Thermal and microstructural analysis of Cu(II) 2,2′-dihydroxy azobenzene and thin films deposition by MAPLE technique

A newly synthesized copper-complex exhibiting nonlinear optical properties, crystalline nature, and generating interest as a material for non-linear optical applications was investigated. As thermal stability studies are indispensable before attempting any laser-assisted processing experiments, the thermal behavior of 2,2′-dihydroxy azobenzene with Cu²⁺ cations that are found to organize themselves as non-central symmetric crystallites, was investigated. The thin films were deposited on silicon substrates by matrix-assisted pulsed laser evaporation using a Nd:YAG laser working at 266 and 355 nm. Thermal analysis of the bulk compound indicates a higher thermal stability in argon flow when compared to the air atmosphere; as well, since, the adhesion of the compound onto the substrate enhances the bonding, the thermal stability of the Cu complex increases. Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy, spectroscopic ellipsometry, and ultraviolet–visible spectroscopy investigations were also performed.     

Thermodynamic properties and oxygen stoichiometry of Ba2Cu3O5 + δ

The thermodynamic properties and oxygen stoichiometry of Ba₂Cu₃O_{5 + δ} are studied by means of the electromotive force (EMF) with a fluoride electrolyte, dissolution calorimetry, and thermogravimetry. It is shown that the temperature dependence of the Gibbs energy of the formation of barium cuprate from simple oxides and oxygen in the temperature range of 860–1120 K can be described by the polynomial Δ_{f, ox} G ^°(Ba₂Cu₃O_{5 + δ}) ± 0.1 (kJ/mol) = ?291.78 + 1.127T ? 0.13207 TlnT (kJ/mol).     

Orientation degree dependence of magnetic properties of Co doped ZnO thin films by sol–gel process

Co-doped ZnO films were successfully fabricated on Si substrates by sol–gel process. The effects of Co concentration and preheating temperature on the structure and magnetic properties of the Zn_1−x Co _x O films were systematically studied. The results revealed that the films were highly c-axis oriented and contained no impurity phase. With preheating temperature increasing, the orientation degree of the films decreased. When the Co concentration and oxygen vacancy of the films are almost changeless, the enhancement of ferromagnetism in films originates from the orientation degree of the films increasing.     

Influence of oxygen atmosphere on the photoluminescence properties of sol–gel derived ZrO2 thin films

Homogeneous and transparent ZrO₂ thin films were prepared by sol?Cgel dip coating method. The prepared ZrO₂ thin films were annealed in air and O₂ atmosphere at 500, 700 and 900?°C for 1, 5 and 10?h. X-Ray diffraction (XRD) pattern showed the formation of tetragonal phase with a change of stress in the films. Scanning electron microscope (SEM) revealed the nucleation and particle growth on the films. An average transmittance of >80?% (in UV?CVis region) was observed for all samples. The refractive index and direct energy band gap were found to vary as functions of annealing atmosphere, temperature and time. Photoluminescence (PL) revealed an intense emission peak at 379?nm weak emission peaks at 294, 586 and 754?nm. An enhancement of PL intensity was observed in films annealed in O₂ atmosphere. This is due to reconstruction of zirconium nanocrystals interfaces, which help passivate the non-radiative defects. At 900?°C, oxygen atoms react with Zr easily at the interface and destroy the interface states acting as emission centres and quench the PL intensity of the film. The enhancement of the luminescence properties of ZrO₂ by the passivation of non radiative defects presents in the films make it suitable for gas sensors development, tuneable lasers and compact disc (CD) read-heads.     

Optical and structural properties of aluminium oxide thin films prepared by a non-aqueous sol–gel technique

Clear aluminium oxide sols without precipitation were synthesized via a non-aqueous sol–gel technique using three different alcohols (ethanol, isopropanol and n-butyl alcohol) as solvent, aluminium sec-butoxide as a precursor and acetyl acetone as a chelating agent. Although all sols could be successfully used to prepare thin films, the most stable one was prepared with n-butyl alcohol. Highly transparent, homogenous and amorphous aluminium oxide thin films were obtained on Si substrates after a heat treatment at 500 °C. X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared absorption (FT-IR) spectroscopy revealed all films were hydroxide free. The optical and structural properties of the films were particularly investigated. Any significant difference except from thickness on the film properties was not observed by changing the alcohol. Refractive index was used as an indication of the porosity of the films and ranged from 1.54 to 1.60.     

Growth and characterization of molybdenum oxide thin films prepared by photochemical metal–organic deposition (PMOD)

Molybdenum oxide thin films have been successfully prepared by direct UV irradiation of amorphous films of a molybdenum dioxide acetylacetonate complex on Si(1 0 0) substrates. Photodeposited films were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) and the surface morphology examined by Atomic Force Microscopy (AFM). It was found that as-photodeposited films are uniform and smooth, with thickness of 350 nm, with rms surface roughness of 28 nm and contain non-stoichiometric oxides (MoO_3−x). The results of XRD analysis showed that post-annealing of the films in air at 450 °C transforms the sub-oxides to α-MoO₃ phase with a much rougher surface morphology (rms = 144 nm). The as-photodeposited MoO_3−x films are amorphous, and exhibit better optical quality than annealed films.     

Hybrid functional RuO2–Al2O3 thin films prepared by atomic layer deposition for inkjet printhead

Hybrid functional RuO₂–Al₂O₃ thin films were prepared by atomic layer deposition using bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp)₂) and trimethyl aluminum (TMA). The intermixing ratios between RuO₂ and Al₂O₃ in the RuO₂–Al₂O₃ thin films were controlled from (RuO₂)_0.16–(Al₂O₃)_0.84 to (RuO₂)_0.72–(Al₂O₃)_0.28. With the RuO₂ intermixing ratio less than 0.43, both temperature coefficient of resistance (TCR) values and resistivities were abruptly changed. The TCR values for RuO₂–Al₂O₃ thin films were changed from ?381 to ?62.3 ppm/K by changing the RuO₂ intermixing ratios from 0.43 to 0.83, while the resistivities were also changed from 1,200 to 243 μΩ·cm. Moreover, the change in the TCR of RuO₂–Al₂O₃ thin films was below 127 ppm/K even after O₂ annealing process at 700 °C. Moreover, it showed that RuO₂–Al₂O₃ thin films had a high corrosion resistance due to the highly corrosion-resistive RuO₂ and Al₂O₃.     

Preparation and properties of VO2 thin films by a novel sol–gel process

Vanadium dioxide (VO₂) thin films were fabricated using a simple and novel sol–gel process in which V₂O₅ was used as the vanadium source; oxalic acid was used as the reducing agent; and polyvinyl alcohol was used as the film former to control the viscosity of the VO₂ precursor solution and bond vanadium ions. The microstructure and surface morphology of VO₂ films were studied by X-ray diffraction and scanning electron microscopy, respectively. The results showed that using polyvinyl alcohol forms porous nanostructure of VO₂ films with a uniform grain size of ~25 nm. The measured optical reflectance shows well-defined phase transition as observed by an increase of reflectance upon heating above the transition temperature from ~11 to ~30 % at 1,100 nm. Upon cooling, the expected hysteresis is observed.     

The morphologies and optoelectronic properties of delafossite CuFeO2 thin films prepared by PEG assisted sol–gel method

Single phase delafossite CuFeO₂ thin films were synthesized by a simple sol–gel method. The influence of polyethylene glycol (PEG) on the morphology and optoelectronic properties of the films was studied by addition of 1.0 g PEG in 10 ml precursor solution. The crystal sizes of the derived CuFeO₂ films with and without addition of PEG were 49 nm, but the sample with addition of PEG (labeled as CFO-PEG) showed weaker c-axis orientation growth. The sample without addition of PEG (labeled as CFO) showed a compact surface without detectable pores and had a thickness around 50 nm. However, the sample CFO-PEG exhibited a porous surface with worm-like grains in nanometric scale and had a thickness around 310 nm. Enhanced absorbance in UV–vis region was observed for the sample CFO-PEG which might ascribe to both the thickness and porous surface. The optical direct bandgaps at near-UV were estimated to be ~3.0 and 3.38 eV for the sample CFO-PEG and CFO, respectively. Though the porous surface of CFO-PEG has improved the absorbance in UV–vis region, the resistivity has also been increased due to the homogeneous distribution of interspaces between the worm-like grains, which makes the incident photon to current efficiency of CFO-PEG lower than that of CFO.     

Reaction dynamics of Mo + O(2) → MoO + O studied by a crossed-beam velocity map imaging technique

The oxidation reaction dynamics of gas-phase molybdenum atoms by oxygen molecules was studied under a crossed-beam condition. The product MoO was detected by a time-of-flight mass spectrometer combined with laser multi-photon ionization. An acceleration lens system designed for the ion-velocity mapping condition, a two-dimensional (2D) detector, and a time-slicing technique were used to obtain the velocity and angular distributions of the products at three collision energies: 10.0, 17.8, and 50.0 kJ/mol. The angular distributions showed forward and backward peaks, whose relative intensities changed by the collision energy. While two peaks had similar intensities at low collision energies, the forward peak became dominant at the highest collision energy, 50 kJ/mol. The product kinetic energy distributions showed a good correlation with the initial collision energies, i.e., almost the same energy as the collision energy appeared as the product kinetic energy. These results suggested that the reaction proceeds via an intermediate complex, and the lifetime of the complex becomes shorter than its rotational period at high collision energy.     

Quantitative analysis of thin films of RBa2Cu3O7−x (R-rare earth elements) and ZrO2 (Y2O3) buffer layers by SNMS

It is shown that RBa₂Cu₃O_7-X single crystals may be used as reference samples for the quantitative analysis of RBa₂Cu₃O_7-X thin films by SNMS. RSF-values for Y and Cu (relative to Ba) determined for ceramic RBa₂Cu₃O_7-X samples are higher than those for single crystals. This difference may be caused by Ba segregation on grain boundaries. The depth profile analysis of YSZ/Al₂O₃ samples was performed by DBM using a Ni grid to prevent sample charging. The reproducibility of analysis was better than 10%.     

Effect of Hg2+doping and of the annealing temperature on the nanostructural properties of TiO2 thin films obtained by sol–gel method

This work is a study of Hg²⁺-doped TiO₂ thin films deposited on silicon substrates prepared by sol–gel method and treated at temperatures ranging between 600 to 1000 °C for 2 h. The structural and optical properties of thin films have been studied using different techniques. We analyzed the vibrations of the chemical bands by Fourier transform infrared (FTIR) spectroscopy and the optical properties by UV–Visible spectrophotometry (reflection mode) and photoluminescence (PL). The X-ray diffraction and Raman spectra of TiO₂ thin films confirmed the crystallization of the structure under the form of anatase, rutile, mercury titanate (HgTiO₃) as a function of the annealing temperature. The observation by scanning electron microscopy (SEM) showed the changing morphology, with respect to nanostructures, nanosheets, nanotubes, with the annealing temperature. The diameters of nanotubes ranged from 50 nm to 400 nm. The photoluminescence and reflectance spectra indicated that these structures should enhance photocatalytic activity.     

Effectively Improving the Electrocatalytic Activity of PrBaMn2 O5+δ Anode by Doping Co，Ni and Fe北大核心CSCD

The development of efficient anode materials plays an important role in the large-scale commercialization of solid oxide fuel cell（SOFC）. Based on the design concept of component engineering,PrBaMn1. 6 X0. 4 O5+δ （PBMX,X = Co,Ni,Fe）layered perovskite anodes are synthesized by simple B-site doping transition metals into Pr0. 5 Ba0. 5 MnO3−δ. The effect of doping with different transition metals on the microstructure and electrochemical properties of PrBaMn2 O5+δ （PBMO）is systematically investigated,and the effect of A-site defects on the PBMX anodes is further analyzed. The results show that the doping effect of Co and Ni is obviously better than that of Fe,PrBaMn1. 6 Co0. 4 O5+δ （PBMC）and PrBaMn1. 6 Ni0. 4 O5+δ （PBMN）will generate more oxygen vacancies during the reduction process,and the electrochemical properties of the materials are better. Among them,PBMC has the highest catalytic activity as an anode material,with a polarization resistance of 0. 170 Ω·cm2 and a peak power density of 874 mW/cm2 at 800 ℃ in H2 ,showing that the enhancement of the electrochemical activity is due to the enhancement of the surface roughness and the increase of oxygen vacancies. In addition,the introduction of A-site deficiency can improve the performance of PBMX,the polarization resistance of P0. 6BMC is only 0. 090 Ω·cm2 and the peak power density is 952 mW/cm2 at 800 ℃. © 2022, Science Press (China). All rights reserved.     

The influence of annealing on electrochromic properties of Al–B–NiO thin films prepared by sol–gel

Al–B–NiO thin films were prepared using the sol–gel process and deposited on Indium tin oxide (ITO)-coated glass substrates via the dip-coating technique for the purpose of developing high performance electrochromic materials. The influence of the anneal on the structural and electrochromic properties of Al–B–NiO films is reported. Thermogravimetry (TG) and differential thermal analysis (DTA), cyclic voltammetry measurements (CV), UV spectrophotometer, atomic force microscopy (AFM) and X-ray diffraction (XRD) have been used to investigate the structural and electrochromic properties. The thickness of the films was determined by spectrophotometric analysis in 350–1,000 nm wavelength. Results showed that the Al–B–NiO thin films treated at high temperature have both the excellent electrochromic properties and good reversibility. The transmittance change (ΔT) of the film treated at 500 °C reaches still ~50% at the wavelength of 550 nm. The microstructure and the surface morphology were considered to play an important role in the electrochromic properties with different temperatures.     

The sensor properties of Fe2O3 · In2O3 films: The detection of low ozone concentrations in air

The detection of low ozone concentrations in air (no higher than 120 ppb) using semiconducting films based on Fe₂O₃ · In₂O₃ obtained by laser ablation of the corresponding targets onto alumina substrates was studied. The temperature of the substrate during film deposition influenced their sensor properties. Temperature effects on the sensitivity of the films with respect to ozone were studied over the temperature range 200–380°C. Maximum sensitivity was reached at 250°C irrespective of the temperature of film deposition. The dependence of film sensitivity on the concentration of ozone in air was determined. At equal ratios between In₂O₃ and Fe₂O₃, the sensitivity of the sensor films prepared by laser ablation was much higher than that of thick-film sensors obtained from aqueous metal oxide suspensions by the stenciling technique. Possible reasons for the effects observed were considered.     

Transport properties of Al doped SmBa2Cu3O6+δ superconductor. Part I: oxygen non-stoichiometry and diffusion

The oxygen non-stoichiometry and diffusion in SmBa₂Cu_3−xAl_xO_6+δ superconductor were investigated by means of thermogravimetric analysis (TGA) in a wide $P({\mathrm{O}}_2)$ $(1⩽P({\mathrm{O}}_2)⩽{10}^{-4}\text{atm})$ and T $(400⩽T⩽800\text{°C})$ range. Thermogravimetric data at fixed oxygen partial pressures were collected using temperature steps and long isotherms. The samples used for TG analysis were previously sieved in order to obtain powders of known particle dimensions. This procedure allowed to determine both the oxygen non-stoichiometry and its diffusion coefficient in SmBa₂Cu_3−xAl_xO_6+δ. With respect to undoped SmBa₂Cu₃O_6+δ, the corresponding δ values are quite similar in oxidising conditions, while the doped material loses less oxygen than the pure one in reducing conditions. For what concern the oxygen diffusion, aluminium doping does not affect the activation energy for that process; on the opposite the absolute D value is at least one order of magnitude lower than in the pure phase and the D varies as a function of $P({\mathrm{O}}_2)$. All the above features are interpreted under the hypothesis that, in the thermodynamic conditions of the experiments, only O4 oxygen ions and sites surrounded by two Cu1 ions are involved into gas–solid equilibria and into diffusion process.     

Evaluation of stability of Pr2−xNdxNiO4+δ by thermogravimetry under various oxygen partial pressures

Journal of Thermal Analysis and Calorimetry - The thermodynamic and kinetic stability of Pr2?xNdxNiO4+δ was evaluated by thermogravimetry (TG) under a varying oxygen partial pressure...