Exploring Electro-active Functionality of Transparent Oxide Materials

Abstract

Ceramics, one of the earliest materials used by humans, have been used since the Stone Age and are also one of the core materials supporting modern society. In this article, I will review the features of transparent oxides, the main components of ceramics, and the progress of research on their electro-active functionalities from the viewpoint of material design. Specifically, the emergence of the functionality of the cement component 12CaO·7Al2O3, the application of transparent oxide semiconductors to thin-film transistors for flat panel displays, and the design of wide-gap p-type semiconductors are introduced along with the progress in their research. In addition, oxide semiconductors are comprehensively discussed on the basis of the band lineup.

Transparent Electrodes for Efficient Optoelectronics

“…Conventional TCOs are mainly formed by metal atoms with the (n -1)d 10 ns [2] electronic configuration. [44,46] Interaction of the metal s states (Ms) and oxygen p states (Op) results in the formation of a wide band gap (E g > 3 eV), allowing the transmittance of photons in the visible range and below. [47] The valence band (VB) is composed of occupied oxygen 2p states, whereas the conduction band (CB) is formed by an overlapping Ms-Op-Ms network.…”

Exploration of new superconductors and functional materials, and fabrication of superconducting tapes and wires of iron pnictides

“…This is the reason why his group started to examine the electronic and magnetic properties of La TM O Pn (where TM = 3 d transition metal, Pn = P and As). This effort resulted in the discovery of iron-based superconductors (IBSCs) through the concentrated effort to find high performance p-type transparent semiconductors, which is a branch of his research home ground, transparent oxide semiconductors [8]. …”

Relation Between Electrical and Optical Properties of p‐Type NiO Films

“…[1] NiO has a bandgapenergy (E g ) at around 3.7-3.8 eV [1,2] and unintentionally-doped (undoped) NiO films typically show p-type conductivity. [1,[3][4][5][6][7] Nowadays, particular interests have been paid to construct photoelectric devices [8] as well as p-n junction-based light emitters using p-type NiO and n-type oxide semiconductors such as ZnO [9] and Ga 2 O 3 . [10] In general, acceptor impurities such as Li þ are intentionally-doped into NiO films to yield p-type conductivity, though there are concerns that Li þ diffuses in the films and transparency loss is induced in the visible spectral region.…”