Highly transparent low resistance ATO/AgNWs/ATO flexible transparent conductive thin films

Indium-free flexible transparent conductive thin films (TCFs) composed of silver nanowire (AgNW) networks and Sb doped SnO₂ (ATO) layers were prepared on polyethylene terephthalate (PET) substrates. The ATO layers were deposited via radio frequency (RF) magnetron sputtering at room temperature. The AgNWs were achieved via a modified polyol reduction method and embedded between the ATO layers. The effects of AgNW networks and ATO layers on electrical and optical properties of the ATO/AgNWs/ATO flexible tri-layer thin films are investigated. The ATO layers can improve the optical transmittance and reduce the resistivity of tri-layers, and the corresponding mechanisms are proposed. Typically, an ATO/AgNWs/ATO flexible tri-layers show a high figure of merit value (30.06 × 10^-3 Ω^-1) with a low sheet resistance of 7.1 Ω/sq. and a high transmittance of 85.7%. Meanwhile, the tri-layers present excellent mechanical flexibility, and the ATO layers acted as the protecting layers improve the adhesive and environmental stability at high temperature and humidity for the ATO/AgNWs/ATO flexible tri-layers. These results indicate that ATO/AgNWs/ATO flexible tri-layer thin films can be useful for the fabrication of wearable electronic devices.     

Fabrication and thermo stability of the SnO2/Ag/SnO2 tri-layer transparent conductor deposited by magnetic sputtering

Using the magnetic sputtering technique, the SnO₂/Ag/SnO₂ tri-layer transparent films were fabricated on float glasses successfully. Compared with the commercial FTO (F-doped SnO₂) film, the SnO₂/Ag/SnO₂ tri-layer films have higher visible-light transmittance and better conductivity. The total thickness of the SnO₂/Ag/SnO₂ films is one third of the commercial FTO film leading to the high visible-light transmittance. The high carrier concentration of the SnO₂/Ag/SnO₂ films contributes to the tri-layer films’ low resistivity. In addition, to further improve the performance of the SnO₂/Ag/SnO₂ tri-layer films, samples were annealed under different temperatures. The results illustrate that the lowest sheet resistance (5.92 Ω/sq) and the highest visible-light transmittance (87.0%) were obtained after annealing at 200 °C. Furthermore, the thermal stability of the films could be enhanced by a multi-step annealing process due to the recrystallization effect.     

Al3+ doping induced changes of structural,morphology, photoluminescence,optical and electrical properties of SnO2 thin films as alternative TCO for optoelectronic applications

Highly transparent and conductive pure (SnO₂) and aluminum doped tin oxide (Al:SnO₂) thin films were deposited on glass substrates by the sol-gel spin-coating method. The structural, morphological, optical and electrical properties of the prepared thin films at different doping rates have been studied. X-ray diffraction results revealed that all the films were polycrystalline in nature with a tetragonal rutile structure. SEM images of the analyzed films showed a homogeneous surface morphology, composed of nanocrystalline grains. The EDS results confirmed the presence of Sn and O elements in pure SnO₂ and Sn, O, Al in doped SnO₂ thin films. The optical results revealed a high transmittance greater than 85% in the visible and near infrared and a band gap varying between 3.82 and 3.89 eV. PL spectra at room temperature showed that the most dominant defects correspond to oxygen vacancies. A low resistivity of order varying between 10^?3 and 10^?4 Ω cm and a high figure of merits ranging between 10^?3 and 10^?2 Ω^?1 in the visible range were obtained. The best performances were obtained for samples containing 2 at. % Al, which could be used as an alternative TCO layer for future optoelectronic devices.     

Essential Macleod Program (EMP) simulated fabrication of high quality Zn:SnO2/Ag/Zn:SnO2 multilayer transparent conducting electrode on flexible substrates

In the quest of promising Indium free amorphous transparent conducting oxide (TCO), Zn-doped SnO₂/Ag/Zn-doped SnO₂ (OMO) multilayer films were prepared on flexible polyethylene terephthalate (PET) substrates by RF sputtering at room temperature (RT). Growth parameters were optimized by varying sputtering power and working pressure, to have high electrical conductivity and optical transmittance. Optimization of the thickness of each layer was done by Essential Macleod Program (EMP) simulation to get the higher transmission through OMO multilayer. The sheet resistance and transmittance of 3 at% Zn-doped SnO₂ thin film (30 nm) were 2.23 kΩ/□, (ρ ~ 8.92×10⁻³ Ω∙cm) and 81.3% (at λ ~ 550 nm), respectively. By using optimized thicknesses of Zn-doped SnO₂ (30 nm) and Ag (12 nm) and optimized growth condition Zn-doped SnO₂/Ag/Zn-doped SnO₂ multilayer thin films were deposited. The low sheet resistance of 7.2 Ω/□ and high optical transmittance of 85.1% in the 550 nm wavelength region was achieved with 72 nm multilayer film.     

Preparation and properties of AZO/PS/AZO tri-layer transparent conductive film with a light-trapping structure

The light-trapping structure is an effective method to increase solar light capture efficiency in the solar cells. In this study, Al-doped ZnO (AZO)/polystyrene (PS)/AZO tri-layer transparent conductive film with light-trapping structure was fabricated by magnetron sputtering and liquid phase methods. The structural, optical and electrical properties of the AZO films could be controlled by different growth conditions. When the sputtering pressure of the under-layer AZO film was 0.2 Pa, the discharge voltage was around 80 V, which was within the optimal process window for obtaining AZO film with high crystallinity. The optimal under-layer AZO film had a large surface roughness and a very low static water contact angle of 75.71°, promoting the relatively uniform distribution of PS spheres. Under this sputtering condition, the prepared AZO/PS/AZO tri-layer film had the highest crystallinity and least point defects. The highest carrier concentration and Hall mobility are 3.0 × 10²¹ cm^-3and 5.39 cm² V^-1 s^-1, respectively. Additionally, a transparent conductive film with the lowest resistivity value (3.88 × 10^-4 Ω cm) and the highest average haze value (26.5%) was obtained by optimizing the process parameters. These properties were comparable to or exceed the reported values of surface-textured SnO₂-based as well as ZnO-based TCOs films, making our films suitable for transparent electrode applications, especially in thin-film solar cells.     

Structural,electrical, and optical properties of Sb-doped SnO2 transparent conductive oxides fabricated using an electrospray technique

Sb-doped SnO₂ (ATO) thin films, for use as transparent conductive oxides (TCOs), were synthesized using an electrospray technique, and their structural, electrical, and optical properties were investigated. To elucidate the optimum fabrication conditions for the best electrical and optical properties, ATO thin films were calcined using four different temperatures, 450 °C, 550 °C, 650 °C, and 750 °C. When calcined at 650 °C, ATO thin films exhibit excellent resistivity (~8.14×10⁻³ Ω cm), superior transmittance (~91.4% at 550 nm), and good figure of merit (~11.4×10⁻⁴ Ω⁻¹) compared to the other samples. The enhanced properties of ATO thin films are attributed to high densification without formation of cracks, and the increased grain size of ATO nanoparticles.     

Laser absorption and infrared stealth properties of Al/ATO composites

In this work, an Al powder was coated with antimony-doped tin oxide (ATO) to obtain an infrared-laser compatible stealth material. The composites are prepared via a coprecipitation method, characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and measured by ultraviolet spectrophotometer and dual band infrared emissometer. The morphology and microstructure show that the flaky Al powder was coated by the ATO nanoparticles and doped into the SnO₂ rutile structure by an Sb⁵⁺ ion_. The optimal Al content was 20%, and the optimized Sn/Sb molar ratio was 10: 1. Meanwhile, the reflectivity of the composites was 43.454%, and the infrared emissivity in 8–14 μm far infrared waveband range was 0.708. It may shed light on a new material design orientation to obtain high performance laser-infrared compatible stealth materials.     

Study on the wet processable antimony tin oxide (ATO) transparent electrode for PLEDs

A polymer light emitting diodes (PLEDs) was fabricated using the wet processable antimony tin oxide (ATO) as the transparent electrode by spin coating method. PLED were fabricated with ATO (or ITO)/PEDOT:PSS/polymer/BaF₂/Ba/Al configurations. Electrical and optical properties of ATO transparent electrode were measured. Transmittance of ATO thin film was more than 90% in the visible region, sheet resistance was 30 Ω/□ and had a strong solvent resistance. The maximum brightness and maximum efficiency of PLED device using an ATO transparent electrode was 3637 cd/m² and 1.03 cd/A, respectively.     

Highly conducting and transparent antimony doped tin oxide thin films: the role of sputtering power density

Sb doped SnO₂ thin films were deposited on quartz substrates by magnetron sputtering at 600 °C and the effects of sputtering power density on the preferential orientation, structural, surface morphological, optical and electrical properties had been studied. The XRD analyses confirm the formation of cassiterite tetragonal structure and the presence of preferential orientation in (2 1 1) direction for tin oxygen thin films. The dislocation density analyses reveal that the generated defects can be suppressed by the appropriate sputtering power density in the SnO₂ lattice. The studies of surface morphologies show that grain sizes and surface roughness are remarkably affected by the sputtering power density. The resistivity of Sb doped SnO₂ thin films gradually decreases as increasing the sputtering power density, reaches a minimum value of 8.23×10⁻⁴ Ω cm at 7.65/cm² and starts increasing thereafter. The possible mechanisms for the change in resistivity are proposed. The average transmittances are more than 83% in the visible region (380–780 nm) for all the thin films, the optical band gaps are above 4.1 eV. And the mechanisms of the variation of optical properties at different sputtering power densities are addressed.     

Polypropylene filled with kaolinite-based conductive powders

Antimony doped tin oxide nanoparticles (Sb–SnO₂) were uniformly coated on the surfaces of rod-/flake-like kaolinites (Kaol) to synthesize kaolinite-based conductive powders (Sb–SnO₂)Kaol, which was then added into polypropylene (PP) matrix to produce conductive (Sb–SnO₂)Kaol–PP nanocomposites. The effects of (Sb–SnO₂)Kaol characteristics on the volume resistivity and mechanical properties of (Sb–SnO₂)Kaol–PP were in detail investigated. The results indicated that surface-modified (Sb–SnO₂)Kaol could improve the dispersion in PP matrix, and the as-synthesized nanocomposites showed better electrical property than that without surface modification. The volume resistivity of (Sb–SnO₂)Kaol–PP reached 7.3 × 10⁸ Ω·cm at the (Sb–SnO₂)Kaol concentration of 40%, 6–7 order of magnitude lower than that of pure PP. The as-synthesized (Sb–SnO₂)Kaol–PP nanocomposites could show potential applications in the conductive fields.     

Synthesis and characterization of Sb–SnO2/kaolinites nanoparticles

In this paper, we reported the synthesis of composite conductive powders of antimony-doped tin oxide (Sb–SnO₂) coated onto kaolinite. Structure and morphology of the samples were systematically characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectrum (XPS). The results showed that Sb–SnO₂ nanoparticles (< 10 nm) were successfully coated as thin layers on the surface of kaolinite. The antimony-doped tin oxide/kaolinite (ATK) composites retained the flake morphology like the original kaolinite and had a resistivity of 273.2 Ω·cm. Sb–SnO₂ layers were proved to attach to the kaolinite surface via the Sn–O–Si or Sn–O–Al bonds. The growth mode of Sb–SnO₂ layers onto the kaolinite was investigated.     

Structural, Electrical and Optical Properties of p-Type Transparent Conducting SnO2:Zn Film

Highly transparent, p-type conducting SnO₂:Zn films were deposited on quartz substrates by radio frequency (RF) magnetron sputtering using a 12 wt% ZnO doped with 88 wt% SnO₂ ceramic target followed by annealing at various temperatures. The effect of annealing temperature on the structural, electrical and optical performances of SnO₂:Zn films has been studied. XRD results show that all the SnO₂:Zn films possess tetragonal rutile structure with the preferred orientation of (101). Hall effect results indicate that at 873 K for 3 h was the optimum annealing parameters for p-type SnO₂:Zn films with relatively high hole concentration and low resistivity of 3.334 × 10¹⁹ cm⁻³ and 3.588 Ω cm, respectively. The average transmission of the p-type SnO₂:Zn films were above 80% in the visible light range. In addition, p-type conductivity was also confirmed by the non-linear characteristics of a p-type SnO₂:Zn/n-type SnO₂:Sb structure.     

Improved electrical and optical properties in epitaxial Cd2SnO4 films

Epitaxial Cd₂SnO₄ films were fabricated on MgO(00l) single crystalline substrates by pulsed laser deposition technique at various substrate temperatures and growth oxygen pressures. The microstructure, transport, and optical properties of the films were studied in detail. High-resolution X-ray diffraction and high-resolution transmission electron microscopy results demonstrate that all the Cd₂SnO₄ films are grown epitaxially on MgO(00l) substrates. Atomic force microscope images indicate that the films have smooth surface morphologies. Hall-effect measurements reveal that the epitaxial film grown at 680^°C and 40 Pa presents the minimum resistivity value of 0.61 mΩcm and maximal Hall mobility of 32.87 cm² V⁻¹ s⁻¹. The metal–semiconductor transitions of Cd₂SnO₄ films were observed and explained by competitive effects of two conductive mechanisms. The optical transmittance of the Cd₂SnO₄ films is higher than 75% in the visible and near-infrared range, and the optical bandgap was determined to be about 3.09 eV for the film grown at optimal condition. The band structure and density of states of the Cd₂SnO₄ were calculated by the density functional theory.     

Structural,photoelectrical and photoluminescence properties of Ta-doped SnO2 monocrystal films grown on MgF2 (110) substrates

Epitaxial Ta-doped SnO₂ films with Ta concentrations from 0 to 8?at.% have been deposited on MgF₂ (110) substrates by the metal-organic chemical vapor deposition (MOCVD) method. The effects of Ta doping on the structural, photoelectrical and photoluminescence (PL) properties of the obtained films were studied in detail. The results showed that the single crystal rutile SnO₂ films were obtained and the heteroepitaxial relationship was SnO₂ (110) || MgF₂ (110) with SnO₂ [001] || MgF₂ [001]. The highest Hall mobility of 74.2?cm²?V^?1?s^?1 was achieved for the 5?at.% Ta-doped SnO₂ film and the minimum resistivity as low as 2.5?×?10^?4?Ω?cm was obtained at 6?at.% of Ta-doping. In the visible region, all the obtained films had average transmittances exceeding 87%. As the Ta concentration increased from 0 to 8?at.%, the optical band gap of the films rose from 3.89 to 4.32?eV. The room temperature PL spectra of Ta-doped SnO₂ films showed intense green emission, weak violet and yellow emissions. The corresponding PL mechanisms were discussed.     

SnO2 nano-spheres/graphene hybrid for high-performance lithium ion battery anodes

SnO₂ nano-spheres/graphene composite was fabricated via a simple one-step hydrothermal method with graphene oxide and SnCl₄·5H₂O as the precursors. The composite was characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and surface area measurement. It is shown that fine SnO₂ nano-spheres with an average size of 50–100 nm could be homogeneously deposited on graphene nano-sheets layer by layer. The structural feature enabled SnO₂ nano-spheres/graphene hybird as an excellent anode material in lithium ion battery. The composite possesses 1306 mA h g^?1 of initial discharge capacity and good capacity retention of 594 mA h g^?1 up to the 50th cycle at a current density of 100 mA g^?1. These results indicate that the composite is a promising anode material in high-performance lithium ion batteries.     

Carbon-coated SnO2/graphene nanosheets as highly reversible anode materials for lithium ion batteries

A simple approach is reported to prepare carbon-coated SnO₂ nanoparticle–graphene nanosheets (Gr–SnO₂–C) as an anode material for lithium ion batteries. The material exhibits excellent electrochemical performance with high capacity and good cycling stability (757 mA h g^?1 after 150 cycles at 200 mA g^?1). The likely contributing factors to the outstanding charge/discharge performance of Gr–SnO₂–C could be related to the synergism between the excellent conductivity and large area of graphene, the nanosized particles of SnO₂, and the effects of the coating layer of carbon, which could alleviate the effects of volume changes, keep the structure stable, and increase the conductivity. This work suggests a strategy to prepare carbon-coated graphene–metal oxide which could be used to improve the electrochemical performance of lithium ion batteries.     

Low temperature processed SnO2 films using aqueous precursor solutions

We present a comparison study of the microstructure developments during aqueous solution deposition of SnO₂, particularly, through chemical bath deposition (CBD) and liquid phase deposition (LPD) at very low temperatures (40–75 °C). The effects of solution chemistry on the microstructural details and electrical properties of SnO₂ thin films are presented and discussed. Smooth, nanoparticulate SnO₂ films were obtained from supersaturated precursor solutions with lower precursor concentrations while more aggregated SnO₂ films were generated from higher precursor concentrations. Loosely-packed and porous structures were obtained from low supersaturation solutions with very low pHs. The deposition rates were also evaluated under various deposition conditions. XRD result shows that annealing process helps improve the degree of crystallinity of the as-deposited films that are composed of 3–10 nm nanocrystalline particles. One advantage of LPD of SnO₂ films is in-situ fluorine doping during deposition. The resulting electrical resistivity of F-doped SnO₂ films was about 18.7 Ω cm after the films were annealed at 450 °C.     

Nonaqueous and template-free synthesis of Sb doped SnO2 microspheres and their application to lithium-ion battery anode

Antimony doped SnO₂ (ATO) microspheres composed of ATO nanoparticles were prepared by using a hydrothermal process in a nonaqueous and template-free solution from the inorganic precursors (SnCl₄ and Sb(OC₂H₅)₃). The physical properties of the as-synthesized samples were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption isotherms, and X-ray photoelectron spectrum (XPS). The resulting particles were highly crystalline ATO microspheres in the diameter range of 3-10 μm and with many pores. The as-prepared samples were used as negative materials for lithium-ion battery, whose charge-discharge properties, cyclic voltammetry, and cycle performance were examined. The results showed that a high initial discharge capacity of 1981 mAh g⁻¹ and a charge capacity of 957 mAh g⁻¹ in a potential range of 0.005-3.0 V was achieved, which suggests that tin oxide-based materials work as high capacity anodes for lithium-ion rechargeable batteries. The cycle performance is improved because the conducting ATO nanoparticles can also perform as a better matrix for lithium-ion battery anode.     

Synthesis of large-area graphene on molybdenum foils by chemical vapor deposition

We report the synthesis of large-area graphene films on Mo foils by chemical vapor deposition. X-ray diffraction indicates that the dissolution and segregation process governs the growth of graphene on Mo foils. Among all processing parameters investigated, the cooling rate is the key one to precisely control the thickness of graphene film. By optimizing the cooling rate between 1.5 and 10 °C/s, we managed to achieve graphene films ranging from mono- to tri-layer. Their uniformity and thickness were confirmed by Raman spectroscopy and optical measurements. The carrier mobility of films reaches as high as 193 cm² V^?1 s^?1. Our experiments show that the Mo substrate has the similar simplicity and large tolerance to processing conditions as Cu.     

Strain effects in epitaxial La-doped SrSnO3 films on lattice-matched PMN-PT substrates

Here we report the effect of the strain states on the structure, optical and electrical transport properties of the La_0.05Sr_0.95SnO₃ (LSSO) thin films grown epitaxially on (001)-oriented 0.70 Pb(Mg_1/3Nb_2/3)O₃-0.30PbTiO₃ (PMN-PT) substrates by pulsed laser deposition. X-ray diffraction results indicate that the films are fully strained up to at least 100 nm thickness, and the in-plane compressive strain gradually releases in thicker films. High-resolution transmission electron microscopy characterizations demonstrate that the LSSO films were grown coherently on PMN-PT(001) substrates. With varying the thicknesses of the fully strained films from 20 to 100 nm, the electrical transport properties are improved significantly. A lowest room-temperature resistivity of 1.88 mΩcm and the highest mobility of 28.1 cm²/Vs are obtained in the 100 nm film. The optical band gap determined from spectroscopic ellipsometry is found to increase from 4.58 to 4.88 eV with the film thicknesses varying from 20 to 500 nm. The results imply that the LSSO epitaxial films exhibit tunable electrical performances and optical band gaps through strain, which may have potential applications in optoelectrical devices.