Transparent Conducting Metal Oxides Research Articles

Structural, electrical and nonlinear optical characterization of Sn-doped CdO thin film synthesized via spray pyrolysis for optoelectronic applications

Transparent conducting metal oxides (TCOs) are well known for their application in optoelectronic devices. However, the nonlinear optical (NLO) study of TCOs helps to understand the characteristic features which give insight into their practical utilization as well as device application in each optical spectrum. In this work, we studied the structural, electrical, optical, and nonlinear optical properties of Sn-doped CdO. The structural, electrical, optical, and nonlinear optical properties of Sn-doped CdO were studied by using an X-ray diffractometer (XRD), Hall measurement system, UV–vis spectrometer, and Z-scan measurement. The XRD analysis shows that Sn-doped CdO is a polycrystalline material with a preferential peak of a plane (111) shifting slightly toward the (200) plane as Sn doping suddenly increases. Sn-doped CdO proved good electrical properties with conductivity increase from 0.192 × 102 Ω−1 cm−1 to 2.03 × 102 Ω−1 cm−1 and decrease in resistivity from 52.1 × 10−3 Ωcm to 4.92 × 10−3 Ωcm as the molar dopant concentration increase from 0.0001 M to 0.0005 M. The obtained bandgap for undoped and 0.0005 M, 0.0004 M, 0.0003 M, 0.0002 M, 0.0001 M Sn-doped CdO are 2.37, 1.63, 1.70, 1.81, 1.86, and 2.09 respectively. The NLO absorption coefficient (β) for 0.0003 M, 0.0004 M and 0.0005 M are 6.31 × 10−3 m/W, 11.47 × 10−3 m/W and 10.6 × 10−3 m/W respectively.

Transparent conducting metal oxides nanoparticles for solution-processed thin films optoelectronics

Semiconductor nanomaterials, and in particular, metal oxides offer great functionality and versatility for many applications at the forefront of material science research. One of the most significant advantage of these compounds at the nanoscale, both for the technological and commercial implications, is the solution synthesis and the consequent exploitation of solution processing. In this work, we present a detailed analysis of ITO nanoparticles solution deposition via the spin coating technique, considering its most common use in optoelectronics as thin films. The results and discussion can provide a list of guidelines for the optimization in the use of these class of materials.

Sub-500 nm patterned synthesis of corrosion resistant SnO2 and Pt@SnO2 using metal-organic precursor

In this study, a thin film of transparent conducting metal oxide, SnO2, is obtained using a novel metal-organic precursor, Sn-TOABr complex. The precursor is synthesized by phase-transferring tin from the aqueous layer to the liquid-liquid interface. The formed precursor is used for depositing SnO2 thin films over arbitrary and even large substrates via the modified atmospheric pressure chemical vapor deposition (MAPCVD) method in a simple furnace at 450 °C. The vapor-deposited SnO2 thin films are crystalline, semiconducting, highly transparent with excellent mechanical robustness against scratch and scotch tape tests, and resistant towards corrosive media. The obtained robust thin films via this MAPCVD technology expand applications towards protective coatings for arbitrary substrates. Using a simple direct micromolding technique, sub-500 nm patterns of SnO2 and Pt@SnO2 were obtained. This single-step soft lithography patterning technique, besides being cost-effective, offers a large throughput.

Detection of H2S gas sensing performance of sol gel prepared metal oxide (In2O3, SnO2, Sn doped In2O3) thin films

Gas monitoring and control of hazardous and polluting gases (CO, H2S, CH4, H2, NH3, and alcohol) are required in industrial and laboratory applications where air quality must be regulated to protect public health, the environment, and security. Transparent conducting metal oxide semiconductors (TCO) have been shown to be extremely sensitive to both reducing and oxidising gases. They are caused by a lack of oxygen, also known as anion deficit. The present emphasis of scientific and technical endeavours is to improve the selectivity, stability, and practicability of response. Wide bandgap semiconducting oxides such as SnO2, In2O3 and Sn doped In2O3 have long been employed in gas sensing. The sensitivity of the gas sensor has increased as the thickness of the metal oxide semiconductor film or particle used to produce it has decreased. In the presence of reducible gases and adsorbed oxygen on the crystal surface, the conductivity is lowered by surface potential, when SnO2 is heated to high temperature, however, conductivity increases noticeably for In2O3 and indium tin oxide films. Indium oxide and tin oxide gas sensors detected H2S gas at working temperatures of 115 °C and 120 °C, respectively. Response and recovery times for indium oxide ranged from 10 s to 26 s and 34 s to 91 s, respectively, and for tin oxide from 3 s to 37 s and 82 s to 40 s. At 100 °C working temperature, ITO sensors with 10% tin concentration had the highest H2S sensitivity.

Synthesis of thin-film layers of electrochromic panels based on SnO2 and WO3 by aerosol pyrolysis

Energy efficiency and energy saving are actively developing. One of the promising areas of optoelectronics is the improvement of electrochromic panels or smart glasses. Smart glasses are divided into electrochromic, thermochromic and photochromic. The devices incorporate thin-film structures that are transparent conductive oxide (TCO) and transition metal oxide (TMO). An urgent scientific task is a systematic comprehensive study of the parameters of specified thin films, as well as the improvement of methods for their synthesis to obtain coatings with specified properties. A promising and most suitable method for the synthesis of the above-listed coatings is the method of aerosol pyrolysis, which has a number of advantages: ease of implementation and the possibility of embedding into the finished technological process while maintaining the coating quality. The article analyzes the results of the study of the following coatings parameters: the efficiency of coloring; TMO response time; the TCO throughput and conductivity.

All‐Printed Multilayers and Blends of Poly(dioxythiophene) Derivatives Patterned into Flexible Electrochromic Displays

AbstractLow‐cost, flexible and thin display technology is becoming an interesting field of research as it can accompany the wide range of sensors being developed. Here, the synthesis of poly(dimethylpropylene‐dioxythiophene) (PProDOT‐Me2) by combining vapor phase polymerization and screen printing is presented. A multilayer architecture using poly(3,4‐ethylenedioxythiophene) (PEDOT) and PProDOT‐Me2 to allow for electrochromic switching of PProDOT‐Me2, thereby eliminating the need for a supporting transparent conductive (metal oxide) layer is introduced. Furthermore, the technology is adapted to a blended architecture, which removes the additional processing steps and results in improved color contrast (∆E* > 25). This blend architecture is extended to other conductive polymers, such as PEDOT and polypyrrole (PPy), to highlight the ability of the technique to adjust the color of all‐printed electrochromic displays. As a result, a green color is obtained when combining the blue and yellow states of PEDOT and PPy, respectively. This technology has the potential to pave the way for all‐printed multicolored electrochromic displays for further utilization in printed electronic systems in various Internet of Things applications.

The characterization of various TCOs and metal oxide layers for dye sensitized solar cells

Dye sensitized solar cells have gained great interest for one decade because of easy fabrication and low cost. In this study, we synthesized various transparent conductive oxide (TCO) electrodes and metal oxide layers in laboratory for dye sensitized solar cells via spray pyrolysis technique. XRD results confirmed that the antimony doped tin oxide (ATO), flor doped tin oxide (FTO) and indium tin oxide (ITO) thin film TCO electrodes were fabricated successfully. UV–Vis spectrometer was employed to obtain transmittance and band gap energy values of the films. According to the UV–Vis spectrometer, all TCO films almost have 80% optical transmittance. The sheet resistance values were obtained by four-point probe technique for all TCO electrodes. SEM was performed for surface morphology of the TCO electrodes and SnO2, ZnO and Zn doped TiO2 metal oxides on the various TCOs. The TCO electrodes and metal oxide layers have homogeneous surfaces.

Gallium-Doped Zinc Oxide Nanoparticle Thin Films as Transparent Electrode Materials with High Conductivity

Gallium-doped zinc oxide (GZO) nanoparticles (NPs) have been synthesized by a solvothermal synthesis method using gallium chloride and zinc chloride as precursors in anhydrous methanol along with bases. Systematic investigations have revealed that H2O, formed through the condensation of metal hydroxides to obtain GZO NPs, not only enhances the production of layered compounds as byproducts but also accelerates Ostwald ripening to reduce the amount of doped gallium ions. To overcome H2O generation during NP growth, we first applied sodium methoxide (NaOMe) as a base for the synthesis of GZO NPs. As a result, high-performance GZO NPs were successfully obtained in a single phase, and the mean particle size of the GZO NPs was controlled from 10 to 35 nm by changing the molar ratio of the sodium hydroxide (NaOH) and NaOMe in the reaction mixture. We further applied the obtained GZO NPs to prepare GZO NP-based transparent conductive metal oxide (TCO) films using an NP-mist deposition strategy as our developed NP-coating method on substrates. The resistivity and transparency of the deposited GZO thin films were compared with those of conventional thin films prepared by a dispersion coating method, showing that NP-mist deposition is a promising method for fabricating high-performance GZO NP-based TCO thin films on substrates under mild atmospheric conditions.

Flexible electrochromic tape using steel foil with [formula omitted] thin film

Intercalation of lithium ions into the crystal lattice of tungsten trioxide is one of the most researched electrochromic mechanisms. Conventional electrochromic devices (ECDs) utilize electrodes made of thin layer coatings of WO3 on optically transparent conductive polymer or metal oxide substrates. A majority of Li+-WO3 based ECDs is built in the so-called “sandwich” configuration, where the optically transparent electrode (OTE) is placed directly on top of the Li+-based electrolyte which separates it from the counter electrode. It is shown here that stainless steel foils can replace conventional electrode substrates with the advantage of higher electrical conductivity and mechanical flexibility. In addition, the so-called “inverted sandwich” ECD architecture is introduced which allows for fabrication of devices without the use of at least one OTE. Electrochromic tape with two stainless steel based electrodes, coated with WO3 and pencil lead carbon, is presented and characterized both electrochemically and optically.

CALCULATION OF THE ELECTRONIC EFt ECTIVE MASS OF TRANSPARENT CONDUCTING METAL OXIDES USED IN OPTOELECTRONIC DEVICES

Transparent conducting metal oxides had become an extremely important in many applications including solar cells, microelectronics, electrochromic displays, heat min-ors and gas sensors. It has high electrical conductivity, high optical transparency in the visible region of the solar spectrum and high reflectivity in the infrared region of the solar spectrum.In this work thin films of Indium Tin Oxide (ITO) were vacuum deposited using an electron beam evaporator Analysis of the films was performed using spectrophotometric , X-ray diffraction and the standard electrical measurement (mobility and resistivity). A model for the free electrons concentration as a function of the carriers effective mass in heavily doped metal oxide semiconductors is introduced. This model is applied on the results of this experimental work and on some of the published data as well. The optimum concentration of the free electrons in indium tin oxide was found to be when the electron effective mass lies between 0.29 mo and 0.32 ma . These results agree with the experimentally measured and published data.

Assessment of horizontal velocity fields in square thermal convection cells with large aspect ratio

Transparent heating plates, consisting of glass coated with a transparent conductive metal oxide, are applied in large aspect ratio turbulent Rayleigh–Benard convection (RBC) to investigate the large-scale patterns of velocity fields with optical flow measurement techniques across the whole horizontal cross section. The square convection cell with an aspect ratio Γ = L/h = 10 was tested inside the scaled convective airflow laboratory experiment (SCALEX) facility which enables experiments with gases as working fluids for pressures of up to 10 bar to achieve very high Rayleigh numbers Ra. For the current study, Ra = 2 × 104 was applied. The velocity fields are measured with 2D3C particle image velocimetry (PIV). The possibility of reliable PIV measurements with reproducible homogenous temperature boundary conditions was demonstrated in the SCALEX facility. The seeding of the tracer particles, their illumination and data evaluation are addressed in detail. The final comparison of experimental data and numerical simulations shows a good agreement for the probability density functions of the horizontal velocity components. Deviations for the vertical out-of-plane velocity component and their dependence on the thickness of the laser sheet are discussed in detail and quantified by measurements with light sheets of different thickness.

Improved opto-electrical properties of spray deposited ytterbium doped cadmium oxide thin films

Transparent conducting metal oxides (TCOs) associate the properties of high optical transparency and electrical conductivity, which makes them suitable for variety of applications such as window layer in liquid crystal and electroluminescent display devices as well as in solar cells. Among different TCO’s, cadmium oxide (CdO) has received tremendous attention as a potential alternative to Sn-doped In2O3 (ITO) due to its high intrinsic dopability coupled with outstanding mobility and high electrical conductivity. In the present study, for first time the doping of ytterbium (Yb) into CdO films prepared using a simple and effective spray pyrolysis technique demonstrated. The structural, morphological and optoelectronic properties of Yb doped CdO thin films as a function of Yb concentration (1–3 at.%) have been studied. X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, optical absorption spectroscopy, luminescence measurements and for electrical properties Hall effect set up in van der Pauw configuration have been employed to study the properties of Yb-doped CdO thin films. Yb doped CdO thin films exhibit excellent optical transparency, with an average transmittance over 75% in the visible region. It is found that Yb doping widens the optical band gap from 2.63 to 2.88 eV, via a Moss–Burstein shift and further decreases to 2.77 eV. The maximum reflectivity of 97.24% achieved for 2.5 at.% Yb:CdO film. The better values of resistivity, carrier concentration, mobility and figure of merit have been obtained for 2.5 at.% Yb:CdO, which are 2.6 × 10−4 Ω cm, 13.9 × 1020 cm−3, 17.39 cm2/Vs and 45.87 × 10−3 (Ω)−1 respectively. The obtained results revealed that Yb dopant has a significant influence on the optoelectronic properties of CdO-based TCO compound.

Quantum chemical calculations of $$\hbox {Cr}_{2}\hbox {O}_{3}/\hbox {SnO}_{2}$$ Cr 2 O 3 / SnO 2 using density functional theory method

Quantum chemical calculations have been employed to study the molecular effects produced by $$\hbox {Cr}_{2}\hbox {O}_{3}/\hbox {SnO}_{2}$$ optimised structure. The theoretical parameters of the transparent conducting metal oxides were calculated using DFT / B3LYP / LANL2DZ method. The optimised bond parameters such as bond lengths, bond angles and dihedral angles were calculated using the same theory. The non-linear optical property of the title compound was calculated using first-order hyperpolarisability calculation. The calculated HOMO–LUMO analysis explains the charge transfer interaction between the molecule. In addition, MEP and Mulliken atomic charges were also calculated and analysed.

Tracking Single DNA Nanodevices in Hierarchically Meso-Macroporous Antimony-Doped Tin Oxide Demonstrates Finite Confinement.

Housing bio-nano guest devices based on DNA nanostructures within porous, conducting, inorganic host materials promise valuable applications in solar energy conversion, chemical catalysis, and analyte sensing. Herein, we report a single-template synthetic development of hierarchically porous, transparent conductive metal oxide coatings whose pores are freely accessible by large biomacromolecules. Their hierarchal pore structure is bimodal with a larger number of closely packed open macropores (∼200 nm) at the higher rank and with the remaining space being filled with a gel network of antimony-doped tin oxide (ATO) nanoparticles that is highly porous with a broad size range of textual pores mainly from 20-100 nm at the lower rank. The employed carbon black template not only creates the large open macropores but also retains the highly structured gel network as holey pore walls. Single molecule fluorescence microscopic studies with fluorophore-labeled DNA nanotweezers reveal a detailed view of multimodal diffusion dynamics of the biomacromolecules inside the hierarchically porous structure. Two diffusion constants were parsed from trajectory analyses that were attributed to free diffusion (diffusion constant D = 2.2 μm2/s) and to diffusion within an average confinement length of 210 nm (D = 0.12 μm2/s), consistent with the average macropore size of the coating. Despite its holey nature, the ATO gel network acts as an efficient barrier to the diffusion of the DNA nanostructures, which is strongly indicative of physical interactions between the molecules and the pore nanostructure.

Low‐Temperature‐Processed Printed Metal Oxide Transistors Based on Pure Aqueous Inks

Additive patterning of transparent conducting metal oxides at low temperatures is a critical step in realizing low‐cost transparent electronics for display technology and photovoltaics. In this work, inkjet‐printed metal oxide transistors based on pure aqueous chemistries are presented. These inks readily convert to functional thin films at lower processing temperatures (T ≤ 250 °C) relative to organic solvent‐based oxide inks, facilitating the fabrication of high‐performance transistors with both inkjet‐printed transparent electrodes of aluminum‐doped cadmium oxide (ACO) and semiconductor (InOx). The intrinsic fluid properties of these water‐based solutions enable the printing of fine features with coffee‐ring free line profiles and smoother line edges than those formed from organic solvent‐based inks. The influence of low‐temperature annealing on the optical, electrical, and crystallographic properties of the ACO electrodes is investigated, as well as the role of aluminum doping in improving these properties. Finally, the all‐aqueous‐printed thin film transistors (TFTs) with inkjet‐patterned semiconductor (InOx) and source/drain (ACO) layers are characterized, which show ideal low contact resistance (Rc < 160 Ω cm) and competitive transistor performance (µlin up to 19 cm2 V−1 s−1, Subthreshold Slope (SS) ≤150 mV dec−1) with only low‐temperature processing (T ≤ 250 °C).

Sensing photosynthetic herbicides in an electrochemical flow cell.

Specific inhibitory reactions of herbicides with photosynthetic reaction centers bound to working electrodes were monitored in a conventional electrochemical cell and a newly designed microfluidic electrochemical flow cell. In both cases, the bacterial reaction centers were bound to a transparent conductive metal oxide, indium-tin-oxide, electrode through carbon nanotubes. In the conventional cell, photocurrent densities of up to a few μA/cm2 could be measured routinely. The photocurrent could be blocked by the photosynthetic inhibitor terbutryn (I 50=0.38±0.14μM) and o-phenanthroline (I 50=63.9±12.2μM). The microfluidic flow cell device enabled us to reduce the sample volume and to simplify the electrode arrangement. The useful area of the electrodes remained the same (ca. 2cm2), similar to the classical electrochemical cell; however, the size of the cell was reduced considerably. The microfluidic flow control enabled us monitoring in real time the binding/unbinding of the inhibitor and cofactor molecules at the secondary quinone site.

Photoelectrochemical investigation of bare transparent conducting oxides for water oxidation

Bare tin-doped indium oxide (ITO) and fluorine-doped tin oxide (FTO), which are widely used transparent conducting metal oxide as anode materials for various electrochemical applications, are not used as anode materials for photoelectrochemical (PEC) oxidation of water as those required high potential to obtain efficient oxidation of water. To reduce the oxidation potential, tedious modification with photoelectrocatalyst is required. A straightforward alternative of using the modified electrode would be established if any bare metal oxide could be used as an efficient electrode material for water oxidation. Here, we report for the first time that commercially available bare gallium doped zinc oxide (GZO) has great potential to be utilized as an anode material for efficient PEC water oxidation at low potential under UV–Vis light. The higher performance of GZO was revealed by comparing the PEC behavior of other commercially available and frequently employed transparent conductive metal oxide electrodes, namely, ITO, FTO, and aluminum-doped zinc oxide. The GZO and AZO show the highest and second highest water oxidation signal, respectively, among the tested electrodes. Moreover, the GZO shows higher stability as compared to AZO under applied experimental conditions. ITO electrode also exhibited a good stability but its efficacy towards water oxidation was the lowest. The efficiency of the GZO toward PEC water oxidation at 0.6 V is ca. 36.5 times higher than that obtained at ITO.

Nanostructured CdO thin films for water treatments

CdO was the very first transparent conducting metal oxide discovered. CdO thin films show electrical and optical properties of interest as photosensitive anode materials for photochemical cells, phototransistors, photodiodes, window electrodes in liquid crystal displays, IR detectors, antireflection coatings, gas sensors and in other solar energy applications. In the present study we report on the spectroscopic, microscopic, electrical and photo-catalytic properties of CdO thin films prepared by a metal organic chemical vapor method. The degenerate semiconducting CdO thin films are useful as photocatalysts for water treatments.

Topographic and Electronic Properties of 3,4,9,10-Perylene Tetra Carboxylic Dianhydride (PTCDA) on Indium Tin Oxide (ITO) Surface

We present the surface characterization and the local electronic properties of archetypical p-type perylene-based semiconductor organic molecule of Perylene Tetra Carboxylic Dianhydride (PTCDA) thermally evaporated on a transparent conducting metal oxide surface. A modified indium tin oxide (ITO) surface was successfully obtained by employing a subsequent chemical and physical treatment. Physisorbed PTCDA molecules exhibited a stacked-grain structure covering completely ITO surface. Scanning tunneling spectroscopy (STS) spectra of physisorbed PTCDA molecules were performed. In contrast to the previous studies of the homolog n-type perylene derivative thin films, here we successfully extracted both of the outmost frontier energy levels by measuring the current-voltage characteristics of PTCDA molecules in an estimated tunneling resistance from 4.17 to 100 GΩ at room temperature. Using numerical derivative of the I-V spectra, we extracted the series of transport gap of PTCDA molecule are lies in the region of 4.70-4.87 eV.

Bias Polarity‐Induced Transformation of Point Contact Resistive Switching Memory from Single Transparent Conductive Metal Oxide Layer

Bias polarity-induced transformation of point contact resistive switching memory from a single transparent conductive metal oxide layer is demonstrated on three kinds of transparent conductive oxide (TCO) layers, including indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide, as conducting electrode and memristive material by the controllably electrical field simultaneously. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.