Oxide Thin Films Research Articles

Vanadium Pentoxide and Bismuth Oxide Thin Films Deposition on PSi for Application in Solar Cells

Vanadium Pentoxide and Bismuth Oxide Thin Films Deposition on PSi for Application in Solar Cells

Oxygen-modulated photoresponse in nickel oxide thin films for wide band gap photodetector application

Metal oxides, due to their wide band gap, are well suited for use in photodetectors as the active light-absorbing layer. While there have been extensive studies on n-type oxides, such as tungsten oxide and zinc oxide, there is relatively little work on the use of p-type oxides, such as nickel oxide (NiO), for photodetectors. Using these p-type oxides along with n-type conducting oxides to form heterojunctions can improve the detection capabilities by efficient separation of charge carriers. In this work, the photoresponse of a p-type NiO thin film, grown by room temperature reactive magnetron sputtering from a pure nickel target onto a conducting n-type indium-doped tin oxide (ITO) substrate, is investigated. Different ratios of oxygen to argon (10/45, 15/45, and 20/45) during sputtering are investigated, and the effect of oxygen concentration on the optical properties of the NiO film is studied, which helps in modulating the photoresponse of the developed detector. The O2/Ar ratio, with a value of 15/45, is found to perform better among the three ratios. For the corresponding photodetector, the current under illumination, is found to be nearly three orders of magnitude higher than the dark current, even at a very low applied voltage of 0.1 V. The calculated responsivity (at 0.012 A/W) is found to be the best among all three values. The device also has an excellent transient current response with a rise time of 0.5 s and a decay time of 1.4 s, which is the fastest transient behavior among all three ratio-based devices. The work paves the way for using metal oxide-based heterojunctions as wide band gap photodetectors.

Study the effect of strontium and copper co-doping on the structural, morphological, and optoelectronic properties of nickel oxide thin films

Study the effect of strontium and copper co-doping on the structural, morphological, and optoelectronic properties of nickel oxide thin films

Influence of Proton Irradiation on Thin Films of AZO and ITO Transparent Conductive Oxides—Simulation of Space Environment

Transparent conductive oxides are essential materials for many optoelectronic applications. For new devices for aerospace and space applications, it is crucial to know how they respond to the space environment. The most important issue in commonly used low-Earth orbits is proton radiation. This study examines the effects of high-energy proton irradiation (226.5 MeV) on thin films of aluminium-doped zinc oxide (AZO) and indium tin oxide (ITO). We use X-ray diffraction and electron microscopy observations to see the changes in the structure and microstructure of the films. The optical properties and homogeneity of the materials are determined by spectrophotometry and spectroscopic ellipsometry (SE). Analysis of the chemical states of the elements with X-ray photoelectron spectroscopy (XPS) gives insight into what proton irradiation changes at the surface of the oxides. All measurements show that ITO is less influenced than AZO. The proton energy and fluence used in this study simulate about a hundred years in low Earth orbit. This research demonstrates that both transparent conductive oxide thin films can function under simulated space conditions, with ITO showing superior resilience. The ITO film was more homogenous in terms of the total thickness measured with SE, had fewer defects and adsorbates present on the surface, as XPS analysis proved, and did not show a difference after irradiation regarding its optical properties, transmission, refractive index, or extinction coefficient.

Annealing Temperature Effects of Seeded ZnO Thin Films on Efficiency of Photocatalytic and Photoelectrocatalytic Degradation of Tetracycline Hydrochloride in Water

In this study, seeded zinc oxide (Z-ZnO) thin films were fabricated by a two-step electrochemical deposition process. Different annealing temperatures (300, 400, 500, and 600 °C) were investigated to determine the most effective temperature for the photocatalytic activity. Comprehensive analyses were conducted using X-Ray Diffraction (XRD), scanning electron microscopy (SEM), and UV–visible spectrophotometry. The XRD results confirmed the formation of a wurtzite hexagonal structure, with the highest crystallinity observed at 400 °C. The lowest band gap value, 3.29 eV, was also recorded for Z-ZnO thin film annealed at 400 °C. SEM images revealed that the thin film treated at 400 °C exhibited a well-defined and uniform structure, contributing to its enhanced properties. The photocatalytic efficiency of ZnO (without seeding layer) and Z-ZnO thin films annealed at 400 °C was evaluated through the degradation of tetracycline hydrochloride (TCH) to prove the effect of the presence of a primary seeding layer on ZnO 400 °C thin film efficiency. The degradation efficiency of ZnO thin film without seeding layer was 69.8%. By applying a seeding layer in Z-ZnO 400 °C thin film, the degradation efficiency has been increased to 75.8%. On the other hand, Z-ZnO 400 °C thin film achieved a high degradation efficiency of 82.6% over 300 min in the photoelectrocatalytic system. The obtained Z-ZnO thin films annealed at 400 °C are highly effective photocatalysts and photoelectrocatalysts, offering a significant potential for the degradation of pharmaceuticals and other pollutants in water.

Correlation between Material Properties, Crystalline Transitions, and Point Defects in RF Sputtered (N,Mg)-Doped Copper Oxide Thin Films

Correlation between Material Properties, Crystalline Transitions, and Point Defects in RF Sputtered (N,Mg)-Doped Copper Oxide Thin Films

The role of RF sputtering parameters on the uniformity and stability of Tb4O7 thin films on silicon substrates for passivation applications

Abstract In this study, the effects of different radio frequency (RF) parameters, were studied from the physical perspective of terbium oxide (Tb4O7) thin films deposited on silicon (Si) substrates, emphasizing their uniformity and stability for passivation applications. The findings for sample B, indicate that an optimal sputtering power of 110 W for 40 min enhances film uniformity while minimizing surface roughness, which is critical for achieving a stable passivation film. Notably, all the studied samples revealed a crystalline nature and maintained a stable phase, with no impurities detected from the grazing incident X-ray diffraction (GIXRD) patterns. Sample B revealed the highest value of crystallite size measured at 38 nm. Additionally, band gap energy (Eg) values between 2.19 and 2.78 eV were measured using the Kubelka-Munk (K-M) method. Photoluminescence (PL) analysis showed sample B achieved the highest peak intensity at 548 nm, corresponding to the 5D4 → 7F5 transition. Studies have been conducted on the formation of Tb4O7thin films deposited by RF sputtering on Si substrates, annealed in an argon (Ar) atmosphere. This study introduces a new approach to enhance film quality by adjusting the RF power during the sputtering process and subsequently annealing the sputtered samples. The aim was to investigate the benefits of nitrogen (N) annealing on the formation of a uniform passivation film of Tb4O7 material.

Investigations on the synthesis and characterization of silver-doped MoO3 thin films for photocatalytic applications.

In this study, we aimed to enhance the photocatalytic performance of molybdenum oxide (MoO3) thin films by doping with silver (Ag) via a spray pyrolysis technique. The primary objective for silver incorporation was intended to introduce additional energy levels into the band structure of MoO3, improving its efficiency. Structural, optical, and photocatalytic properties were analyzed using X-ray diffraction (XRD) and optical spectroscopy. XRD results confirmed an orthorhombic phase with a (040) preferential orientation for all samples. Optimal crystallinity was observed with 2% Ag doping, yielding an 84nm crystallite size, while higher doping levels reduced crystallite size. Band gap energy narrowed from 3.07eV (undoped) to 2.94eV (2% Ag-doped), indicating electronic structure changes. Impedance spectroscopy revealed superior electrical properties at 4% Ag doping, enhancing charge transport. Photocatalytic performance, assessed via dye degradation, showed significant improvement with silver doping, the degradation rate peaking at 4% Ag. These results demonstrate that silver doping optimizes structural and electronic properties of MoO3 thin films, leading to enhanced photocatalytic activity.

Designing Electroless Deposited RuO2 Thin Films for Laminated Quasi‐Solid‐State Symmetric Supercapacitor

AbstractProducing energy storage electrodes with exceptional performance using pseudocapacitive materials presents significant challenges. This study introduces a binder‐free, economical, and scalable method for the synthesis of a thin film of ruthenium oxide (RuO2) suitable for symmetric supercapacitors through electroless deposition. The influence of annealing temperature (373, 473, 573, and 673 K) on electrochemical performance is investigated. The RO‐573 thin film electrode demonstrated an impressive specific capacitance of 1006 F g−1 at a scan rate of 10 mV s−1. Additionally, a laminated quasi‐solid‐state symmetric device has been developed, showcasing a remarkable specific capacitance of 198 F g−1, ultrahigh energy density of 59.01 Wh kg−1, and a power density of 2.4 kW kg−1. The laminated, symmetric, quasi‐solid‐state supercapacitor device demonstrates impressive stability over 10,000 cycles, achieving a retention rate of 92%. The characteristics and design of laminated quasi‐solid‐state symmetric supercapacitors render them highly appropriate for real‐time applications in advanced energy storage systems.

Studying room temperature RF magnetron-sputtered indium tin oxide (ITO) thin films for large scale applications

Studying room temperature RF magnetron-sputtered indium tin oxide (ITO) thin films for large scale applications

Exploring the morphological and optical properties of N-doped ZnO heterojunctions

Nitrogen-doped zinc oxide (N:ZnO) thin films were deposited on glass substrates via radio frequency (RF) magnetron sputtering and subsequently annealed at 300 °C, 400 °C, 500 °C, and 600 °C to assess their viability and stability as transparent conductive oxide (TCO) materials. Structural and compositional analyses were performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). XRD analysis revealed preferential crystallite orientations along the (100), (002), (101), and (110) planes. Atomic force microscopy (AFM) measurements indicated particle sizes two to four times larger than those derived from XRD, suggesting a sub-granular internal structure, as XRD probes coherently diffracting domains. XPS analysis of the N 1 s spectra identified two distinct peaks at approximately 397 eV and 407.5 eV, indicating nitrogen incorporation into the ZnO matrix. Photoluminescence spectroscopy revealed that nitrogen doping induced the formation of interstitials and defects associated with oxygen and zinc vacancies. Optical measurements showed that the (N:ZnO) thin films exhibited an average optical band gap of approximately 3.1 eV, with 80% transmittance in the visible spectrum. A linear relationship was observed between the band gap energy and the tail width. Except for the film annealed at 600 °C, all annealed films showed a reduction in peak photoluminescence intensity with increasing annealing temperature. Finally, no significant changes in the electrical performance of the p-N/n-Si diode were observed as a result of annealing-induced surface modifications. The results provide valuable insights into the optimization of (N:ZnO) thin films for use in international optoelectronic and photovoltaic research, where advancements in TCOs are critical for the development of high-performance, sustainable technologies.

An approach to the description of the correlation between the electrical conductivity and the band gap of F-doped zinc oxide thin films

An approach to the description of the correlation between the electrical conductivity and the band gap of F-doped zinc oxide thin films

DC field-biased multibit/analog artificial synapse featuring an additional degree of freedom for performance tuning.

Multibit/analog artificial synapses are in demand for neuromorphic computing systems. A problem hindering the utilization of memristive artificial synapses in commercial neuromorphic systems is the rigidity of their functional parameters, plasticity in particular. Here, we report fabricating polycrystalline rutile-based memristive memory segments with Ti/poly-TiO2/Ti structures featuring multibit/analog storage and the first use of a tunable DC-biasing for synaptic plasticity adjustment from short- to long-term. The unbiased device is of short-term plasticity, positive biasing increases the remanence of the recorded events and the device gains long-term plasticity at a specific biasing level determined from the device geometry. The adjustability of the biasing field provides an additional degree of freedom allowing performance tuning; the paired-pulse facilitation index of the device is tuned by the biasing level adjustment providing further functional versatility. An appropriately biased segment provides more than 10 synaptic weight levels linearly depending on the number and duration of the stimulating spikes. The relationship with spike magnitude is exponential. The experimentally determined nonlinearity coefficient of the biased device for 50 potentiating spikes is comparable to the best published data. The spike-timing-dependent plasticity determined experimentally for the biased device in its long-term plasticity mode fits the mathematical relationship developed for biological synapses. Fabricated on a titanium metal foil, the produced memristors are sturdy and flexible making them suitable for wearable and implantable intelligent electronics. Our findings are anticipated to raise the potential of forming artificial synapses out of polycrystalline metal oxide thin films.

Impact of heat treatment on properties of molybdenum oxide thin films and performance of MoO3-x based c-Si solar cells

Impact of heat treatment on properties of molybdenum oxide thin films and performance of MoO3-x based c-Si solar cells

Proton-controlled Dzyaloshinskii-Moriya interaction and topological Hall effect in hydrogenated strontium ruthenate.

The Topological Hall effect (THE) is a fascinating physical phenomenon related to topological spin textures, serving as a powerful electrical probe for detecting and understanding these unconventional magnetic orders and skyrmions. Recently, the THE has been observed in strontium ruthenate (SrRuO3, SRO) thin films and its heterostructures, which originates from the disruption of interfacial inversion symmetry and Dzyaloshinskii-Moriya interaction (DMI). Here, we demonstrate a practically pure proton doping effect for controlling the DMI and THE in the SRO epitaxial films using the Pt electrode-assisted hydrogenation method. The hydrogenation process can realize approximately 0.8 protons per unit cell incorporating into the SRO films (thickness >10 nm) without causing significant lattice expansion and oxygen vacancies. Consistent with first-principles calculations, atomic-scale observations confirm that the proton doping induces a vertical displacement of Ru and O atoms in hydrogenated SRO (H-SRO), which remarkably enhances the DMI and leads to the emergence of the THE. More importantly, the proton doping drives two distinct topological signals in the ferromagnetic H-SRO, exhibiting greater THE values but no occurrence of structural transition. Our study has demonstrated that catalysis-assisted hydrogenation is an efficient strategy for manipulating the emerging THE and magnetic textures in correlated oxide thin films.

Stoichiometry modulation of molybdenum oxide thin films by direct sputtering for energy applications

Stoichiometry modulation of molybdenum oxide thin films by direct sputtering for energy applications

Impact of -OH surface defects on the electronic and structural properties of nickel oxide thin films.

Nickel oxide-based thin films and nanomaterials are a current focus of intense research efforts due to the broad range of end uses in a variety of applications. While the chemico-physical properties of bulk NiO crystals, characterized by a wide band gap (4.0-4.3 eV), antiferromagnetic ordering and p-type character, have been extensively studied, for NiO films/nanomaterials the microscopic-level relationships between the surface defect structure and electronic properties are far from being completely elucidated. In the present work, we show that, by using density functional theory with the Hubbard correction (DFT+U), -OH surface defects, almost ubiquitous on oxide surfaces, can directly influence the electronic structure of NiO(100) model slabs. Depending on the exact defect chemical structure and surface defect density, the energy gap of the -OH bearing NiO(100) system can be engineered, and its behaviour can be modulated from p-type to n-type. The insights provided herein may be of importance for the modulation of NiO nanosystem properties as a function of specific applications, an important issue for their eventual real-world utilization.

Understanding the Variations of Optical Bandgap in AZO Nanostructured Thin Films: Analysis of Possible Influences

Aluminum doped zinc oxide (AZO) thin films with varying thicknesses are fabricated using radio frequency (RF) sputtering combined with substrate rotation. The films display distinct nanocolumnar structures characterized by a hexagonal ZnO phase and a noticeable shift of the primary diffraction peak to lower 2θ angles. Lattice parameters a and c are used to evaluate residual stress and structural relaxation, both of which vary with increasing film thickness. Despite these structural changes, the films consistently maintain an average optical transmittance close to 85% in the range of 400–900 nm. The absorption edge and bandgap energy shift toward lower photon energies, decreasing from 3.51 to 3.38 eV as the thickness increases. The interplay between residual stress, structural relaxation, and bandgap energy is analyzed, offering insights into the complex dynamics influencing AZO thin‐film fabrication and the potential effects of quantum confinement. Lastly, the findings are compared with recent studies on ZnO thin films.

Tailoring Nickel Oxide Thin Films: Comparative Study of Oxidizing Agents in Thermal and Plasma-Enhanced Atomic Layer Deposition

Tailoring Nickel Oxide Thin Films: Comparative Study of Oxidizing Agents in Thermal and Plasma-Enhanced Atomic Layer Deposition

Effect of pressure and current density on metastable argon dynamics in low-pressure Ar-O2 plasma

Abstract Non-thermal plasma demonstrates a significant enhancement in efficiency when oxygen is added into the plasma mixture, particularly in processes such as thin-film oxide deposition, poly film removal, and photoresist mask ashing. This study examines the behavior of metastable argon states (1s5 and 1s3) in Ar-O2 mixture plasma, generated by a 50 Hz pulsed DC power supply under low-pressure conditions ranging from 1 mbar to 7 mbar. The densities of metastable argon states were assessed at varying conditions of current density, argon concentration, and filling gas pressure, utilizing optical emission spectroscopy (OES). The argon emission line ratio technique was employed to determine the plasma parameters. Experimental results indicate that electron density increases with current density, driven by enhanced excitation and ionization processes, while higher argon concentrations facilitate efficient ionization. The declining trend of the electron density with an increase in filling gas pressure is attributed to higher-pressure collisional processes. Metastable argon atoms exhibit heightened density with increased current density and argon percentage but decrease with elevated pressure due to loss processes. The regulation of metastable states is crucial for processes like etching, surface modification, and sterilization, providing a crucial step to the optimization and enhancing these applications.