Amorphous In-Ga-Zn-O Thin-Film Transistors for Next Generation Ultra-High Definition Active-Matrix Liquid Crystal Displays.

Next generation ultra-high definition (UHD) active-matrix flat-panel displays have resolutions of 3840x2160 (4K) or 7680x4320 (8K) pixels shown at 120 Hz. The UHD display is expected to bring about immersive viewing experiences and perceived realness. The amorphous In-Ga-Zn-O (a-IGZO) thin-film transistor (TFT) is a prime candidate to be the backplane technology for UHD active-matrix liquid crystal displays (AM-LCDs) because it simultaneously fulfills two critical requirements: (i) sufficiently high field-effect mobility and (ii) uniform deposition in the amorphous phase over a large area. We have developed a robust a-IGZO density of states (DOS) model based on a combination of experimental results and information available in the literature. The impact of oxygen partial pressure during a-IGZO deposition on TFT electrical properties/instability is studied. Photoluminescence (PL) spectra are measured for a IGZO thin films of different processing conditions to identify the most likely electron-hole recombination. For the first time, we report the PL spectra measured within the a IGZO TFT channel region, and differences before/after bias-temperature stress (BTS) are compared. To evaluate the reliability of a-IGZO TFTs for UHD AM-LCD backplane, we have studied its ac BTS instability using a comprehensive set of conditions including unipolar/bipolar pulses, frequency, duty cycle, and drain biases. The TFT dynamic response, including charging characteristics and feedthrough voltage, are studied within the context of 4K and 8K UHD AM-LCD and are compared with hydrogenated amorphous silicon technology. We show that the a-IGZO TFT is fully capable of supporting 8K UHD at 480 Hz. In addition, it is feasible to reduce a-IGZO TFT feedthrough voltage by controlling for non-abrupt TFT switch-off.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111526/1/ekyu_1.pd

Review of Display Technologies Focusing on Power Consumption

Producción CientíficaThis paper provides an overview of the main manufacturing technologies of displays, focusing on those with low and ultra-low levels of power consumption, which make them suitable for current societal needs. Considering the typified value obtained from the manufacturer’s specifications, four technologies—Liquid Crystal Displays, electronic paper, Organic Light-Emitting Display and Electroluminescent Displays—were selected in a first iteration. For each of them, several features, including size and brightness, were assessed in order to ascertain possible proportional relationships with the rate of consumption. To normalize the comparison between different display types, relative units such as the surface power density and the display frontal intensity efficiency were proposed. Organic light-emitting display had the best results in terms of power density for small display sizes. For larger sizes, it performs less satisfactorily than Liquid Crystal Displays in terms of energy efficiency.Junta de Castilla y León (Programa de apoyo a proyectos de investigación-Ref. VA036U14)Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA013A12-2)Ministerio de Economía, Industria y Competitividad (Grant DPI2014-56500-R

Printed electronics : the next inkjet revolution

Thesis (S.M.M.O.T.)--Massachusetts Institute of Technology, Sloan School of Management, Management of Technology Program, 2003.Includes bibliographical references.Inkjet printing has proven to be a remarkable disruptive technology. From its humble beginnings in 1984 it has grown to become the dominant technology for personal computer-based printing. However, after almost two decades of strong growth, the Inkjet printing market is maturing. Companies large and small are now beginning to explore use of inkjet in a diverse range of new applications ranging from manufacture of next generation flat panel displays and low cost circuits to generation of biochips and fast-prototyping of 3-D objects. These new applications present existing inkjet players with exciting opportunities to leverage their knowledge and assets to exploit these new markets. This thesis explores the opportunities for inkjet technology in two emerging industries: 1) next-generation flat panel displays based on organic light-emitting diodes and 2) low cost, disposable circuits required for products such as radio-frequency identification tags and smart cards. These are likely to be the two biggest opportunities for non-traditional applications of inkjet technology. In both cases, inkjet provides a flexible, low cost manufacturing method that is a very compelling alternative to the expensive wafer fab processing required to produce today's flat panel displays and circuits. Each of these industries is analyzed in considerable depth to provide context for assessing the disruptive potential of inkjet. The potential of inkjet to become an important enabling technology is then analyzed using ideas and frameworks from the management ofteclmology literature. Both organic LED displays and low cost circuits appear likely to become disruptive technologies. The best early opportunity for non-traditional application of inkjet technology appears to be in display manufacturing. Here the technology fit with Inkjet capabilities is good and the strength of competing manufacturing technologies is relatively weak. Establishment of inkjet as an important production method for low cost circuits appears more challenging. The technology fit is not as good and competing low-cost technologies are further along in their development. It is recommended that existing inkjet players first address the display opportunity to gain experience with transitioning inkjet from a consumer printing technology to one well suited to high-volume electronics manufacturing. Once this capability has been demonstrated the bigger challenges in circuit manufacturing can be addressed.by Todd A. Cleland.S.M.M.O.T

Active Matrix Organic Light-Emitting Displays: Novel Amorphous Silicon Thin-Film Transistors and Pixel Electrode Circuits.

Today active-matrix organic light-emitting displays (AM-OLEDs) are considered as next generation flat panel display. In this thesis, several hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT) technologies have been developed to accelerate the AM-OLED development. Among others to address the charging time delay issue of the conventional current-driven a-Si:H TFT pixel electrode circuit, a non-linear current scaling-function by cascaded-capacitors connected to the driving TFT was investigated. To enhance the performance of fabricated pixel electrode circuit, novel design of a-Si:H pixel circuit with cascaded storage capacitors was investigated based on the current-mirror structure. The electrical and thermal stability of the proposed a-Si:H TFT pixel electrode circuits were also explored in comparison to the conventional current-driven circuit. To address the inherent electrical stability issue of the a-Si:H TFT, two novel a-Si:H TFT structures were proposed: Corbino and Hexagonal TFTs. It was shown that both a-Si:H TFT structures have the asymmetric electrical characteristics under different drain bias conditions. To extract the electrical device parameters, asymmetric geometric factors were developed for different drain bias conditions. By using multiple Hexagonal TFT structure, the output current of Hexagonal a-Si:H TFT connected in parallel increases linearly with their number within a given pixel circuit. Current-voltage measurements indicate that a high ON-OFF current ratio and a low sub-threshold slope can be maintained for multiple Hexagonal TFTs connected in parallel while the field-effect mobility and threshold voltage remain identical to a single HEX a-Si:H TFT. Due to a unique device geometry, enhanced electrical stability and larger pixel aperture ratio can be achieved in the multiple a-Si:H HEX-TFT in comparison to standard single a-Si:H TFT having same channel width. Lastly, the dynamic responses of different a-Si:H TFT structures with various storage capacitor size were explored for AM-OLEDs. The effect of dofferent storage capacitors and overlap capacitors of TFTs on the charging time and feed-through voltage characteristics of the a-Si:H switching TFT were explored. Feed-through voltage behavior of Corbino a-Si:H TFT was also discussed in comparison to normal rectangular a-Si:H TFT as a switching TFT for AM-OLEDs.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/58418/1/hojinny_1.pd

Implant Activated Source/Drain Regions for Self-Aligned IGZO TFT

In this work, amorphous Indium Gallium Zinc Oxide (IGZO) TFTs with channel lengths scaled as small as L = 1 µm are presented which demonstrate excellent electrical characteristics, however the traditional metal-contact defined source/drain regions typically require several microns of gate overlap in order to provide ohmic behavior with minimal series resistance and ensure tolerance to overlay error. In addition, further scaling the channel length by simply reducing the source/drain metal gap is not feasible. The focus of this study is to investigate techniques to realize self-aligned (SA) IGZO TFTs that are not subject to gate-source/drain misalignment due to overlay error or process bias. Top gate (TG) co-planar and bottom gate (BG) staggered TFTs are fabricated using plasma immersion and ion implantation to selectively form conductive IGZO regions, with the channel region blocked by a gate-defined mask. Among the investigated treatments, oxygen plasma activation and ion implanted activation via 11B+ and 40Ar+ has been successfully demonstrated. Due to metal gate charging during ion implantation of SA-TG devices, the characteristics show a significant left-shift whereas SA-BG devices do not show this behavior. Electrical results suggest a defect-induced mechanism is involved with 40Ar+ implant activation of the S/D regions. However, 11B+ implant activation is attributed to the formation of an electrically active donor species involving chemical bonding. Both boron and argon demonstrate pronounced degradation in charge injection at higher dose treatments. Finally, a novel lithographic strategy which utilizes top-side flood exposure rather than a back-side through-glass exposure has also been explored, which would enable SA-BG devices on non-transparent substrates

O2 플라즈마, 자외선 조사, Biased-H2O 어닐링을 통한 저온 용액공정을 이용한 산화물 박막트랜지스터의 특성 향상에 대한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2013. 8. 한민구.Zinc tin oxide (ZTO)나 indium gallium zinc oxide (IGZO)를 이용한 용액공정형 산화물 박막 트랜지스터는 고이동도, 빛 투명성, 플렉서블 적합성, 물질의 광범위함, 분자 구성비에 의한 전기적 특성 조절 용이성 등의 장점 때문에 실리콘 기반의 박막 트랜지스터와 유기물 박막 트랜지스터를 대체하며 능동 매트릭스형 디스플레이의 구동 소자로서 상당한 주목을 받고 있다. 용액공정형 산화물 박막 트랜지스터는 능동 매트릭스형 액정표시장치와 능동 매트릭스형 유기발광다이오드 디스플레이 백플레인으로서 많은 문제점을 가지고 있는 실리콘 기반의 박막 트랜지스터와 유기물 박막 트랜지스터와 비교하여 우수한 특성을 보여주고 있다. 더욱이, 용액공정형 산화물 박막 트랜지스터는 우수한 균일성과 고처리량 덕분에 대면적 공정에 적합하다. ZnO 기반의 산화물 반도체 중에서, Sn 물질을 이용한 ZTO 박막 트랜지스터는 Sn이 널리 사용되고 있는 In 보다 상당히 저가의 물질이기 때문에 저가 공정을 확립하는데 유망한 소자이다. 추가적인 가격 절감과 플렉서블 디스플레이로의 응용성 확장을 위해서 용액공정형 ZTO 박막 트랜지스터는 저렴하고 플렉서블한 기판에 제작되어야 한다. 플렉서블한 기판은 고온에서 쉽게 손상되기 때문에 플렉서블한 기판에 용액공정형 ZTO 박막 트랜지스터가 제작되기 위해서는 저온 공정이 요구된다. 그러나, 저온에서 제작된 용액공정형 ZTO 박막 트랜지스터는 낮은 on-currnet, 높은 문턱 접압, 낮은 이동도 등의 열등한 특성을 가지므로, 우수한 특성의 용액공정형 ZTO 박막 트랜지스터를 제작하기 위해서는 500도 이상의 고온 공정이 필요하다. 저온에서 제작된 용액공정형 산화물 박막 트랜지스터의 소자 특성을 향상시키기 위해서는, 용액공정형 산화물 박막 트랜지스터에 대한 어닐링 온도의 영향성과 더불어 저온 공정에서 제작되더라도 우수한 소자 특성을 가지도록 하는 연구가 요구된다. 기존에 용액공정형 산화물 박막 트랜지스터에 대한 어닐링 온도의 영향상을 분석하려는 시도가 있었지만, 용액공정형 산화물 박막 트랜지스터에 대한 어닐링 온도 영향성의 전기적, 화학적 메커니즘은 거의 연구되지 않았다. 이 논문의 목적은 용액공정을 이용하여 다양한 어닐링 온도에서 산화물 박막 트랜지스터를 제작하여 문턱 전압, 포화 이동도, 신뢰성 등의 용액공정형 산화물 박막 트랜지스터의 전기적 특성에 대한 어닐링 온도의 영향성을 분석하고, 제안된 O2 플라즈마, 자외선 조사, Biased-H2O 어닐링 등의 방법을 통하여 능동 매트릭스형 디스플레이를 위한 저온 용액공정 산화물 박막 트랜지스터의 전기적 특성을 향상시키는 것이다.Solution-processed oxide thin film transistors (TFTs) with zinc-tin-oxide (ZTO) and indium-gallium-zinc-oxide (IGZO) have attracted considerable attention for the driving elements of active matrix display, instead of Si-based TFTs and organic TFTs, because of high mobility, visible light transparency, flexibility, wide range of materials, and controllability of electrical properties by atomic composition. Solution-processed oxide TFTs show superior performance for active matrix liquid crystal display (AMLCD) and active matrix organic light emitting diode (AMOLED) display backplanes, compared with solution-processed Si and organic TFTs which have a number of issues. Furthermore, solution-processed oxide TFTs are compatible with large area due to good uniformity and high throughput, so that could be a method for achieving low cost fabrication contrary to vacuum processes. Among various ZnO-based oxide semiconductors, ZTO TFTs employing tin (Sn) material maybe promising candidates for achieving low cost processes because Sn is a quite low cost material compared with widely used indium (In). Solution-processed ZTO TFTs need to be fabricated on inexpensive and flexible substrates such as glass and plastic for additional cost reduction and application extension to a flexible display. For solution-processed ZTO TFTs fabrication with these flexible substrates, low temperature processes are necessary because these substrates are easily damaged at high annealing temperatures. At low annealing temperature, however, solution-processed ZTO TFTs have poor performance such as low on-current, high threshold voltage and low mobility, so a rather high annealing temperature exceeding 500 °C is required in solution-processed ZTO TFTs. To improve the device characteristics of solution-processed oxide TFTs even at low annealing temperature on an active layer, a study of the effects of annealing temperature on the electrical characteristics of solution-processed oxide TFTs and the efforts to achieve high device characteristics of solution-processed oxide TFTs even at low annealing temperature on active layer are desired. There were some efforts to investigate the effects of annealing temperature on solution-processed oxide TFTs, but the electrical and chemical mechanisms of annealing temperature on solution-processed oxide TFTs have been scarcely studied. The purpose of this thesis is to fabricate oxide TFTs employing solution-process for an oxide semiconductor active layer with various annealing temperatures to investigate the effects of annealing temperature on the electrical characteristics of solution-processed oxide TFTs such as threshold voltage, saturation mobility, and reliability, and to improve the electrical characteristics of low temperature solution-processed oxide TFTs for low cost, stable, and flexible active matrix display backplane. The effects of annealing temperature on the bonding structure of ZTO active layer in solution-processed ZTO TFTs were investigated and the chemical formation equation of the ZTO active layer with regard to the annealing temperature was established. To improve the electrical characteristics of low temperature solution-processed oxide TFTs according to the investigation of effects of annealing temperature in regard of the chemical formation of ZTO active layer, O2 plasma treatment, UV radiation treatment, and the biased-H2O annealing were proposed to achieve high device characteristics of solution-processed oxide TFTs even at low annealing temperature. Moreover, the effects on electrical and chemical characteristics of solution-processed oxide TFTs with proposed methods were investigated in detail. These proposed methods to improve the electrical characteristics of low temperature solution-processed oxide TFTs would be suitable for the low cost, stable, and flexible active matrix display backplane.Abstract i Contents iv List of Tables vii List of Figures ix Chapter 1 Introduction 1 1.1 Recent flat panel display technology 2 1.2 Device parameter extraction 12 1.3 Dissertation organization 14 Chapter 2 Review of solution-processed oxide TFTs 16 2.1 Overview of oxide TFTs 17 2.2 Advantages of solution-process 25 2.3 Solution-processed oxide TFTs 30 Chapter 3 Optimization of the fabrication process of solution-processed oxide TFTs 36 3.1 Overview 37 3.2 Structure of solution-processed oxide TFTs 38 3.3 Stirring time on solution-processed oxide TFTs 47 3.4 Active layer thickness on solution-processed oxide TFTs 56 3.5 Effects of passivation on solution-processed oxide TFTs 60 3.6 Electrical characteristics of solution-processed oxide TFTs 63 3.6.1 Transfer characteristics 63 3.6.2 Reliability characteristics 68 Chapter 4 Effects of Annealing Temperature on Solution-processed oxide TFTs 75 4.1 Motivation 76 4.2 Fabrication of solution-processed ZTO TFTs with various annealing temperature 78 4.3 Electrical characteristics with the increase in annealing temperature 80 4.4 Dechlorination on threshold voltage with the increase in annealing temperature 83 4.5 Dechlorination and crystallization on saturation mobility with the increase in annealing temperature 89 4.6 Reliability characteristics with the increase in annealing temperature 93 4.7 Chemical formation equations with the increase in annealing temperature 95 4.8 Conclusion 99 Chapter 5 Improvement of low temperature solution-processed oxide TFTs 100 5.1 Improvement of low temperature solution-processed oxide TFTs employing O2 plasma treatment 101 5.1.1 Motivation 101 5.1.2 Fabrication of solution-processed ZTO TFTs employing O2 plasma treatment 104 5.1.3 Electrical characteristics with O2 plasma treatment 108 5.1.4 Preferential dissociation of Cl on threshold voltage by O2 plasma treatment 111 5.1.5 Increase of electron concentration on saturation mobility by O2 plasma treatment 116 5.1.6 Reliability characteristics with O2 plasma treatment 119 5.1.7 Conclusion 122 5.2 Improvement of low temperature solution-processed oxide TFTs employing Ultra-Violet radiation treatment 123 5.2.1 Motivation 123 5.2.2 Fabrication of solution-processed ZTO TFTs employing UV radiation treatment 126 5.2.3 Electrical characteristics with UV radiation treatment 130 5.2.4 Effects of UV radiation treatment on oxide active layer semiconductors 133 5.2.5 Generation of hydroxide(-OH) bonding by UV radiation treatment on oxide active layer semiconductors 137 5.2.6 Conclusion 141 5.3 Improvement of low temperature solution-processed oxide TFTs employing biaed-H2O annealing 142 5.3.1 Motivation 142 5.3.2 Effects of various annealing condition 145 5.3.3 Effects of H2O wet annealing according to the annealing temperature 148 5.3.4 Proposed biased-H2O annealing to improve low temperature solution-processed oxide TFTs 154 5.3.5 Conclusion 161 Chapter 6 Summary 162 Bibliography 171 초 록 191Docto

Assessing the Potential for Civil-Military Integration: Selected Case Studies

This paper presents material from three of the case studies undertaken during the assessment: flat panel displays, polymeric composites, and shipbuilding. The three cases illustrate both the opportunities and the challenges facing those designing policies to increase the level of civil–military integration (CMI)

Why did video screens get slimmer? A study of the role of Intellectual Property in the commercial development of organic light-emitting diodes

PhDThis research project consists of a critical analysis of the role of intellectual property amongst other factors in the successful commercial development at the Cavendish Laboratory of optoelectronic light emitting diode display devices based on novel organic semiconductor materials. It begins by giving the background to the quantum mechanical properties upon which the technology is based, followed by a discussion of the path of innovation, describing the interaction between the different socioeconomic factors that influence this path. It then draws an analogy with the development of an analogous technology - inorganic semiconductors - to signpost the factors that may affect the developmental history of the technology. This is followed by an analysis of a chronology derived initially from patents downloaded from the World Patents Database of the European Patent Office to showcase the technology’s development steps, and to study the patenting strategy of Cambridge Display Technology (CDT) - the company that was set up to commercialise the novel technology - through a patent trends analysis. From that, the major socioeconomic factors critical to the technology’s development are analysed, followed by a test and extension of an existing Black Box mathematical model for studying the dynamics of innovation that is based on the interaction of those factors. Finally, through a patent citation analysis, CDT’s commercial strategy for the technology is shown as being based on its patents portfolio to build an extensive licensing programme that pooled major academic, industry and commercial partners for the furtherance of the technology. This later evolved into a new ecosystem for the innovation, of which CDT occupied a central and indispensable position

The micro-LED roadmap: status quo and prospects

Micro light-emitting diode (micro-LED) will play an important role in the future generation of smart displays. They are found very attractive in many applications, such as maskless lithography, biosensor, augmented reality (AR)/mixed reality etc, at the same time. A monitor that can fulfill saturated color rendering, high display resolution, and fast response time is highly desirable, and the micro-LED-based technology could be our best chance to meet these requirements. At present, semiconductor-based red, green and blue micro-LED chips and color-conversion enhanced micro-LEDs are the major contenders for full-color high-resolution displays. Both technologies need revolutionary ways to perfect the material qualities, fabricate the device, and assemble the individual parts into a system. In this roadmap, we will highlight the current status and challenges of micro-LED-related issues and discuss the possible advances in science and technology that can stand up to the challenges. The innovation in epitaxy, such as the tunnel junction, the direct epitaxy and nitride-based quantum wells for red and ultraviolet, can provide critical solutions to the micro-LED performance in various aspects. The quantum scale structure, like nanowires or nanorods, can be crucial for the scaling of the devices. Meanwhile, the color conversion method, which uses colloidal quantum dot as the active material, can provide a hassle-free way to assemble a large micro-LED array and emphasis the full-color demonstration via colloidal quantum dot. These quantum dots can be patterned by porous structure, inkjet, or photo-sensitive resin. In addition to the micro-LED devices, the peripheral components or technologies are equally important. Microchip transfer and repair, heterogeneous integration with the electronics, and the novel 2D material cannot be ignored, or the overall display module will be very power-consuming. The AR is one of the potential customers for micro-LED displays, and the user experience so far is limited due to the lack of a truly qualified display. Our analysis showed the micro-LED is on the way to addressing and solving the current problems, such as high loss optical coupling and narrow field of view. All these efforts are channeled to achieve an efficient display with all ideal qualities that meet our most stringent viewing requirements, and we expect it to become an indispensable part of our daily life

An Investigation Of The Relationship Between Visual Effects And Object Identification Using Eye-tracking

The visual content represented on information displays used in training environments prescribe display attributes as brightness, color, contrast, and motion blur, but considerations regarding cognitive processes corresponding to these visual features require further attention in order to optimize the display for training applications. This dissertation describes an empirical study with which information display features, specifically color and motion blur reduction, were investigated to assess their impact in a training scenario involving visual search and threat detection. Presented in this document is a review of the theory and literature describing display technology, its applications to training, and how eye-tracking systems can be used to objectively measure cognitive activity. The experiment required participants to complete a threat identification task, while altering the displays settings beforehand, to assess the utility of the display capabilities. The data obtained led to the conclusion that motion blur had a stronger impact on perceptual load than the addition of color. The increased perceptual load resulted in approximately 8- 10% longer fixation durations for all display conditions and a similar decrease in the number of saccades, but only when motion blur reduction was used. No differences were found in terms of threat location or threat identification accuracy, so it was concluded that the effects of perceptual load were independent of germane cognitive load