The present review takes a semiconductor physics perspective to summarize the state-of-the art of In2O3 in relation to applications. After discussing conventional and novel applications, the crystal structure, synthesis of single-crystalline material, band-structure and optical transparency are briefly introduced before focussing on the charge carrier transport properties. The issues of unintentional n-type conductivity and its likely causes, the surface electron accumulation, and the lack of p-type conductivity will be presented. Intentional doping will be demonstrated to control the electron concentration and resistivity over a wide range, but is also subject to compensation. The control of the surface accumulation in relation to Schottky and ohmic contacts will be demonstrated. In the context of scattering mechanisms, the electron mobility and its limits will be discussed. Finally, the Seebeck coefficient and its significance will be shown, and ferromagnetic doping of In2O3 will be critically discussed. With this overview most if not all ingredients for the use of In2O3 as semiconductor material in novel or improved conventional devices will be given.

http://iopscience.iop.org/article/10.1088/0268-1242/30/2/024001/pdf

Indium oxide—a transparent, wide-band gap semiconductor for (opto)electronic applications

Magnetic and optical properties of Fe doped ZnS nanoparticles synthesized by microemulsion method

We give a brief introduction to the oxide (ZnO, TiO2, In2O3, SnO2, etc.)-based magnetic semiconductors from fundamental material aspects through fascinating magnetic, transport, and optical properties, particularly at room temperature, to promising device applications. The origin of the observed ferromagnetism is also discussed, with a special focus on first-principles investigations of the exchange interactions between transition metal dopants in oxide-based magnetic semiconductors.

https://iopscience.iop.org/article/10.1088/1674-1056/22/8/088505/pdf

Oxide magnetic semiconductors: Materials, properties, and devices

Transition metal (Co, Fe, Mn)-doped In2O3−y mesoporous oxides are synthesized by nanocasting using mesoporous silica as hard templates. 3D ordered mesoporous replicas are obtained after silica removal in the case of the In-Co and In-Fe oxide powders. During the conversion of metal nitrates into the target mixed oxides, Co, Fe, and Mn ions enter the lattice of the In2O3 bixbyite phase via isovalent or heterovalent cation substitution, leading to a reduction in the cell parameter. In turn, non-negligible amounts of oxygen vacancies are also present, as evidenced from Rietveld refinements of the X-ray diffraction patterns. In addition to (In1−xTMx)2O3−y, minor amounts of Co3O4, α-Fe2O3, and MnxOy phases are also detected, which originate from the remaining TM cations not forming part of the bixbyite lattice. The resulting TM-doped In2O3−y mesoporous materials show a ferromagnetic response at room temperature, superimposed on a paramagnetic background. Conversely, undoped In2O3−y exhibits a mixed diamagnetic-ferromagnetic behavior with much smaller magnetization. The influence of the oxygen vacancies and the doping elements on the magnetic properties of these materials is discussed. Due to their 3D mesostructural geometrical arrangement and their room-temperature ferromagnetic behavior, mesoporous oxide-diluted magnetic semiconductors may become smart materials for the implementation of advanced components in spintronic nanodevices.

Nanocasting of Mesoporous In‐TM (TM = Co, Fe, Mn) Oxides: Towards 3D Diluted‐Oxide Magnetic Semiconductor Architectures

Dilute magnetic semiconductors (DMSs) show great promise for applications in spin-based electronics, but in most cases continue to elude explanations of their magnetic behavior. Here, we combine quantitative x-ray spectroscopy and Anderson impurity model calculations to study ferromagnetic Fe-substituted ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$ films, and we identify a subset of Fe atoms adjacent to oxygen vacancies in the crystal lattice which are responsible for the observed room temperature ferromagnetism. Using resonant inelastic x-ray scattering, we map out the near gap electronic structure and provide further support for this conclusion. Serving as a concrete verification of recent theoretical results and indirect experimental evidence, these results solidify the role of impurity-vacancy coupling in oxide-based DMSs.

Adjacent Fe-Vacancy Interactions as the Origin of Room Temperature Ferromagnetism in ( In 1 − x Fe x ) 2 O 3

Fe-doped In2O3 films with well defined bcc (440) texture were grown on r-cut sapphire at different oxygen pressures by pulsed laser deposition Nonmonotonic dependence of ferromagnetism on oxygen pressure has been observed Under optimal deposition conditions, the saturation magnetization can reach 25μB/Fe atom Moreover, the ferromagnetism can be reversed between the higher magnetization state and the lower magnetization state by alternate annealing in vacuum and in air All these features are well explained by a modified model of F-center mediated ferromagnetism

Z. Zhang

Papers

Tunable ferromagnetism by oxygen vacancies in Fe-doped In2O3 magnetic semiconductor