High-quality c-axis oriented non-vacuum Er doped ZnO thin films

Preparation, growth, structure and optical properties of high-quality c-axis oriented non-vacuum Er doped ZnO thin films were studied. Zn_1−xEr_xO (x=0.0, 0.01, 0.02, 0.04, and 0.05) precursor solutions were prepared by sol–gel synthesis using Zn, and Er based alkoxide which were dissolved into solvent and chelating agent. Zn_1−xEr_xO thin films with different Er doping concentration were grown on glass substrate using sol–gel dip coating. Thin films were annealed at 600 °C for 30 min, and tried to observe the effect of doping ratio on structural and optical properties. The particle size, crystal structure, surface morphologies and microstructure of all samples were characterized by X-Ray diffraction (XRD) and Scanning Electron Microscope (SEM). The UV–vis spectrometer measurements were carried out for the optical characterizations. The surface morphology of the Zn_1−xEr_xO films depend on substrate nature and sol–gel parameters such as withdrawal speed, drying, heat treatment, deep number (film thickness) and annealing condition. Surface morphologies of Er doped ZnO thin films were dense, without porosity, uniform, crack and pinhole free. XRD results showed that, all Er doped ZnO thin films have a hexagonal structure and (002) orientation. The optical transmittance of rare earth element (Er) doped ZnO thin films were increased. The Er doped ZnO thin films showed high transparency (>85) in the visible region (400–700 nm).     

Effects of aqueous ethanol solutions on the structural and magnetic properties of NiZn ferrite thin films prepared by spin-spray deposition

Although substrate wettability greatly impacts deposition processes using the spin-spray technique, there are few substrates suitable for the deposition of spin-sprayed ferrite thin films. To tune substrate wettability without changing the type of substrate, we demonstrate a Ni_0.17Zn_0.52Fe_2.31O₄ ferrite film deposited by the spin-spray technique on a 0.2 mm glass substrate with 0–5% aqueous ethanol solutions. All samples showed (222) preferential orientation and triangular grain morphology. The effects of aqueous ethanol solutions on the microstructure and magnetic properties of ferrite thin films were also investigated. When the ethanol volume percent concentration equaled 3%, the columnar morphology of the microstructure was most evident and the saturation magnetization and the real permeability reached their maximum values. Because of the shape anisotropy of the columnar structure, the coercivity of the parallel magnetic field increased, whereas the coercivity of the perpendicular magnetic field decreased. First-order inversion curve measurements revealed that ethanol-containing ferrite thin films had a more uniform grain size.     

Synthesis and investigation of environmental protection and earth-abundant kesterite Cu2MgxZn1-xSn(S,Se)4 thin films for solar cells

We have synthesized Cu₂Mg_xZn_1–xSn(S,Se)₄ (0?≤?x?≤?0.6) thin films by a facile sol-gel method, and studied the influence of Mg concentration on the crystal structure, surface morphology and photoelectric performance of Cu₂Mg_xZn_1–xSn(S,Se)₄ thin films systematically. It was shown that the smaller Zn²⁺ in Kesterite phase Cu₂ZnSn(S,Se)₄ will be replaced by larger Mg²⁺, forming uniform pure phase Cu₂Mg_xZn_1–xSn(S,Se)₄. The band gap of Cu₂Mg_xZn_1–xSn(S,Se)₄ films can be adjusted from 1.12 to 0.88?eV as the x value changes from 0 to 0.6. Furthermore, the Cu₂Mg_xZn_1–xSn(S,Se)₄ thin films with large grain size, smooth surface and less grain boundaries was obtained at an optimized condition of x?=?0.2. The carrier concentration of Cu₂Mg_xZn_1–xSn(S,Se)₄ thin film reaches the maximum 6.47?×?10¹⁸ cm^?3 at x?=?0.2, which is a potential material to be the absorption layer of high efficiency solar cells.     

Effect of substrate temperature on the properties of TiO2 nanoceramic films

TiO₂ nanoceramic films were deposited on glasses by rf magnetron sputtering. This method provides more advantages in controlling the microstructure and composition of the films. TiO preferentially formed and the deposited films tended to become nonstoichiometric by increasing substrate temperature. The morphologies and hydrophilic properties of TiO₂ films were significantly affected by the substrate temperature. The nonlinear refractive index of the TiO₂ film on the glass substrate measured by Moiré deflectometry was of the order of 10^?8 cm² W^?1. Smaller grain size, higher optical energy gap, visible transmission and linear refractive index, and lower stress-optical coefficient were obtained at lower substrate temperature.     

Sol–gel derived amorphous/nanocrystalline MgZnO thin films annealed by atmospheric pressure plasma jets

This paper reports the characterization of sol–gel derived MgZnO thin films annealed by atmospheric pressure plasma jets (APPJs). Mg_xZn_1−xO films exhibit high transparency (> 80%) in the visible light wavelength region. When 20 at% Mg is incorporated into the film, the optical bandgap reveals a blue shift from ~3.25 to ~3.5 eV and the resistivity increases by three to four orders of magnitude, owing to the substitution of Mg atoms into the Zn lattice sites. The absorption band edge becomes sharper and the bandgap becomes slightly narrower as the APPJ treatment time increases. This can be attributed to slight grain growth in the films. When the material is amorphous/nanocrystalline, the quantum confinement effect causes a slight decrease in the bandgap as the grain size increases, resulting in slope alteration at the absorption edge. Compressive stresses caused by the difference in the thermal expansion coefficients between the film and the substrate are generated during the drying process. This leads to surface wrinkling on the sol–gel derived Mg_0.2Zn_0.8O thin films.     

Investigation into the effect of substrate material on microstructure and optical properties of thin films deposited via magnetron sputtering technique

This study aims at investigating the effect of the substrate material on growth mechanism and also microstructure of Ta₂O₅ thin films. For this purpose, atomic force microscopy, scanning electron microscopy, and interferometry analyses were implemented to reveal the influence of silicon wafer and amorphous BK7 glass substrates on the nucleation and growth mechanisms of Ta₂O₅ thin films deposited via the radio frequency magnetron sputtering technique. Results indicated that those films with finer morphologies had relatively higher nucleation densities. Compared with BK7 glass substrate, crystals formed on the silicon wafer were shown to be finer and had lower mean areas in more nucleation sites. Moreover, optical properties and morphological characteristics of the films on the silicon substrates had much more endurance after the annealing treatment. It was observed that shift in the transmission spectra of the deposited films after the treatment was insignificant, implying high packing density of the films. However, a 6-nm shift in the transmission spectra indicated low density and high porosity of the films. Finally, atomic force microscopy analysis along with the light scattering measurements confirmed the formation of a low-roughness film on the silicon wafer substrates.     

Sol-gel processed highly (100)-textured (K,Na)NbO3-based lead-free thin films: Effect of pyrolysis temperature

Recently, lead-free piezoelectric thin films have received increasing attention due to the growing demands for mircoelectromechanical systems and the significant progress in lead-free piezoelectric research. Here, potassium sodium niobate [(K, Na)NbO₃ (KNN)]-based thin films were fabricated via a sol-gel method. The effects of pyrolysis temperature on the resulting microstructure and electrical properties of KNN-based films were investigated. The KNN-based film pyrolyzed at 550°C and annealed at 700°C shows a dominant (100) orientation with a high texturing degree of 91.7%. The microstructures, morphologies, piezo- and ferroelectric properties of the KNN-based films were discussed in association with different pyrolysis temperatures. The crystallization mechanism of the (100) textured KNN-based thin films was elaborated in detail.     

Controlled synthesis of Mg(OH)2 thin films by chemical solution deposition and their thermal transformation to MgO thin films

The chemical solution deposition of Mg(OH)₂ thin films on glass substrates and their transformation to MgO by annealing in air is presented. The chemical solution deposition consists of a chemical reaction employing an aqueous solution composed of magnesium sulfate, triethanolamine, ammonium hydroxide, and ammonium chloride. The as-deposited films were annealed at different temperatures ranging from 325 to 500?°C to identify the Mg(OH)₂-to-MgO transition temperature, which resulted to be around 375?°C. Annealing the as-deposited Mg(OH)₂ films at 500?°C results in homogeneous MgO thin films. The properties of the Mg(OH)₂ and MgO thin films were analyzed by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, UV–Vis spectroscopy, and by circular transmission line model. Results by X-ray diffraction show that the as-deposited thin films have a brucite structure (Mg(OH)₂), that transforms into the periclase phase (MgO) after annealing at 500?°C. For the as-deposited Mg(OH)₂ thin film, a nanowall surface morphology is found; this morphology is maintained after the annealing to obtain MgO, which occurred with the evident formation of pores on the nanowall surface. The assessed chemical composition from X-ray photoelectron spectroscopy yields Mg_0.36O_0.64 (O/Mg ratio of 1.8) for the as-deposited Mg(OH)₂ film, where the expected stoichiometric composition is Mg_0.33O_0.67 (O/Mg ratio of 2.0); the same assessment yields Mg_0.60O_0.40 (O/Mg ratio of 0.7) for the annealed thin film, which indicates the obtainment of a MgO material with oxygen vacancies, given the deviation from the stoichiometric composition of Mg_0.50O_0.50 (O/Mg ratio of 1.0). These results confirm the deposition of Mg(OH)₂ films and the obtainment of MgO after the heat-treatment. The energy band gap of the films is found to be 4.64 and 5.10?eV for the as-deposited and the film annealed at 500?°C, respectively. The resistivity of both Mg(OH)₂ and MgO thin films lies around 10⁸?Ω·cm.     

Effects of annealing temperatures on energy storage performance of sol-gel derived (Ba0.95, Sr0.05) (Zr0.2, Ti0.8) O3 thin films

Dielectric polarization and breakdown strength of dielectrics generally show directly and inversely dependent upon their crystallization, respectively. Therefore, achieving the maximum energy storage density should be expected by controlling the crystallization. A serial of ferroelectric (Ba_0.95, Sr_0.05)(Zr_0.2, Ti_0.8)O₃ (BSZT) thin films were prepared by the sol-gel method. Effects of annealing temperatures on the microstructure, dielectric and energy storage performance of the films were investigated. The results indicate that BSZT thin films annealed at 600 °C for 30 min demonstrate the highest recoverable energy density and efficiency (50.5 J/cm³ and 91.9%). Such superior energy storage performance is attributed to an ultrahigh electric breakdown strength (6.65 MV/cm) induced by the dense amorphous-nanocrystalline microstructure. This work creates a new way for optimizing the energy storage performance of dielectric thin films via balancing their dielectric polarization and breakdown strength at appropriate heating processing temperature.     

Improved Crystal Quality of Transparent Conductive Ga‐doped ZnO Films by Magnesium Doping Through Radio‐Frequency Magnetron Sputtering Preparation

This study investigates the enhanced structural, and optoelectronic properties of transparent conductive Ga‐doped Mg_xZn_{1 ? x}O (GMZO) thin films with a varied magnesium (Mg) composition of 2% and 8%, respectively. The X‐ray diffraction (XRD) measurements revealed that GMZO with an 8% Mg composition shows a stronger (002) diffraction intensity and narrower linewidth than that with a 2% Mg composition. Improved crystallinity and enlarged grain size in the postgrowth thermal annealed GMZO thin films were also observed in XRD and morphological measurements by atomic force microscopy. Photoluminescence measurements were conducted to investigate the improved GMZO thin‐film quality, and the oxygen vacancy signal was found to decrease with increased Mg content, consistent with X‐ray photoelectron spectroscopy measurements. This study also shows high optical transmittance over 98%, and a low resistivity of 5.7 × 10^?4 Ω·cm in Ga‐doped Mg_xZn_{1 ? x}O (x = 0.02) thin film, which indicates the highly promising candidate for use in optoelectronic devices.     

Growth of Zn2GeO4 thin film by thermal evaporation on ITO substrate for thermoelectric power generation applications

In this paper, we have reported the growth of Zn₂GeO₄ thin film and investigated its potential for thermoelectric power generation applications. Zn₂GeO₄ alloy thin film was grown on Indium coated glass substrate by the evaporation of Zn and Ge metals with constant oxygen gas flow rate of 100 sccm in tube furnace. The grown film was cut into pieces and annealed at various temperatures from 500° to 700°C with a step of 100?°C in a programmable furnace for one hour. The structure of as grown and annealed thin films was verified by XRD and Raman spectroscopy measurements. The XRD data evident that Zn₂GeO₄ alloy hexagonal structure along with GeO₂ and ZnO phases were observed at annealing temperatures 600 and 700?°C but below this temperature no alloy phase was detected by XRD and Raman Spectroscopy. To calculate the thermoelectric properties, temperature dependent Seebeck measurements were performed in the temperature range of 25–100?°C. It was observed that the value of Seebeck coefficient was increased from 91 to 847?μV/K as the annealing temperature increases from 500° to 700°C. This behavior was explained as; high temperature causes stress and cracks in the grown films which may induce electric and thermal discontinues at tips of cracks which cause high thermoelectric concentration. Scanning electron microscope images verified the development of cracks in the samples as annealing temperature increases. The behavior of Seebeck coefficient with the measurement temperature was also observed and explained in detail. The high value of Seebeck coefficient suggested that this material can be a potential candidate for thermoelectric power generation applications in near future.     

Synthesis and characterization of Cu1-xZnxO composite thin films for sensor application

Cu_1-xZn_xO composite thin films were prepared using industrially applicable spray pyrolysis technique for volatile organic compound (VOCs) sensor application. Sensing properties for different concentration of VOCs such as acetone, ethanol and methanol were studied at different sensor operating temperature. XRD studies on prepared thin films confirmed formation of CuOZnO composite thin films with presence of different peaks for monoclinic structured CuO and hexagonal structure ZnO, it was also observed that formation of composite material improves sensing property towards VOCs. Granular morphology observed from SEM images were also contributed to enhance sensitivity of Cu_1-xZn_xO thin films. Hot probe experiment reveals that all the thin films were p-type in conductivity nature. Maximum electrical conductivity was achieved for Cu_0.75Zn_0.25O composite thin films, which also showed highest sensing property for VOCs. Cu_0.75Zn_0.25O thin films were selective towards ethanol and were capable of detecting 1 ppm of ethanol at operating temperature of 290 °C.     

溶胶-凝胶法制备Sm2O3光学薄膜

以氯化钐为起始原料,采用溶胶-凝胶法在玻璃和Si(100)基板上制备了Sm2O3光学薄膜,在300～800℃对薄膜进行1～3 h热处理.采用X射线衍射、原子力显微镜和紫外-可见自记式分光光度计等对薄膜的结晶取向、显微结构和光学性能进行了表征.结果表明:Sm2O3薄膜在玻璃基板和Si(100)基板上均表现出沿(311)晶面定向生长的特征;Si基板更有利于生长致密而且结晶良好的薄膜;所制备的薄膜对紫外线有强烈吸收作用,而对可见光有较好的透过作用,随着热处理温度的升高,薄膜结晶性变好,取向性增强,光吸收性能增强,薄膜的禁带宽度减小.     

Influence of Ca/Al Ratio on Properties of Amorphous/Nanocrystalline Cu–Al–Ca–O Thin Films

This article reports the characterization of thin films sputtered from CuAl_1?xCa_xO targets (x = 0, 0.05, 0.1, 0.15, and 0.2) at room temperature. All films exhibit amorphous/nanocrystalline structures. Their transparency increases slightly with the addition of Ca. Furthermore, the resistivity decreases as the Ca/Al atomic ratio increases. Transmission electron microscopy with energy dispersive spectroscopy mapping indicates that the composition is uniform throughout the films deposited from the highest Ca doping concentration target. Some nanocrystals are present at the top surface of the CuAl_0.8Ca_0.2O thin film as well as the interface region between the CuAl_0.8Ca_0.2O thin film and the glass substrate, whereas the interior of the film is pretty amorphous with some embedded nanocrystals. X‐ray photoelectron spectroscopy shows that the Cu²⁺/Cu⁺ atomic ratio increases with the Ca/Al atomic ratio, indicating the enhancement of p‐type conductivity from the nonisovalent Cu–O alloying.     

STRUCTURAL AND OPTICAL PROPERTIES OF ZNO THIN FILMS PREPARED BY DIFFERENT SOL-GEL PROCESSES

ZnO thin films were prepared on quartz glass substrates by different sol-gel methods using a spin-coating technique. The structural and optical properties of ZnO thin films were studied by X-ray diffraction (XRD) and transmission spectra analysis. The results show that different factors such as Zn²⁺ concentration, solvent, sol stabilizer, pre-heat treatment temperature, and annealing temperature have a great impact on the structural and optical properties of ZnO thin films.     

Fabrication of CaLa4(Zr0.05Ti0.95)4O15 thin films by RF magnetron sputtering

Crystalline CaLa₄(Zr_0.05Ti_0.95)₄O₁₅ thin films deposited on n-type Si substrates byRF magnetron sputtering at a fixed RF power of 100 W, an Ar/O₂ ratio of 100/0, an operating pressure of 3 mTorr, and different substrate temperatures were investigated. The surface structural and morphological characteristics analyzed by X-ray diffraction and atomic force microscopy were sensitive to the deposition conditions, such as the substrate temperature. The diffraction pattern showed that the deposited films had a polycrystalline microstructure. As the substrate temperature increased, the quality of the CaLa₄(Zr_0.05Ti_0.95)₄O₁₅ thin films improved, and the kinetic energies of the sputtered atoms increased, resulting in a structural improvement of the deposited CaLa₄(Zr_0.05Ti_0.95)₄O₁₅ thin films. A high dielectric constant of 16.7 (f=1 MHz), a dissipation factor of 0.19 (f=1 MHz), and a low leakage current density of 3.18×10⁻⁷ A/cm² at an electrical field of 50 kV/cm were obtained for the prepared films.     

Preparation and characterization of heteroepitaxial Zn2SnO4 single crystalline films prepared on MgO (100) substrates

Zinc stannate (Zn₂SnO₄) films were deposited on MgO (100) substrates by pulsed laser deposition, and Zn₂SnO₄ monocrystalline films were obtained by postannealing process. The structures, surface morphologies, and optical properties of the Zn₂SnO₄ films annealed at different temperatures were investigated in detail. Crystal structure analyses showed that the film annealed at 800°C was single crystal Zn₂SnO₄ with an inverse-spinel structure. The heteroepitaxial mechanism was further clarified by a schematic diagram, and the epitaxial relationships between the film and substrate were Zn₂SnO₄ (400) || MgO (200) with Zn₂SnO₄ [001] || MgO [001]. The obtained Zn₂SnO₄ films exhibited excellent transparency. The optical band gap of the 800°C-annealed Zn₂SnO₄ film was about 3.97 eV. The extinction coefficients and refractive indexes of the Zn₂SnO₄ films annealed at different temperatures as a function of wavelength were analyzed in detail.     

空气和氮气气氛中热处理温度对ITO薄膜性能影响

以InCl_3·4H_2O和SnCl_4·5H_2O为主要原料,采用溶胶-凝胶法和旋转涂膜工艺。在玻璃基片上制备掺锡氧化铟透明导电薄膜(ITO),采用x-射线粉末衍射、紫外-可见透射光谱和四探针技术,研究了在空气和氮气气氛中,不同热处理温度对ITO薄膜的微结构、光学和电学性能的影响。     

Effects of annealing atmospheres on the structure and ferromagnetic properties of Fe0.12Cu0.02Zn0.86O thin films

Fe_0.12Cu_0.02Zn_0.86O thin film was deposited on a Si substrate using r. f. sputtering with no heating and an Ar/O₂ ratio of 10%. After deposition, the specimens were annealed at 400 °C for 1 h, in nitrogen and hydrogen atmospheres. The X-ray diffractometry (XRD) analysis results show that the crystallinity of Fe_0.12Cu_0.02Zn_0.86O thin film annealed in a nitrogen atmosphere is better than that of the film annealed in a hydrogen atmosphere. The X-ray photoelectron spectroscope (XPS) results show that there are more oxygen vacancies in the Fe_0.12Cu_0.02Zn_0.86O thin film annealed in a hydrogen atmosphere. The magnetic force microscope (MFM) analysis results also demonstrate that some magnetism particles are precipitated for the Fe_0.12Cu_0.02Zn_0.86O thin film annealed in a hydrogen atmosphere. This results in an improvement in the ferromagnetic properties, and the saturation magnetization is 70.2 emu/cm³, which is about 25% larger than that for the as-grown Fe_0.12Cu_0.02Zn_0.86O thin film.     

Influence of post-annealing atmosphere on microstructure,optical and electrical properties of zinc cadmium oxide films deposited by DC and RF magnetron co-sputtering

Zinc cadmium oxide (Zn_1−xCd_xO) films were deposited on quartz substrates by direct current (DC) and radio frequency (RF) reactive magnetron co-sputtering and the influence of post-annealing atmosphere on their microstructure, optical and electrical properties were investigated by X-ray diffraction (XRD), optical absorbance, photoluminescence (PL) and Hall measurements. Results indicate that the band gap (E_g) of all Zn_1−xCd_xO films annealed in different atmospheres are smaller than that of the undoped ZnO, the observed shifts in E_g being 0.43, 0.37 and 0.32 eV for the Zn_1−xCd_xO films annealed in argon, oxygen and vacuum, respectively. Hall measurement results indicate that all Zn_1−xCd_xO films annealed in different atmospheres show the n-type conduction, but the Zn_1−xCd_xO film annealed in vacuum has low resistivity and high concentration, which has room-temperature resistivity of 1.59 Ω cm and carrier concentration of 2.07×10¹⁷ cm⁻³. Compared with Zn_1−xCd_xO films annealed in oxygen and argon, Zn_1−xCd_xO film annealed in vacuum has the best crystal quality, luminescence and electrical properties. The influencing mechanism of the post-annealing atmosphere on the electrical and optical properties of the Zn_1−xCd_xO film is discussed.