Absolute Transmittance Research Articles

Monolithic High Contrast Grating Integrated with Metal: Infrared Electrode with Exceptionally High Conductivity and Transmission

AbstractThe design of transparent conductive electrodes (TCEs) for optoelectronic devices requires a trade‐off between high conductivity and transmittivity, limiting their efficiency. This paper demonstrates the best ever achieved TCEs with the novel approach to fabricating TCEs that effectively alleviates this trade‐off: a monolithic high contrast grating integrated with metal (metalMHCG). The metalMHCG enables higher electrical conductivity than other TCEs, while providing transmissive and antireflective properties. It focuses on infrared spectrum TCEs, which are essential for sensing, thermal imaging, and automotive applications. However, due to elevated free carrier absorption, they are much more demanding than TCEs for the visible spectrum. It demonstrates a record 75% absolute transmittiance of unpolarized light, resulting in a record 108% transmittance relative to plain GaAs substrate. It achieves even larger absolute transmittance of polarized light, reaching 92% or 133% relative transmittance. Despite the record high transmittance, the sheet resistance of the metalMHCG is the best ever reported, several times lower than any other TCE, ranging from 0.5 to 1 Ω Sq−1.

An absolute-zero-stiffness vibration isolator for continuously varying mass: Theoretical design and numerical simulation

Nonlinear quasi-zero-stiffness (QZS) vibration isolators can provide low dynamic but high static stiffness, and thus attract much attention in the fields of vibration isolation and reduction. However, it seems difficult for QZS isolators to protect continuously varying mass from the surrounding vibratory disturbance of relatively large amplitude. In this article, an adjustable absolute-zero-stiffness vibration isolator is designed by updating the classical QZS isolator in two steps. First, each hinged constraint in the QZS isolator that connects the oblique spring with the outer rigid framework, is released and replaced by a sliding constraint supported on an additional vertical linear side-spring. Second, the two oblique springs in the QZS isolator are further replaced by two identical oblique cam-roller-spring units, which can synthetically provide a constant negative-stiffness at will in the vertical direction. Once the stiffness ratios among the main-spring (as in the QZS isolator), side-springs and oblique-units of the new isolator are rationally determined, for a target object with any weight to be protected, absolute zero stiffness and transmittance can always be achieved by appropriately exerting an additional time-independent vertical force on each sliding constraint. The validity and efficiency of the theoretical design are fully verified by numerical simulations for both fictitious loads and real seismic spectra. This work provides a possible means for nonlinear vibration isolations of continuously varying mass.

Multifunctional smart window based on transparent embedded Ni-mesh electrodes

Flexible electrochromic devices (ECDs) are a future technology with huge impact on wearable displays, energy saving, and adaptive camouflage. In this work, we used embedded nickel (Ni) mesh transparent electrodes combined with a thin polymer film of poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) to build a multifunctional flexible electrochemical device that integrates the functions of electrochromic and supercapacitor devices. The multi-layer architecture improves the device performance in terms of optical contrast and mechanical strength. Ni-mesh electrodes have a high optical transparency (84.8%), good mechanical flexibility, and low resistance (0.5 Ω/sq), which is conducive to efficient electron injection, benefiting to the response time of the constructed device. The thin polymer film of PEDOT:PSS is an electrochromic (EC) material that also uniformly distributes electrons for a uniform coloration. The fabricated device shows fast response to coloring and bleaching (1.2 and 0.8 s, respectively), an absolute transmittance contrast ratio of 40%, and area capacitance of up to 2.48 mF/cm2. Furthermore, the device exhibits excellent flexibility, and the electrochromic and electrochemical properties of the device are only partially diminished upon folding, which is beneficial for the construction of multifunctional flexible electrochromic devices. With its response time, working stability, and bending ability, our multifunctional device paves the way for the next generation of flexible electronics.

Survey of the mechanical and physical behaviors of yttria-stabilized zirconia from multiple dental laboratories

BackgroundWhen selecting zirconia for a dental restoration, laboratory prescriptions often refer to high strength and high translucency. In this survey, zirconia specimens were ordered from various dental laboratories for posterior (high strength) and anterior (high translucency) clinical indications. The specimens were then tested and evaluated for their mechanical and physical behaviors. MethodsIn a double-blinded manner, 9 laboratories provided 32 specimens from 17 different zirconia blanks, which were tested in the American Dental Association laboratory. Flexural strength tests were performed on standard specimens, and fracture surfaces were examined using both optical and scanning electron microscopy. Chemical composition, Vickers hardness, and absolute transmittance measurements were also performed. ResultsA large scatter in the strength values was observed. The zirconia intended for posterior applications displayed strengths (SD) from 195 through 783 MPa (490 [183] MPa), which overlapped greatly with the strengths (SD) of the zirconia intended for anterior applications, 320 through 768 MPa (581 [136] MPa). However, when the strength values were recalculated on the basis of yttria content, the strengths (SD) were 584 (158) MPa for 3 mol% yttria and 373 (104) MPa for 5 mol% yttria. ConclusionsWhen a prescription was given to dental laboratories to request zirconia on the basis of clinical requirements, there was a large scatter and no consistency in the resulting strength values partly because of mixed use of 3 mol% and 5 mol% yttria zirconia. The 3 mol% materials had much higher strength when the strength values were grouped according to yttria content. Strength was also highly dependent on processing and finishing at the dental laboratories.

Synthesis and characterization of goethite (α-FeOOH) magnetic nanofluids

Magnetic nanofluids consisting of goethite nanoparticles in aqueous suspensions have been successfully synthesized using two sodium-free routes. Nanoparticle morphology, nanofluid stability and optical properties have been studied and compared with a goethite nanofluid whose nanoparticles are synthesized with a different protocol using NaOH. The synthesis procedure determines the nanoparticle size and morphology, which, in turn, is connected to optical properties and their sensitivity to external magnetic fields. The highest sensitivity is shown by the sample synthesized with NaOH, which is characterized by the largest nanoparticles (261±5 nm hydrodynamic size) and whose absolute transmittance values increase or decrease by about 11% and 20%, respectively, depending on to the mutual directions of magnetic field and electromagnetic wave polarization/wave vector, for an applied magnetic field of 5.60 mT. Nanoparticles in the fluid are therefore able to discriminate both the absolute value and the direction of the magnetic field and, moreover, being their response non-spectrally flat, specific spectral ranges exist where their response is maximized.

Self-Driven Electrochromic Window System Cu/WOx-Al3+/GR with Dynamic Optical Modulation and Static Graph Display Functions.

Electrochromic devices with unique advantages of electrical/optical bistability are highly desired for energy-saving and information storage applications. Here, we put forward a self-driven Al-ion electrochromic system, which utilizes WOx films, Cu foil, and graphite rod as electrochromic optical modulation and graph display electrodes, coloration potential supplying electrodes, and bleaching potential supplying electrodes, respectively. The inactive Cu electrode can not only realize the effective Al3+ cation intercalation into electrochromic WOx electrodes but also eliminate the problem of metal anode consumption. The electrochromic WOx electrodes cycled in Al3+ aqueous media exhibit a wide potential window (∼1.5 V), high coloration efficiency (36.0 cm2/C), and super-long-term cycle stability (>2000 cycles). The dynamic optical modulation and static graph display function can be achieved independently only by switching the electrode connection mode, thus bringing more features to this electrochromic system. For a large-area electrochromic system (10 × 10 cm2), the absolute transmittance value in its color-neutral state can reach about 41% (27%) at 633 nm (780 nm) by connecting the Cu and WOx electrodes for 140 s. The original transparent state can be readily recovered by replacing the Cu foil with the graphite rod. This work throws light on next-generation electrochromic applications for optical/thermal modulation, privacy protection, and information display.

Influence of yttria content and surface treatment on the strength of translucent zirconia materials

Statement of problemNewly developed translucent zirconia materials have been used for anterior monolithic complete coverage restorations. Surface treatments can improve adhesion, as well as decrease or increase the strength of ceramics. However, information on the influence of surface treatments on the strength of translucent zirconias is sparse. PurposeThe purpose of this in vitro study was to measure and characterize the effects of different surface treatments, including airborne-particle abrasion, on the strength of different translucent 4 mol% and 5 mol% yttria-stabilized zirconia materials. Materials and methodsDisks (N=160) made from 4 types of translucent yttria-stabilized zirconia materials were surface-treated in 4 ways: Control groups were hand-polished with 2000-grit silicon carbide abrasive paper; as-machined; glass bead airborne-particle abraded; and alumina airborne-particle abraded. The biaxial flexural strength was measured by using a piston-on-3-ball test in a universal testing machine. The simple main effects of material type and surface treatment and their interaction on biaxial flexural strength were evaluated with 2-way ANOVA (α=.05). A priori, 1-way ANOVA and the Tukey multiple comparisons tests were used within material and treatment types (α=.05). Surface morphology was assessed by using scanning electron microscopy. Translucency, absolute transmittance, was measured by using a spectrophotometer. ResultsTwo-way ANOVA revealed that the effects of zirconia type, surface treatment, and their interaction all significantly affected biaxial flexural strength (P<.001). One-way ANOVA revealed that the 4Y material was stronger than all 5Y materials, regardless of surface treatment; all 5Y materials were ranked from strongest to weakest as polished; as-machined, or glass bead abraded; and alumina abraded. The 4Y material was stronger when alumina abraded than when glass bead abraded. Scanning electron microscopy showed that as-polished surfaces were smoother than all others; as-machined and glass bead abraded surfaces displayed little difference; alumina abraded was the roughest; and differences among materials were not discerned. The 1-way ANOVA and multiple comparisons testing showed that the 4Y material had less absolute transmittance, approximately 5% less, than all the 5Y materials. ConclusionsZirconia material type and surface treatment influenced the strength of translucent zirconia materials; a 4 mol% zirconia material was stronger than 5 mol% zirconia materials for all surface treatments tested; airborne-particle abrasion using alumina had a slight strengthening effect on a 4 mol% zirconia but had a weakening effect on 5 mol% materials; airborne-particle abrasion by using alumina produced the roughest surfaces on all materials; and the 4 mol% material was slightly less translucent than the 5 mol% materials.

Ultrathin-metal-film-based transparent electrodes with relative transmittance surpassing 100%

Flexible transparent electrodes are in significant demand in applications including solar cells, light-emitting diodes, and touch panels. The combination of high optical transparency and high electrical conductivity, however, sets a stringent requirement on electrodes based on metallic materials. To obtain practical sheet resistances, the visible transmittance of the electrodes in previous studies is typically lower than the transparent substrates the electrode structures are built on, namely, the transmittance relative to the substrate is <100%. Here, we demonstrate a flexible dielectric-metal-dielectric-based electrode with ~88.4% absolute transmittance, even higher than the ~88.1% transmittance of the polymer substrate, which results in a relative transmittance of ~100.3%. This non-trivial performance is achieved by leveraging an optimized dielectric-metal-dielectric structure guided by analytical and quantitative principles described in this work, and is attributed to an ultra-thin and ultra-smooth copper-doped silver film with low optical loss and low sheet resistance.

Light scattering and extinction in polydisperse systems

A simple approach to predict transmittance spectra of polydisperse systems is recalled and applied to various model systems (spinel-like particles in water, pores in a spinel-like matrix) and real systems (spinel in water, diamond in water, amorphous carbon soot in isopropanol) in order to investigate principal effects of size distributions (normal/lognormal, narrow/wide, monomodal/bimodal, shift of mode positions, shift of mode heights) and optical properties (refractive index contrast, with or without absorption) on the in-line transmittance. A comparison of predicted and measured spectra showed that size distributions with more small particles cause a more significant decrease in transmittance (at least for sufficiently short wavelengths) and that laser diffraction may seriously underestimate the amount of small particles (for absorbing particles, for which the influence on transmittance is enormous, a difference of up to 30% in absolute transmittance measured via spectrophotometry has been found against predictions based on laser diffraction results).

Highly flexible electrochromic devices enabled by electroplated nickel grid electrodes and multifunctional hydrogels.

Flexible electronics, as a futuristic technology, is presenting tremendous impact in areas of wearable displaying, energy saving, and adaptive camouflage. In this work, we constructed a simple triple-layered electrochemical device with high flexibility using the electroplated nickel (Ni) grid electrode and the multifunctional hydrogel. The Ni grid electrode with low resistance (0.5 Ω/sq), high optical transparency (84.8%) and good mechanical flexibility, is beneficial for efficient electron injection, while the transparent lithium chloride hydrogel functions simultaneously for ion storage, ion transportation and counter-conducting. The thin polymer poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) film is utilized as the electrochromic (EC) material and it also distributes the electrons evenly for uniform coloration. The triple-layered EC architecture not only simplifies the manufacturing procedures but also improves the device performance in terms of optical contrast and mechanical robustness. The device shows fast response for coloration and bleaching with an absolute transmittance contrast of 40% and a contrast retention over 72% after 2500 bending cycles. The ability of the flexible electrochromic device for conformable attaching was also investigated without obvious performance degradation. The electroplated Ni grid electrode and the multifunctional hydrogel are advantageous in constructing flexible electrochromic devices in terms of the response time, the working stability and the bending capability, paving a way for next-generation flexible electronics.

High-contrast optical switching using an epsilon-near-zero material coupled to a Bragg microcavity.

Epsilon-near-zero (ENZ) materials have recently been suggested as excellent candidates for constructing all-optical and electro-optical switches in the infrared. The performance of previously reported ENZ material-based optical switches, however, has been greatly hampered by the low quality- (Q-) factor of the ENZ cavity, resulting in a large required optical pump fluence or applied voltage, a large insertion loss, or a small modulation depth. Here, we propose a solution by integrating the ENZ material into a Bragg microcavity, such that the Q-factor of the coupled cavity can be dramatically enhanced. Using high-mobility Dysprosium-doped cadmium oxide (CdO) as the prototype ENZ material, we numerically show an infrared all-optical switch with its reflectance modulated from near-zero to 94% under a pump fluence of only 7 μJ cm-2, about a 59-time-reduction compared with a state-of-the-art Berreman-type cavity. Moreover, the high-Q coupled cavity can also be adopted to realize a reflective electro-optical switch. Its reflectance can be switched from near-zero to 89%, with a bias electric field well below the breakdown field of conventional gate dielectrics. The switching operation can further be extended to the transmission mode with a slightly modified cavity geometry, with its absolute transmittance modulated by 40%.

Broadband antireflective and superhydrophobic coatings for solar cells

High-performance, broadband antireflective (AR) and superhydrophobic coatings are fabricated on glass through deposition of silica nanoparticles with spin coating method, followed by calcination and hydrophobic modification. Silica particles with unique porous structures not only increase the roughness of the coating, but also enhance the transmittance of the glass. The coated glass has displayed a large transmittance of 99% at wavelength of 580 nm, an absolute transmittance increase by 6% or more in the wavelength range of 480–900 nm, and an excellent hydrophobicity with a water contact angle (WCA) of 147° and a sliding angle < 10°. As a result, this coating effectively improves the short-circuit current density from 13.27 to 14.17 mA/cm2 and the conversion efficiency from 6.03 to 6.64% for dye-sensitized solar cells (DSSCs), with a 10.12% improvement. This work thus has shown a promising approach to enhance the performance of solar cells with broadband antireflective coating surfaces.

In Situ Surface Oxidized Copper Mesh Electrodes for High‐Performance Transparent Electrical Heating and Electromagnetic Interference Shielding

AbstractMetallic mesh is a significant candidate of transparent conductive electrodes (TCEs) to substitute the current state‐of‐the‐art material indium tin oxide for optoelectronic devices. However, there remains a challenge to fabricate stable and good‐visibility metallic mesh with the low‐cost copper (Cu) material. A metallic Cu mesh electrode (on glass) with a high absolute transmittance of ≈82% combined with an adjustable low electrical resistance of ≈0.2 Ω sq−1 and a low total light reflectance of 8.7% is demonstrated here. The Cu mesh TCE shows excellent visibility and good thermal, moisture, and environmental stability that can be used in practical applications. This was achieved by in situ forming an oxidation‐resistive and light‐absorptive capping layer of oxide on the surface of Cu meshes. The electrode was fabricated by UV‐lithography and electroplating, and then directly annealing in the air. To assess the application potentials, transparent electrical heating up to 100 °C under 3 V supply and transparent shielding of radiofrequency with ≈24 dB attenuation in Ku band are achieved. Good photoelectric properties, low‐cost material, and excellent stability imply that this Cu mesh electrode is a striking candidate for low‐cost TCE for efficient optoelectronic devices.

Abstract B37: Value of penetrated NIR spectroscopy in the diagnostic process of lung cancer

Abstract Background: Recently due to advances in biological therapy and immunotherapy there is an increased need for precise morphological and mutational verification of lung cancer. We have been testing the possibilities of NIR (near infrared) n spectroscopy in the process lung cancer detection. Methods: For the analyses, we used a custom-made endoscopic lensed microprobe consisting of one excitation and one collection optical fibers that were coupled to a NIR spectrometer. In 55 patients with lung cancer diagnosis undergoing bronchoscopy we carried on 110 measurements of NIR penetrated spectra from both normal and malignant lung tissues. Detected spectral curves of absolute transmittance for normal tissue and pathological tissue were further analyzed utilizing two chosen parameters which are corresponding to important characteristics of the curves. First parameter was statical moment of area under spectral curve referenced to vertical axis of maximal wavelength whose value reflected average intensity of detected signal as well as rate of shifting higher intensities to shorter wavelengths of spectral band (that means how much is investigated tissue permeable on shortest possible wavelengths). As the second parameter serve horizontal coordinates of the centrum of gravity of the area under spectral curve referenced to vertical axis of maximal wavelength whose value reflected just the rate of shifting signal to shorter wavelengths of spectral band regardless absolute intensity (this parameter compared shifting to shorter wavelengths for spectral curves as if were normalized to its maximal intensity value). Finally ratio of pathological to normal value for both parameters was calculated. Results: Resulting values of these ratios for both above mentioned parameters were higher than 1 for all types of pathologies. Moreover ratio for second parameter is significantly higher for adenocarcinoma than for any type of pathologies. Conclusion: NIR spectroscopy showed a potential for a reliable discrimination between normal and pathological lung tissue. We observed spectral differences between adenocarcinoma and all other types of lung pathologies. Acknowledgement: PROGRAM MPO-TRIO PROJECT: FV 10657, OPROX, a.s. Research and development of technologies and methods for optical penetrating spectroscopy of atypical lung tissue nodules. Note: This abstract was not presented at the conference. Citation Format: Tomas Bruha, Jiri Votruba, Vladimír Cech, Josef Skvarek. Value of penetrated NIR spectroscopy in the diagnostic process of lung cancer [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr B37.

Anodic copper oxide nanowire and nanopore arrays with mixed phase content: synthesis, characterization and optical limiting response

Thin films consisting of copper oxide nanowires (NWs) containing a mixture of copper oxide phases were formed by electrochemical anodization in de-ionized water (DI) and methanol based electrolytes. Well-defined arrays of vertical nanopores were obtained via anodization in ethylene glycol (EG)-based electrolytes. Optical absorption spectra revealed the electronic bandgap of the NWs formed in DI and methanol to be 2.50 eV, and that of nanopores formed in EG electrolytes to be 1.94 eV. The nanostructures were found to exhibit p-type conduction through Mott–Schottky analysis. The as-formed nanostructures exhibited two photon photoluminescence with lifetimes ranging between 200 and 1100 ps. They also displayed strong optical limiting in the form of a 25% decrease in optical transmission at 800 nm at a relatively low fluence of 0.1 J cm−2 and an absolute transmittance <50% over the entire range of laser fluence values used in this study. The optical transmittance decreased from 40% at an incident Ti-sapphire laser fluence of 20 mJ cm−2 to ∼9% when the fluence was increased to 700 mJ cm−2. Furthermore, the damage threshold of 0.7 J cm−2 compares favorably with advanced optical limiting materials such as gold-graphene composites and single-walled carbon nanotube composites even without further optimization of nanoscale morphology to maximize scattering. Therefore the nanostructures of mixed copper oxide films studied in this report are particularly promising as optical limiters for protecting low damage threshold (<1 J cm−2) photonic devices and are an important addition to the narrow selection of optical limiting materials that are currently available.

Synthesis and Characterization of Ag Nanoparticles for Orthopaedic applications

Bacterial infections are a leading cause of death for millions of people worldwide, while few antibiotics have been proved effective against multidrug-resistant bacteria. Recently, nanoparticles have been used for the delivery of therapeutic agents to reduce bacterial infections due to their antimicrobial activity and unique mode of action. In our studies, silver nanoparticles (Ag NPs) have been used in order to meddle with associated infections for orthopaedic applications, due to their unique morphology and size. Nanoprecipitation method was used for the development of the NPs, using PVP (polyvinylpyrrolidone) as a reducing agent. Chitosan was used as a stabilizing and a coating agent at different concentrations (0.1%, 0.01% and 0.001%) in order to evaluate the most optimum capped coating. Atomic Force Microscopy (AFM) was the appropriate indicator for the morphological and topography analysis. Results showed that chitosan-capped NPs with 0.01% were found to be the most optimum. Transmittance measurements at plasmon emission at ∼320nm wavelength have showed Ag nanoparticles which were identified due to the sharp absorption peak. Variations of the absolute transmittance values due to the different thickness of the samples confirmed the coating of chitosan in Ag NPs. XRD measurements further took place and successfully have indicated the presence of chitosan in Ag nanoparticles’ surface. Electrospinning System was used for the formation of PCL (poly-ε-caprolactone) scaffolds where Ag NPs were deposited via Electrospraying System. The final scaffolds were then studied with AFM and SEM (Scanning Electron Microscopy) Images. As a conclusion, the fabricated Ag NPs into polymer scaffolds appeared to be a valuable tool with antibacterial properties towards implant-associated orthopedic infections.

Application of a portable 3He-based polarization insert at a time-of-flight neutron reflectometer

The suitability of a transportable 3He-spin filter as temporary broadband polarizer for a Time-of-Flight neutron reflectometer is demonstrated. A simple two-wavelength method for characterisation of a 3He-spin filter is proposed, which can be applied even if the absolute transmittance of the 3He-spin filter cannot be accurately determined. We demonstrate the data treatment procedure for extracting the spin-up and spin-down neutron reflectivity from measurements obtained with a time dependent 3He polarization. The extraction of a very weak magnetic signal from reflectivity data, measured on the in-situ grown magnetic heterostructure Fe1nm/Cu20nm/Sisubstrate in an externally applied magnetic field of 30mT is presented and compared to similar measurements on the growth stage Cu20nm/Sisubstrate of the very same sample, which does not yet contain any magnetic material.

Do small‐aperture presbyopic corrections influence the visual field?

To explore the effect of small-aperture optics, designed to aid presbyopes by increasing ocular depth-of-focus, on measurements of the visual field. Simple theoretical and ray-tracing models were used to predict the impact of different designs of small-aperture contact lenses or corneal inlays on the proportion of light passing through natural pupils of various diameters as a function of the direction in the visual field. The left eyes of five healthy volunteerswere tested using three afocal, hand-painted opaque soft contact lenses (www.davidthomas.com). Two were opaque over a 10mm diameter but had central clear circular apertures of 1.5 and 3.0mm in diameter. The third had an annular opaque zone with inner and outer diameters of 1.5 and 4.0mm, approximately simulating the geometry of the KAMRA inlay (www.acufocus.com). Afourth, clear lens was used for comparison purposes. Visual fields along the horizontal meridian were evaluated up to 50° eccentricity with staticautomated perimetry (Medmont M700, stimulus Goldmann-size III; www.medmont.com). According to ray-tracing, the two lenses with the circular apertures were expected to reduce the relative transmittance of the pupil to zero at specific field angles (around 60° for the conditions of the experimental measurements). In contrast, the annular stop had no effect on the absolute field but relative transmittance was reduced over the central area of the field, the exact effects depending upon the natural pupil diameter. Experimental results broadly agreed with these theoretical expectations. With the 1.5 and 3.0mm pupils, only minor losses in sensitivity (around 2dB) in comparison with the clear-lens case occurred across the central 10° radius of field. Beyond this angle, sensitivity losses increased, to reach about 7dB at the edge of the measured field (50°). The field results with the annular stop showed at most only a slight loss in sensitivity (≤3dB) across the measured field. The present theoretical and experimental results support earlier clinical findings that KAMRA-type annular stops, unlike circular artificial pupils, have only minor effects on measurements of the visual field.

The influence of oxygen flow rate on properties of SnO2 thin films grown epitaxially on c-sapphire by chemical vapor deposition

Tin dioxide (SnO2) thin films were grown on c-plane sapphire substrates by chemical vapor deposition using SnI2 and O2 as reactants. The growth experiments were carried out at a fixed substrate temperature of 510°C and different O2 flow rates. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, UV–Vis–IR spectrophotometry and Hall-effect measurement were used to characterize the films. All films consisted of pure-phase SnO2 with a rutile structure and showed an epitaxial relationship with the substrate of SnO2(100)||Al2O3(0001) and SnO2[010]||Al2O3<11–20>. The crystalline quality and properties of the films were found to be sensitively dependent on the O2 flow rate during the film growth. The absolute average transmittance of the SnO2 films exceeded 85% in the visible and infrared spectral region. The films had optical band-gaps (3.72–3.89eV) that are in line with the band gap of single-crystal SnO2. The carrier concentration and Hall mobility of the films decreased from 3.3×1019 to 9×1017cm−3 and from 19 to 2cm2V−1s−1, respectively, while the resistivity increased from 0.01 to 3Ωcm with increasing of the O2 flow rate from 5 to 60sccm.

Polycrystalline SnO2 films grown by chemical vapor deposition on quartz glass

Tin dioxide (SnO2) thin films were deposited on quartz glass substrates by chemical vapor deposition using SnI2 and O2 as reactants. The growth experiments were carried out in the substrate temperature range of 300–900 °C. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, spectrophotometry and Raman spectroscopy were used to characterize the films. The films were polycrystalline with their crystallites having a preferred orientation, which was dependent on the film thickness. The average grain size increased with increasing thickness of the films. The binding energies of Sn 3d5/2 and O 1s for all samples showed the Sn4+ and O-Sn4+ bonding state from SnO2. The absolute average transmittance of SnO2 films exceeded 90% in the visible and infrared range. The obtained SnO2 films had optical band gaps between 3.78 and 3.92 eV.