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... The synthesis of TiO 2 nanoparticles and the sol preparation was similar to that described  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)  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. ...
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 . Since then, it has been proven to be very effective for multiple applications in spectroscopic ellipsometry (SE) . B-splines are constructed from piecewise polynomial functions connected smoothly at a set of points on the x-axis * Electronic mail: email@example.com. ...
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 , ion beam sputtering (IBS) , pulsed-laser deposition (PLD)  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 , the RF power , the working and oxygen partial pressures  and the target to substrate distance have impacts on the optical and electrical properties of ITO thin films . ...
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. ...
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.  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 . But the B-spline representation of the dielectric functions also has two main disadvantages. ...
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. ...
Calcium phosphates offer outstanding biological adaptability. Thanks to their specific physico-chemical properties they are one of the most widely used materials in bone tissue engineering applications. The search for an innovative and economic strategy of synthesizing their different forms has been drawing considerable attention in the field. Herein, we report on a facile hydrothermal process in the presence of ethylenediamine tetraacetic acid and monoethanolamine to obtain various forms of calcium phosphates. The monoethanolamine served as an alkaline source and crystal growth modifier, while ethylenediamine tetraacetic acid was used to control the Ca²⁺ supersaturation level under high temperature and high pressure conditions. The obtained inorganic compounds were examined for their elemental composition, morphology, and structure using scanning electron microscopy, Raman spectroscopy, and powder x-ray diffraction. We were able to selectively synthesize monetite plate-like microcrystals as well as hydroxyapatite plates and nanofibers by simply varying the concentration of monoethanolamine.
... 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 . But obviously, "everything has its drawbacks…", as has been noted by Jerome K. Jerome . ...
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  . 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: ...
Ellipsometry is a highly sensitive and powerful optical technique of thin film characterization. However, the indirect and nonlinear character of the ellipsometric equations requires numerical extraction of interesting information, such as thicknesses and optical constants of unknown layers. A method is described to perform the inversion of ellipsometric spectra for the simultaneous determination of thickness and optical constants without requiring particular assumptions about the shape of a model dielectric function like in the traditional method of data fitting. The method is based on a Kramers-Kronig consistent description of the imaginary part of the dielectric function using a set of points joined by pieces of third-degree polynomials. Particular connection relations constrain the shape of the constructed curve to a physically meaningful curve avoiding oscillations of natural cubic splines. The connection ordinates conditioning the shape of the dielectric function can be used, together with unknown thickness or roughness, as fitting parameters with no restriction on the material nature. Typical examples are presented concerning metal and semiconductors.
Highly conductive indium tin oxide (ITO) nanocrystals and inks have been synthesized by solvothermal dehydration condensation of metal hydroxide in combination with in-situ ethanolamine capping. It is found that the addition of ethanolamine can effectively reduce the size of nanocrystals and chemically modify their surfaces. The synthesized ITO nanocrystals can be well dispersed in ethanol with high solid content and the suspension is stable for days. Such small-molecule capped ITO suspension has been used as a conductive ink to make transparent conductive films by spin coating. Furthermore, a water washing step has been introduced in the ITO film preparation process to improve its conductivity, resulting in low resistivity of 8.9×10-3Ω•cm after 2 hours annealing at 300oC in mixed Ar and H2 atmosphere.
An optically active ITO/Au/ITO multilayer coating (where ITO stands for an indium tin oxide with the composition 90% In2O3 + 10% SnO2 and Au is nanoparticulate gold on a thin-film poly(ethylene terephthalate) substrate) has been prepared by a solution-phase process using an ITO nanopowder dispersion in isopropanol and a solution of chloroauric acid, which was converted to colloidal gold by photolysis. A sol–gel process has been proposed for the synthesis of tin-doped indium oxide nanopowder. The properties and composition of the powder were assessed by IR spectroscopy, thermal analysis, electron microscopy, and X-ray diffraction. The phase composition of the ITO nanopowder and the optical properties of the films grown using the nanopowder have been shown to depend on the thermal annealing conditions during synthesis. Layer-by-layer growth of metal oxide films in ITO/Au/ITO coatings influences the absorption in the composite in the IR spectral region.
This work reports the synthesis of Indium Tin Oxide (ITO) nanoparticles via sonochemical process at various calcination temperature using InCl3 and SnCl4·5H2O as starting precursors for In and Sn sources, respectively. The crystal structure properties of the samples were investigated by X-ray diffraction. Meanwhile, the size, shape and microstructure of the particles were observed by field emission scanning electron microscope and chemical composition was investigated by energy dispersive X-ray Spectrophotometer. The corresponding optical band gap was determined by diffuse reflectance spectra. The XRD results showed that the as-prepared powders were initially formed in amorphous phase and the crystalline structure of powders were obtained after calcination beyond specific temperature. The correlated reactions and mechanisms during sonochemical process responsible for ITO formation are suggested. The comparison between ITO powders prepared by sonochemical process and co-precipitation process is additionally carried out and the results show significant differences in their morphology and crystallite sizes of the particles.
Spin coating method was employed to deposit the thin films using redispersed nanoparticle suspensions of tin doped indium oxide (ITO). These films were then annealed in air at 450, 500, 550, 600, and 650 °C for 1 hour. The effect of annealing temperature on the structural, optical, morphological, and electrical properties were studied by XRD, UV–Vis spectroscopy, SEM, and four point probe technique, respectively. XRD analysis revealed that all thin films have cubic bixbyite structure with dominant (2 2 2) plane. Williamson-Hall analysis of XRD patterns showed that crystallite size increases with the rise in annealing temperature. SEM images of ITO thin film depicted spherical and non-spherical shaped particles of uneven size. The transmission spectra obtained from UV–Vis spectroscopy reveals that transparency of thin films undulate with annealing temperature. With the rise in annealing temperature the optical band gap increases, while the Urbach energy and electrical resistivity decreases. The optical band gap, Urbach energy, and electrical resistivity were found to have systematic dependence on the crystallite size. The figure of merit is maximum for ITO thin film annealed at 550 °C.
Transparent conducting films (TCFs) are a critical component in many personal electronic devices. Transparent and conductive doped metal oxides are widely used in industry due to their excellent optoelectronic properties as well as the mature understanding of their production and handling. However, they are not compatible with future flexible electronics developments where large-scale production will likely involve roll-to-roll manufacturing. Recent studies have shown that carbon nanotubes provide unique chemical, physical, and optoelectronic properties, making them an important alternative to doped metal oxides. This Review provides a comprehensive analysis of carbon nanotube transparent conductive films covering detailed fabrication methods including patterning of the films, chemical doping effects, and hybridization with other materials. There is a focus on optoelectronic properties of the films and potential in applications such as photovoltaics, touch panels, liquid crystal displays, and organic light-emitting diodes in conjunction with a critical analysis of both the merits and shortcomings of carbon nanotube transparent conductive films.
Silver (Ag) introduced colloidal Sn-doped In2O3 (ITO) ink for transparent conductive electrodes (TCEs) was prepared to overcome the limitation of colloidally prepared thin film; low density thin film, high resistance. ITO@Ag colloid ink was made by controlling the weight ratio of ITO and Ag nanoparticles through ball-milling and fabricated using spin coating. These films were dried at 220 °C and heat-treated at 450–750 °C in an air atmosphere to pyrolyze the organic ligand attached to the nanoparticles. All thin films showed high crystallinity. As the thermal treatment temperature increased, films showed a cracked surface, but as the weight percentage of silver increased, a flattened and smooth surface appeared, caused by the metallic silver filling the gap between the nano-particles. This worked as a bridge to allow electrical conduction, which decreases the resistivity over an order of magnitude, from 309 to 0.396, and 0.107 Ω⋅cm for the ITO-220 °C, ITO-750 °C, and ITO@Ag (7.5 wt.%)-750 °C, respectively. These films also exhibited >90% optical transparency. Lowered resistivity is caused due to the inclusion of silver, providing a sufficient number of charge carriers. Furthermore, the work function difference between ITO and silver builds an ohmic junction, allowing fluent electrical flow without any barrier.
Chemical co-precipitation method was used to synthesize tin-doped indium oxide (ITO) nanoparticles, and the subsequent solution co-blend was employed to fabricate ITO/PVB nanocomposites. UV(Ultra-violet)-Vis(Visible)-NIR( Near Infrared) spectra show that the addition of ITO nano particles can significantly enhance the thermal insulating efficiency of ITO/PVB nanocomposites. With increasing ITO content, the thermal insulating efficiency is increased. UV is almost fully absorbed by all ITO/PVB nanocomposites. Vis transmittance-haze spectra reveal that ITO/PVB nanocomposites exhibit higher Vis transmittance over 71.3% and lower haze below 2% when ITO content is in the range of 0.1 wt%-0.7 wt%. The UV-Vis -NIR spectroscopy shows that, under the premise of over 70% transmittance to the visible light, the screening effect of the NIR can be enhanced by 80% with 0.7% ITO/PVB nanocomposite membrane compared with the undoped PVB. The thermal insulating tests indicate that, in comparison with the pure PVB film, nanocomposite films with 0.1 wt%-0.9 wt% ITO can reduce temperature by 3-8 °C. The results show that this novel nanocomposite can be used for energy-saving glass.
Tin-doped indium oxide or indium tin oxide (ITO) has many promising uses in applications, such as, transparent conductive oxides, flat panel displays, and energy-saving windows. In this work, nanorice particles of tin-doped indium oxide (ITO) were obtained by a simple sol-gel method. Indium salts and stannous fluoride precursors were mixed ultrasonically in an aqueous medium. The crystallinity and chemical bonds were studied by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). FTIR spectra before calcination showed the characteristic bonds of In–OH and Sn–OH at 1160 cm ⁻¹ and 1380 cm ⁻¹ , respectively. After calcination at 400 ° C for 2 h, these characteristic bonds disappeared, confirming the formation of crystalline oxide. Moreover, scanning electron micrographs revealed well-defined structure, called nanorice, emerging from controlled crystal growth at 85 ° C for 90 min. The particle size of ITO was approximately 500 nm in length and diameter of 150 nm. The effect of crystallinity was studied by UV absorbance and NIR reflectance. These demonstrated promising results for use as energy-saving windows.
Solution-processed solar cells are appealing because of the low manufacturing cost, the good compatibility with flexible substrates, and the ease of large-scale fabrication. Whereas solution-processable active materials have been widely adopted for the fabrication of organic, dye-sensitized, and perovskite solar cells, vacuum-deposited transparent conducting oxides (TCOs) such as indium tin oxide, fluorine-doped tin oxide, and aluminum-doped tin oxide are still the most frequently used transparent electrodes (TEs) for solar cells. These TCOs not only significantly increase the manufacturing cost of the device, but also are too brittle for future flexible and wearable applications. Therefore, developing solution-processed TEs for solar cells is of great interest. This paper provides a detailed discussion on the recent development of solution-processed TEs, including the chemical synthesis of the electrode materials, the solution-based technologies for the electrode fabrication, the optical and electrical properties of the solution-processed TEs, and their applications on solar cells.
In this research work, the photocatalytic degradation methyl orange (MO) was carried out using Al2O3-NP/InSnO2 nanocomposite under UV illumination. The Al2O3-NP electrode was successfully formed by a two-step anodization method and Al2O3-NP/InSnO2 electrode was obtained via the sol–gel spin coating method. The structural properties of the samples have been characterized by a series of techniques, including field-emission scanning electron microscope, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and the contact angle and surface energy measurements. The influence of variables such as initial MO concentration, initial pH value, temperature, and reusability was researched. The kinetics of the photocatalytic degradation of MO can be best described by the pseudo-first-order model. Moreover, the activation energy (Ea), change of enthalpy (ΔH), free energy (ΔG), and entropy (ΔS) are evaluated. The activation energy has been found at 20.89 kJ/mol. The results indicated that the Al2O3-NP/InSnO2 photocatalyst has an excellent activity for photocatalytic degradation in the treatment of wastewater.
A few critical issues in preparing transparent conductive electrodes (TCEs) based on solution-processable conductive nanomaterials are their low electrical conductivity and the unfavorable trade-off between electrical conductivity and optical transparency, which are closely related to the organic ligands bound to the nanomaterial surface. In particular, bulky/insulating organic ligands bound to the surface of conductive nanomaterials unavoidably act as high contact resistance sites at the interfaces between neighboring nanomaterials, which adversely affects the charge transfer kinetics of the resultant TCEs. This article reviews the latest research status of various interfacial control approaches for solution-processable TCEs. We describe how these approaches can be effectively applied to conductive nanomaterials and how interface-controlled conductive nanomaterials can be employed to improve the electrical and/or electrochemical performance of various transparent nanocomposite electrodes, including TCEs, energy storage electrodes, and electrochromic electrodes. Last, we provide perspectives on the development direction for next-generation transparent nanocomposite electrodes and breakthroughs for significantly mitigating the complex trade-off between their electrical/electrochemical performance and optical transparency.
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 the actual effectiveness of the B-spline parameterization in spectro-scopic 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, a measure introduced in this work. The proposed procedure provides a possibility to determine the knot locations automatically (or, at least, semi-automatically) and excludes widespread modeling ambiguities associated with uncertain knot vector. Moreover, our 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 the study.
This review article comprises of detailed discussions about different types of thin-film coating techniques in which Indium-doped Tin Oxide (ITO) has been coated by various researchers across the world. Since, it is indispensable to incorporate the working of the coating processes to make ITO films for specific applications, working of each coating technique has also been explained in detail. This work provides a comprehensive details about the previously reported works on ITOs. The details include precursors used in the preparation of ITO substrates, electrical and optical properties of ITO, resistivity, transparency, growth rate and structure of the coated films, characterization techniques studies carried out for the ITO films. It was noted that the films coated by CVD technique had the highest transmission of 90-95%. Minimum resistivity of 0.7-12 × 10⁻⁴ Ω cm was obtained for Evaporation technique. This review article will provide a detailed discussion on used techniques for developing the ITO films for TCO applications and their applications.
Indium tin oxide (ITO) is a promising transparent conducting oxide material for photoelectric devices. In this work, the low-resistivity cubic ITO (c-ITO) nanopowders were synthesized via polyacrylamide gel route. The orthogonal experiment design was applied to optimize preparation process that was as follows: n(AM)/n(MBAM) = 25:6, c(In3+) = 0.3 mol/L, calcination temperature (T) = 700 °C, holding time (t) = 9 h. Subsequently, the thermal decomposition process of ITO xerogel, crystal structure, morphology, and electrical conductivity of the optimum sample were characterized systematically. The results indicated that the thermal decomposition of ITO xerogel was a multi-step kinetic reaction process, and the activation energy of reaction depended on the conversion of ITO xerogel. The powders were well indexed to cubic ITO crystal phase, and presented a concentrated particle size distribution of 34–54 nm and nearly spherical-like morphology. The low-resistivity value of 0.161 Ω·cm was obtained under the optimum preparation process. Moreover, the formation mechanism of ITO nanopowders prepared via polyacrylamide gel route was also investigated. The synthesized ITO nanopowders with low resistivity present wide application prospects of next-generation ITO functional materials.
The present work proposes a method to fabricate indium tin oxide (ITO) particles using precursor particles synthesized with a combination of a homogeneous precipitation method and a seeding technique, and it also describes their electronic conductivity properties. Seed nanoparticles were produced using a co-precipitation method with aqueous solutions of indium (III) chloride, tin (IV) chloride aqueous solution and sodium hydroxide. Three types of ITO nanoparticles were fabricated. The first type was fabricated using the co-precipitation method (c-ITO). The second and third types were fabricated using a homogeneous precipitation method with the seed nanoparticles (s-ITO) and without seeds (n-ITO). The as-prepared precursor particles were annealed in air at 500 °C, and their crystal structures were cubic ITO. The c-ITO nanoparticles formed irregular-shaped agglomerates of nanoparticles. The n-ITO nanoparticles had a rectangular-parallelepiped or quasi-cubic structure. Most s-ITO nanoparticles had a quasi-cubic structure, and their size was larger than the n-ITO particles. The volume resistivities of the c-ITO, n-ITO and s-ITO powders decreased in that order because the regular-shaped particles were made to strongly contact with each other.
An environmentally friendly aqueous sol–gel process has been developed to fabricate thin films of indium tin oxide (ITO). A stable sol was prepared from indium nitrate and tin acetate precursors together with acetic acid and ethylene glycol. The sol transformed into an amorphous gel during heating, which decomposed and crystallized further to nano-crystalline ITO at 300 °C. The nano-crystalline ITO powders prepared from the precursor gel were homogeneous and single phase with particle sizes around 15 nm. The aqueous sol was applied for spin coating of ITO films on glass substrates. The deposited thin films were homogeneous and continuous with no cracks or pin-holes and exhibited very good and reproducible optical transparency and electrical conductivity, with a specific resistance of 4.59 × 10−3 Ω cm, thereby demonstrating the potential of this Pechini related sol–gel process. Experiments to determine the robustness of the process with respect to the concentration of the precursors and substitution of the organic components with other alcohols or acids were also performed, and some important aspects of the chemistry of the sol–gel process are addressed.
Two kinds of nanocrystalline indium tin oxide (ITO) powders with different crystal structures—rhombohedral and cubic—were prepared using a coprecipitation process through the control of pH of a mixing solution and aging time after coprecipitation. The two powders have the same particle size of 15nm in diameter but different morphologies (spherical for rhombohedral and rectangular for cubic). The gaseous ethanol sensing characteristics of the sensors prepared by the two ITO powders were quite different. The sensitivity of rhombohedral ITO sensor was high compared to that of the cubic ITO sensor across all temperatures. The reason for this is explained through the viewpoint of the binding energy as shown in XPS measurement and the surface structure relating to the crystal structure.
Conductive and highly transparent indium tin oxide (ITO) thin films were prepared on photosensitive glass substrates by the combination of sol–gel and spin-coating techniques. First, the substrates were coated with amorphous Sn-doped indium hydroxide, and these amorphous films were then calcined at 550∘C to produce crystalline and electrically conductive ITO layers. The resulting thin films were characterized by means of scanning electron microscopy, UV-Vis spectroscopy, X-ray photoelectron spectroscopy and spectroscopic ellipsometry. The measurements revealed that the ITO films were composed of spherical crystallites around 20 nm in size with mainly cubic crystal structure. The ITO films acted as antireflection coatings increasing the transparency of the coated substrates compared to that of the bare supports. The developed ITO films with a thickness of ∼170–330 nm were highly transparent in the visible spectrum with sheet resistances of 4.0–13.7 kΩ/sq. By coating photosensitive glass with ITO films, our results open up new perspectives in micro- and nano-technology, for example in fabricating conductive and highly transparent 3D microreactors.
Indium tin oxide (ITO) films containing different In : Sn atomic ratios, viz. 90 :10, 70 :30, 50 : 50, 30 :70, were deposited
on two types of glass substrates by sol-gel spinning technique. XPS analysis of the films was done under as-received and after-sputtering
conditions. The narrow spectra obtained for the Na1s, In3d, Sn3d and O1s have been discussed. Oxygen was found to exist in
three chemical environments in as-received samples due to the existence of (i) environmental hydroxyl (-OH) group, (ii) crystalline
ITO and (iii) amorphous ITO; but it was in two chemical environments, (ii) and (iii), after surface cleaning by sputtering.
The presence of both tin metal and tin oxides was confirmed by the peak analysis of Sn3d. The In : Sn atomic ratio taken in
the precursor sols did not change considerably in the case of developed films of low Sn content, but considerable change was
observed in the films having high Sn content.
The deposition of SnO2:Sb (ATO) and In2O3:Sn (ITO) transparent conducting coatings on glass substrate has been demonstrated by many techniques such as CVD, sputtering, vacuum deposition and sol-gel process. This paper presents an alternative process for the deposition of such coatings at room temperature by spin, dip and spray coating techniques using solutions prepared with crystalline nanoparticles fully redispersed in water (for ATO, ITO) or alcohol (for ITO) with solid contents up to 10–15 Vol.%, respectively. The deposited green coatings have been sintered at temperature as high as 900°C. In2O3:Sn coatings have a resistivity of 1.5×10−2 Ω cm as sintered and 3.4×10−3 Ω cm after annealing in nitrogen atmosphere. The resistivity of ATO single coatings shows a minimum ρ=1.7×10−2 Ω cm after annealing at 550°C. SnO2:Sb coatings present long term stability but the resistivity of annealed ITO coatings steadily increases with time to a value three times higher. All coatings have a high optical quality with transmission in the visible range larger than 90%.
To analyse the var gene repertoire and characterise the chondroitin sulphate A (CSA)-binding activity of the Duffy-binding like (DBL) domains encoded by the var2csa gene of a Plasmodium falciparum (P. falciparum) isolate in Hainan Province, China.
The sequences of var DBL1 regions were PCR-amplified, sequenced and the sequence characteristics was bioinformatically analysed. Recombinant proteins encoded by the var2csa genes were expressed and purified. The binding activities of the recombinant proteins to CSA receptor was detected by ELISA assays.
Fifty six unique DBL α sequences were obtained, and the sequences represented similar diversity to the var genes of the genome parasite 3D7. There are two var2csa genes in the P. falciparum isolated from Hainan Province. Unlike in other falciparum parasites such as HB3, the two var2csa genes are more diverged. The receptor-binding capacity of DBL-5ε and DBL-6ε domains of HN var2CSA was studied.
This work represented the diversity of var genes of a P. falciparum isolate in China.
Indium-tin-oxide(ITO) films were prepared on the quarts glass by sol-gel technique. Effects of different heat treatment temperatures and cooling methods on the morphological, optical and electrical properties of ITO films were measured by TG/DTA, IR, XRD, SEM, UV-VIS spectrometer and four-probe apparatus. It is found that the crystallized ITO films exhibit a polycrystalline cubic bixbyite structure. The heat treatment process has significant effects on the morphological, optical and electrical properties of ITO films. Elevating the heat treatment temperature can perfect the crystallization process of ITO films, therefore the optical and electrical properties of ITO films are improved. But the further increasing of heat treatment temperature results in the increment of ITO films' resistivity. Compared with ITO films elaborated by furnace cooling, those prepared through air cooling have following characteristics as obviously decreased crystalline size, deeply declined porosity, more compact micro-morphology, improved electrical property and slightly decreased optical transmission.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.