Electron concentration and mobility in In2O3
TL;DR: In this article, the electron concentration and mobility in polycrystalline In 2 O 3 have been measured as a function of temperature and partial oxygen pressure, in the temperature range from 25 to 700°C.
About: This article is published in Journal of Physics and Chemistry of Solids.The article was published on 1977-01-01. It has received 100 citations till now. The article focuses on the topics: Mass action law & Atmospheric temperature range.
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TL;DR: The theoretical defect model for In(2)O(3) and ZnO finds that intrinsic acceptors have a high Delta H explaining high n-dopability, and the O vacancy V(O) has a metastable shallow state, explaining the paradoxical coexistence of coloration and conductivity.
Abstract: Existing defect models for ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$ and ZnO are inconclusive about the origin of conductivity, nonstoichiometry, and coloration. We apply systematic corrections to first-principles calculated formation energies $\ensuremath{\Delta}H$, and validate our theoretical defect model against measured defect and carrier densities. We find that (i) intrinsic acceptors (``electron killers'') have a high $\ensuremath{\Delta}H$ explaining high $n$-dopability, (ii) intrinsic donors (``electron producers'') have either a high $\ensuremath{\Delta}H$ or deep levels, and do not cause equilibrium-stable conductivity, (iii) the O vacancy ${V}_{\mathrm{O}}$ has a low $\ensuremath{\Delta}H$ leading to O deficiency, and (iv) ${V}_{\mathrm{O}}$ has a metastable shallow state, explaining the paradoxical coexistence of coloration and conductivity.
1,496 citations
TL;DR: In this article, the state of the art in the field of experimental techniques possible to be applied to the study of conductometric gas sensors based on semiconducting metal oxides is reviewed.
Abstract: The paper critically reviews the state of the art in the field of experimental techniques possible to be applied to the study of conductometric gas sensors based on semiconducting metal oxides. The used assessment criteria are subordinated to the proposed R&D approach, which focuses on the study, and subsequent modelling, of sensors’ performance in realistic operation conditions by means of a combination of phenomenological and spectroscopic techniques. With this viewpoint, the paper presents both the to-date achievements and shortcomings of different experimental techniques, describes – by using selected examples – how the proposed approach can be used and proposes a set of objectives for the near future.
1,416 citations
TL;DR: In this paper, the authors compared the results of different gap-correction methods and concluded that to date there is no universal scheme for band gap correction in general defect systems, and they turn instead to classification of different types of defect behavior to provide guidelines on how the physically correct situation in an LDA defect calculation can be recovered.
Abstract: Contemporary theories of defects and impurities in semiconductors rely to a large extent on supercell calculations within density-functional theory using the approximate local-density approximation (LDA) or generalized gradient approximation (GGA) functionals. Such calculations are, however, affected by considerable uncertainties associated with: (i) the ``band-gap problem,'' which occurs not only in the Kohn-Sham single-particle energies but also in the quasiparticle gap (LDA or GGA) calculated from total-energy differences, and (ii) supercell finite-size effects. In the case of the oxygen vacancy in ZnO, uncertainties (i) and (ii) have led to a large spread in the theoretical predictions, with some calculations suggesting negligible vacancy concentrations, even under Zn-rich conditions, and others predicting high concentrations. Here, we critically assess (i) the different methodologies to correct the band-gap problem. We discuss approaches based on the extrapolation of perturbations which open the band gap, and the self-consistent band-gap correction employing the $\text{LDA}+U$ method for $d$ and $s$ states simultaneously. From the comparison of the results of different gap-correction, including also recent results from other literature, we conclude that to date there is no universal scheme for band gap correction in general defect systems. Therefore, we turn instead to classification of different types of defect behavior to provide guidelines on how the physically correct situation in an LDA defect calculation can be recovered. (ii) Supercell finite-size effects: We performed test calculations in large supercells of up to 1728 atoms, resolving a long-standing debate pertaining to image charge corrections for charged defects. We show that once finite-size effects not related to electrostatic interactions are eliminated, the analytic form of the image charge correction as proposed by Makov and Payne leads to size-independent defect formation energies, thus allowing the calculation of well-converged energies in fairly small supercells. We find that the delocalized contribution to the defect charge (i.e., the defect-induced change of the charge distribution) is dominated by the dielectric screening response of the host, which leads to an unexpected effective $1/L$ scaling of the image charge energy, despite the nominal $1/{L}^{3}$ scaling of the third-order term. Based on this analysis, we suggest that a simple scaling of the first order term by a constant factor (approximately 2/3) yields a simple but accurate image-charge correction for common supercell geometries. Finally, we discuss the theoretical controversy pertaining to the formation energy of the O vacancy in ZnO in light of the assessment of different methodologies in the present work, and we review the present experimental situation on the topic.
968 citations
TL;DR: In this article, a defect model for tin-doped In2O3:Sn is developed, which comprises two kinds of interstitial oxygen, one of which is loosely bound to tin, the other forming a strongly bound Sn2O4 complex.
Abstract: Tin-doped In2O3 layers were prepared by the spray technique with doping concentrationsc
Sn between 1 and 20 at. % and annealed at 500 °C in gas atmospheres of varying oxygen partial pressures. The room-temperature electrical properties were measured. Maximum carrier concentrationsN=1.5×1021cm−3 and minimum resistivities ϱ=1.3×10−4 Ω cm are obtained if the layers are doped withc
Sn≈9 at. % and annealed in an atmosphere of oxygen partial pressurep
O2 ⋦10−20 bar. At fixed doping concentration, the carrier mobility increases with decreasing oxygen pressure. The maximum obtainable mobility can be described in terms of electron scattering by ionized impurities. From an analysis of the carrier concentration and additional precision measurements of the lattice constants and film thicknesses, a defect model for In2O3:Sn is developed. This comprises two kinds of interstitial oxygen, one of which is loosely bound to tin, the other forming a strongly bound Sn2O4 complex. At low doping concentrationc
Sn≲4 at. % the carrier concentration is governed by the loosely bound tin-oxygen defects which decompose if the oxygen partial pressure is low. The carrier concentration follows from a relationN=K
1 ·p
O2
−1/8 ·(3 ×1010 × cSn −N)1/4 with an equilibrium constantK
1=1.4×1015 cm−9/4bar1/8, determined from our measurements.
551 citations
TL;DR: In this review, the merits of solution-processed metal oxide semiconductors are discussed and their application in thin-film transistors for large-area electronics is considered.
Abstract: In this review, we discuss the merits of solution-processed metal oxide semiconductors and consider their application in thin-film transistors for large-area electronics.
250 citations
References
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TL;DR: In this article, the authors measured the Hall coefficient and the electrical conductivity of single-crystal specimens of ZnO at temperatures between 55\ifmmode^\circ\else\text degree\fi{}K and 300\ifmode^ \circ/else\ text degree\ fi{}k.
Abstract: Measurements of the Hall coefficient and the electrical conductivity of single-crystal specimens of $n$-type ZnO at temperatures between 55\ifmmode^\circ\else\textdegree\fi{}K and 300\ifmmode^\circ\else\textdegree\fi{}K are reported. An analysis of carrier concentration vs temperature indicates that "as-grown" crystals contain more than one active donor. Crystals with low initial donor concentrations were doped with H or interstitial Zn or Li, allowing a single-donor-level analysis. Doping was accomplished by interstitial diffusion followed by a rapid quench. Each of the added donors gives rise to a hydrogen-atom-model donor center whose ionization energy is ${E}_{D}=0.051$ ev for ${N}_{D}l5\ifmmode\times\else\texttimes\fi{}{10}^{16}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. Lithium was also found to introduce a small concentration of acceptors, presumably due to an exchange between interstitial and substitutional positions. The quantity ${(\frac{{m}^{(N)}}{m})}^{\frac{3}{2}}{D}^{\ensuremath{-}1}$, where ${m}^{(N)}=\mathrm{d}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{i}\mathrm{t}\mathrm{y}\ensuremath{-}\mathrm{o}\mathrm{f}\ensuremath{-}\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{s}''$ effective mass and $D=\mathrm{donor}\mathrm{degeneracy}$, was found to be about 0.19 for all three donors, indicating that if $D=2$ then ${m}^{(N)}=0.5$. The low-frequency dielectric constant of ZnO was redetermined as $\ensuremath{\kappa}=8.5$. The effective mass associated with the electron found in a hydrogen-like orbit is then ${m}^{(H)}=0.27m$, and the observed decrease of ${E}_{D}$ with increasing ${N}_{D}$ corresponds to the overlap of these large orbits.The Hall mobility is 180 ${\mathrm{cm}}^{2}$ ${\mathrm{volt}}^{\ensuremath{-}1}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ at 300\ifmmode^\circ\else\textdegree\fi{}K and increases with decreasing temperature. It has been analyzed for lattice and impurity scattering. The optical-mode scattering mobility has been calculated from both the perturbation and intermediate-coupling theories making use of the effective mass, ${m}^{(H)}$, so that no adjustable parameters were included. The two theories agree for ZnO since it turns out to have a polar-mode electron coupling constant of $\ensuremath{\alpha}=1$. The mobility so obtained is in good agreement with experiment and indicates that optical-mode scattering is important above 200\ifmmode^\circ\else\textdegree\fi{}K. Some acoustical-mode scattering also appears to be present. At low temperatures the mobility appears to be limited by impurity scattering.
317 citations
TL;DR: In this paper, an investigation of electrical properties of indium oxide single crystals has been made and it has been found that indium oxides are an n-type excess semiconductor over a wide temperature range.
Abstract: An investigation of electrical properties of indium oxide single crystals has been made. Indium oxide has been found to be a n‐type excess semiconductor over a wide temperature range. The electrical conductivity at room temperature is of the order of 10 Ω cm−1 and the mobility is approximately 160 cm2 V‐sec−1. The temperature dependence of the mobility has been quantitatively interpreted in terms of lattice and ionized impurity scattering. The donor ionization energy has been found to decrease with increasing impurity concentrations. High ``apparent intrinsic'' conductivity with an activation energy of 1.55 eV has been observed at elevated temperatures.
205 citations
200 citations
TL;DR: In this paper, a spray technique was used to obtain indium oxide films with conductivities between 1.5 × 102 and 4.3 × 103 Ω−1cm−1 and free-carrier concentrations between 6 × 1020 cm−3.
Abstract: Nach dem „Spruhverfahren” wurden n-leitende Indiumoxydschichten mit Schichtdicken zwischen 0,1, und 0,5 μm auf Glasplatten hergestellt und die Herstellungsbedingungen dieser Schichten untersucht. Die Leitfahigkeit der Schichten liegt je nach Dotierung zwischen 1,5 × 102 und 4,3 × 103 Ω−1cm−1 und die Konzentration and freien Ladungstragern zwischen 1019 und 6 × 1020 cm−3. Die Beweglichkeit der freien Ladungstrager hangt erheblich von der jeweiligen Dotierung ab und wird vermutlich durch Streuung an den Korngrenzen der mikrokristallinen Schicht bestimmt. Die Schichten sind im sichtbaren Spektralbereich absorptionsfrei und zeigen im Ultrarot wegen der hohen Konzentration freier Ladungstrager ein hohes Reflexionsvermogen.
Films of n-type indium oxide of thickness between 0.1 and 0.5 μm are prepared by a „spray technique”. By incorporating different impurities, films are obtained with conductivities between 1.5 × 102 and 4.3 × 103 Ω−1cm−1 and free-carrier concentrations between 1019 and 6 × 1020 cm−3. The carrier mobility is strongly dependent on the particular impurity used. This suggests that the carrier scattering is strongly dependent on the particular impurity used. This suggests that the carrier scattering is mainly due to the grain boundaries. The films show little optical absorption in the visible region but, due to the high concentration of free carriers, they have high infrared reflectivity.
136 citations
TL;DR: In this article, the concentration of conduction electrons is changed by a heat treatment between ne = 1017 and 1020 cm−3 (T = 300°K), indicating an intense scattering at charged imperfection centres which are due to a considerable intrinsic lattice disorder.
Abstract: Thin films of n-conducting In2O3 are prepared by reactive sputtering. The concentration of conduction electrons is changed by a heat treatment between ne = 1017 and 1020 cm−3 (T = 300°K). Concentration and temperature dependence of the electron mobility indicate an intense scattering at charged imperfection centres which are due to a considerable intrinsic lattice disorder. The intrinsic absorption is also influenced by this disorder.
Dunne, n-leitende In2O3-Schichten wurden durch reaktive Kathodenzerstaubung hergestellt. Durch Tempern konnte die Konzentration der Leitungs-Elektronen in weiten Grenzen (ne = 1017 bis 1020 cm−3 bei T = 300°K) variiert werden. Betrag und Temperaturabhangigkeit ihrer elektrischen Beweglichkeit lassen auf eine starke Streuung an ionisierten Storstellen-hervorgerufen durch eine erhebliche Eigen-Fehlordnung-schliesen. Durch diese Fehlordnung wird auch die Eigenabsorption beeinflust.
133 citations