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Sol–gel synthesis of nanostructured indium tin oxide with controlled morphology and porosity

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... The synthesis of TiO 2 nanoparticles and the sol preparation was similar to that described [47][48][49] with the exception that neither doping agents nor solvothermal treatment were applied. 50 mL of 2-propanol and then 100 mL of distilled water was added carefully to 13.3 mL of TiCl 4 . ...
... The thickness of the coating was studied by spectroscopic ellipsometry and the measurements revealed that the thickness of the coatings were 10-12 nm, which is in good agreement with the size of the nanoparticles determined by dynamic light scattering (11.3 nm by Zetasizer). The thickness of the coatings and the volume fraction of the nanoparticles were perfectly fitted by a model assuming a homogeneous effective medium approximation (EMA) [49] of TiO 2 (50-55%) and void (45-50%). Furthermore, the volume fraction of void was also in agreement with a spherical geometry of the TiO 2 particles. ...
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Plasmon-enhanced in situ spectroscopic ellipsometry was realized using the Kretschmann geometry. A 10-μL flow cell was designed for multi-channel measurements using a semi-cylindrical lens. Dual-channel monitoring of the layer formation of different organic structures has been demonstrated on titania nanoparticle thin films supported by gold. Complex modeling capabilities as well as a sensitivity of ~40 pg/mm2 with a time resolution of 1 s was achieved. The surface adsorption was enhanced by the titania nanoparticles due to the larger specific surface and nanoroughness, which is consistent with our previous results on titanate nanotubes.
... B-spline (or Basis-spline) parameterization is a popular and relatively new approach to express the dielectric function of materials in a purely mathematical way which has been introduced by Johs and Hale [1]. Since then, it has been proven to be very effective for multiple applications in spectroscopic ellipsometry (SE) [2][3][4][5][6][7][8][9][10][11]. B-splines are constructed from piecewise polynomial functions connected smoothly at a set of points on the x-axis * Electronic mail: dmitriy.likhachev@globalfoundries.com. ...
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B-spline representation of the dielectric functions provides many theoretical and practical benefits for material modeling in spectroscopic ellipsometry. However, the number of knots (and their locations, in general) defines actual performance of B-splines in ellipsometric data analysis. On the one hand, too large number of knots can result in serious overfitting of the experimental data. On the other hand, this number should be sufficient to fit all essential spectral features. Selection of the right number of knots is, in practice, a very subjective and empirically-driven task. In this paper, we discuss the choice of the number of knots utilizing three well-established versions of statistical information criteria in form of Akaike, corrected Akaike and Bayesian Information Criteria (AIC, AICc and BIC, respectively). The criteria establish a compromise between over- and underfitting of experimental data and allow formalized selection of the right number of knots. Effectiveness of the proposed methodology is illustrated using a few real-data examples.
... Although various techniques including thermal evaporation [6], ion beam sputtering (IBS) [7], pulsed-laser deposition (PLD) [8] and sol-gel [9,10] have been used for the deposition of ITO thin films, the radio frequency (RF) magnetron sputtering is preferred because of its ability to produce highly pure large-area thin films with good adhesion and homogeneity. In the RF magnetron sputtering technique, deposition parameters such as substrate temperature [11], the RF power [12], the working and oxygen partial pressures [13] and the target to substrate distance have impacts on the optical and electrical properties of ITO thin films [14]. ...
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High quality indium tin oxide/polyethylene terephthalate (ITO/PET) electrode with sheet resistance as low as 1.16 Ω/□ and the optical transmittance of 91 % at the wavelength of 600 nm was fabricated. The room-temperature radio frequency (RF) magnetron sputtering technique was used to deposit ITO thin film on PET substrate under low RF power without oxygen flow or post treatment. The remarkable value of 118.5 × 10−3 Ω−1 was achieved for the figure of merit in the 93 nm thick ITO thin film, due to the fine tuning of the sputtering parameters. An entirely Ohmic behavior was recorded for the ITO/PET electrode on the copper contacts suggesting that the product is highly capable for application in optoelectronic devices. The results of field emission scanning electron microscopy and atomic force microscopy demonstrated film consistency with a desired surface morphology giving a Rrms value of 2.073 nm. The elemental, chemical and phase analyses further revealed that the deposited ITO thin film on the PET substrate was pure and amorphous.
... Obviously, for an excessive total number of knots (more than ~ 35 knots, in this particular 14 case) the performance of optimized and regular knot positioning schemes becomes fully indistinguishable. The latter is not a serious concern since the general goal in application of a B-spline model is to use as few knots as possible while providing optimal data fitting. ...
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Published in: J. Appl. Phys. 129, 034903 (2021); https://doi.org/10.1063/5.0035456 UPDATED VERSION - A FEW TYPOS HAVE BEEN FIXED Dielectric function representation by B-splines became quite popular and widely used in the context of spectroscopic ellipsometry data interpretation. B-splines are defined by a polynomial degree and a sequence of knots (i.e., the number and positions of knots). Defining the knot sequence is non-trivial, and this task has a significant effect on actual effectiveness of the B-spline parameterization in spectroscopic ellipsometry data analysis. In this paper, we propose a simple, practical and systematic knot placement scheme that improves ordinary trial-and-error technique in establishing the knot spacing. The approach suggested here is based on an Integral Span (IS), a measure proposed in this work. New procedure provides a possibility to determine the knot locations automatically (or, at least, semi-automatically) and exclude widespread modeling ambiguities associated with uncertain knot vector. Moreover, the new approach guarantees the absence of non-monotonic behavior of the mean-squared-error function and thereby improves the accuracy of our analysis. The performance of the proposed method has been tested for several real cases of study.
... Ref. [13] also provides a glimpse into many of the practical issues that accompany use of B-spline parameterization of the dielectric functions including, in particular, knot termination and possible issues with presence of absorption features outside of the spectral range. B-splines have already shown their effectiveness for material modeling in multiple spectroscopic ellipsometry applications [16][17][18][19][20][21][22][23][24][25][26][27]. But the B-spline representation of the dielectric functions also has two main disadvantages. ...
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Accuracy of the spectroscopic ellipsometry data analysis strongly depends on appropriate modeling of the complex dielectric function ε (or the complex index of refraction N) over required spectral range. In this paper, we outline penalized B-spline (P-spline) formulation for an arbitrary dielectric function ε modeling in spectroscopic ellipsometry data analysis. The main idea is to first use a generous number of equally-spaced knots (up to the number of spectral points) to describe even highly complicated structure in the imaginary part ε2 of the dielectric function and then provide a certain penalty on the coefficients of adjacent B-splines to tune the smoothness of the ε curve. Two real-data applications have been provided to evaluate the practical performance and effectiveness of the proposed penalized formulation for dielectric function representation. A comparison of obtained results with the findings of our previous studies without penalization demonstrates a good agreement between the proposed method and ordinary B-spline representation in an equally-spaced fashion with optimal number of knots.
... On the other hand, we also have MEA present in the solution, thanks to which we manage to create a stable solution in a wide pH range, i.e. from 4.0-11.0. MEA is a water-soluble primary amine and coordination agent, used for the synthesis of various nanomaterials 27,40 and to examine its effect on the morphology of synthesized particles 41 . However, the effect of MEA on the morphology of calcium phosphates synthesized through hydrothermal method has not yet been studied. ...
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... Reduction of the number of knots suppresses this "wiggly" overfitting behavior. B-splines have already shown their effectiveness for material modeling in multiple spectroscopic ellipsometry applications [16][17][18][19][20][21][22][23][24][25][26][27]. But obviously, "everything has its drawbacks…", as has been noted by Jerome K. Jerome [28]. ...
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Accuracy of the spectroscopic ellipsometry data analysis strongly depends on appropriate modeling of the complex dielectric function ε (or the complex index of refraction N) over required spectral range. In this paper, we outline penalized B-spline (P-spline) formulation for an arbitrary dielectric function ε modeling in spectroscopic ellipsometry data analysis. The main idea is to first use a generous number of equally-spaced knots (up to the number of spectral points) to describe even highly complicated structure in the the imaginary part ε 2 of the dielectric function and then provide a certain penalty on the coefficients of adjacent B-splines to tune the smoothness of the ε curve. Two real-data applications have been provided to evaluate the practical performance and effectiveness of the proposed penalized formulation for dielectric function representation. A comparison of obtained results with the findings of our previous studies without penalization demonstrates a good agreement between the proposed method and ordinary B-spline representation in an equally-spaced fashion with optimal number of knots.
... Less than ten years ago, Johs and Hale 19 proposed to use a class of splines called B-splines (or Basis-splines) for modeling of the dielectric functions in SE data analysis. Since then, B-splines were applied very successfully to multiple applications in spectroscopic ellipsometry [22][23][24][25][26][27] . A fundamental theorem of B-splines 28 states that every spline curve S(x), which represents ε 2 (cf. Figure 1), can be uniquely expressed as a linear combination (weighted sum) of localized Bspline basis functions of some degree: ...
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One-step synthesis of wurtzite-structured ZnS thin nanorods with mean diameters of about 6 nm is achieved by a novel ethanol amine (EA)-assisted solvothermal approach adopting ZnO and Na2S2O3·5H2O as starting reagents. The as-prepared ZnS nanorods are well-crystallized single crystals with growth direction along [0 0 1]. The effects of solvents, sources of zinc and sulfur are investigated in details and it is found that EA solvent plays a key role to control both the phase and morphology of the ZnS nanorods. The possible growth mechanism involving EA-mediated nucleation and one-dimensional (1D) growth is discussed. The optical properties of the wurtzite ZnS thin nanorods are characterized by UV–Vis absorption and photoluminescence spectra.
Article
The effect of SnO2 content on the sintering behavior of nanocrystalline indium tin oxide (ITO) ceramics was examined. Nanocrystalline ITO powders with different SnO2 content from 0 to 12at.% were prepared by a coprecipitation method. The particle size of the ITO powders was in the range of 20–26nm. The temperature that showed maximum densification increased as the content of SnO2 increased. Since the solubility limit of SnO2 in In2O3 is known to be about 6–8at.%, the samples with 8 and 12at.% Sn showed second phases after sintering. Various phase development processes of the second phases were observed, i.e., In2SnO5, which was observed at a low temperature, decomposed into In2O3 and SnO2 at over 1000°C, then synthesized again into In4Sn3O12 at over 1300°C. The densification behavior with respect to the SnO2 content was explained from a viewpoint of the second phase development at different sintering temperatures.
Article
Indium tin oxide (ITO) films have been prepared by the sol-gel method using both organic and inorganic precursors. A computer-controlled dip-coating unit is designed and fabricated in our laboratory for a precise control of the parameters during the dip-coating process. These films have been characterized by X-ray diffraction optical and electrical study and also by atomic absorption spectroscopy. The optimized coatings exhibit a sheet resistance of ara und 100 Ω/□ and an average visible solar transmission of around 85%.A five-layer electrochromic system using these ITO layers as transparent electrodes was fabricated and tested. The performance of the electrochromic system indicates the high potential of these films for such applications, especially for large area coaling.
Article
An ethylenediamine-assisted route has been designed for one-step synthesis of lithium niobate particles with a novel rodlike structure in an aqueous solution system. The morphological evolution for these lithium niobate rods was monitored via SEM: The raw materials form large lozenges first. These lozenges are a metastable intermediate of this reaction, and they subsequently crack into small rods after sufficiently long time. These small rods recrystallize and finally grow into individual lithium niobate rods. Interestingly, shape-controlled fabrication of lithium niobate powders was achieved through using different amine ligands. For instance, the ethylenediamine or ethanolamine ligand can induce the formation of rods, while n-butylamine prefers to construct hollow spheres. These as-obtained lithium niobate rods and hollow spheres may exhibit enhanced performance in an optical application field due to their distinctive structures. This effective ligand-tuned-morphology route can provide a new strategy to facilely achieve the shape-controlled synthesis of other niobates.
Article
We report the synthesis and separation of colloidal indium tin oxide (ITO) nanocrystals in the stable cubic bixbyite (bcc-ITO) and metastable corundum (rh-ITO) phase under identical conditions, based on the size−structure correlation. Both phases are obtained in the same reactions, with nanocrystals below ca. 5 nm in size having corundum crystal structure. This bimodal size distribution allows for the separation of the nanocrystal phases by size selective precipitation. A comparative study of bcc-ITO and rh-ITO nanocrystals reveals a dramatic difference in their optical and electrical properties. Unlike smaller rh-ITO nanocrystals, bcc-ITO nanocrystals exhibit a strong absorption in the near-infrared (NIR) region arising from the plasmon oscillations due to the presence of free electrons. The difference in the free electron concentration in bcc-ITO and rh-ITO nanocrystals is related to the different electronic structure of the donor states, associated with Sn4+ dopants, in these two nanocrystal allotropic modifications. The donor activation energy is significantly higher in rh-ITO NCs, prohibiting any appreciable concentration of free electrons in the conduction band. The increased replacement of organic protective ligands by anions in the solution leads to the oriented attachment of larger sized bcc-ITO nanocrystals and the formation of flowerlike clusters. These results demonstrate tuning of the optical and electrical properties of complex oxide nanocrystals by selecting their crystal and electronic structures through size and composition and allow for a designed preparation and controlled self-assembly of ITO nanocrystals.
Article
Es werden verschiedene physikalische Konstanten heterogener Körper aus den Konstanten ihrer homogenen Bestandteile nach einer einheitlichen Methode berechnet. In dieser ersten Arbeit wird die Berechnung der Dielektrizitätskonstanten und der Leitfähigkeiten für Elektrizität und Wärme der Mischkörper aus isotropen Bestandteilen behandelt. Die Genauigkeit der älteren Formeln wird untersucht und die bis jetzt unbekannten Konstanten dieser Formeln werden berechnet. Sodann wird die Theorie geprüft an Messungen der Leitfähigkeit bei heterogenen Metallegierungen und an den DK. von gepreßten Pulvern und Emulsionen; die verschiedenen Formeln werden bestätigt. Bei dieser Anwendung werden einige Widersprüche zwischen früheren Untersuchungen aufgehoben und es wird versucht, einige ungenau bekannte DK. genauer zu bestimmen.
Article
Accurate dielectric function values are essential for spectroscopic ellipsometry data analysis by traditional optical model-based analysis techniques. In this paper, we show that B-spline basis functions offer many advantages for param- eterizing dielectric functions. A Kramers–Kronig consistent B-spline formulation, based on the standard B-spline recursion relation, is derived. B-spline representations of typical semiconductor and metal dielectric functions are also presented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Article
Indium tin oxide (ITO) thin films with well-controlled layer thickness were produced by dip-coating method. The ITO was synthesized by a sol–gel technique involving the use of aqueous InCl3, SnCl4 and NH3 solutions. To obtain stable sols for thin film preparation, as-prepared Sn-doped indium hydroxide was dialyzed, aged, and dispersed in ethanol. Polyvinylpyrrolidone (PVP) was applied to enhance the stability of the resulting ethanolic sols. The transparent, conductive ITO films on glass substrates were characterized by X-ray diffraction, scanning electron microscopy and UV–Vis spectroscopy. The ITO layer thickness increased linearly during the dipping cycles, which permits excellent controllability of the film thickness in the range ~ 40–1160 nm. After calcination at 550 °C, the initial indium tin hydroxide films were transformed completely to nanocrystalline ITO with cubic and rhombohedral structure. The effects of PVP on the optical, morphological and electrical properties of ITO are discussed.
Article
Indium (III) and tin (IV) hydroxides (precursor) were synthesized by a co-precipitation process at the different reaction temperature in a water bath. Nanocrystalline indium tin oxide (ITO) powders with spherical and rod shapes were obtained upon calcination. The phase transformations during calcination process in Ar gas at ambient temperature −1100 °C were investigated by TG/DTA system, X-ray diffraction and transmission electron microscopy. A mixture of In(OH)3, InOOH and Sn3O2(OH)2 preferred the path of pure In(OH)3→In2O3 during calcinations in Ar gas and the powders with rhombohedral and cubic structured crystalline ITO were obtained at 600 °C. The crystal parameters changed with calcination temperature. Oxygen vacancies were developed at about 400 °C determined by resistivity decrease and the color change of powders. Characterized by TEM and FESEM, the spherical and rod shapes of the particles were prepared at bath temperature of 40 and 100 °C, respectively, and remained after calcination in Ar gas. The particles’ size showed obvious shrinkage compared with the precursors. At higher bath temperature In(OH)3 octahedral nuclei in the cubic structure cell stacks along the closest plane (1 0 0) and evolves nano-rod due to the influence of NH4+ on the orientation of crystals.
Article
The nanocrystalline indium tin oxide (ITO) powders with different particle size were prepared using a coprecipitation process and the sintering characteristics of the powders at different heating rate were examined. Decrease of particle size in nano-sized powder regime promoted the densification in normal rate sintering as temperature increased, while this retarded severely the densification at high temperature in rapid rate sintering. It is explained due to the differential densification, that is, the outmost region of the sample is well densified, while many large pores are observed inside of the densified ring. The differential densification may easily occur in the sample sintered at high temperature with small particles in rapid rate sintering, because smaller particle size has higher densification rate and higher sintering temperature in rapid rate sintering accompanies higher thermal gradient between the surface and center of a sample.
Article
An ellipsometer utilizing the polarizer-sample-retarder-rotating analyser configuration measures all four elements of the Stokes vector. Consequently the ellipsometric parameters ψ and Δ as well as the polarization transfer factor D of the sample can be measured simultaneously as a function of the photon energy E. The measurement of all four elements of the Stokes vector is shown to be well suited for the ellipsometric characterization of non-ideal samples, e.g. laterally inhomogeneous or rough samples, and it may be used to improve the precision of high lateral resolution (“microspot”) measurements. Formulae for the error spectra δψ(E), δΔ(E), and δD(E) were derived by analysing the influence of the random errors of the measurement. These error spectra provide the weights in minimization procedures for the determination of the geometrical and strutural sample parameters and results, via the analysis of the hessian matrix, in the errors of the sample parameters adjusted to the spectra. The effect of systematic alignment errors is discussed and fast Kramers-Kronig-consistent spectral inversion is shown to be a useful tool for the reduction of systematic model errors.
Article
We review work on In 2 O 3 :Sn films prepared by reactive e‐beam evaporation of In 2 O 3 with up to 9 mol % SnO 2 onto heated glass. These films have excellent spectrally selective properties when the deposition rate is ∼0.2 nm/s, the substrate temperature is ≳150 °C, and the oxygen pressure is ∼5×10<sup>-</sup><sup>4</sup> Torr. Optimized coatings have crystallite dimensions ≳50 nm and a C‐type rare‐earth oxide structure. We cover electromagnetic properties as recorded by spectrophotometry in the 0.2–50‐μm range, by X‐band microwave reflectance, and by dc electrical measurements. Hall‐effect data are included. An increase of the Sn content is shown to have several important effects: the semiconductor band gap is shifted towards the ultraviolet, the luminous transmittance remains high, the infrared reflectance increases to a high value beyond a certain wavelength which shifts towards the visible, phonon‐induced infrared absorption bands vanish, the microwave reflectance goes up, and the dc resisitivity drops to ∼2×10<sup>-</sup><sup>4</sup> Ω cm. The corresponding mobility is ∼30 cm<sup>2</sup>/V s. The complex dielectric function ϵ is reported. These data were obtained from carefully selected combinations of spectrophotometric transmittance and reflectance data. It is found that ϵ can be reconciled with the Drude theory only by assuming a strongly frequency‐dependent relaxation energy between the plasma energy and the band gap. We review a recently formulated quantitative theoretical model for the optical properties which explicitly includes the additive contributions to ϵ from valence electrons, free electrons, and phonons. The theory embodies an effective‐mass model for n‐doped semiconductors well ab- ove the Mott critical density. Because of the high doping, the Sn impurities are singly ionized and the associated electrons occupy the bottom of the conduction band in the form of an electron gas. The Sn ions behave approximately as point scatterers, which is consistent with pseudopotential arguments. Screening of the ions is described by the random phase approximation. This latter theory works well as a consequence of the small effective electron radii. Exchange and correlation in the electron gas are represented by the Hubbard and Singwi–Sjölander schemes. Phonon effects are included by three empirically determined damped Lorentz oscillators. Free‐electron properties are found to govern the optical performance in the main spectral range. An analysis of the complex dynamic resistivity (directly related to ϵ) shows unambiguously that Sn ions are the most important scatterers, although grain‐boundary scattering can play some role in the midvisible range. As a result of this analysis one concludes that the optical properties of the best films approach the theoretical limit. Band‐gap shifts can be understood as the net result of two competing mechanisms: a widening due to the Burstein–Moss effect, and a narrowing due to electron‐electron and electron‐ion scattering. The transition width—including an Urbach tail—seems to be consistent with these notions. Window applications are treated theoretically from detailed computations of integrated luminous, solar, and thermal properties. It is found that In 2 O 3 :Sn films on glass can yield∼78% normal solar transmittance and ∼20% hemispherical thermal emittance. Substrate emission is found to be insignificant. Antireflection with evaporated MgF 2 or high‐rate sputtered aluminum oxyfluoride can give ∼95% normal luminous transmittance, ∼5% normal luminous reflectance, little pe
Article
The electrical and optical properties, structure and morphology of ITO thin films were investigated. Ten percent by weight Sn-doped indium oxide (ITO) films were prepared on soda-lime-silicate glass substrate by the sol-gel spin coating method using inorganic metal salts. All layers studied with a thickness range of 50–350 nm were polycrystalline with grain sizes in the range 20–30 nm depending on the annealing conditions. SnO or SnO2 phase was not detected in terms of XRD, TEM analysis techniques and the resultant phase was only In2O3 cubic bixbyite. The sheet resistance of 250 nm thin films annealed at 400°C was 6.18×103 Ω/□ in air, 1.09×103 Ω/□ in nitrogen, 15.21×103 Ω/□ in oxygen, respectively. Four-hundred degree centigrade-annealed 150 nm films showed more than 85% of the average visible transmittance, regardless of annealing atmospheres. According to AFM analysis RMS roughness was 18 Å for a 50 nm film and 25 Å for a 350 nm film, respectively. XPS results revealed that Sn was incorporated into In2O3 structure substitutionally.
Article
Indium tin oxide (ITO) is a transparent conducting oxide in wide use today. ITO can be difficult to work with since this material displays a complicated (graded) microstructure, and the optical properties of ITO can vary widely with deposition conditions and post-deposition processing. For this reason it is common to characterize ITO films via optical measurements. However, accurate results are difficult to obtain due to the graded microstructure of the film introducing variations in the refractive index throughout the film thickness. Thus the typical ITO film does not have a single, well-defined set of optical constants due to grading in the microstructure. Several optical models for ITO will be presented which include the graded microstructure of the material and work reasonably well in fitting spectroscopic ellipsometry data for ITO film thickness, index grading, and optical constants. Since the film thickness, optical constants, and microstructure grading are all intermixed in the experimental data the issue of determining a unique best-fit optical model for ITO will also be discussed.
Article
Indium tin oxide (ITO) thin films have been deposited onto quartz glass substrates by a sol–gel process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. 0–20% by weight Sn-doped indium oxide (ITO) films were prepared by heat-treatment at above 400°C. The electrical, optical and structural properties of ITO thin films were investigated. The thickness of ITO film was measured by ellipsometer. The electrical resistivity was measured by using four-point probe method. The ITO thin films containing 10 wt.% Sn showed the minimum resistivity of ρ=1.5×10−3 Ω-cm. The spectral transmittance of ITO thin films was measured in the wavelength range from 275 to 900 nm by a UV-vis spectrometer. The film has high transmittance above 80% and has an absorption edge at 300 nm. X-Ray diffraction measurements employing CuKα radiation were performed to determine the crystallinity of the ITO films which showed that the ITO films were polycrystalline with a cubic bixbyite structure. XRD results show that a single phase is detected for In-Sn oxide and X-ray photoelectron spectroscopy (XPS) results show that a single valence state and chemical bonding state is observed for In and Sn in In-Sn oxides. Therefore, we can say that Sn is incorporated into the In2O3 structure substitutionally.
Article
In this paper we discuss the connection between the microstructure of a heterogeneous thin film and its macroscopic dielectric response ε. Effective medium theory is developed from a solution of the Clausius-Mossotti problem from basic principles. The solution is generalized to obtain the Lorentz-Lorenz. Maxwell Garnett and Bruggeman expressions. The connection between microstructure and absolute limits to the allowed values of the dielectric response of two-phase composites is reviewed. The form of these limits for two-phase composites of known composition and two- or three-dimensional isotropy can be used to derive simple expressions for ε and also for the average fields within each phase. These results are used to analyze dielectric function spectra of semiconductor films for information about density, polycrystallinity and surface roughness. Examples illustrating the detection of unwanted overlayers and the real-time determination of nucleation growth are also given.
Book
The declared objective of this book is to provide an introductory review of the various theoretical and practical aspects of adsorption by powders and porous solids with particular reference to materials of technological importance. The primary aim is to meet the needs of students and non-specialists who are new to surface science or who wish to use the advanced techniques now available for the determination of surface area, pore size and surface characterization. In addition, a critical account is given of recent work on the adsorptive properties of activated carbons, oxides, clays and zeolites.
Article
We report high-performance fully transparent thin-film transistors (TTFTs) on both rigid and flexible substrates with transfer printed aligned nanotubes as the active channel and indium-tin oxide as the source, drain, and gate electrodes. Such transistors have been fabricated through low-temperature processing, which allowed device fabrication even on flexible substrates. Transparent transistors with high effective mobilities (approximately 1300 cm(2) V(-1) s(-1)) were first demonstrated on glass substrates via engineering of the source and drain contacts, and high on/off ratio (3 x 10(4)) was achieved using electrical breakdown. In addition, flexible TTFTs with good transparency were also fabricated and successfully operated under bending up to 120 degrees . All of the devices showed good transparency (approximately 80% on average). The transparent transistors were further utilized to construct a fully transparent and flexible logic inverter on a plastic substrate and also used to control commercial GaN light-emitting diodes (LEDs) with light intensity modulation of 10(3). Our results suggest that aligned nanotubes have great potential to work as building blocks for future transparent electronics.