Kazumasa Nomoto

Bio: Kazumasa Nomoto is an academic researcher from Sony Broadcast & Professional Research Laboratories. The author has contributed to research in topics: Thin-film transistor & Layer (electronics). The author has an hindex of 25, co-authored 103 publications receiving 2409 citations.

Organic transistors in optical displays and microelectronic applications

Abstract: Organic thin-film transistors (OTFTs) offer unprecedented opportunities for implementation in a broad range of technological applications spanning from large-volume microelectronics and optical displays to chemical and biological sensors. In this Progress Report, we review the application of organic transistors in the fields of flexible optical displays and microelectronics. The advantages associated with the use of OTFT technology are discussed with primary emphasis on the latest developments in the area of active-matrix electrophoretic and organic light-emitting diode displays based on OTFT backplanes and on the application of organic transistors in microelectronics including digital and analog circuits.

A flexible full‐color AMOLED display driven by OTFTs

Abstract: — Organic thin-film-transistor (OTFT) technologies have been developed to achieve a flexible backplane for driving full-color organic light-emitting diodes (OLEDs) with a resolution of 80 ppi. The full-color pixel structure can be attained by using a combination of top-emission OLEDs and fine-patterned OTFTs. The fine-patterned OTFTs are integrated by utilizing an organic semiconductor (OSC) separator, which is an insulating wall structure made of an organic insulator. Organic insulators are actively used for the OTFT integration, as well as for the separator, in order to enhance the mechanical flexibility of the OTFT backplane. By using these technologies, active-matrix OLED (AMOLED) displays can be driven by the developed OTFT backplane even when they are mechanically flexed.

Solution-processed organic thin-film transistors with vertical nanophase separation

Abstract: We have found that spin coating a solution of 6,13-bis(triisopropyl-silylethynyl)-pentacene (TIPS-pentacene) blended with poly(α-methylstyrene) (PαMS) induces vertical nanophase separation, which results in a trilayer film: a TIPS-pentacene layer, a mixed layer of TIPS-pentacene/PαMS, and a TIPS-pentacene layer Organic thin-film transistors (TFTs) made from this TIPS-pentacene/PαMS solution have remarkably improved uniformity and thermal stability without degradation of electrical characteristics compared to organic TFTs with a conventional TIPS-pentacene sole channel layer

A high-performance short-channel bottom-contact OTFT and its application to AM-TN-LCD

Abstract: We have demonstrated an organic thin-film-transistor (OTFT)-driven active-matrix twisted-nematic liquid crystal display (AM-TN-LCD) on a glass substrate, with a resolution of 160/spl times/120 pixels, 79 ppi. Substrate temperature was kept below the plastic-compatible temperature of 180/spl deg/C throughout the fabrication process. In order to realize an OTFT-driven display with fine resolution, we employed short-channel bottom-contact (BC) pentacene OTFTs. It has been known that their drivability is limited by contact resistance at source/drain (S/D). We found that the S/D contact resistance was markedly reduced when the thickness of the nonohmic Ti adhesion layer for ohmic Au S/D electrodes was reduced less than /spl sim/3 nm. We elucidate that this 3 nm corresponds to the thickness of the accumulating layer in a pentacene channel. When we use a self-assembled monolayer of mercapto-silane-coupling agent as the adhesion layer, the contact resistance becomes negligibly small and BC OTFTs scalable below 10 /spl mu/m were obtained. In addition to this OTFT-cell technology, we developed a low-damage pentacene patterning technique for integration of OTFTs and introduced low-temperature panel assembly process to suppress thermal-stress degradation of pentacene OTFTs, which are the key technologies to achieve OTFT-driven AM-TN-LCD.

An OTFT-driven rollable OLED display

Abstract: — An 80-μm-thick rollable AMOLED display driven by an OTFT is reported. The display was developed so as to be rollable in one direction with an integrated OTFT gate driver circuit. It was successfully operated by an originally developed organic semiconductor, a peri-xanthenoxanthene derivative. The display retained its initial electrical properties and picture quality even after being subjected to 1000 cycles of a roll-up-and-release test with a radius of 4 mm.

Semiconducting π-conjugated systems in field-effect transistors: a material odyssey of organic electronics.

Abstract: Since the discovery of highly conducting polyacetylene by Shirakawa, MacDiarmid, and Heeger in 1977, π-conjugated systems have attracted much attention as futuristic materials for the development and production of the next generation of electronics, that is, organic electronics. Conceptually, organic electronics are quite different from conventional inorganic solid state electronics because the structural versatility of organic semiconductors allows for the incorporation of functionality by molecular design. This versatility leads to a new era in the design of electronic devices. To date, the great number of π-conjugated semiconducting materials that have either been discovered or synthesized generate an exciting library of π-conjugated systems for use in organic electronics. 11 However, some key challenges for further advancement remain: the low mobility and stability of organic semiconductors, the lack of knowledge regarding structure property relationships for understanding the fundamental chemical aspects behind the structural design, and realization of desired properties. Organic field-effect transistors (OFETs) are a kind of device consisting of an organic semiconducting layer, a gate insulator layer, and three terminals (drain, source, and gate electrodes). OFETs are not only essential building blocks for the next generation of cheap and flexible organic circuits, but they also provide an important insight into the charge transport of πconjugated systems. Therefore, they act as strong tools for the exploration of the structure property relationships of πconjugated systems, such as parameters of field-effect mobility (μ, the drift velocity of carriers under unit electric field), current on/off ratio (the ratio of the maximum on-state current to the minimum off-state current), and threshold voltage (the minimum gate voltage that is required to turn on the transistor). 17 Since the discovery of OFETs in the 1980s, they have attracted much attention. Research onOFETs includes the discovery, design, and synthesis of π-conjugated systems for OFETs, device optimization, development of applications in radio frequency identification (RFID) tags, flexible displays, electronic papers, sensors, and so forth. It is beyond the scope of this review to cover all aspects of π-conjugated systems; hence, our focus will be on the performance analysis of π-conjugated systems in OFETs. This should make it possible to extract information regarding the fundamental merit of semiconducting π-conjugated materials and capture what is needed for newmaterials and what is the synthesis orientation of newπ-conjugated systems. In fact, for a new science with many practical applications, the field of organic electronics is progressing extremely rapidly. For example, using “organic field effect transistor” or “organic field effect transistors” as the query keywords to search the Web of Science citation database, it is possible to show the distribution of papers over recent years as shown in Figure 1A. It is very clear

25th anniversary article: organic field-effect transistors: the path beyond amorphous silicon.

Abstract: Over the past 25 years, organic field-effect transistors (OFETs) have witnessed impressive improvements in materials performance by 3–4 orders of magnitude, and many of the key materials discoveries have been published in Advanced Materials. This includes some of the most recent demonstrations of organic field-effect transistors with performance that clearly exceeds that of benchmark amorphous silicon-based devices. In this article, state-of-the-art in OFETs are reviewed in light of requirements for demanding future applications, in particular active-matrix addressing for flexible organic light-emitting diode (OLED) displays. An overview is provided over both small molecule and conjugated polymer materials for which field-effect mobilities exceeding > 1 cm2 V–1 s–1 have been reported. Current understanding is also reviewed of their charge transport physics that allows reaching such unexpectedly high mobilities in these weakly van der Waals bonded and structurally comparatively disordered materials with a view towards understanding the potential for further improvement in performance in the future.

Electron transport through double quantum dots

Abstract: Electron transport experiments on two lateral quantum dots coupled in series are reviewed. An introduction to the charge stability diagram is given in terms of the electrochemical potentials of both dots. Resonant tunneling experiments show that the double dot geometry allows for an accurate determination of the intrinsic lifetime of discrete energy states in quantum dots. The evolution of discrete energy levels in magnetic field is studied. The resolution allows one to resolve avoided crossings in the spectrum of a quantum dot. With microwave spectroscopy it is possible to probe the transition from ionic bonding (for weak interdot tunnel coupling) to covalent bonding (for strong interdot tunnel coupling) in a double dot artificial molecule. This review is motivated by the relevance of double quantum dot studies for realizing solid state quantum bits.

Semiconductor device, and manufacturing method thereof

Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Single-electron devices and their applications

Abstract: The goal of this paper is to review in brief the basic physics of single-election devices, as well as their-current and prospective applications. These devices based on the controllable transfer of single electrons between small conducting "islands", have already enabled several important scientific experiments. Several other applications of analog single-election devices in unique scientific instrumentation and metrology seem quite feasible. On the other hand, the prospect of silicon transistors being replaced by single-electron devices in integrated digital circuits faces tough challenges and remains uncertain. Nevertheless, even if this replacement does not happen, single electronics will continue to play an important role by shedding light on the fundamental size limitations of new electronic devices. Moreover, recent research in this field has generated some by-product ideas which may revolutionize random-access-memory and digital-data-storage technologies.