of a VO₂... 33
Figure 10. Schematics illustrating diffraction of X-rays irradiated to the solid at angle θ by lattice planes with an interplanar spacing d 35
Figure 11. (a) R-T Curve of VO₂ thin film and (b) dlogRT/dT graph and fit curve of VO₂ thin film, calculated from the R-T curve 37
Figure 12. (a) Multi-channel I-V.easurement system with temperature controller (b) Pd electrode pattern on WₓV₁₋ₓO₂ film for... 39
Figure 13. (a) Illustration of a WₓV₁₋ₓO₂ film deposited from W-V.arget with the film regions analyzed by EDX marked (white box) (b) EDX... 41
Figure 14. (a)-(d) AFM images of WₓV₁₋ₓO₂ film on SiOx/Si substrate and the height profile extracted from these images at points marked in... 44
Figure 15. (a) Raman spectra of WₓV₁₋ₓO₂ films with different W-doping concentrations with Si substrate peak reference (grey line) and M1... 46
Figure 16. (a) Illustration of WₓV₁₋ₓO₂ film after electrode patterning in which the film region used for XRD analysis marked (red box)... 48
Figure 17. R-T curves of WₓV₁₋ₓO₂ films with lateral W-doping gradation (LGW) deposited from the V target for 30 minutes and from... 51
Figure 18. Tₕ, Tc and TMIT of LGW films deposited from the V.arget for 30 minutes and from the W-V.arget for (a) 30 seconds, (b) 1 minute,...[이미지참조] 52
Figure 19. Resistivity ratio ρ of LGW films deposited from the V target for 30 minutes and from the W-V target for (a) 30 seconds, (b) 1... 53