Transparent Oxide Films Research Articles

CMOS-Compatible High-Performance Silicon Nanowire Array Natural Light Electronic Detection System.

In this article, we propose a novel natural light detector based on high-performance silicon nanowire (SiNW) arrays. We achieved a highly controllable and low-cost fabrication of SiNW natural light detectors by using only a conventional micromachined CMOS process. The high activity of SiNWs leads to the poor long-term stability of the SiNW device, and for this reason, we have designed a fully wrapped structure for SiNWs. SiNWs are wrapped in transparent silicon nitride and silicon oxide films, which greatly improves the long-term stability of the detector; at the same time, this structure protects the SiNWs from breakage. In addition, the SiNW arrays are regularly distributed on the top of the detector, which can quickly respond to natural light. The response time of the detector is about 0.015 s. Under the illumination of 1 W·m-2 light intensity, multiple SiNWs were detected together. The signal strength of the detector reached 1.82 μA, the signal-to-noise ratio was 47.6 dB, and the power consumption was only 0.91 μW. The high-intensity and highly reliable initial signal reduces the cost and complexity of the backend signal processing circuit. A low-cost and high-performance STM32 microcontroller can realize the signal processing task. Therefore, we built a high-performance SiNW natural optoelectronic detection system based on an STM32 microcontroller, which achieved the real-time detection of natural light intensity, with an accuracy of ±0.1 W·m-2. These excellent test performances indicate that the SiNW array natural light detector in this article meey the requirements of practicality and has broad potential for application.

Niobium Oxide Thin Films Grown on Flexible ITO-Coated PET Substrates

Niobium oxide thin films were grown on both rigid and flexible substrates using DC magnetron sputtering for electrochromic applications. Three experimental series were conducted, varying the oxygen to argon flow rate ratio and deposition time. In the first series, the oxygen to argon ratio was adjusted from 0 to 0.32 while maintaining a constant growth time of 30 min. For the second and third series, the oxygen to argon ratios were fixed at 0.40 and 0.56, respectively, with deposition times ranging from 15 to 60 min. A structural transition from crystalline to amorphous was observed at an oxygen to argon flow rate ratio of 0.32. This transition coincided with a change in appearance, from non-transparent with metallic-like electrical conductivity to transparent with dielectric behavior. The transparent niobium oxide films exhibited thicknesses between 51 nm and 198 nm, with a compact, dense, and featureless morphology, as evidenced by both top-view and cross-sectional images. Films deposited on flexible indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrates displayed a maximum surface roughness (Sq) of 9 nm and a maximum optical transmission of 83% in the visible range. The electrochromic response of niobium oxide thin films on ITO-coated PET substrates demonstrated a maximum coloration efficiency of 30 cm2 C−1 and a reversibility of 96%. Mechanical performance was assessed through bending tests. The ITO-coated PET substrate exhibited a critical bending radius of 6.5 mm. Upon the addition of the niobium oxide layer, this decreased to 5 mm. Electrical resistance measurements indicated that the niobium oxide film mitigated rapid mechanical degradation of the underlying ITO electrode beyond the critical bending radius.

Pulsed Laser Ablation Characteristics of Light-Absorbing Mask Layer Based on Coating Thicknesses under Laser Lift-Off Patterning Process.

Thin transparent oxide layers are typically patterned for use in electronic products including semiconductors, displays, and solar cells for applications such as transparent electrodes, insulating films, and encapsulation films. Conventional patterning methods have traditionally been used in photolithography and lift-off processes. Photolithography employs the wet development process, which has disadvantages such as potential undercut effects, swelling, chemical contamination, and high process costs. On the other hand, laser ablation, which has the advantages of high accuracy, high speed, a noncontact nature, and selective processing, can be used to pattern thin films. However, absorption in transparent oxide films is usually low. In this study, experiments were conducted to determine the ablation characteristics of mask layers. The factors affecting ablation, including beam radii, fluences, overlap ratios, and coating thicknesses, were examined; and the parameters characteristic of residue-free ablation, namely the ablation threshold, minimum fluence, and minimum ablation linewidth, were also examined. The experimental results revealed that the beam radius was an important parameter in determining the resolutions of transparent films and substrates.

Synthesis of multiple layers of alternating ZnO and TiO2 using atomic layer deposition and their optical characterization

We report the optical characterization of bi-layer and quadri-layers of TiO2/ZnO transparent oxide films having a net thickness of 100 nm. The atomic layer deposition (ALD) was used to grow these multiple-layered films. We examined their optical properties to understand the impact of the number of layers. The grazing incidence X-ray diffraction (GIXRD) was used to assess the microstructure of the films, which showed that the ZnO layers were polycrystalline, while the TiO2 layers were (X-ray) amorphous. The optical transmission and reflection spectra of the investigated films were recorded in the range of 150–2500 nm at room temperature. The refractive index (n), extinction coefficient (k), real and imaginary parts of the dielectric constant, optical conductivity, and loss factor agree well with those of other amorphous oxides. It was established that the indirect allowed optical transitions are favorable and the optical gap (Eg) increases from 3.03 eV to 3.14 eV as the number of layers increases. The contribution of polarizability (ξ) and electrical susceptibility (χe) to the dielectric constant was also discussed. The relation between the relative density (D) and the porosity (Pro) with the crystalline quality, layer thickness, and the number of layers was also estimated. The results obtained from the study of TiO2/ZnO multilayer films indicate that multilayer thin films improve the quality of film crystallinity and optical properties with the increase of the layers numbers, and could guide the development of potential applications.

High-Resolution Printing of Various Electronic Materials by Electrophotography

Electrophotography is a digital, on-demand, dry, and page printing technique that operates based on toner particles of electronic materials using an electrostatic force and generates an electrical circuit via distribution of the toner particles. We developed a 10 μm linewidth resolution with various electronic materials, including conductors, semiconductors, and insulators, without any chemical pretreatments on the substrate films, while a 5 μm resolution was also possible for limited materials. The electrical resistivity of the printed Ag–Ni after an intense pulse light sintering was comparable to that of commercial indium tin oxide transparent films.

Analysis of the Chemical Composition and Structure of Micrometer-Thick Complex Oxide Films: A Case Study of a MgAl2O4 Film on SiO2 Using Electron Probe Microanalysis and Confocal Raman Spectroscopy

Methodological approaches to both qualitative structural analysis and quantitative compositional analysis of transparent complex oxide films on dielectric substrates, performed using a Horiba LabRAM HR800 confocal Raman spectrometer and a Cameca SX100 electron probe microanalyzer, are described. The studies were carried out using magnesium–aluminum spinel films of a thickness of 1–3 µm on a quartz glass substrate, obtained by magnetron sputtering. The characterization of the film structure consisted of recording 3D arrays of its Raman spectra based on z depth profiling. The film has a disordered spinel structure with a partially reversed distribution of Mg and Al cations over octa- and tetra-positions. Operation parameters are identified to evaluate the concentration of structure-forming elements (Mg and Al) and impurities (Ti, Cr, Ca, P, Fe, Ni, and Gd) in the film using various X-ray emission lines (optimal accelerating voltage, etc.). The performance of the procedure was determined, and its capabilities and limitations were assessed. The resulting data on the chemical composition of the film are presented.

Sintering densification of ITO targets with low tin oxide content for depositing TCO films as electrodes of solar cells

Highly efficient solar cells demand transparent and conductive oxide films with high electronic mobility. Decreasing SnO2 content in In2O3 targets (ITO) is one of important ways, but resulting in difficulty of sintering densification. ITO targets with SnO2 contents of 1 wt%, 2 wt.% and 3 wt% were prepared by microwave sintering. Harmless sintering additives of TiO2 and trances of SiO2 promotes sintering densification. All the targets show the cubic bixbyite phase and dense microstructure. The fine grains with the average size of several microns were obtained. Higher sintering temperature contributes to eliminating the pores in targets, enhancing density and decreasing resistivity. The optimal sintering temperature of 1550 °C obtains the highest relative density (>99 %) and low resistivity (<3.4 × 10−4 Ω cm). The enhanced density of these ITO targets with low SnO2 content can effectively inhibit the formation of nodules on the surface of target during magnetron sputtering.

High-temperature wear behavior of Tribaloy 400 deposited 17-4 PH stainless steel using spark plasma sintering

Surface modification techniques are extensively utilized to improve the performance of the engineering components in their service life when exposed to elevated temperatures. Herein, the Tribaloy 400 (T 400) particles were deposited on the 17-4 PH stainless steel through the spark plasma sintering (SPS) technique to improve the high-temperature wear resistance of exhaust valve components which are typically manufactured using 17-4 PH stainless steel. The identification of phases, microstructure and the morphology of phases in the coatings, elemental composition and distribution, interfacial behavior, and defects like porosities were investigated using advanced characterization techniques. The obtained results revealed the presence of FCC and HCP – Co along with 52 vol% of laves phases (CoMoSi). The presence of laves phases in the Co matrix, fine grained structure and superior interfacial bond strength were promoted the hardness of the coating (~885 HV) than the substrate (~363 HV). The ball-on-disc wear studies were carried out using alumina balls as counter material at room temperature and high temperature (650 °C). The T 400 coating specimen provided better wear properties than the substrate at both temperature. The specific wear rate obtained for the T 400 coated specimen and 17-4PH substrate at room temperature was found to be 1.29 × 10−5 mm3/Nm and 120 × 10−5 mm3/Nm, whereas at 650 °C, it was found to be 0.037 × 10−5 mm3/Nm and 10.26 × 10−5 mm3/Nm, respectively. In T 400 coating, the developed transparent oxide film at 650 °C decreased the possibilities for metal-to-metal contact between the specimen and the counterpart.

Investigation on highly flexible CZTS solar cells using transparent conductive ZnO/Cu/ZnO films

Transparent conductivity oxide (TCO) films played an essential part in flexible CZTS solar cells (CSCs), which required excellent transparent conductivity and flexibility of TCO films. The inferior flexibility of ITO films, a commonly used material in TCO films, limited the development of flexible CSCs. In this paper, the ZnO/Cu/ZnO (ZCZ) TCO film with high transmittance and flexibility was prepared by radio frequency magnetron sputtering and applied as a transparent conductive layer for flexible CSCs to improve the flexibility of CSCs. The CSCs with ZnO/Cu(9 nm)/ZnO (ZC9Z) film exhibited a power conversion efficiency (PCE) of 6.01% without bending, higher than that of CSCs with ITO film. The PCE ratio of CSCs with ZC9Z film to that of CSCs with ITO film was 5.83 and 9.09 after a bending diameter of 8 mm and 1000 cyclic bending, showing that CSCs with ZC9Z film were of excellent flexibility.

Structural and Electrical Studies of NixSn1-xO2 Sn Dopped Nickel Oxide Thin Film by Jet Nebulizer Spray Pyrolysis Technique for Photodiode and Solar Cell Applications

The dissertation deals with preparation and characterization of NixSn1-xO2 thin films by the jet nebulizer spray pyrolysis technique at optimized temperature 450°C with Ni dopants. The films were analysed to understand the structural, surface morphology, optical and electrical studies for NixSn1-xO2 thin. Moreover, in the case of transparent oxide films, the thickness increases linearly with time of spray. Also, the growth of thin films is temperature dependent. At low temperatures, the growth rate is controlled by activated processes, such as adsorption, surface diffusion chemical reaction and desorption. However, at high temperatures, the activated processes occur so fast and the molecules do not dam up on the substrate. Growth rate also depends on the size of the droplets, because the decomposition of droplet is temperature dependent. If the droplet size is large, the heat absorbed from the surroundings will not be sufficient to vaporize entirely the solvent on the way to the substrate and adversely affect the kinetics of the reaction. The XRD Pattern of NixSn1-xO2 shows the polycrystalline nature with orthorhombic structure and is oriented through (021) direction. The grain size of the prepared films is increased up to x=0.2 and then decreased slightly, for x= 0.8 the grain increases. The conductivity of NixSn1-xO2(x=0) at room temperature is 2.8×10-4s/cm and the other compositions (x=0.2, 0.4, 0.8) show the decrease of conductivity to 2.4×10-6s/cm. The maximum transmittance ( 75%) shows in IR region and 70%of transmittance in the visible region at x=0.4. The band gap value of NixSn1-xO2 films is 2.96, 2.98 and 3.0 ev for x=0.8 0.2 and 0.4 respectively. It can be used for diode and solar cell applications due to the higher transmittance and decreases of band gap energy.

Design and fabrication superhydrophobic surface with enhanced mechanical durability: Interface bonding effects regulated by an introduced transition oxide layer

Electrodeposited surface with higher superhydrophobicity and durability was designed and fabricated by molecular dynamics simulation and experiment in order to further enhance the service performance of materials. The sample that was identified as [CH3(CH2)16COO]3Ce possessed a better superhydrophobicity with a contact angle up to 173° while the rolling angle reducing to 1.5°. The typical petallike microstructure with a size around 1.2 μm and the interlaced nanorods with a breadth around 56 nm together contributed to the reservation of air-pockets on the [CH3(CH2)16COO]3Ce surface, leading to the further improvement of superhydrophobicity. A transparent oxide film (thickness of 1.55 μm) was designed to promote surface durability through a facile chemical impregnation method. Molecular dynamics simulation revealed that a higher adhesion at interface was mainly attributed to the Van der Waals forces between hydrogen elements on superhydrophobic surface and oxygen elements on oxide layer. Therefore, Al2O3 with higher surface oxygen density of 0.132/ Å2 became the ideal choice to improve the bonding strength at interface, which greatly improved the durability of cerous carboxylate surface. Subsequently, micro-scratch experiments and cyclic abrasion test verified that the durability of [CH3(CH2)16COO]3Ce surface on Al2O3 substrate was 49.7 % and 41.5% higher than that on Al substrate, respectively. The introduction of transition oxide layer can significantly improve the durability of superhydrophobic surfaces, demonstrating a great potential in practical application.

Optically transparent ultrathin NiCo alloy oxide film: Precise oxygen vacancy modulation and control for enhanced electrocatalysis of water oxidation

Oxygen evolution reaction (OER) impedes the electrochemical water splitting for H2 production primarily because of the sluggish kinetics. Cobalt oxides with abundant oxygen vacancies (Vos) have been proved to be the promising OER electrocatalysts showing high catalytic performance. However, precisely controlling the concentration of the Vos and large-scale synthesis of these electrocatalysts are still not resolved. Herein, we propose an e-beam evaporation alloy-UV/O3 oxidation method for fabricating optically transparent alloy oxide films (f-Ni0.1Co0.9Ox) only 10 nm thick. The concentration of the oxygen vacancies is positive correlated with the Ni content in the alloy oxides. The optimum binary Ni/Co (1/9) alloy oxide with the best defect O/lattice O ratio (0.952) exhibits ultrahigh OER mass activity of 3055 A g−1 at 250 mV overpotential in 1.0 M KOH, almost 7.5 times and 190 times as high as CoOx and the commercial benchmark RuO2 OER catalysts, respectively. Moreover, directly depositing f-Ni0.1Co0.9Ox film on the top of the tandem-junction a-Si PV cell realizes wireless unassisted solar-driven water splitting with high solar-to-hydrogen conversion efficiency. The key roles of modulating the electron structure, stably reversible spinel structure and the reaction barrier reduction were revealed in situ spectroscopy and density functional theory calculations. This study provides a new perspective of oxygen vacancy modulation for high electrocatalysis performance via large-scale synthesis of such bimetallic alloy oxides.

Transparent Oxide Films to Protect Food from Light Radiation

Transparent Oxide Films to Protect Food from Light Radiation

Hole Transport Layer based on atomic layer deposited V2Ox films: Paving the road to semi-transparent CZTSe solar cells

This work explores the use of very thin transparent vanadium oxide films deposited by atomic layer deposition (ALD) technique as hole transport layer for CZTSe solar cells as alternative of opaque molybdenum based contacts. Contact resistivity between the CZTSe absorber and the ALD V2Ox contact was measured. In order to improve contact quality, a cleaning bath using hydrofluoric acid (HF) dip, was also analyzed and its influence on kesterite surface was studied. Elementary material characterization and composition analysis of the V2Ox layers was performed. Contact quality was assessed yielding contact resistivity values below 9 and 30 mΩcm2 for ALD and thermal evaporated V2Ox films respectively.The proposed ALD V2Ox based hole transport layer was deposited onto a glass covered with a transparent conductive oxide forming part of the rear contact scheme of a vertical CZTSe solar cell with a conventional ITO/CdS stack as electron transport layer. The impact of subsequent thermal post-annealing treatments in the cell performance was also analyzed yielding efficiency up to 3.9% on a semi-transparent CZTSe solar cell without any additional optimization process. In this way, a CZTSe solar cell with both transparent electrodes has been demonstrated paving the way to obtain in the future high efficiency bifacial and/or semitransparent Building –integrated photovoltaic devices.

Preparation of transparent and hydrophobic cerium oxide films with stable mechanical properties by magnetron sputtering

Transparent and hydrophobic cerium oxide films with stable mechanical properties are deposited onto glass substrates by magnetron sputtering technique. It is found that water contact angle is correlated with surface roughness and surface chemistry. Under the synergistic effect of the two factors, water contact angle reaches 109.4° when deposited with 14% oxygen concentration. Meanwhile, the film shows a high optical transmittance of ~84.0% at 550 nm wavelength. On the other hand, the stable mechanical property could protect the film surface from solid particle bombardment, tape peeling and mechanical abrasion. The results make the practical applications of transparent hydrophobic film with stable mechanical properties in our daily life more feasible.

Optical characterization and γ-irradiation response of conductive transparent oxide of SnO2:Sb films

We are concerned in synthesizing conductive transparent oxide (CTO) films by spray pyrolysis deposition (SPD) for SnO2 (undoped) and SnO2:Sb (doped) film. The average value of the optical energy gap for CTO films of SnO2 and SnO2:Sb were found 4.01and 3.92 eV, respectively for direct transition before gamma irradiation. The optical conductivity of undoped and doped CTO film was calculated 8 × 1014 and 24 × 1014 Ω-1cm-1, respectively. The average value of refractive index for SnO2 and SnO2:Sb films was found 1.93 and 1.67, respectively at 0.0 kGy. The average value of refractive index of annealed SnO2:Sb films was decreased from 2.07 to 1.55 after γ-irradiation (22.0 kGy). The values of real part for the thermal annealed SnO2:Sb films were found positive before and after γ-irradiation in Vis-NIR range; accordingly the thin film material is said to have an intrinsically capacitive optical response. The imaginary part values of annealed SnO2:Sb film were decreased after γ-irradiation (22.0 kGy) in Vis-NIR range but still have positive value; so the material is said to have a resistive optical response. The optimum contact angle of doped CTO films was found 30° with hydrophilic surface. This property of CTO could be applied as covers for solar cells and other devices to keep its efficiency during rains and high humidity.

UV-response of aluminum-doped zinc oxide transparent films with different microstructures and electrical properties

Pure and aluminum doped-zinc oxide thin films were grown by spray-pyrolysis on glass substrates. The addition of increasing amounts of Al led to significant changes in the microstructure of the films. The texture coefficient of the (002) crystallographic plane was observed to decrease in heavily-doped films. Moreover, films with 10% at. Al showed a rare grain morphology characterized by worm-shaped grains. The presence of Al led to films of lower resistivity when compared to the pure-ZnO film, but the excess of doping agent had an opposed effect. This effect may be due to trap states in the form of ionized impurities and aluminum in interstitial sites. The electrical response of the films to UV light was evaluated, being the undoped films the ones showing the most intense response. The time needed for recovering the original current value after interrupting illumination was also measured and discussed.

Photo-stimulated evolution of different structural forms of silver in solutions, composite and oxide coatings

The influence of UV irradiation on the formation Ag-containing composite and oxide films has been studied. UV irradiation accelerates the formation and growth Ag small molecular clusters and nanoparticles in Ag-containing film-forming solutions, composite and oxide coatings. Photochemical processes and evolution of different structural forms of silver during coatings synthesis were studied by the optical spectroscopy, luminescence methods, SEM analysis. Prepared transparent Ag-containing oxide films containing different structural forms of silver demonstrate high antibacterial activity against bacteria Staphylococcus aureus ATCC 209P.

Direct Photolithographic Deposition of Color‐Coded Anti‐Counterfeit Patterns with Titania Encapsulated Upconverting Nanoparticles

AbstractCreating security labels as anti‐counterfeit measures can require multi‐step methods, clean room processing, and high‐cost equipment. Some labels also have a limited applicability due to the ease of creating a counterfeit. Herein, a photochemical metal‐organic deposition (PMOD) based approach that enables creation of high‐resolution luminescent patterns that retain nanoparticles in transparent metal oxide films is reported. This low‐cost, photoresist‐free process creates high‐resolution patterns of metal oxides without requiring processes such as etching or lift‐off. Upconverting nanoparticles (UCNPs) with tunable red/green or blue emission are prepared by doping Yb3+/Er3+ and Yb3+/Tm3+ into β‐NaYF4 hosts, respectively. Luminescent inks are prepared by suspending UCNPs in solutions with titanium di‐n‐butoxide bis(2‐ethylhexanoate). Customizable luminescent patterns are prepared by casting inks onto substrates, followed by exposure to ultraviolet light through photomasks. Photodecomposition of the titanium precursor yields amorphous oxide films encapsulating the UCNPs. Security labels are prepared by selectively patterning luminescent inks using PMOD. Distinct patterns of red‐green‐blue (RGB) luminescence are discernible only upon excitation with a near‐infrared (NIR) laser. These customizable, anti‐counterfeit labels exhibit the merits of low‐cost, high‐throughput, and simple manufacturing techniques. Yet, the versatility of customizing their emissive properties suggests a practical application as an anti‐counterfeiting measure.

Plasmonic nanostructures of SnO2:Sb thin film under gamma radiation response

Abstract This paper is a part of a natural dye solar cell project. Conductive transparent oxide (CTO) films have been deposited onto preheated glass substrates using a spray pyrolysis technique. The optical, electrical, structural properties as well as thermal annealing and gamma radiation response were studied. The average optical energy gap of doped films for direct allowed and direct forbidden transitions were found to be 3.92 and 3.68 eV, respectively. The plasmon frequency and plasmon energy after doping were found to be 3.48 × 1014 s −1 and 0.23 eV. The negative absorbance of the doped film was observed in UV-Vis range after applying both thermal annealing and γ-dose irradiation with 22 kGy. The negative refractive index of the doped film in UV range (220 – 300 nm) is promising for optical applications. The electron mobility μe reached a maximum of 27.4 cm2 V−1 s−1 for Sb concentration of 10 %. The corresponding resistivity ρ, and sheet resistance Rs reached their minimum values of 1.1 × 10−3 Ω cm and 35 Ω sq−1, respectively. The dopant concentration has been increased from 4.13 × 1019 to 2.1 × 1020cm−3. The doped film was found to exhibit three diffraction peaks associated with (2 2 2), (2 0 0), and (2 1 1) reflection planes, of which the peak of (2 2 2) of Sb2O3 and the peak of (2 0 0) were very close.