Oxide Thin Films Research Articles

Strain free thin film growth of vanadium dioxide deposited on 2D atomic layered material of hexagonal boron nitride investigated by their thickness dependence of insulator-metal transition behavior

Abstract We report preparation of Vanadium dioxide (VO2) ultrathin films on hexagonal boron nitride (hBN), which is a typical two-dimensional material, to show clear Metal -Insulator transition owing to weak van der Waals interaction at their surface. It is confirmed that VO2 films on hBN with the thickness ranging from 10 to 40 nm exhibit bulk like Metal -Insulator transition without degradation by using the Raman scattering spectroscopy and electric transport measurements. These results are demonstrating the importance of 2D material nature of hBN for producing the strain-free oxide thin films.

Thin film epitaxy of high quality ferromagnetic semiconductor EuO using pulsed laser deposition equipped with Nd:YAG laser

Abstract Pulsed laser deposition with the fourth harmonic wave of Nd-doped Y3Al5O12 laser was applied to thin film epitaxy of a ferromagnetic semiconductor EuO which contains metastable Eu2+ ions. Highly crystalline, flat, and stoichiometric EuO (001) epitaxial thin films were successfully grown on YAlO3 (110) single crystal substrates. The EuO film exhibited ferromagnetism reflecting the 4f electronic configuration of Eu2+. These results indicate that Nd-doped Y3Al5O12 laser is useful for deposition of oxide thin films requiring oxygen stoichiometry.

LPG gas sensing performance of the SnO2 thin films influenced by the dielectric and conducting properties

This study presents a comprehensive investigation of the dielectric properties and DC conductivity of three tin (IV) oxide (SnO2) thin films with varying thicknesses 30 nm, 90 nm, and 150 nm and explores their influence on gas sensing performance. The gas sensing response of the three SnO2 sensor structures were evaluated for detecting 300 ppm of liquefied petroleum gas (LPG). X-ray diffraction (XRD) and atomic force microscopy (AFM) were used to study the structural and morphological properties of SnO2 thin films. The results of these studies were subsequently correlated to achieve a deeper insight into the gas sensing phenomenon. The dielectric analysis revealed that the SnO2 thin film of 90 nm thickness exhibited the lowest value of dielectric constant ε′(ω), measuring 2.7 at 1 kHz. To gain deeper insights, the capacitance (Cp) of the 90 nm SnO2 thin film was analyzed across a frequency range from 100 Hz to 1 MHz. Pronounced frequency dispersion was observed at elevated temperatures, which was attributed to the presence of a surface barrier. The DC conductivity (σdc) of all the SnO2 thin films was found to be relatively low, approximately 1.7 × 10⁻⁷ Ω⁻1 cm⁻1. The decreased conductivity indicates a high concentration of adsorbed oxygen on the surface and grain boundaries, which traps free electrons and lowers the number of charge carriers. Such characteristics are significant for gas sensing applications, as they can enhance the sensitivity of the sensor by facilitating a pronounced change in conductivity upon exposure to target gases.

Atomic layer deposition of crystalline molybdenum trioxide and suboxide thin films using molybdenum(II) acetate dimer precursor

Molybdenum oxide thin films are of interest due to a large range of possible phases, high work functions, and catalytic activity. These films have applications in areas, such as sensors, chromic, and semiconductor devices. In this work, a molybdenum(II) acetate dimer precursor was used with ozone for the atomic layer deposition of molybdenum oxide thin films. The films were grown at 200–300 °C yielding highly crystalline films even at the lowest deposition temperatures. X-ray diffraction measurements showed that the as-deposited films consist of molybdenum suboxides and/or a phase-pure orthorhombic molybdenum trioxide phase depending on the deposition conditions. Time-of-flight elastic recoil detection analysis showed that the stoichiometry was close to molybdenum trioxide, and the films were exceptionally pure with main impurities being hydrogen and carbon, which were at the detection limit of the instrument (0.1 at. %). This process, allowing the deposition of very pure and highly crystalline thin films with tunable phases and oxidation states, is very promising for future industrial applications.

Impact of heat treatment on structural and optical properties of 5,10,15,20-tetraphenyl-21H,23H-porphine vanadium (IV) oxide thin films

Thin films of 5,10,15,20-tetraphenyl-21H,23H-porphine vanadium (IV) oxide, VOTPP, were placed on glass with an overall thickness of 495 nm utilizing the thermal deposition process. The films underwent annealing at various temperatures (323, 373, 423, 473, 573 K) for 3 h. The thermal behaviour of VOTPP powder was tested by DTA. The crystalline molecular structure, and surface morphology of as-deposited and annealed films were examined utilizing XRD, SEM, and AFM. The crystallinity of VOTPP film was enhanced and the crystallite size grew by boosting the annealing temperature. The RMS roughness of annealed film at 573 K is 14.87 nm. Optical parameters of as-deposited and annealed VOTPP films were determined by spectrophotometric measurements in the spectrum of (200–2500 nm). The absorbance spectrum of VOTPP films is characterized by the Soret band, which exhibits Davydov splitting into two peaks, Bx and By in the annealed films at 473 and 573 K. Additionally, Q and N bands are observed. Annealing reduces both the linear and nonlinear refractive index, as well as the dispersion parameters. Calculations for molar refractivity and absorptivity, nonlinear parameters, and optical conductivity at different annealing temperatures have been done. Additionally, the energy loss functions at different annealing temperatures were obtained. The electronic transition is indirectly allowed. Optical energies such as Egonset, Egopt1, Egopt2, and EU were observed to reduce as the annealing temperature elevated. All the optical parameters were compared with other porphyrin derivatives. This study demonstrates that thermally annealing is an efficient method in enhancing the optical and synthetic characteristics of VOTPP films, which serve as a viable absorbing layer in renewable energy systems.

Low-Frequency Noise Characterization in UV-Sensitive Indium Tungsten Oxide Thin-Film Photodetectors via Sputtering Deposition.

Abstract This study explores the deposition of indium tungsten oxide (IWO) thin films on glass substrates using sputtering techniques, with the aim of developing photodetectors sensitive to both ultraviolet (UV) and visible light spectra. The films were designed in a metal-semiconductor-metal configuration to enhance electrical conductivity, which is critical for efficient photodetection. This structure achieved a dark-to-light current ratio of 6.23×10² and a responsivity of 0.48 A/W at a reverse bias of 2 V. Furthermore, when configured as UV photodetectors, the IWO films demonstrated significant improvement, achieving a dark-to-light current ratio of 1.32×10⁴ under the same bias conditions. The photodetectors exhibited a detectivity (D*) of 2.18 × 10¹⁰ cm·Hz⁰.⁵·W⁻¹ and a noise equivalent power (NEP) of 6.88 × 10⁻¹⁰ W. These findings highlight the potential of IWO to improve photodetector performance across different light spectra, reinforcing its viability for cost-effective integration into advanced optoelectronic devices.

High Harmonics Generation in an Optical Fiber Functionalized with Zinc Oxide Thin Films

High Harmonics Generation in an Optical Fiber Functionalized with Zinc Oxide Thin Films

High-Performance Hydrogen Sensing at Room Temperature via Nb-Doped Titanium Oxide Thin Films Fabricated by Micro-Arc Oxidation.

Metal oxide semiconductor (MOS) hydrogen sensors offer advantages, such as high sensitivity and fast response, but their challenges remain in achieving low-cost fabrication and stable operation at room temperature. This study investigates Nb-doped TiO2 (NTO) thin films prepared via a one-step micro-arc oxidation (MAO) with the addition of Nb2O5 nanoparticles into the electrolyte for room-temperature hydrogen sensing. The characterization results revealed that the incorporation of Nb2O5 altered the film's morphology and phase composition, increasing the Nb content and forming a homogeneous composite thin film. Hydrogen sensing tests demonstrated that the NTO samples exhibited significantly improved sensitivity, selectivity, and stability compared to undoped TiO2. Among the fabricated samples, NTO thin film prepared at Nb2O5 concentration of 6 g/L (NTO-6) showed the best performance, with a broad detection range, excellent sensitivity, rapid response, and good specificity to hydrogen. A strong linear relationship between response values and hydrogen concentration (10-1000 ppm) highlights its potential for precise hydrogen detection. The enhanced hydrogen sensing mechanism of NTO thin films primarily stems from the influence of Nb2O5; nanoparticles doping in the anatase-phase TiO2 structure on the semiconductor surface depletion layer, as well as the improved charge transfer and additional adsorption sites provided by the Nb/Ti composite metal oxides, such as TiNb2O7 and Ti0.95Nb0.95O4. This study demonstrates the potential of MAO-fabricated Nb-doped TiO2 thin films as efficient and reliable hydrogen sensors operating at room temperature, offering a pathway for novel gas-sensing technologies to support clean energy applications.

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

Epitaxial Cu2O Thin Films Deposited from Solution: the Enabling Role of Cu Diffusion into the GaAs Substrate.

Cuprous oxide (Cu2O) thin films were chemically deposited from a solution onto GaAs(100) and (111) substrates using a simple three-component solution at near-ambient temperatures (10-60 °C). Interestingly, a similar deposition onto various other substrates including Si(100), Si(111), glass, fluorine-doped tin oxide, InP, and quartz resulted in no film formation. Films deposited on both GaAs(100) and (111) were found alongside substantial etching of the substrates. The etching of GaAs(100) was uneven, resulting in pyramid-like vacancies, while for GaAs(111), the etching was more even and resulted in a flat interface. X-ray diffraction measurements indicated highly preferential (110) growth of Cu2O regardless of GaAs substrate orientation, while TEM and a selected area of electron diffraction pointed out epitaxial growth on both substrates. X-ray photoelectron spectroscopy confirmed the diffusion of copper ions into the GaAs up to depths of 20 nm and the formation of intermediate phases at the interface. Raman spectroscopy indicated high structural quality of the films and showed good agreement with TEM and XRD results and Raman shifts corresponding to Cu2O, with no frequencies typical of CuO. The GaAs substrate appears to play a critical and unusual role in the deposition of Cu2O thin films on GaAs, which allows for growth of Cu2O in a previously unreported mechanism.

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

Solution Shearing of Sustainable Aluminum Oxide Thin Films for Compliance‐Free, Voltage‐Regulated Multi‐Bit Memristors

Solution Shearing of Sustainable Aluminum Oxide Thin Films for Compliance‐Free, Voltage‐Regulated Multi‐Bit Memristors

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