Recently we have reported the room temperature fabrication of transparent and flexible thin film transistors on a polyethylene terephthalate (PET) film substrate using an ionic amorphous oxide ...semiconductor (IAOS) in an In2O3–ZnO–Ga2O3 system. These transistors exhibit a field effect mobility of ∼10cm2 (Vs)−1, which is higher by an order of magnitude than those of hydrogenated amorphous Si and pentacene transistors. This article describes a chemical design concept of IAOS, and its unique electron transport properties, and electronic structure, by comparing them with those of conventional amorphous semiconductors. High potential of IAOS for flexible electronics is addressed.
Electrides are materials in which electrons serve as anions. Here, the concept of inorganic electrides is extended in several respects: from ionic crystals to intermetallic compounds in host ...materials, from crystalline to amorphous solids, and from 0-dimensional to 1- and 2-dimensional materials in electron-confined spaces. In particular, 2D electrides, in which anionic electrons are sandwiched by cationic slabs, can form a bulk crystal of a 2-dimensional electron gas, thus exhibiting a large electron mobility and providing a platform for topological materials. Exploration of new electrides by computation and high pressure has advanced, revealing that an electride is a stable equilibrium phase of many elements and compounds under high pressure. This review describes the history and current status of electride research and next summarizes the chemical application of electrides and relevant materials. An emphasis is placed on catalysts for ammonia synthesis from N2 and H2 at mild conditions. This subject is accelerated by a demand for on-site ammonia synthesis using hydrogen produced by renewable energy sources. A wide applicability of electride for chemical reactions such selective hydrogenation and carbon–carbon coupling is shown by extending the concept of electrides. Finally, a view for the relationship between electrides and crystallographic voids and current issues are described.
Electron transfer from transition metal (TM) catalysts deposited on support to reaction molecules adsorbed is a key step in many catalysis reactions. Electron donation from a certain type of support ...and/or a promotor much enhances this electron transfer. In this paper the author considers requirements for efficient support materials based on a contact resistance between support and metal catalyst, showing metallic nature of the support is much favorable for this purpose. The origin of high performance in cesium promotors is suggested to be electride nature of their suboxides derived from the salts under the reaction conditions. TM-loaded alkali(A)/alkaline earth (AE) hydrides work as efficient catalysts. Since TM forms stronger or comparable bonding with H
−
compared with A/AE-H bonding, the formation of H-vacancy is much enhanced by TM-deposition. Thus, their high activity may be understood by the formation of surface electride, which serves as an electronic promotor, by deposition of TM on these hydrides. Improvement of electron transfer may be expected for insulating supports if Fermi-level pinning occurs at surface defects created by TM-deposition.
Graphic Abstract
Amorphous oxide semiconductors (AOSs) have been commercialized since 2012 as thin‐film transistor (TFT) backplanes in flat‐panel displays. This review first provides a brief history and current ...status of AOS technology, and then introduces electronic defects in AOSs reported to date that are critically important for understanding and controlling the instability of TFTs that is the most serious issue in the development of the AOS technology. In particular, it is important to know that many AOS defects are related to oxygen and hydrogen impurities, though oxygen is the major constituent of AOS and hydrogen is not intentionally incorporated. Instability issues and their underlying mechanisms are also discussed in relation to these defects.
Amorphous oxide semiconductors are currently employed in several flat‐panel displays, including large‐sized organic light‐emitting diode televisions. This paper reviews the defects in AOSs reported to date as well as provides a brief history and current status of AOS technology. TFT instability issues, their underling mechanisms, and optimum fabrication conditions are discussed in relation to these defects.
The present status and recent research results on amorphous oxide semiconductors (AOSs) and their thin-film transistors (TFTs) are reviewed. AOSs represented by amorphous In-Ga-Zn-O (a-IGZO) are ...expected to be the channel material of TFTs in next-generation flat-panel displays because a-IGZO TFTs satisfy almost all the requirements for organic light-emitting-diode displays, large and fast liquid crystal and three-dimensional (3D) displays, which cannot be satisfied using conventional silicon and organic TFTs. The major insights of this review are summarized as follows. (i) Most device issues, such as uniformity, long-term stability against bias stress and TFT performance, are solved for a-IGZO TFTs. (ii) A sixth-generation (6G) process is demonstrated for 32″ and 37″ displays. (iii) An 8G sputtering apparatus and a sputtering target have been developed. (iv) The important effect of deep subgap states on illumination instability is revealed. (v) Illumination instability under negative bias has been intensively studied, and some mechanisms are proposed. (vi) Degradation mechanisms are classified into back-channel effects, the creation of traps at an interface and in the gate insulator, and the creation of donor states in annealed a-IGZO TFTs by the Joule heating; the creation of bulk defects should also be considered in the case of unannealed a-IGZO TFTs. (vii) Dense passivation layers improve the stability and photoresponse and are necessary for practical applications. (viii) Sufficient knowledge of electronic structures and electron transport in a-IGZO has been accumulated to construct device simulation models.
The lack of efficient catalysts for ammonia synthesis from N
and H
gases at the lower temperature of ca. 50 °C has been a problem not only for the Haber-Bosch process, but also for ammonia production ...toward zero CO
emissions. Here, we report a new approach for low temperature ammonia synthesis that uses a stable electron-donating heterogeneous catalyst, cubic CaFH, a solid solution of CaF
and CaH
formed at low temperatures. The catalyst produced ammonia from N
and H
gases at 50 °C with an extremely small activation energy of 20 kJ mol
, which is less than half that for conventional catalysts reported. The catalytic performance can be attributed to the weak ionic bonds between Ca
and H
ions in the solid solution and the facile release of hydrogen atoms from H
sites.
•An up-to-date review by the discoverer and a theoretical pioneer of iron-based superconductor.
Since the discovery of high Tc iron-based superconductors in early 2008, more than 15,000 papers have ...been published as a result of intensive research. This paper describes the current status of iron-based superconductors (IBSC) covering most up-to-date research progress along with the some background research, focusing on materials (bulk and thin film) and pairing mechanism.
Abstract
M
n+1
AX
n
phases are a large family of compounds that have been limited, so far, to carbides and nitrides. Here we report the prediction of a compound, Ti
2
InB
2
, a stable boron-based ...ternary phase in the Ti-In-B system, using a computational structure search strategy. This predicted Ti
2
InB
2
compound is successfully synthesized using a solid-state reaction route and its space group is confirmed as
P
$$\bar 6$$
6
¯
m2
(No. 187), which is in fact a hexagonal subgroup of
P6
3
/mmc
(No. 194), the symmetry group of conventional M
n+1
AX
n
phases. Moreover, a strategy for the synthesis of MXenes from M
n+1
AX
n
phases is applied, and a layered boride, TiB, is obtained by the removal of the indium layer through dealloying of the parent Ti
2
InB
2
at high temperature under a high vacuum. We theoretically demonstrate that the TiB single layer exhibits superior potential as an anode material for Li/Na ion batteries than conventional carbide MXenes such as Ti
3
C
2
.
Cs2SnI6, a rarely studied perovskite variant material, is recently gaining a lot of interest in the field of photovoltaics owing to its nontoxicity, air-stability and promising photovoltaic ...properties. In this work, we report intrinsic defects in Cs2SnI6 using first-principles density functional theory calculations. It is revealed that iodine vacancy and tin interstitial are the dominant defects that are responsible for the intrinsic n-type conduction in Cs2SnI6. Tin vacancy has a very high formation energy (>3.6 eV) due to the strong covalency in the Sn-I bonds and is hardly generated for p-type doping. All the dominant defects in Cs2SnI6 have deep transition levels in the band gap. It is suggested that the formation of deep defects can be suppressed significantly by employing an I-rich synthesis condition, which is inevitable for photovoltaic and other semiconductor applications.
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