Effects of annealing temperature on the microstructure,ferroelectric and dielectric properties of W-doped Na0.5Bi0.5TiO3 thin films

The effects of annealing temperature on the structure, morphology, ferroelectric and dielectric properties of Na_0.5Bi_0.5Ti_0.99W_0.01O_3+δ (NBTW) thin films are reported in detail. The films are deposited on indium tin oxide/glass substrates by a sol-gel method and the annealing temperature adopted is in the range of 560–620 °C. All the films can be well crystallized into phase-pure perovskite structures and show smooth surfaces without any cracks. Particularly, the NBTW thin film annealed at 600 °C exhibits a relatively large remanent polarization (P_r) of 20 μC/cm² measured at 750 kV/cm. Additionally, it shows a high dielectric constant of 608 and a low dielectric loss of 0.094 as well as a large dielectric tunability of 62%, making NBTW thin film ideal in the room-temperature tunable device applications.     

The effect of the annealing atmosphere on the properties of Sr2Bi4Ti5O18 ferroelectric thin films

The Sr₂Bi₄Ti₅O₁₈ (SBT-5) ferroelectric thin films were prepared on Pt/Ti/SiO₂/Si substrate using the sol-gel method and annealing in oxygen, air, and nitrogen. Their properties were measured. After annealing in oxygen, the films showed good crystallization and a larger average grain size of approximately 34.05 nm. XPS analysis clearly showed that annealing in oxygen inhibited the generation of oxygen vacancies in the films, which contributed to the melioration of the ferroelectric properties. The remanent polarization was 20.09 μC/cm² and the coercive field was 75 kV/cm. When the electric field was 15 kV/cm, the leakage current density was approximately 3.88 × 10⁻⁷A/cm², while the Ohmic conduction was the dominating leakage mechanism. Because the content of the oxygen vacancy in the samples annealed in oxygen atmosphere was lower, the fixing effect on the domain structure was weaker and the volume effect was not obvious, so the aging degree of the samples was low. The larger relative dielectric constant was 742, while the dielectric loss was 0.037 when the test frequency was 2.0 × 10⁵ Hz.     

Effects of the annealing atmosphere on the microstructure and properties of BiFe0.99Zn0.01O3 films

BiFe_0.99Zn_0.01O₃ (BFZO) films were annealed in different atmospheres (Air, N₂ and O₂) on ITO/glass substrates. The influences of the different annealing atmospheres on the oxygen vacancy concentration, microstructure, ferroelectric behavior, leakage current, leakage mechanism, aging and dielectric performance of the BFZO films were studied. The crystallization and grain development for the sample annealed in an O₂ atmosphere improved, and the concentrations of the Fe²⁺ and oxygen vacancies were the lowest among the samples studied herein. The BFZO film had the lowest leakage current density and the best ferroelectric performance in an O₂ annealing atmosphere among the samples studied herein, and the leakage was due to the F-N tunneling effect mechanism. From the perspective of the volume effect, the aging model was established, and the aging mechanism of the BFZO films was discussed in depth. Compared with Air and N₂, the annealed film in O₂ exhibited no obvious aging.     

Effect of annealing on SiC thin films prepared by pulsed laser deposition

Crystalline cubic SiC thin films were successfully fabricated on Si(100) substrates by using laser deposition combined with a vacuum annealing process. The effect of annealing conditions on the structure of the thin films was investigated by X-ray diffraction and Fourier transform infrared spectroscopy. It was demonstrated that amorphous SiC films deposited at 800°C could be transformed into crystalline phase after being annealed in a vacuum and that the annealing temperature played an important role in this transformation, with an optimum annealing temperature of 980°C. Results of X-ray photoelectron spectroscopy revealed the approximate stoichiometry of the SiC films. The characteristic microstructure displayed in a scanning electron microscope image of the films was indicative of epitaxial growth along the (100) plane.     

Ferroelectric properties of pure ZrO2 thin films by chemical solution deposition

Ferroelectricity in pure zirconia (ZrO₂) thin films, manufactured on Si (100) substrates via the chemical solution deposition method using all-inorganic aqueous salt precursor, has been demonstrated for the first time. The influence of thickness on the crystalline structure and ferroelectric properties of the thin films were measured and showed that they were strongly affected by the film thickness. The structural data indicated that as the film thickness increased from 30 nm to 50 nm, the m-phase fraction increased, and a phase transition from orthorhombic to cubic and then tetragonal occurred near the main diffraction peak of 30.7°. The lowest m-phase fraction of 15.4% was obtained in the pure ZrO₂ film with a thickness of 30 nm, and after 10³ field cycling, it exhibited the highest relative permittivity of 39.6 as well as the highest residual polarization of 8.5 μC/cm².     

Study of Cu-based Al-doped ZnO multilayer thin films with different annealing conditions

AZO/Cu/AZO multilayer thin films produced under different annealing conditions are studied in this paper, to examine the effects of atmosphere and annealing temperature on their optical and electrical properties. The multilayer thin films are prepared by simultaneous RF magnetron sputtering (for AZO) and DC magnetron sputtering (for Cu). The thin films were annealed in a vacuum or an atmosphere of oxygen at temperatures ranging from 100 to 400 °C in steps of 100 °C for 3 min. High-quality multilayer films (at Cu layer thickness of 15 nm) with resistivity of 1.99×10⁻⁵ Ω-cm and maximum optical transmittance of 76.23% were obtained at 400 °C annealing temperature in a vacuum. These results show the films to be good candidates for use as high quality electrodes in various displays applications.     

Ferroelectric yttrium doped hafnium oxide films from all-inorganic aqueous precursor solution

We report a unique aqueous solution deposition method to prepare yttrium doped hafnium oxide (Y:HfO₂) thin films using all-inorganic reagents. The composition and chemical bonding features of the films were investigated using X-ray photoelectron spectroscopy. The Y:HfO₂ film was integrated into metal-insulator-semiconductor (MIS) structure capacitors for electrical measurements. A transition of the polarization behavior from apparent ferroelectric-type to linear dielectric-type was observed for films with thickness increasing from 25?nm to 80?nm, which is correlated to the dominant crystal structure change from high-symmetry phase to monoclinic phase evidenced by grazing incidence X-ray diffraction analysis.     

Effect of doping concentration on the properties of aluminium doped zinc oxide thin films prepared by spray pyrolysis for transparent electrode applications

Zinc oxide possesses many interesting properties, such as modifiable conductivity, wide band gap, high excitonic binding energy, piezo-electric polarisation and cathodoluminiscence. In this study transparent conducting aluminium doped zinc oxide (ZnO:Al) thin films were deposited on float glass substrates by tailor made spray pyrolysis with adaptation for measuring the actual temperature of the substrate surface during deposition. The films were characterised and the effect of aluminium doping concentration [Al/Zn] on their optical, electrical and structural properties was investigated as a function of aluminium doping between 0 and 10 at.%. There was widening of optical band gap with increasing doping concentration. ZnO:Al films with low resistivity of 2.8 × 10⁻² Ω cm and high transmittance of over 85% at 550 nm which are crucial for opto-electrical applications were obtained at a doping ratio of 2 at.%.     

Gallium oxide films deposition by RF magnetron sputtering; a detailed analysis on the effects of deposition pressure and sputtering power and annealing

In this study, gallium oxide (Ga₂O₃) thin films were deposited on sapphire and n-Si substrates using Ga₂O₃ target by radio frequency magnetron sputtering (RFMS) at substrate temperature of 300 °C at variable RF power and deposition pressure. The effects of deposition pressure and growth power on crystalline structure, morphology, transmittance, refractive index and band gap energy were investigated in detail. X-ray diffraction results showed that amorphous phase was observed in all the as-deposited thin films except for the thin films grown at low growth pressure. All the films showed conversion to poly-crystal β-Ga₂O₃ phase after annealing process. When the deposition pressure increased from 7.5 mTorr to 12.20 mTorr, change in the 2D growth mode to 3D columnar growth mode was observed from the SEM images. Annealing clearly showed formation of larger grains for all the thin films. Lower transmission values were observed as the growth pressure increases. Annealing caused to obtain similar transmittance values for the thin films grown at different pressures. It was found that a red shift observed in the absorption edges and the energy band gap values decrease with increasing growth pressure. For as-deposited and annealing films, increasing sputtering power resulted in the increase refractive index.     

The effect of calcium zirconate modifications on the microstructure and functional properties of sodium niobate thin films prepared by chemical solution deposition

Sodium niobate thin films doped with manganese (NN), and NN films modified with 5 or 10 mol % calcium zirconate (CZ) on platinized silicon substrates were prepared by chemical solution deposition. The 250-nm-thick films crystallize in a perovskite phase with fine, equiaxed grains. The NN films exhibit well-shaped ferroelectric loops with a remanent polarization and coercive field of ～10 μC/cm² and ～100 kV/cm, respectively. The modification with CZ strongly influences the ferroelectric response of the films: the remanent polarization progressively decreases to around 2.5 μC/cm². The absence of an anti-ferroelectric response, which has previously been confirmed in bulk NN-CZ ceramics, is attributed to the nanoscale microstructure and residual thermal stresses. All the studied films exhibit a piezoelectric response with the highest piezoelectric d₃₃ coefficient of 35 pm/V at 300 kV/cm bias field for the NN modified films with 5 mol % CZ, making them candidates for lead-free piezoelectric thin-film applications.     

Impacts of thickness reduction and heat treatment on the optical properties of thin chalcogenide films

Bi-based chalcogenides, in the form of thin crystalline films, were deposited at different thicknesses onto highly cleaned glass slides with the aid of vacuum thermal evaporation technique. The influence of thermal annealing on the optical properties of Bi₂Te₃-Bi₂Se₃ films at different thicknesses is investigated in this work. Wavelength dependence of the optical transmittance and reflectance was recorded, for the as-prepared and the annealed films, in the wavelength range from 350 to 2700 nm using a double beam spectrophotometer. Fundamental optical properties such as absorption coefficient and energy band gap were derived based on the measured spectra and film's thickness. We demonstrate in the present work that the synergy of annealing and thickness reduction can be exploited for light transmittance enhancements, and consequently for optoelectronic applications including transparent conductive electrodes.     

The influence of the crystallization temperature on the reliability of PbTiO3 thin films prepared by chemical solution deposition

The preparation of quality ferroelectric PbTiO₃ (PT) thin films at the lowest possible temperature preserving its functional properties is necessary for their integration in microdevices. The crystallization below, close or above the para-ferrolectric transition temperature of the PbTiO₃ must produce an important effect on the microstructure, texture and residual stress state of the films and on functional properties. In this paper, the Chemical Solution Deposition method has been used to prepare PbTiO₃ films at different temperatures around that of the ferroelectric to paraelectric phase transition. The films were analyzed by X-ray diffraction, Optical and Scanning Electron Microscopy, and their microstructure, texture and residual stress correlated with their functional properties. The results show that these PT films prepared with crystallization temperatures close or below the phase transition develop a favorable microstructure and texture that lead to high remnant and saturation polarization values, making them good candidates for their integration in microdevices.     

Highly conducting and transparent antimony doped tin oxide thin films: the role of sputtering power density

Sb doped SnO₂ thin films were deposited on quartz substrates by magnetron sputtering at 600 °C and the effects of sputtering power density on the preferential orientation, structural, surface morphological, optical and electrical properties had been studied. The XRD analyses confirm the formation of cassiterite tetragonal structure and the presence of preferential orientation in (2 1 1) direction for tin oxygen thin films. The dislocation density analyses reveal that the generated defects can be suppressed by the appropriate sputtering power density in the SnO₂ lattice. The studies of surface morphologies show that grain sizes and surface roughness are remarkably affected by the sputtering power density. The resistivity of Sb doped SnO₂ thin films gradually decreases as increasing the sputtering power density, reaches a minimum value of 8.23×10⁻⁴ Ω cm at 7.65/cm² and starts increasing thereafter. The possible mechanisms for the change in resistivity are proposed. The average transmittances are more than 83% in the visible region (380–780 nm) for all the thin films, the optical band gaps are above 4.1 eV. And the mechanisms of the variation of optical properties at different sputtering power densities are addressed.     

Effects of oxygen sources on properties of atomic-layer-deposited ferroelectric hafnium zirconium oxide thin films

Orthorhombic Hf_xZr_1-xO₂ (HZO) is a promising ferroelectric material for realizing ferroelectric devices in the modern semiconductor industry because of its excellent CMOS compatibility and scalability. Atomic layer deposition (ALD) facilitates the growth of robust ferroelectric HZO films that can be used in nanoelectronic devices. Herein, we provide a comprehensive understanding of the effects of the oxygen source, either H₂O or O₃, on the properties of ALD-grown HZO films. Although the growth per cycle promoted by ALD does not change with the type of oxygen source, the impurity content of the HZO film grown with H₂O are higher than that with O₃. The low impurity content of the HZO film grown with O₃ results in low leakage current. The ALD process with O₃ further suppresses the emergence of the nonferroelectric monoclinic phase in the ferroelectric orthorhombic HZO matrix. Consequently, the HZO film grown with O₃ exhibits a small coercive field for ferroelectric domain switching and high electrical reliability. This study demonstrates that O₃ is more favorable for growing high-quality HZO films via ALD by using metal precursors comprising tetrakis(ethylmethylamino) ligands.     

Effect of oxygen flow ratio on crystallization and structural characteristics of gallium oxide thin films

Beta-gallium oxide (β-Ga₂O₃) thin films were prepared on a MgO (100) substrate under different oxygen flow ratios via magnetron sputtering. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and UV–visible near-infrared (UV–vis–NIR) analyses were conducted to study how the oxygen flow ratio affected the crystalline quality and the surface topography of the films. Microstructure analysis revealed a clear out-of-plane orientation of β-Ga₂O₃ (100) || MgO (100). The film deposited under an oxygen flow ratio of 1% presented the optimal single-crystalline structure, while excess oxygen was confirmed to negatively impact the crystallization characteristics of the films. SEM measurements indicated that the increase in the oxygen flow ratio reduced the grain size and RMS roughness. The average transmittance of the β-Ga₂O₃ films in the visible range exceeded 83%, with a broad luminescence band exhibited at approximately 485 nm in the photoluminescence (PL) spectra.     

Electrochromism in spray deposited iridium oxide thin films

Electrochromic iridium oxide thin films were deposited onto fluorine doped tin oxide coated glass substrates from an aqueous iridium chloride solution by pneumatic spray pyrolysis technique. The as-deposited samples were X-ray amorphous. The electrochromic properties of thin films were studied in an aqueous electrolyte (0.5N H₂SO₄) using cyclic voltammetry (CV), chronoamperometry (CA) and spectrophotometry. Iridium oxide films show pronounced anodic electrochromism owing to Ir⁺⁴ ↔ Ir⁺³ intervalency charge transition. The reversibility of cyclic process in Ir oxide films is found to be higher, which increases with increasing number of colour-bleach cycles.     

Effect of annealing temperature on the evolution of structural,microstructural, and optical properties of spin coated ZnO thin films

Zinc oxide (ZnO) thin films were sol-gel spin coated on glass substrates and annealed at various temperatures from 300–500 °C. Zinc acetate dihydrate (ZAD), monoethanolamine (MEA), and 2-methoxyethanol were used as the starting materials, stabilizer and solvent, respectively. The effect of annealing temperature on the structural and optical properties of the ZnO thin films was investigated by X-ray diffractometer (XRD), atomic force microscope (AFM), UV–VIS spectrophotometry and ellipsometry. The XRD results showed the films to have a preferential c-axis orientation, whereas the AFM results confirmed a columnar structure. The surface roughness increased with the increase in annealing temperature. Parameters such as ratio of free charge carrier concentration to effective mass (N/m*) and plasma frequency (ω_p) were determined from the transmittance graph using the Wemple di Domenico model. Both N/m* and ω_p were noticed to reduce with the increase in annealing temperature. Band gap decreased with the increase in the annealing temperature indicating absorption edge shift towards the red region.     

Transformation of sputtered calcium copper titanate thin film into nanorods by sequential annealing

Rapid synthesis of long calcium copper titanate (CCTO) nanorods was carried out by sequential annealing. CCTO thin films have been deposited on p-Si substrate by RF sputtering technique and afterwards, the samples were thermally treated using a preheated furnace by varying the annealing temperature from 850 °C to 1100 °C. CCTO nanorods of 12 µm lengths and 400–600 nm diameters were synthesized at 1100 °C. Based on the FESEM observations, a plausible growth mechanism has been proposed to explain the formation of nanorods. The (220) XRD peak of the CCTO film became prominent for the annealing temperature of 950 °C. The presence of nanoscale crystals in amorphous matrix has been observed by HRTEM studies. The elemental mapping of CCTO nanorod has shown a spatial variation of elements throughout the nanorod. The oxide and interface charge density was found to be increased with the rise in annealing temperature.     

Effect of doped niobium pentoxide on structure and properties of hafnium oxide films deposited by ion beam assisted deposition

Hafnium oxide is widely used in optical coating materials because of its high refractive index, broad band gap, high laser damage threshold and its high transparency in the wavelength range from ultraviolet to middle infrared (0.20–12 μm). However, hafnium oxide has some defects such as strong crystallinity and poor surface quality, which results in enhanced absorption and reflection of light wave and limits its application in optical field. As a pentoxide with high transparency and excellent optical properties in the wavelength range from ultraviolet to mid-infrared(0.35–9 μm), the doping of niobium pentoxide can effectively improve the surface quality and optical properties of the films. Mixed films with different chemical compositions were prepared by ion beam assisted deposition, and the microstructure, crystallinity, surface quality, optical properties and mechanical properties of the mixed films with different chemical compositions were investigated. The doping of niobium pentoxide inhibits the crystallization of hafnium oxide, optimizes the surface quality of the films, and improves the refractive index and mechanical properties of mixed films, effectively broadens the application of hafnium oxide in the field of optical films.