Function Cultivation of Transparent Oxides Utilizing Built-In Nanostructure

Abstract

This review article describes recent progress in our research on cultivation of functionality in crystalline and amorphous transparent oxides utilizing nanostructures embedded in the material itself. It includes the background of our research and approach. Subjects included are material exploration and device application of transparent oxide semiconductors for transparent electronics, function emergence in nano-porous crystal 12CaO Á 7Al 2 O 3 utilizing active anion species stabilized by sub-nanometer-sized cages, and modified silica glass for vacuum/deep ultraviolet lasers. Our description of each subject include: background and approach, material design concept, fabrication or modification method, properties, and device fabrication. Emphasis is placed on the importance of a variety of built-in nanostructures in transparent oxides for novel function realization and the high potential of transparent oxides as ingredients for an ubiquitous element strategy of material research in this century.

Material characteristics and applications of transparent amorphous oxide semiconductors

“…Separate from the above line of oxide device development, our group started systematic material exploration of ionic oxide semiconductors in 1994 as a part of a strategy to expand the development of transparent conducting oxides [42]. To attain high electrical conductivity in an amorphous oxide was a big challenge because the conventional and most familiar amorphous oxide, glass, is a very good electrical insulator.…”

Device applications of transparent oxide semiconductors: Excitonic blue LED and transparent flexible TFT

“…[1,6,7,36] for details). We Springer found that layered oxychalcogenides LaCuOCh would be a new promising candidate because they offer various materials that have p-type conduction and excitonic light emission at room temperature.…”

“…Among oxide semiconductors, TOSs are of special interest both in solidstate physics and technology because optical transparency and good controllability of electrical conductivity coexist in TOSs although it is in general believed that wider bandgap materials are more difficult to attain good electrical properties. However, it is a misconception as demonstrated by recent works: electronic activities can indeed be rendered in many wide bandgap materials if we properly understand electronic structures and find a suitable way to design their chemical compositions and structures [6,7].…”

Transparent Oxide Semiconductors: Fundamentals and Recent Progress

“…The hole becomes stable as the IP decreases, whereas the electron becomes stable as the EA increases. group VI compound semiconductors [4]. One may note that the CBM for n-type TCOs (TOSs) is belowÀ4 eV from the vacuum level, whereas the VBM of p-type oxides is located above À6 eV.…”

“…So far, the conduction type of TCO materials had been limited to n-type. This achievement has significantly changed our understanding of TCOs and has opened a new frontier, that of TOSs [4]. Therefore, we now consider that TOSs have the Year FET proposed [13] 1935 In 1954 2 O 3 Solar Cell [14] 1954 TCO [1] [11] a-Si:H 1975 TFT [12] a-Si:H 1979 OLED [15] 1987 TAOS [5] 1996 p-TCO, CuAlO 1997 2 [2] C12A7 transparent conductor [9] 2002 TOS homo-junction diode CuInO 2002 2 TAOS-TFT [6] 2004 TiO 2005 2 homo-junction blue LED [17] ZnO 2005 :Nb TCO [8] Front Drive Structure [18] 2006 ITO / organic gate TFT [19] OLED using a-IGZO TFT [20] 4.5"…”