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Hideo Hosono - One of the best experts on this subject based on the ideXlab platform.
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Oxide Semiconductors for display applications
High Quality Liquid Crystal Displays and Smart Devices - Volume 1: Development display applications and components, 2019Co-Authors: Hideo HosonoAbstract:Amorphous hydrogenated Si (a-Si:H) had been exclusively used until ~2012 as the backplane TFTs to drive flat panel displays. However, Oxide semiconductor-TFTs are becoming a strong alternative due to their high mobility, low off-current, and easy fabrication by conventional sputtering. In particular, transparent amorphous Oxide Semiconductors (TAOS) with In-Ga-Zn-O (IGZO) compositions are practically applied as the backplane for high-resolution and energy-saving liquid crystal displays (LCDs) and large-sized organic light emitting diode (OLED) TVs. Oxide Semiconductors have rather different characteristics compared with conventional Semiconductors based on diamond structure. This chapter describes the fundamentals of Oxide Semiconductors and their TFTs in comparison with a-Si: H from views of chemical bonding and electronic state. In addition, concepts for p-type materials and p/n control are explained along with concrete materials.
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ultra wide bandgap amorphous Oxide Semiconductors for nbis free thin film transistors
APL Materials, 2019Co-Authors: Junghwan Kim, Joonho Bang, Nobuhiro Nakamura, Hideo HosonoAbstract:The transparency of Oxide Semiconductors is a significant feature that enables the fabrication of fully transparent electronics. Unfortunately, practical transparent electronics using amorphous Oxide Semiconductors (AOSs) have not yet been realized, owing to significant photo-instabilities of these materials. Previous studies have revealed that the photo-instability can be attributed to sub-gap states (SGSs) near the valence-band maximum (VBM). Thus, it is inferred that the energy difference between the SGSs and the conduction-band minimum must be widened sufficiently in order to make it fully transparent over the entire visible-light region. In this work, we examined the electronic structures of a variety of AOSs and found that their ionization potentials vary greatly, depending upon the specific metal cations. This finding enabled us to increase the optical bandgap by modifying the VBM levels, resulting in a high mobility of 9 cm2/Vs and an ultra-wide bandgap of 3.8 eV for amorphous Zn–Ga–O (a-ZGO). We show that a-ZGO thin-film transistors exhibit no negative-bias illumination-stress instability with no passivation and no light-shielding layer.The transparency of Oxide Semiconductors is a significant feature that enables the fabrication of fully transparent electronics. Unfortunately, practical transparent electronics using amorphous Oxide Semiconductors (AOSs) have not yet been realized, owing to significant photo-instabilities of these materials. Previous studies have revealed that the photo-instability can be attributed to sub-gap states (SGSs) near the valence-band maximum (VBM). Thus, it is inferred that the energy difference between the SGSs and the conduction-band minimum must be widened sufficiently in order to make it fully transparent over the entire visible-light region. In this work, we examined the electronic structures of a variety of AOSs and found that their ionization potentials vary greatly, depending upon the specific metal cations. This finding enabled us to increase the optical bandgap by modifying the VBM levels, resulting in a high mobility of 9 cm2/Vs and an ultra-wide bandgap of 3.8 eV for amorphous Zn–Ga–O (a-ZGO). We ...
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transparent amorphous Oxide Semiconductors for organic electronics application to inverted oleds
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Hideo Hosono, Toshio Kamiya, Junghwan Kim, Yoshitake Toda, Satoru WatanabeAbstract:Efficient electron transfer between a cathode and an active organic layer is one key to realizing high-performance organic devices, which require electron injection/transport materials with very low work functions. We developed two wide-bandgap amorphous (a-) Oxide Semiconductors, a-calcium aluminate electride (a-C12A7:e) and a-zinc silicate (a-ZSO). A-ZSO exhibits a low work function of 3.5 eV and high electron mobility of 1 cm2/(V · s); furthermore, it also forms an ohmic contact with not only conventional cathode materials but also anode materials. A-C12A7:e has an exceptionally low work function of 3.0 eV and is used to enhance the electron injection property from a-ZSO to an emission layer. The inverted electron-only and organic light-emitting diode (OLED) devices fabricated with these two materials exhibit excellent performance compared with the normal type with LiF/Al. This approach provides a solution to the problem of fabricating Oxide thin-film transistor-driven OLEDs with both large size and high stability.
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Transparent amorphous Oxide Semiconductors: Materials design, electronic structure, and device applications
2017 75th Annual Device Research Conference (DRC), 2017Co-Authors: Hideo HosonoAbstract:In 1995, I presented a materials design concept for transparent amorphous Oxide Semiconductors with a large electron mobility (TAOS) at the 16'h International conference on amorphous Semiconductors along with concrete example materials of TAOS and the paper was published in 1996 [1[. The basic concept of TAOS is that large electron mobility should be retained even in amorphous materials if the conduction band minimum is mainly composed of spatially large spread of metal ns-orbitals.1 The validity of this design concept was demonstrated by analysis of electronic structure using photoemission experiments combined with calculations based on X-ray structural analysis[2].
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69 4 nbis stable Oxide thin film transistors using ultra wide bandgap amorphous Oxide Semiconductors
SID Symposium Digest of Technical Papers, 2016Co-Authors: Junghwan Kim, Toshio Kamiya, Nobuhiro Nakamura, Hideo HosonoAbstract:Ultra-wide bandgap amorphous Oxide Semiconductors (UWB-AOSs) were newly developed to improve photo-stability of conventional AOS TFTs. The UWB-AOSs have much larger bandgaps (∼3.8 eV) than conventional AOSs. Photo-stable TFTs using a UWB-AOS were fabricated at 200°C, which exhibited high saturation mobilities (∼7 cm2/Vs), high on/off ratios (>108) and small S values (0.3 V/dec). The UWB-AOS TFT showed no threshold voltage shift against NBIS test under white LED illumination (11,000 lux). This strong photo-stability would enable completely transparent applications such as window displays.
Toshio Kamiya - One of the best experts on this subject based on the ideXlab platform.
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transparent amorphous Oxide Semiconductors for organic electronics application to inverted oleds
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Hideo Hosono, Toshio Kamiya, Junghwan Kim, Yoshitake Toda, Satoru WatanabeAbstract:Efficient electron transfer between a cathode and an active organic layer is one key to realizing high-performance organic devices, which require electron injection/transport materials with very low work functions. We developed two wide-bandgap amorphous (a-) Oxide Semiconductors, a-calcium aluminate electride (a-C12A7:e) and a-zinc silicate (a-ZSO). A-ZSO exhibits a low work function of 3.5 eV and high electron mobility of 1 cm2/(V · s); furthermore, it also forms an ohmic contact with not only conventional cathode materials but also anode materials. A-C12A7:e has an exceptionally low work function of 3.0 eV and is used to enhance the electron injection property from a-ZSO to an emission layer. The inverted electron-only and organic light-emitting diode (OLED) devices fabricated with these two materials exhibit excellent performance compared with the normal type with LiF/Al. This approach provides a solution to the problem of fabricating Oxide thin-film transistor-driven OLEDs with both large size and high stability.
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69 4 nbis stable Oxide thin film transistors using ultra wide bandgap amorphous Oxide Semiconductors
SID Symposium Digest of Technical Papers, 2016Co-Authors: Junghwan Kim, Toshio Kamiya, Nobuhiro Nakamura, Hideo HosonoAbstract:Ultra-wide bandgap amorphous Oxide Semiconductors (UWB-AOSs) were newly developed to improve photo-stability of conventional AOS TFTs. The UWB-AOSs have much larger bandgaps (∼3.8 eV) than conventional AOSs. Photo-stable TFTs using a UWB-AOS were fabricated at 200°C, which exhibited high saturation mobilities (∼7 cm2/Vs), high on/off ratios (>108) and small S values (0.3 V/dec). The UWB-AOS TFT showed no threshold voltage shift against NBIS test under white LED illumination (11,000 lux). This strong photo-stability would enable completely transparent applications such as window displays.
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widely bandgap tunable amorphous cd ga o Oxide Semiconductors exhibiting electron mobilities 10 cm2 v 1 s 1
Applied Physics Letters, 2015Co-Authors: Hiroshi Yanagi, Toshio Kamiya, Chiyuki Sato, Yota Kimura, Issei Suzuki, Takahisa Omata, Hideo HosonoAbstract:Amorphous Oxide Semiconductors exhibit large electron mobilities; however, their bandgaps are either too large for solar cells or too small for deep ultraviolet applications depending on the materials system. Herein, we demonstrate that amorphous Cd–Ga–O Semiconductors display bandgaps covering the entire 2.5–4.3 eV region while maintaining large electron mobilities ≥10 cm2 V−1 s−1. The band alignment diagram obtained by ultraviolet photoemission spectroscopy and the bandgap values reveal that these Semiconductors form type-II heterojunctions with p-type Cu2O, which is suitable for solar cells and solar-blind ultraviolet sensors.
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origin of definite hall voltage and positive slope in mobility donor density relation in disordered Oxide Semiconductors
Applied Physics Letters, 2010Co-Authors: Toshio Kamiya, Kenji Nomura, Hideo HosonoAbstract:Amorphous Oxide Semiconductors (AOSs) are expected for alternative channel materials in thin-film transistors owing to their large electron mobilities. While, it is known that AOSs exhibit peculiar electron transport properties. Definite Hall voltages are observed even for mobilities <0.2 cm2/V s, which correspond to a very short mean free path (MFP) of 0.008 nm. Furthermore, Hall mobility increases with increasing the donor density. This paper reports that a percolation conduction model explains them; quantitative analyses based on the Boltzmann’s transport theory prove that carriers within the potential barriers have large MFPs of 0.5–1 nm. The percolation model also explains variable-range-hoppinglike and weak-localizationlike behaviors.
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material characteristics and applications of transparent amorphous Oxide Semiconductors
Npg Asia Materials, 2010Co-Authors: Toshio Kamiya, Hideo HosonoAbstract:Transparent amorphous Oxide Semiconductors have unique electron transport properties, such as large electron mobility (10–50 cm2/Vs) and the absence of a Hall voltage sign anomaly, that are not seen in conventional amorphous Semiconductors. This class of materials has been attracting much attention as a channel layer in thin-film transistors (TFTs) utilizing the above features along with the processing advantage that thin films can be deposited at low temperatures by conventional sputtering methods. The primary driving force for this trend is a rapidly emerging demand for backplane TFTs that can drive the next generation of flat-panel displays. This article reviews the recent advances in fundamental science of these materials and their TFT applications. Emphasis is placed on the view that high ionicity in chemical bonding and large spherical spread of unoccupied metal s orbitals in p-block metal Oxides lead to the realization of electronic structures that are advantageous for n-channel TFT applications. Amorphous Oxide Semiconductors are compared with conventional hydrogenated amorphous silicon, which is used widely as the channel material for backplane TFTs in current liquid-crystal displays.
Krishnan Rajeshwar - One of the best experts on this subject based on the ideXlab platform.
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Solution Combustion Synthesis of Complex Oxide Semiconductors
International Journal of Self-Propagating High-Temperature Synthesis, 2018Co-Authors: M. K. Hossain, E. Kecsenovity, A. Varga, M. Molnár, C. Janáky, Krishnan RajeshwarAbstract:This is a perspective of the role that combustion synthesis, specifically solution combustion synthesis, has played in the development of ternary and quaternary metal Oxide Semiconductors, and materials derived from these compounds such as composites, solid solutions, and doped samples. The attributes of materials, collectively termed ‘complex Oxides’ within the context of this discussion, are discussed in terms of their applicability in the generation of solar fuels from water splitting and CO_2 reduction, and environmental pollution remediation via heterogeneous photocatalysis.
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tungsten based Oxide Semiconductors for solar hydrogen generation
Catalysis Today, 2013Co-Authors: Krishnan Rajeshwar, Csaba Janaky, N R De Tacconi, Wilaiwan Chanmanee, Muhammad N HudaAbstract:Abstract In this focused review the progress achieved in solar water splitting over tungsten based Oxide photocatalysts is summarized. Beyond simple doping of WO 3 , both binary and ternary Oxides are discussed, presenting the various synthesis methods and resulting crystal structures. Theoretical considerations on the band structure are also given including a perspective on possible strategies for band engineering. The effectiveness of such strategies for designing tungsten-based Oxide Semiconductors as robust photocatalysts for stoichiometric solar water splitting, is reviewed. In addition, progress on Z-scheme based strategies using combined photocatalysts, where WO 3 is responsible for water photooxidation (O 2 -evolution) while H 2 generation takes place on its counterpart, is also reviewed.
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solution combustion synthesis of Oxide Semiconductors for solar energy conversion and environmental remediation
Chemical Society Reviews, 2009Co-Authors: Krishnan Rajeshwar, Norma R De TacconiAbstract:In this tutorial review, we summarize recent research on the solution combustion synthesis of Oxide Semiconductors for applications related to photovoltaic solar energy conversion, photoelectrochemical hydrogen generation, and heterogeneous photocatalytic remediation of environmental pollutants. First, the advantages of combustion synthesis relative to other strategies for preparing Oxide Semiconductors are discussed followed by a summary of process variants in combustion synthesis. The possibility of in situ chemical modification of the Oxide during its formation in the combustion environment is addressed. Morphological and crystal structure aspects of the combustion-synthesized products are discussed followed by a summary of trends in their photocatalytic activity relative to benchmark samples prepared by other methods.
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Hydrogen generation at irradiated Oxide semiconductor–solution interfaces
Journal of Applied Electrochemistry, 2007Co-Authors: Krishnan RajeshwarAbstract:This review focuses on the use of inorganic Oxide Semiconductors for the photoassisted generation of hydrogen from water. Representative studies spanning approximately three decades are included in this review. The topics covered include a discussion of the types of water photosplitting approaches, an ideal photoelectrolysis system, an examination of why Oxide Semiconductors are attractive for this application, a review of both classical and more recent studies on titanium diOxide, tungsten triOxide, and other binary metal Oxides, perovskites and other ternary Oxides, tantalates and niobates, miscellaneous multinary Oxides, semiconductor alloys and mixed semiconductor composites, and twin-photosystem configurations for water splitting.
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Hydrogen generation at irradiated Oxide semiconductor-solution interfaces
Journal of Applied Electrochemistry, 2007Co-Authors: Krishnan RajeshwarAbstract:This review focuses on the use of inorganic Oxide Semiconductors for the photoassisted generation of hydrogen from water. Representative studies spanning approximately three decades are included in this review. The topics covered include a discussion of the types of water photosplitting approaches, an ideal photoelectrolysis system, an examination of why Oxide Semiconductors are attractive for this application, a review of both classical and more recent studies on titanium diOxide, tungsten triOxide, and other binary metal Oxides, perovskites and other ternary Oxides, tantalates and niobates, miscellaneous multinary Oxides, semiconductor alloys and mixed semiconductor composites, and twin-photosystem configurations for water splitting.
Junghwan Kim - One of the best experts on this subject based on the ideXlab platform.
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ultra wide bandgap amorphous Oxide Semiconductors for nbis free thin film transistors
APL Materials, 2019Co-Authors: Junghwan Kim, Joonho Bang, Nobuhiro Nakamura, Hideo HosonoAbstract:The transparency of Oxide Semiconductors is a significant feature that enables the fabrication of fully transparent electronics. Unfortunately, practical transparent electronics using amorphous Oxide Semiconductors (AOSs) have not yet been realized, owing to significant photo-instabilities of these materials. Previous studies have revealed that the photo-instability can be attributed to sub-gap states (SGSs) near the valence-band maximum (VBM). Thus, it is inferred that the energy difference between the SGSs and the conduction-band minimum must be widened sufficiently in order to make it fully transparent over the entire visible-light region. In this work, we examined the electronic structures of a variety of AOSs and found that their ionization potentials vary greatly, depending upon the specific metal cations. This finding enabled us to increase the optical bandgap by modifying the VBM levels, resulting in a high mobility of 9 cm2/Vs and an ultra-wide bandgap of 3.8 eV for amorphous Zn–Ga–O (a-ZGO). We show that a-ZGO thin-film transistors exhibit no negative-bias illumination-stress instability with no passivation and no light-shielding layer.The transparency of Oxide Semiconductors is a significant feature that enables the fabrication of fully transparent electronics. Unfortunately, practical transparent electronics using amorphous Oxide Semiconductors (AOSs) have not yet been realized, owing to significant photo-instabilities of these materials. Previous studies have revealed that the photo-instability can be attributed to sub-gap states (SGSs) near the valence-band maximum (VBM). Thus, it is inferred that the energy difference between the SGSs and the conduction-band minimum must be widened sufficiently in order to make it fully transparent over the entire visible-light region. In this work, we examined the electronic structures of a variety of AOSs and found that their ionization potentials vary greatly, depending upon the specific metal cations. This finding enabled us to increase the optical bandgap by modifying the VBM levels, resulting in a high mobility of 9 cm2/Vs and an ultra-wide bandgap of 3.8 eV for amorphous Zn–Ga–O (a-ZGO). We ...
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transparent amorphous Oxide Semiconductors for organic electronics application to inverted oleds
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Hideo Hosono, Toshio Kamiya, Junghwan Kim, Yoshitake Toda, Satoru WatanabeAbstract:Efficient electron transfer between a cathode and an active organic layer is one key to realizing high-performance organic devices, which require electron injection/transport materials with very low work functions. We developed two wide-bandgap amorphous (a-) Oxide Semiconductors, a-calcium aluminate electride (a-C12A7:e) and a-zinc silicate (a-ZSO). A-ZSO exhibits a low work function of 3.5 eV and high electron mobility of 1 cm2/(V · s); furthermore, it also forms an ohmic contact with not only conventional cathode materials but also anode materials. A-C12A7:e has an exceptionally low work function of 3.0 eV and is used to enhance the electron injection property from a-ZSO to an emission layer. The inverted electron-only and organic light-emitting diode (OLED) devices fabricated with these two materials exhibit excellent performance compared with the normal type with LiF/Al. This approach provides a solution to the problem of fabricating Oxide thin-film transistor-driven OLEDs with both large size and high stability.
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69 4 nbis stable Oxide thin film transistors using ultra wide bandgap amorphous Oxide Semiconductors
SID Symposium Digest of Technical Papers, 2016Co-Authors: Junghwan Kim, Toshio Kamiya, Nobuhiro Nakamura, Hideo HosonoAbstract:Ultra-wide bandgap amorphous Oxide Semiconductors (UWB-AOSs) were newly developed to improve photo-stability of conventional AOS TFTs. The UWB-AOSs have much larger bandgaps (∼3.8 eV) than conventional AOSs. Photo-stable TFTs using a UWB-AOS were fabricated at 200°C, which exhibited high saturation mobilities (∼7 cm2/Vs), high on/off ratios (>108) and small S values (0.3 V/dec). The UWB-AOS TFT showed no threshold voltage shift against NBIS test under white LED illumination (11,000 lux). This strong photo-stability would enable completely transparent applications such as window displays.
Nobuhiro Nakamura - One of the best experts on this subject based on the ideXlab platform.
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ultra wide bandgap amorphous Oxide Semiconductors for nbis free thin film transistors
APL Materials, 2019Co-Authors: Junghwan Kim, Joonho Bang, Nobuhiro Nakamura, Hideo HosonoAbstract:The transparency of Oxide Semiconductors is a significant feature that enables the fabrication of fully transparent electronics. Unfortunately, practical transparent electronics using amorphous Oxide Semiconductors (AOSs) have not yet been realized, owing to significant photo-instabilities of these materials. Previous studies have revealed that the photo-instability can be attributed to sub-gap states (SGSs) near the valence-band maximum (VBM). Thus, it is inferred that the energy difference between the SGSs and the conduction-band minimum must be widened sufficiently in order to make it fully transparent over the entire visible-light region. In this work, we examined the electronic structures of a variety of AOSs and found that their ionization potentials vary greatly, depending upon the specific metal cations. This finding enabled us to increase the optical bandgap by modifying the VBM levels, resulting in a high mobility of 9 cm2/Vs and an ultra-wide bandgap of 3.8 eV for amorphous Zn–Ga–O (a-ZGO). We show that a-ZGO thin-film transistors exhibit no negative-bias illumination-stress instability with no passivation and no light-shielding layer.The transparency of Oxide Semiconductors is a significant feature that enables the fabrication of fully transparent electronics. Unfortunately, practical transparent electronics using amorphous Oxide Semiconductors (AOSs) have not yet been realized, owing to significant photo-instabilities of these materials. Previous studies have revealed that the photo-instability can be attributed to sub-gap states (SGSs) near the valence-band maximum (VBM). Thus, it is inferred that the energy difference between the SGSs and the conduction-band minimum must be widened sufficiently in order to make it fully transparent over the entire visible-light region. In this work, we examined the electronic structures of a variety of AOSs and found that their ionization potentials vary greatly, depending upon the specific metal cations. This finding enabled us to increase the optical bandgap by modifying the VBM levels, resulting in a high mobility of 9 cm2/Vs and an ultra-wide bandgap of 3.8 eV for amorphous Zn–Ga–O (a-ZGO). We ...
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69 4 nbis stable Oxide thin film transistors using ultra wide bandgap amorphous Oxide Semiconductors
SID Symposium Digest of Technical Papers, 2016Co-Authors: Junghwan Kim, Toshio Kamiya, Nobuhiro Nakamura, Hideo HosonoAbstract:Ultra-wide bandgap amorphous Oxide Semiconductors (UWB-AOSs) were newly developed to improve photo-stability of conventional AOS TFTs. The UWB-AOSs have much larger bandgaps (∼3.8 eV) than conventional AOSs. Photo-stable TFTs using a UWB-AOS were fabricated at 200°C, which exhibited high saturation mobilities (∼7 cm2/Vs), high on/off ratios (>108) and small S values (0.3 V/dec). The UWB-AOS TFT showed no threshold voltage shift against NBIS test under white LED illumination (11,000 lux). This strong photo-stability would enable completely transparent applications such as window displays.
