Title Page
Contents
ABSTRACT 10
Ⅰ. Introduction 13
Ⅱ. Theoretical background 14
1. Metal-insulator transition of VO₂ 14
2. Substitutional doping 17
Ⅲ. Experimental methods 18
1. Synthesis of laterally graded W-doped VO₂ thin films 18
1.1. Sputtering 18
2. Characterization of VO₂ thin films 23
2.1. X-ray diffractometer 23
2.2. Raman spectroscopy 26
2.3. Atomic force microscopy 28
Ⅳ. Results and discussion 29
1. Electrical characterization 29
1.1. Resistance-temperature loops 29
1.2. Resistance ratio 32
1.3. MIT temperature 34
1.4. Temperature coefficient of resistance performance 36
2. Structural characterization 39
2.1. X-ray diffraction 39
2.2. Raman spectroscopy 41
2.3. Surface analysis 43
Ⅴ. Summary and conclusion 46
Ⅵ. References 47
ABSTRACT IN KOREAN 50
Figure 1. Concept of MIT. 15
Figure 2. MIT characteristics triggered by thermal excitation. 16
Figure 3. Schematic diagram of the sputtering process. 20
Figure 4. Side-view of laterally graded W-doped VO₂. 21
Figure 5. Top-view of laterally graded W-doped VO₂. position of the sample located closest to the W-V target was set to d=0.... 22
Figure 6. Principle of Bragg's law. 25
Figure 7. Schematic diagram of Raman spectroscopy. 27
Figure 8. R-T loops in 1-3 region. Numbers 1-3 mean the R-T measurement at d=0,20,40 mm, respectively. 30
Figure 9. R-T loops showing the gradient effect of W concentration in thin film. 31
Figure 10. ρ in 1-3 region. 33
Figure 11. TMIT in 1-3 region.[이미지참조] 35
Figure 12. Comparison of TCR performance of pure VO₂ and laterally graded W-doped VO₂ thin film. 38
Figure 13. XRD spectra taken from pure VO₂ and laterally graded W-doped VO₂ thin film. 40
Figure 14. Raman spectra taken from pure VO₂ and laterally graded W-doped VO₂ thin film. 42
Figure 15. Surface topography of laterally graded W-doped VO₂ thin film. 44
Figure 16. Surface morphology characteristics of laterally graded W-doped VO₂ thin film. 45