Title Page
VITA
ABSTRACT
Contents
Chapter 1. Introduction 17
1.1. Background 17
1.2. Research Objective 22
1.3. Dissertation Outline 22
Chapter 2. Compact Folded Dipole Metasurface for High Anomalous Reflection Angles with Low Harmonic Levels 24
2.1. Introduction 24
2.2. Theoretical Analysis 27
2.3. Simulation Analysis 29
2.3.1. Folded Dipole Unit Cell Design 29
2.3.2. Design and Simulation of Folded Dipole Based Metasurface 31
2.4. Performance Comparison with Patch-Based Metasurface 33
2.5. Power Flow and Surface Current Analysis 35
2.6. Experimental and Measurement Result 37
2.6.1. Device Fabrication and Experimental Setup 37
2.6.2. Frequency and Time Domain Analysis of Measurement Result 38
2.6.3. Suppression of Undesired Harmonics 40
2.6.4. Reflection Efficiency of Metasurfaces 43
2.7. Discussion and Conclusion 46
Chapter 3. Bowtie Nanoantenna Coupled Metal-Oxide-Silicon (p-doped) Diode for 28.3 THz IR Rectification 47
3.1. Introduction 47
3.2. Design Geometry and Simulation Method 49
3.2.1. Antenna Length Optimization for Maximum Field Enhancement 51
3.2.2. Connecting Wire Length Optimization 52
3.3. Device Fabrication 53
3.4. Result and Discussion 54
3.5. Discussion 58
Chapter 4. Nanoantenna-Coupled Complimentary Metal-Oxide-Silicon (CMOS) Diode for Energy Harvesting at 28.3 THz 60
4.1. Introduction 60
4.2. Materials and Methods 62
4.3. Result and Discussion 66
4.4. Conclusion 72
Chapter 5. Nanoantenna Coupled Diode Fabrication and Measurement Setups 73
5.1. Nanoantenna Coupled Diode Fabrication 73
5.1.1. Buffered Oxide Etch (BOE) Removal 73
5.1.2. Deposition of Substrate and Ground Layer 74
5.1.3. Align Key Fabrication and Dry Etching 76
5.1.4. Ion Implantation and Thermal Annealing 77
5.1.5. Fabrication of Bowtie Nanoantenna with Connecting Wire 78
5.1.6. Fabrication of Measurement Pad 80
5.1.7. Dry Etching of Isolation Lines 81
5.2. Nanoantenna Measurement Setup 82
5.3. Conclusion 84
Chapter 6. Conclusions and Future Work 85
6.1. Discussion and Conclusion 85
6.2. List of Publications 87
REFERENCES 88
Table 2.1. Dimensions of the Unit Cell 31
Table 4.1. Performance comparison with single antenna diodes at 28.3 THz 71
Table 5.1. The detailed recipe used in the 200 nm-thick W ground plane deposition using DC sputtering method. 75
Table 5.2. The detailed recipe used in the deposition of 1.2 μm thick-SiO₂ process using plasma-enhanced chemical vapor deposition (LPCVD) method. 75
Figure 1.1. The relative permittivity and conductivity of gold as a function of frequency in the THz range. 18
Figure 1.2. Demonstration of wave bending through metamaterial 19
Figure 1.3. Application of reflective metasurface 20
Figure 2.1. Reflection phase distribution for one period of metasurfaces to reflect a normal incident plane wave into reflection angle of 56° and 70° (black dashed line: R1 from the... 29
Figure 2.2. (a) Schematic of a folded dipole unit cell with geometrical dimensions. (b) Reflection phases in degrees at 10 GHz as a function of length (l) and width (w) of the... 30
Figure 2.3. Folded dipole unit cells in one period for (a) θr=56° and (b) θr=70°. Far-field 3D radiation pattern at 10 GHz for the finite 7 by 9 periods of (c) 56° and (d) 70°...[이미지참조] 32
Figure 2.4. (a) Geometry of a patch-shaped 70° reflection metasurface with unit cell phases. (b) The far-field 3D radiation pattern for a finite 7 by 8 array of 70° reflective... 33
Figure 2.5. Surface current distribution inside the folded dipole unit cells (a, b) and the patch-shaped unit cells (c, d) in the metasurfaces for a 70° reflection angle. (a, c) are from... 35
Figure 2.6. Power flow (Re{Sz}) on a plane located at z=4.5 mm (λ/6.67) from (a) the folded dipole metasurface and (b) the patch-shaped metasurface.[이미지참조] 36
Figure 2.7. (a) Fabricated folded dipole metasurface with 7 by 9 periods. (b) Fabricated patch type metasurface with 7 by 8 periods. (c) Measurement setup for the metasurfaces.... 37
Figure 2.8. Transmission coefficient (S₂₁) at θ=70° in (a) the time-domain with a 2.8 ns-wide gating window (20 ns - 22.8 ns) for considering the main peak of reflection from... 39
Figure 2.9. Transmission coefficients (S₂₁) at θ=-70° in (a) the time-domain signal with a 2.4 ns-wide gating window (21.4 ns - 23.8 ns) for considering only the main peak of... 41
Figure 2.10. Reflection coefficient (S₁₁) magnitude at θ=0° in (a) the time-domain signals from both metasurfaces and the metallic plate with a size of the patch metasurface... 43
Figure 3.1. (a) Simulation model geometry of the nanoantenna-coupled p-doped MOS tunnel diode, (b) cut view of the device geometry with layer thicknesses, (c) detailed... 50
Figure 3.2. (a) Averaged field enhancement at 28.3 THz with variation of the antenna length at the oxide tunnel barrier below antenna edges and (b) cross-sectional view of field... 51
Figure 3.3. (a) Geometry of a nanoantenna-coupled p-doped MOS diode device with measurement pads, (b) bowtie-shaped nanoantenna connected with the measurement pads... 52
Figure 3.4. (a) Top view of the fabricated device from an optical microscope with contact pads for optical measurements, (b) top view scanning electron microscopy (SEM) image of... 53
Figure 3.5. Schematic of the IR measurement setup. 54
Figure 3.6. (a) (c) Diode I-V curve and (b) (d) differential diode resistance (Rd) measurement from the linear and non-linear devices, respectively. 56
Figure 3.7. Polarization-dependent output voltage (Voc) from the device with the linear I-V curve. 57
Figure 4.1. (a) Working principle from the cut view geometry of nanoantenna-integrated metal oxide semiconductor (MOS) tunnel diode with a bipolar p-n junction. (b) Energy... 62
Figure 4.2. Real and Imaginary dielectric permittivity of Al₂O₃ 63
Figure 4.3. Simulation model of the bowtie-shaped nanoantenna integrated with MOS tunnel diode. (a) Simulation model of the antenna integrated with p-n tunnel diode where... 64
Figure 4.4. Fabricated device with the measurement contact pad. (a) Fabricated top view from an optical microscope of the bipolar MOS tunnel diode device with contact pad for... 66
Figure 4.5. Measurement setup block diagram 67
Figure 4.6. (a) (c) Diode I-V curve and (b) (d) differential diode resistance (Rd) measurement from the linear and non-linear devices, respectively. 68
Figure 4.7. Polarization-dependent output voltage (Voc) from the device with the linear I-V curve. 69
Figure 4.8. Transmission Electron Microscopy (TEM) images from the cut view of the (a) linear response and (b) nonlinear response devices. 71
Figure 4.9. Electron Device Spectroscopy (EDS) images from the cut view of the (a) linear response and (b) nonlinear response devices. 72
Figure 5.1. The overall devices after W and poly-silicon deposition using DC sputtering and LPCVD, respectively. 76
Figure 5.2. Align key pattern for lithography process alignment 76
Figure 5.3. (a) p+ doped area from nanoantenna-coupled MOS (p-doped) diode (b) Nanoantenna-coupled CMOS tunnel diode 77
Figure 5.4. SEM image from the cut view of our device showing different layer thickness 78
Figure 5.5. Ellipsometry data of 4nm Al₂O₃ deposition through ALD process 78
Figure 5.6. Nanoantenna fabrication process though e-beam lithography and evaporation 79
Figure 5.7. Metal pad fabrication through UV lithography 81
Figure 5.8. Dry etching of isolation lines to separate electrical connection between each device 82
Figure 5.9. Schematic of measurement setup for nanoantenna coupled p-doped MOS diode 83
Figure 5.10. Schematic of measurement setup for nanoantenna coupled pn-doped MOS diode 84