Figure 2.1. Developments in transparent electronics, the past, today, and the future. 37

Figure 2.2. Conceptual roll-to-roll manufacturing process 40

Figure 2.3. Ink-jet technologies map. 48

Figure 2.4. Continuous type ink-jet printing system. 49

Figure 2.5. Drop-on-demand ink-jet printing system. 50

Figure 2.6. (a) Representative photo sequence of drop formation for two different fluids: aqueous ZnO precursor and isopropyl alcohol (IPA)-added aqueous ZnO precursor.... 54

Figure 2.7. Transfer characteristics of the spin-coated transistors using two different fluids: (a) aqueous ZnO precursor and (b) isopropyl alcohol (IPA)-added aqueous ZnO precursor.... 55

Figure 2.8. Two-dimensional profiles of an inkjet-printed ZTO single dot: (a) on an IPA-cleaned SiO₂/n++ Si substrate at 50 ℃ and 80 ℃ and (b) on an HMDS-treated SiO₂/n++ Si substrate at 50 ℃ and 80 ℃....(이미지참조) 62

Figure 2.9. (a) Transfer characteristics of an inkjet-printed transistor fabricated under different surface conditions as a function of the pre-heated substrate temperature; (b) Channel-width-normalized contact resistance of devices fabricated under different... 63

Figure 2.10. SEM images showing cross-sections of the channel region in inkjet-printed ZTO transistors fabricated either (a) on an IPA-cleaned substrate or (b) on an HMDS-treated substrate.... 64

Figure 2.11. (a) TGA and DSC curves of ZTO sol-gel precursor material. The Sn concentration in the ZTO precursor is 30 mol%. (b) Transfer characteristics of transistors fabricated using a ZTO layer annealed at different temperatures ranging... 70

Figure 2.12. Typical transfer and output characteristics (insets) of ZTO transistors fabricated by (a) spin-coating and (b) inkjet printing.[J. Jeong, K. Song, D. Kim, C. Y. Koo, J. Moon, Journal of The Electrochemical Society, 156, H808 (2008).] 71

Figure 2.13. The stability behavior of the spin-coated and the inkjet-printed ZTO-TFTs: (a) time-dependence of the threshold voltage shift as a function of the bias-stress duration with a gate bias of 20 V, and (b) the variation in the subthreshold slope... 72

Figure 2.14. HRTEM images showing the sol-gel-derived ZTO film microstructure produced by (a) spin-coating and (b) inkjet printing.[J. Jeong, K. Song, D. Kim, C. Y. Koo, J. Moon, Journal of The Electrochemical Society, 156, H808 (2008).] 73

Figure 2.15. Various structures of organic thin-film transistor [A. Facchetti, M. Yoon, and T. J. Marks, Adv. Mater., 17, 1705 (2005)]. 75

Figure 2.16. Variations of ITO resistivity with SniIn ratio (C. 1. Bright in Transparent Electronics: From Synthesis to Applications [Eds: A. Facchetti and T. J. Marks), John Wiley & Sons Ltd, UK (2010)] 86

Figure 2.17. Simplified crystal structure and doping model for ITO. (C. 1. Bright in Transparent Electronics: From Synthesis to Applications [Eds: A. Facchetti and T. J. Marks), John Wi ley & Sons Ltd, UK (2010)] 87

Figure 2.18. Schematic orbital drawings for the carrier transport paths in crystalline and amorphous semiconductors. (a) Covalent semiconductors have directive sp³ orbitals.... 91

Figure 2.19. Schematics representing the orbitals. (left) The asymmetrical sp orbitals, showing the angles θ between theorbitals and the separation vector r. (right) The symmetric s orbitals, where r is the distance between the center of orbitals and a... 94

Figure 3.1. (a) Carrier concentration and Hall mobility of the sol-gel derived ZIO thin films as a function of the composition. (b) Sheet resistance of the ZIO thin films as a function of annealing temperature and post-treatment method. 108

Figure 3.2. (a) High resolution X-ray diffraction patterns obtained from the ZIO films as a function of annealing temperatures from 200℃ to 700℃. 110

Figure 3.3. HRTEM images (center) showing the cross section of ZIO inkjet-printed electrodes on spin-coated ZTO semiconductor. Magnified ZIO inkjet-printed HRTEM image (left) shows a quasi amorphous phase embedded nanocrystals. ZTO semiconductor image (right) is represented wholly amorphous phase.... 113

Figure 3.4. Microscope images of ink-jet printed patterns obtained from ZIO ink as a function of droplet interspacing: (a) 110, (b) 90, (c) 60, and (d) 40 ㎛. Scale bar represents 100 ㎛. 116

Figure 3.5. (a) Transfer characteristics of ZTO TFT with ZIO ink-jet-printed electrodes (left) and vacuum-deposited aluminum electrodes (right). (b) Output characteristics of the corresponding solution processed transistors.... 119

Figure 3.6. Optical microscopic image showing the ink-jet-printed ZIO electrode onto ZTO semiconductor with varying channel widths. Scale bar represents 300 ㎛. 122

Figure 3.7. Channel-width-normalized contact resistance of the ZTO TFTs with ZIO ink-jet-printed electrode and vacuum-deposited aluminum. 123

Figure 3.8. Optical transmittance spectrum of spin-coated bilayer of ZIO/ZTO on the quartz substrate. The insets show photographic image of the invisible TFT with ink-jet printed oxide electrode on glass substrate. 125

Figure 3.9. Thermal behavior and evolution of chemical bond structures for the ITO precursor dried at 130℃ as a function of the annealing temperatures (from 100℃ to 700℃) determined by TG-DSC analysis. 130

Figure 3.10. Thermal behavior and evolution of chemical bond structures for the ITO precursor dried at 130℃ as a function of the annealing temperatures (from 100℃ to 700℃) determined by FT-IR spectroscopy.... 132

Figure 3.11. Electrical characteristics of the sol-gel derived ITO thin films annealed in a furnace at 600 ℃ in air as a function of the Sn doping content. The average values with a standard deviation were reported in all the plotted data: (a) sheet... 136

Figure 3.12. A series of XRD patterns of (a) furnace- and (b) microwave- annealed ITO layers as a function of the annealing temperature. The diffraction patters correspond to cubic bixbyite In₂O₃ (JCPDS no. 06-0416) when annealed at above... 138

Figure 3.13. Optical images of the ITO patterns generated by various patterning methods. Photolithographically defined micro-patterns of (a, e) the 50-nm-thick vacuum-deposited ITO and (b, t) the 10-nm-thick spin-coated ITO pattern. Non-conventionally defined micro-patterns based on the sol-gel ITO ink by (c, g) a liquid bridge-mediated nanotransfer molding (LB-nTM) and (d, h)... 140

Figure 3.14. Optical images of microscale ITO patterns fabricated by LB-nTM on SiO₂/Si substrates materials using the ITO inks with varying solution concentrations: (a) 0.05 M, (b) 0.15 M, (c) 0.25 M, and (d) 0.35 M.... 141

Figure 3.15. (a) The dynamics of ITO ink droplet formation under the optimized driving conditions. Microscope images of inkjet-printed line patterns as a function of droplet interspacing: (b) 160, (c) 130, (d) 100, (e) 70, and (f) 40 ㎛. 142

Figure 3.16. (a) AFM topographic images of the photolithographically patterned ITO films from vacuum- (left) and solution-deposited (right). (b) Schematic of conductive AFM setup and (c) the corresponding current map of the patterned ITO films. 144

Figure 3.17. (a) Optical transmittance spectrum for the 20-nm-thick spin-coated and vacuum-deposited ITO films on glass substrate. (b) A photograph of the ITO spin-coated on large-area glass (300 x 400 ㎟).... 146

Figure 3.18. TFT characteristics of solution-processed ZnO-TFTs with (a, b) spin-coated ITO (s-ITO) and (c, d) vacuum-deposited ITO (v-ITO) gate electrodes. TFT characteristics of solution-processed ZTO-TFTs with (e, f) inkjet-printed ITO and (g,... 149

Figure 3.19. The characteristic of fully transparent TFT (TTFT) in which solution ITO materials are used gate (G), source (S) and drain (D) electrodes on the glass substrate at the same time exhibits in here.... 153

Figure 3.20. HRTEM images showing (b) the cross-sectional structure of ZTO-TFTs with solution-processed ITO electrodes: the close-up images of (a) the spin-coated ITO gate electrode and and (c) the inkjet-printed as source/drain electrodes/ZTO... 154

Figure 3.21. Energy diagram before (black) and after (blue) interdiffusion between the semiconductor and the electrode interface. An undesirable interdiffusion at the interface is likely to alter energy levels.... 156

Figure 4.1. (a) A schematic showing the chemical structure of the sol-gel derived organic-inorganic hybrid dielectric annealed at 200℃. (b) AFM topographic image of the spin-coated hybrid dielectric material.... 171

Figure 4.2. Capacitance-voltage (C - V) curves of a 100 nm-thick hybrid dielectric on n+-Si substrate as measured from the Au top electrode/hybrid dielectric/n+-Si bottom electrode as shown in the inset (left)....(이미지참조) 173

Figure 4.3. Surface morphologies of the organic-inorganic hybrid dielectric after exposure to the IZO semiconductor precursor solution as a function of time: (a) 1 h, (b) 2 h, and (c) 3 h. 175

Figure 4.4. (a) A schematic of an IZO-TFT with a 420 nm thick hybrid dielectric in a bottom-gate configuration. (b) Cross-sectional TEM image of the IZO-TFT and (c) magnified TEM image showing the interface between the IZO semiconductor and the... 177

Figure 4.5. (a) Transfer (ID-VG) and (b) output (ID-VD) curves of IZO-TFTs with an organic-inorganic hybrid dielectric. The semiconductor and the dielectric solution-deposited on Si substrate were annealed at 200℃....(이미지참조) 180

Figure 4.6. Optical transmittance spectrum for various films: bare-glass films, hybrid dielectric spin-coated on a glass substrate, and IZO film/hybrid dielectric spin-coated on a glass substrate. 182

Figure 4.7. Fundamentally material analysis of solution-processed high-k dielectric material, YOx (a) Thermal behaviors using TG-DSC (b) A series of XRD patterns of YOx layers as a function of the annealing temperature....(이미지참조) 187

Figure 4.8. Capacitance of soluble YOx dielectrics. (a) Frequency-dependent capacitance (C versus f) of twice coated YOx dielectrics. (b) This plot shows a current density-electric field (J - E) 180 nm-thick hybrid dielectric on n+-Si substrate as measured from the Au top electrode/Y₂O₃ dielectrics/n+-Si bottom electrode....(이미지참조) 189

Figure 5.1. Typical transfer and output characteristics (insets) of ZTO transistors fabricated by (a) spin-coating and (b) ink-jet printing. (Y. Jeong, K. Song, D. Kim, C. Y. Koo, J. Moon, Journal of The Electrochemical Society, 2009, 156,... 203

Figure 5.2. (a) √ID vs VG plot used to extract the threshold voltage shift for the spin-coated ZTO-TFT after bias stressing with a gate bias of 20 V for 60 min and (b) the time dependence of the threshold voltage shift as a function of bias stress duration....(이미지참조) 204

Figure 5.3. (a) Transfer characteristics for the spin-coated ZTO-TFT before and after bias stressing with a gate bias of 20 V for 10 min. The device recovers its original state after a short period of relaxation at room temperature and (b) the variation of the... 208

Figure 5.4. (a) Transfer characteristics for the spin-coated ZTO-TFT before and after bias stressing with various gate bias voltages ranging from -20 to 30 V for 10 min and (b) the variation in the threshold voltage shift as a function of the gate bias voltage.... 209

Figure 5.5. The stability behavior of the spin coated and the ink-jet printed ZTO-TFTs: (a) time dependence of the threshold voltage shift as a function of bias stress duration with a gate bias of 20 V and (b) the variation in the subthreshold... 211

Figure 5.6. Transfer (IDS-VGS) curve of IZO-TFT as a function of In/Zn composition (mol%). [C. Y. Koo, K. Song, T. Jun, D. Kim, Y. Jeong, S. H. Kim, J. Ha, and 1. Moon, 157, J111 (2010)](이미지참조) 217

Figure 5.7. The saturation mobility, threshold voltage, and on/off ratio of IZO-TFT (In/Zn＝50/50) as a function of the semiconducting layer thickness. [C. Y. Koo, K. Song, T. Jun, D. Kim, Y. Jeong, S. H. Kim, J. Ha, and J. Moon, 157, J111 (2010)] 220

Figure 5.8. (a) Transfer (IDS-VGS) curve and (b) output (IDS-VDS) curve of IZO-TFTs (In/Zn＝50/50) with ~ 10 nm-thick channel. The annealing temperature was 300℃. [C. Y. Koo, K. Song, T. Jun, D. Kim, Y. Jeong, S. H. Kim, J. Ha, and J. Moon, 157, J111 (2010)](이미지참조) 223

Figure 5.9. Time-dependent transfer (IDS-VGS) curve of IZOTFT (In/Zn＝50/50) with a 10 nm thick channel. The annealing temperature was 300℃. [C. Y. Koo, K. Song, T Jun, D. Kim, Y. Jeong, S. H. Kim, J. Ha, and J. Moon, 157, J111 (2010)](이미지참조) 224

Figure 5.10. Transfer characteristics of (a) hot plate heated and (b) microwave-annealed IZO TFTs fabricated on SiO₂/n+-Si substrates at different temperatures. At the same temperature, microwave annealed IZO-TFTs show higher performance than hot plate heated ones....(이미지참조) 227

Figure 5.11. Transfer characteristics of (a) hotplate- and (b) microwave-annealed ZnO-TFTs fabricated on SiO₂/n+-Si substrates at different temperatures. The green arrows indicate the bias double sweep direction to measure a hysteresis. [T. Jun, K. Song, Y. Jeong, K. Woo, D. Kim, C. Bae, and J. Moon, 21, 1102, (2011)](이미지참조) 230

Figure 5.12. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) curves of a dried Zn(OH)x(NH₃)y(2-x)+ gel. [T. Jun, K. Song, Y. Jeong, K. Woo, D. Kim, C. Bae, and J. Moon, 21, 1102, (2011)](이미지참조) 231

Figure 5.13. The electrical performance of transparent, flexible TFTs with channels made from microwave-annealed ZnO layers at 140 ℃ on SiOx/ITO/PES substrates: (a) transfer characteristics; (b) output curves; and (c) a photograph of transparent,... 233

Figure 5.14. All solution-processed fully transparent ZnO TFT. (a) cross-sectional schematic diagram (upper) and images of ink-jet printed source & drain electrodes as a function of channel length.... 238