Oxide Thin Films Research Articles

Effect of Annealing Time on Pitting, Intergranular Corrosion, and Hardness of Stainless Steels

Stainless steels are the material that has chromium as a main component. The chromium content reacts with oxygen in air, subsequently, forms thin chromium oxide film on the surface of stainless steels. Thus, when these steels are exposed to high temperature for a long period of time in many applications, chromium carbide could precipitate along the grain boundary and reduce the corrosion resistance. This project is conducted to study annealing time effect on stainless steels when exposed to high temperature at various exposure time periods. Three different kind of stainless steels, namely, AISI 304, AISI 304D and AISI 2205 were used in this study. Stainless steels were heated at 600°C for 0, 6, 24, 48 and 96 hours, then cool down in air. Consequently, the investigations were performed by using double-loop Electrochemical Potentiokinetic Reactivation (DL-EPR) and Cyclic Potentiodynamic Polarization (CPP) to study degree of sensitization and film properties. In addition, chromic acid and oxalic acid were used as reagent of acid etching to observe microstructures. Finally, Vickers hardness test were also conducted. Percentage degree of sensitization increased from 2.93% to 62.20% in AISI 304, increased from 5.26% to 55.54% in AISI 304D and from 12.19% to 69.35% in AISI 2205. The pitting potential decreased from 0.47 mV to 0.23 mV for AISI 304 but remained relatively constant for AISI 304D and AISI 2205. The results indicated that after the specimens were exposed to high temperature for a long period of time, all specimens had more chromium depleted areas, more carbide along the grain boundaries, worse film quality and small changes in hardness value.

Influence of the Deviation from Stoichiometry on Transport Properties of Titanium Oxides Thin Films

Influence of the Deviation from Stoichiometry on Transport Properties of Titanium Oxides Thin Films

Phase tailoring of silver oxide thin films for improved antimicrobial activity

This paper reports on routes to control the silver oxide phase and morphology in thin films to enhance their antimicrobial efficacy. The Ag:O atomic ratio was tailored during the pulsed laser deposition process by adjusting the O2 environment, and thus, a wide range of silver oxide phases ranging from Ag to AgxO was achieved. Simultaneously, the morphology was controlled from island-like (Volmer–Weber) formations to nanoparticle arrays, ultimately culminating in cauliflower-like dendrite structures. Through this synergistic approach, enhancing the oxygen content while expanding the active surface area yielded optimal enhancement of the antimicrobial properties. Remarkably, films deposited at elevated O2 pressures exhibited heightened inhibitory effects against bacterial biofilms, with films featuring nanoparticle morphology demonstrating notable antistaphylococcal efficacy.

Interfacial Electronic Charge Trapping and Photonic Carrier Excitation Coupling in Solution-Processed Zinc-Tin Oxide Thin-Film Transistors Applied for Logic Gate Design and Quantized Neural Network.

Components needed in Artificial Intelligence with a higher information capacity are critically needed and have garnered significant attention at the forefront of information technology. This study utilizes solution-processed zinc-tin oxide (ZTO) thin-film phototransistors and modulates the values of VG, which allows for the regulation of electron trapping/detrapping at the ZTO/SiO2 interface. By coupling the excited photonic carrier and electronic trapping, logic gates such as "AND," "OR," "NAND," and "NOR" can be achieved. With the exponential growth in data generation, efficient processing and storage solutions are imperative. However, extensive data transfer between computing units and storage limits the level of artificial neural networks (ANNs). Consequently, quantized neural networks (QNNs) have gained interest for their reduced computational resource requirements and lower consumption. In this context, we introduce an optimized ternary logic circuit based on ZTO devices. By utilizing optical modulation to adjust the turn-on voltage of the single device, we demonstrate the achievement of ternary current states, thereby providing three distinct discrete states. This configuration can be extended to QNN computing, demonstrating multilevel quantized current values for in-memory computation. We achieved a handwriting digit recognition rate of 91.6%, thereby demonstrating reliable QNN hardware performance. This robust QNN performance indicates that the metal oxide phototransistor shows significant potential for future ternary computing systems.

Insights into the Electrochemical Oxidation and Reduction of Nickel Oxide Surfaces.

Surface oxidation/reduction processes, driven by varying electrochemical potentials, can substantially impact catalyst effectiveness and, consequently, electrolyzer performance. This study combines theoretical and experimental approaches to explore the surface redox behavior of nickel oxides, which are cost-effective and efficient catalysts for many electrochemical reactions. Surface Pourbaix diagrams for three different phases of nickel oxides, i.e., nickel hydroxide (Ni(OH)2), nickel oxyhydroxide (NiOOH), and nickel dioxide (NiO2), were constructed using density functional theory-based simulations. Various experimental methods, including cyclic voltammetry, in situ Raman spectroscopy, and electrochemical titration, were employed to probe the surface redox processes of nickel oxide thin films. Our findings indicate that the ABAB stacking sequence of Ni(OH)2 lacks stability under oxidizing conditions to host the surface oxidation (deprotonation) events, while the AABBCC stacking sequence of NiOOH is energetically favorable due to the presence of interlayer hydrogen bonding. Rapid charge transfer facilitated by interlayer hydrogen bonding accounts for the higher reactivity of partially oxidized/reduced NiOOH (001) surfaces compared to Ni(OH)2 (001) and NiO2 (001) surfaces with the same stoichiometry, where interlayer hydrogen bonding is absent. Insights presented in this work can offer guidelines for optimizing operational conditions and tailoring the surface structures and oxidation states of nickel oxides to enhance performance in applications such as electrocatalysis and supercapacitors.

Investigating the effects of etching systems and low-temperature thermal processing on hafnium zirconium oxide thin film properties

Investigating the effects of etching systems and low-temperature thermal processing on hafnium zirconium oxide thin film properties

Performance Analysis and Characterization of Natural Dye-sensitized Solar Cells (DSSCs) of Titanium Oxide (TiO2) Thin Film

Dye-sensitized solar cells (DSSCs) thin films of titanium oxide (TiO2) sensitized with the dyes of the almond and copper leaves extracted using ethanol and water (AE, AW, CE and CW) each, have been successfully deposited on FTO conductive glass substrate using the Dr Blading method. The deposited TiO2-DSSC thin films were subjected to UV-Vis spectroscopy, X-ray diffraction, scanning electron microscopy and I-V characteristics analysis to determine their optical, structural, morphological properties and solar cell parameters respectively. The results of the analysis showed that copper leaves dye-sensitized films (CE and CW) has absorbance is in the range of 0.45 to 0.9 and 0.25 to 0.45 respectively within the visible (VIS) regions. The absorbance of the films sensitized with almond leaves dye is lower in the range of 0.15 - 0.25 for AE and 0.04 – 0.09 for AW within the region. The percentage transmittance of the films was found to be in the range of 82.5% – 90% for the film AW, 35% – 55% for CW while the film AE has the lowest value of the order 12.5% - 35% within the VIS region. The reflectance percent of the films were generally low with the film CE having the highest value in the range of 27%-43%, CW in the range 17.5% - 26%, AE in the range 10% - 15%, while the film AW has values in the range 2.5% - 5.5% within the VIS region. All the deposited DSSCs films have high refractive index values throughout the VIS region. The bandgap energy values obtained for the films are 2.5 eV for film CE, 2.6 eV for CW, and 2.4 eV for the films AE and AW each. These are in the range of wide bandgap energies and are favourable for application in the device that required high temperature and fabrication of blue LEDs. The results of the structural analysis on the deposited thin films showed that both the films exhibited crystalline structure with crystallite sizes of 24.55 nm for CE, 27.68 nm for CW, 22.27 for AE and 36.30 for AW films. The films have low cell conversion efficiency but still within the margin of error for most DSSCs materials.

Electron-Beam-Evaporated Nickel Oxide Thin Films for Application as a Hole Transport Layer in Photovoltaics

We present the growth of nickel oxide (NiO) thin films as a hole transport material in photovoltaic devices using the e-beam evaporation technique. The metal oxide layers were reactively deposited at a substrate temperature of 200 °C using an electron beam evaporator under an oxygen atmosphere. The oxide films reactively grown through electron-beam evaporation were optimized for carrier transport layers. Optical and structural characterizations were performed using ultraviolet–visible (UV–Vis) spectrometry, X-ray diffraction, contact angle measurements, scanning electron microscopy, and Hall effect measurements. The study of these films confirmed that the NiO layer is a suitable candidate for use as a hole transport layer based on Hall effect measurements. A morphological study using field-emission scanning electron microscopy confirmed the growth of compact, uniform, and defect-free metal oxide layers. Contact angle measurements revealed that the films possessed semi-hydrophilic properties, contributing to improved stability by repelling water from their surfaces. The stoichiometry of the films was influenced by the oxygen pressure during deposition, which affected both their morphological and optical features. The NiO films exhibited a transmittance exceeding 80% in the visible spectrum. These findings highlight the potential applications of such nickel oxide films as hole transport material layers.

Effect of annealing temperature onto physical properties of Cu doped ZnO thin films prepared using spray pyrolysis

Abstract Herein we report the effect of annealing on spray-pyrolysis-deposited Cu-doped zinc oxide thin films, with a fixed 3 wt% copper concentration and annealing temperatures of 450 and 500 °C. Various analytical techniques were employed to evaluate the effect of annealed films, which exhibited high stability in physical properties and minimal influence from the annealing process. XRD analysis confirmed that all films maintained a hexagonal ZnO structure without any additional phases, indicating the high purity of the films, with the (002) peak serving as the main diffraction peak for both as-deposited and annealed films. Crystallite size, calculated using the Halder-Wagner equation, revealing an increase from 13.96 nm for the as-deposited film to 14.26 nm for film annealed at 450 °C and 14.65 nm for film annealed at 500 °C. Microstrain values were measured at 2.3 × 10−3, 2.5 × 10−3, and 1.3 × 10−3 for the as-deposited and annealed films. Surface imaging with FE-SEM revealed average grain sizes of 57.25 nm, 68 nm, and 67.8 nm for the as-deposited film and those annealed at 450 °C and 500 °C, respectively. The estimated band gap values were 3.14 eV for the as-deposited films, 3.15 eV for those annealed at 450 °C, and 3.16 eV for films annealed at 500 °C. According to the Spitzer-Fan model, both the density of states and plasma frequency remained constant across the films, while the relaxation time and optical mobility were lowest at 450 °C, where the high-frequency dielectric constant reaches its peak.

Lead-free dielectric thin films: Synthesis of Ag(Nb1−xTax)O3 via reactive dc magnetron sputtering

Growing environmental concerns have driven the switch from lead-containing dielectric perovskite ceramics to lead-free alternatives such as silver niobate tantalate [Ag(Nb1−xTax)O3], where tantalum (Ta) substitution for niobium (Nb) enhances energy-storage density. Thin film deposition presents a promising way for fabricating these materials for use in capacitors. In this study, Ag(Nb1−xTax)O3 (0 ≤ x ≤ 0.5) thin films are synthesized via combinatorial reactive dc magnetron sputtering from metallic targets. The chemical and phase compositions of the films are comprehensively analyzed using scanning electron microscopy coupled with energy dispersive x-ray spectroscopy, elastic recoil detection analysis, Rutherford backscattering spectrometry, x-ray diffraction, Raman spectroscopy, and x-ray photoelectron spectroscopy. The findings demonstrate that reactive dc magnetron sputtering is a feasible technique for producing complex perovskite oxide thin films with customized chemical composition and microstructure. By enhancing the understanding of the Ag(Nb1−xTax)O3 material system, this study aims to contribute to the development of environmentally benign high-performance dielectrics that could replace lead-based ceramics in energy-storage applications.

Growth and characterization of Indium Tin Oxide (ITO) thin films deposited on KBr(h00) single crystal substrate

Filmes finos de óxido de índio e estanho (ITO) foram depositados em um substrato monocristalino de KBr (h00) usando a técnica de spray ultrassônico a uma temperatura de 300 °C. Além disso, o filme de ITO foi submetido a um recozimento a 700 °C por 1 hora. A análise de difração de raios X indica que os filmes são policristalinos, com orientação preferencial dos grãos ao longo do plano (400), e sua cristalinidade melhora devido à alta temperatura de recozimento. A espectroscopia Raman revela a presença de vibrações de alongamento In–O–In nos filmes recozidos a 700 °C. A análise da morfologia da superfície mostra que os filmes recozidos consistem em aglomerados com tamanhos variando de 300 a 350 nm, enquanto o filme depositado apresenta uma camada densa de ITO com tamanhos de grãos menores que 80 nm. A análise UV-vis confirmou uma transmitância média de aproximadamente 65% na região visível, com a largura de banda óptica variando entre 3,91 e 4,10 eV. Os filmes recozidos a 700 °C exibiram baixa resistividade (0,31 × 10⁻³ Ω cm).

Temperature and Flexural Endurances of Aluminum-Doped Zinc Oxide Thin Films on Flexible Polyethylene Terephthalate Substrates: Pathways to Enhanced Flexibility and Conductivity

This work investigates the endurance and performance of aluminum-doped zinc oxide (AZO) thin films fabricated on flexible polyethylene terephthalate (PET) substrates, providing new insights into their degradation linked to mechanical flexing and accelerated thermal cycling (ATC). The current study uniquely combines cyclic bending fatigue at 23 °C and 70 °C with ATC between 0 °C and 100 °C, simulating operational stresses in real-world environments, in contrast to previous research that has focused primarily on either isolated mechanical or thermal effects. The 425 nm thick films showed high transparency and conductivity, making them suitable materials for flexible electronics and optoelectronic devices. In this work, electrical resistivity, one of the most important performance parameters, was investigated after each mechanical or thermal cycle. The results indicate that mechanical cycling at high temperatures can drastically enhance the crack formation and electrical degradation, with an over 250% change in the electrical resistance (PCER) after 12,000 cycles at 70 °C and more than 300% after 500 thermal cycles. The highly deleterious effects of combined stressors on the structural integrity and electrical properties of AZO films are underlined by these observations. This study further suggests that the design of more robust AZO-based materials/coatings would contribute toward achieving better durability in flexible electronic applications. These findings also go hand in glove with the ninth goal of the United Nations’ Sustainable Development Goals, specifically Target 9.5: Enhance Research and Upgrade Industrial Technologies.

Electrode Elastic Modulus as the Dominant Factor in the Capping Effect in Ferroelectric Hafnium Zirconium Oxide Thin Films.

The discovery of ferroelectricity in hafnia based thin films has catalyzed significant research focused on understanding the ferroelectric property origins and means to increase stability of the ferroelectric phase. Prior studies have revealed that biaxial tensile stress via an electrode "capping effect" is a suspected ferroelectric phase stabilization mechanism. This effect is commonly reported to stem from a coefficient of thermal expansion (CTE) incongruency between the hafnia and top electrode. Despite reported correlations between ferroelectric phase fraction and electrode CTE, the thick silicon substrate dominates the mechanics and CTE-related stresses, negating any dominant contribution from an electrode CTE mismatch toward the capping effect. In this work, these discrepancies are reconciled, and the origin of these differences deriving from electrode elastic modulus, not CTE, is demonstrated. Pt/M/TaN/Hf0.5Zr0.5O2/TaN/Si devices, where M is platinum, TaN, iridium, tungsten, and ruthenium, were fabricated. Sin2(ψ)-based X-ray diffraction measurements of biaxial stress in the HZO layer reveal a strong correlation between biaxial stress, remanent polarization, and electrode elastic modulus. Conversely, a low correlation exists between the electrode CTE, HZO biaxial stress, and remanent polarization. A higher elastic modulus enhances the resistance to electrode elastic deformation, which intensifies the capping effect during crystallization, and culminates in the tandem restriction of out-of-plane hafnia volume expansion and preferential orientation of the polar c-axis normal to the plane. These behaviors concomitantly increase the ferroelectric phase stability and polarization magnitude. This work provides electrode material selection guidelines toward the development of high-performing ferroelectric hafnia into microelectronic devices, such as nonvolatile memories.

Inkjet printing of sustainable ZTO/AlOx thin film transistors

Abstract Even though printed metal oxide thin film transistors (TFTs) have been a central topic of research in the past decade, the most notable results still require scarce elements such as gallium and indium, or high annealing temperatures (≥ 400 °C) when used non-critical raw materials such as zinc and tin.
In this work, safe, abundant and inexpensive materials such as zinc, tin and aluminum are explored to reach low-cost thin films and devices with both the semiconductor and dielectric layers deposited by inkjet printing and annealed at lower temperatures (300 °C). Alumina (AlOx) and zinc tin oxide (ZTO) inks containing a theoretical optimal V% of ethylene glycol (EG) were optimized for production of uniform and reproducible AlOx/ZTO thin film layers. Common ink parameters (such as the reverse Ohnesorge, capillary, Webber and Reynolds numbers) were evaluated and compared with relevant literature on inkjet drop formation mechanisms. Inks within theoretical optimal parameter values were printing optimized in terms of drops per inch, number of layers, UV substrate surface activation, print speed, and post annealing. A high-quality dielectric of two alumina layers was printed, having a breakdown field above 2.93 ± 0.33 MV.cm-1, and a dielectric constant of 7.74 ± 0.73 at 1 kHz. Thin film transistors (TFTs) of inkjet printed (IJP) ZTO/AlOx layers were produced with a maximum IOn/IOff ratio of 103 and a saturation mobility of 2.2 cm2.V-1.s‑1. This approach not only advances the field of printed electronics but also addresses concerns related to material scarcity, thermal budget, and production costs.

Uniformity and Reliability of Enhancement-Mode Polycrystalline Indium Oxide Thin Film Transistors Formed by Solid-Phase Crystallization

Uniformity and Reliability of Enhancement-Mode Polycrystalline Indium Oxide Thin Film Transistors Formed by Solid-Phase Crystallization

Effect of film thickness on phase structure of epitaxial non-doped hafnium oxide films

HfO2 has been widely used in the electronics industry as a dielectric material with excellent properties. It has attracted much attention since HfO2 was first reported to be ferroelectric in 2011. With the continuous advancement of research, various methods such as oxygen vacancy control and interface control have been proven to be able to stabilize the metastable polar o-phase structure in doped hafnium oxide thin films. However, there are still some shortcomings in the relevant issues concerning non-doped hafnium oxide thin film materials. Here, polycrystalline non-doped HfO2 thin films were grown on SrTiO3 substrates by pulsed laser deposition (PLD). Atomic force microscopy investigation suggests that the surface roughness of HfO2 thin films increases as the film thickness increases. X-ray photoelectron spectroscopy analyses indicate that the HfO2 thin film has a high purity and contain only Hf4+ ions. The band gap of HfO2 was measured by valence EELS and UV–visible spectra. Atomic structures of the HfO2/SrTiO3 heterointerface have been studied by the aberration-corrected transmission electron microscopy and energy-dispersive X-ray spectroscopy. The HfO2/SrTiO3 heterointerface is atomically abrupt and incoherent. Our findings suggest that non-doped HfO2 films with o-phase structure through PLD technology.

Plasma Power Effect to the Structure and Morphology of Strontium Stannate Thin Film

Hybrid p-n heterojunction requires a suitable n-type material to support the charge transfer process in photodiode or solar cell applications. Numerous materials have been researched in terms of wet and dry processes. This paper investigated the effect of varied plasma power levels of 50 W, 80 W and 100 W at room temperature on the structure and morphology of an alkaline-earth-based perovskite oxide thin film. Strontium stannate (SrSnO3) thin films are deposited on an indium tin oxide (ITO) substrate using radio frequency (RF) magnetron sputtering at various power levels. The crystallographic orientation of the thin films was examined and it was observed that the (102) plane exhibited dense growth at low power, while the (002) plane showed increased intensity at higher power levels. Additionally, the increase in RF power resulted in larger crystallite and grain sizes, along with modified grain boundaries. Contrarily, surface roughness, resistivity, macrostrain and work adhesion were reduced. The nearly zero W-H linear fitting plot observed at 80 W can serve as a valuable reference for the fabrication of preferred films. These findings provide valuable insights for optimising the growth conditions of alkaline-earth-based perovskite oxide thin films for various applications.

Adjustable repetition rate mode-locked fiber laser using a ZnO nanolaminate

This paper experimentally demonstrates the use of a zinc oxide (ZnO) nanolaminate as a polarization-dependent loss element to control the frequency repetition rate in a passive mode-locked fiber laser. The ZnO nanolaminate was deposited via the atomic layer deposition technique. The system achieves repetition frequencies ranging from 2.2 to 6.6 MHz, with emission peaks occurring at wavelengths between 1569.1 nm and 1570.8 nm, exhibiting three to four peaks. The fiber exhibits a minimal pulse duration of around 9.78 ns; the maximal pulse-to-pulse separation was 452 ns. The fiber laser demonstrates excellent stability in both power and wavelength emission. The compact experimental setup leverages the properties of the thin film of zinc oxide, offering a versatile laser system capable of quickly altering pulse repetition rates by simply adjusting the polarization state.

Effect of holmium on structural and optical properties of sol–gel spin coating-derived cadmium oxide thin films

Effect of holmium on structural and optical properties of sol–gel spin coating-derived cadmium oxide thin films

Remediation of crude oil contaminated oily wastewater using nanostructured ZnO-decorated ceramic membrane: Membrane fouling and their mitigation using photo-catalytic self-cleaning process

In membrane-based oil water separation, the fouling of oil on the membrane pores due to the adsorption of oily feed components (crude oil) is a major disadvantage. In order to address the problem of membrane fouling, in this work, the filtration membrane itself was coated with a photoactive semiconducting material to self-clean the fouled membrane by photo-catalytic degradation. In addition to the self-cleaning, the other major functionality of the coating is to render a favorable surface wettability, conducive for water passing oil water separation. The basic membrane is porous alumina (Al2O3) substrate, on which a layer of crystalline Zinc Oxide (ZnO) thin film was coated by single step RF magnetron sputtering. The fabricated membrane is super-hydrophilic in the air and super-oleophobic underwater, and this contrasting wettability is crucial for the water passing oil water separation. The advantage of preferentially water passing membrane is that the oil clogging on the membrane surface is less than that of the oil passing membrane. However, after prolonged use with crude oil-contaminated feed, the accumulation of organic pollutants on the membrane surface hinders the smooth permeation of water through the membrane. The oil water filtration system involves cross flow through the ZnO-deposited Al2O3 membrane with the application of trans-membrane pressure. The membrane achieved an excellent separation efficiency (99.66 %) of oil and water from the oil emulsified water, and high permeates flux (908.4 L/m2.h.bar) for 200 ppm crude oil contaminated oily feed (surfactant stabilized crude oil-in-water emulsion). After a prolonged use of 540 min, the permeate flux declined due to the accumulation of organic pollutants present in the oily water. The original flux was restored by initiating photocatalytic degradation of organic pollutants by the exposure of UV radiation on the used membrane surface. The ZnO-deposited Al2O3 membrane shows an excellent light induced photocatalytic self-cleaning and antifouling with flux recovery ratio of around 88 %. In addition to this application, this manuscript also presents the morphological, elemental, structural, and topological characterizations of coated membrane.