Structural stability of ZnFe2O4 nanoparticles under different annealing conditions

We study the structural stability of surfactant coated ZnFe₂O₄ (ZF) nanoparticles of average particle size 10 nm annealed under different environments. The X-ray diffraction studies in oleic acid coated ZF (OC-ZF) show distinctly different phase transitions under different annealing conditions. The OC-ZF is reduced to α-Fe/ZnO phase under vacuum while it forms FeO/ZnO under argon whereas the ZnFe₂O₄ phase remains stable under air annealing. The simultaneous thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC) coupled mass spectra (MS) in OC-ZF under argon atmosphere suggests that the residual carbon removes oxygen from the lattice to reduce the ZnFe₂O₄ phase into FeO/ZnO during argon annealing. Apart from CO and CO₂ gas evolution at high temperature under argon annealing, creation of oxygen vacancies due to the random removal of oxygen under vacuum annealing, leads to direct interaction between Fe–Fe and the formation of metal Fe. It appears that the residual carbon aids the reduction of ZF and the formation of α-Fe/ZnO during vacuum annealing. After annealing at 1000 °C in vacuum, the magnetization is increased abruptly from 13.8 to 106.5 emu g⁻¹. In sharp contrast, the air and argon annealed samples show a diminished magnetization of 1 emu g⁻¹. The field cooled (FC) and zero FC magnetization of vacuum and argon annealed samples exhibit superparamagnetic and spin-glass type behavior respectively. Our results offer possibilities to switch a magnetically inactive material to an active one.     

Optical and electrical properties of heat-resistant Sb-doped Sn1 − xHfxO2 transparent conducting films

To examine variations in the transparent conducting properties after annealing at high temperatures, 300-nm thick Sb-doped Sn_1 − xHf_xO₂ (x = 0.00-0.10) films were deposited onto silica glass substrates by the RF sputtering method and annealed in air up to 1000 °C at 200 °C increments. After annealing, all the Sb-doped SnO₂ films were transparent and electrically conductive, but large cracks, which decreased the electrical conductivity, were generated in several films due to crystallization or the thermal expansion difference between the film and substrate. Only the film deposited at room temperature in an Ar and O₂ mixed atmosphere did not crack after annealing, and its electrical conductivity exceeded 100 S cm^− 1 even after annealing at 1000 °C in air. Hf-doping blue shifted the fundamental absorption edges in the UV region in the Sb-doped Sn_1 − xHf_xO₂ films. Additionally, the optical transmission at 310 nm, T₃₁₀, increased as the Hf concentration increased, whereas the electrical conductivity was inversely proportional to the Hf concentration. On the other hand, thinner films (150-nm thick) with x = 0.00 showed both a high electrical conductivity over 100 S cm^− 1 and a high transparency T₃₁₀ = 65% after high temperature annealing.     

Effect of annealing on the electrical and optical properties of electron beam evaporated ZnO thin films

Zinc oxide thin films have been grown on (100)-oriented silicon substrate at a temperature of 100 °C by reactive e-beam evaporation. Structural, electrical and optical characteristics have been compared before and after annealing in air by measurements of X-ray diffraction, real and imaginary parts of the dielectric coefficient, refractive index and electrical resistivity. X-ray diffraction measurements have shown that ZnO films are highly c-axis-oriented with a full width at half maximum (FWMH) lower than 0.5°. The electrical resistivity increases from 10⁻² Ω cm to reach a value about 10⁹ Ω cm after annealing at 750 °C. The FWHM decreases after annealing treatment, which proves the crystal quality improvement. Ellipsometer measurements show the improvement of the refractive index and the real dielectric coefficient after annealing treatment at 750 °C of the ZnO films evaporated by electron beam. Atomic force microscopy shows that the surfaces of the electron beam evaporated ZnO are relatively smooth. Finally, a comparative study on structural and optical properties of the electron beam evaporated ZnO and the rf magnetron deposited one is discussed.     

Preparation and properties of Mg0.2Zn0.8O:Al UV transparent conducting thin films deposited by RF magnetron sputtering at room temperature with rapid annealing

Mg_0.2Zn_0.8O:Al UV transparent conducting thin films were deposited by RF magnetron sputtering at room temperature with a rapid annealing process. Effects of sputtering power, argon gas pressure and annealing temperature on structure, optical and electrical properties of Mg_0.2Zn_0.8O:Al films were investigated. The experimental results show that Mg_0.2Zn_0.8O:Al thin films exhibit high preferred c-axis-orientation. The sputtering power, argon gas pressure and annealing temperature all exert a strong influence on the electrical resistivity of Mg_0.2Zn_0.8O:Al thin films due to the variation of carrier concentration and mobility in films derived from the change of effective doping and crystallinity. The lowest electrical resistivity of Mg_0.2Zn_0.8O:Al thin films is 3.5 × 10⁻³ Ω·cm when the sputtering power is 200 W, the argon gas pressure is 2.0 Pa and the annealing temperature is above 500 °C. The transparent spectrum range of Mg_0.2Zn_0.8O:Al thin films extend to ultraviolet band and the optical transmittance is between 80 and 90%, but the sputtering power, argon gas pressure and annealing temperature all exert little influence on optical transmittance.     

Electrical, optical and morphological properties of nanoparticle indium-tin-oxide layers

Porous layers were prepared from DEGUSSA's ITO (In₂O₃:Sn) nanoparticle dispersion by doctor blading followed by annealing in air. We investigated the influence of various annealing parameters on electrical, optical and morphological thin film properties.Conductance rises with increasing annealing temperature and time by more than three orders of magnitude up to 44 Ω^− 1cm^− 1. Besides this we found an abrupt decrease in free charge carrier concentration above a critical annealing temperature of 250 °C, which leads to a step in conductance curve. In spite of particle growing during annealing no decrease in porosity was observed and in opposite to compact material, nanoparticle layers do not exhibit an appreciable shrinkage below recrystallisation temperature. These both indicate a densification hindering particle pinning effect, which is believed to be currently the main obstruction to achieve higher electrical conductivities.     

Some physical properties of CuInSe2 thin films

Semiconducting thin films of CuInSe₂ have been grown by thermal annealing in air of evaporated layers of Cu, In and Se on glass substrates. The structure of the films has been studied using the X-ray diffraction (XRD). The films were polycrystalline and showed mixture phases (binary and ternary) depending on the annealing temperature. The electrical properties revealed resistivity range of 10¹–10⁴Ωcm, respectively. The resistivity influenced with the annealing temperature and decreased with increasing temperature. The films have been analyzed for optical band gap.     

Effects of heat treatment on properties of ITO films prepared by rf magnetron sputtering

Indium tin oxide (ITO) films were deposited on glass substrates by rf magnetron sputtering using a ceramic target (In₂O₃-SnO₂, 90-10 wt%) without extra heating. The post annealing was done in air and in vacuum, respectively. The effects of annealing on the structure, surface morphology, optical and electrical properties of the ITO films were studied. The results show that the increase of the annealing temperature improves the crystallinity of the films, increases the surface roughness, and improves the optical and electrical properties. The transmittance of the films in visible region is increased over 90% after the annealing process in air or in vacuum. The resistivity of the films deposited is about 8.125×10⁻⁴ Ω cm and falls down to 2.34×10⁻⁴ Ω cm as the annealing temperature is increased to 500°C in vacuum. Compared with the results of the ITO films annealed in air, the properties of the films annealed in vacuum is better.     

Influence of bond defects on coiling of graphite

The effect of annealing at 1400 °C in argon on the bond structure of graphite ball milled for 100 h at 400 rpm in polar (water) and in non-polar (n-dodecane) liquids was investigated primarily by near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and transmission electron microscopy (TEM). Carbon K-edge NEXAFS allows the distortion of bonds in the hexagonal lattice to be investigated. It is shown that in-plane sp² bonds are strained and distorted after ball milling because sp³ bonds are introduced. Not surprisingly, annealing of the milled product restores sp² bonds but at the same time, coiling and formation of tube-like structures takes place. It is well established that graphite is not formed on annealing, and hence the results shown here demonstrate that the loss of sp³ carbons on annealing must proceed via a different mechanism by which they are formed by milling.     

Improvement of physical properties of IGZO thin films prepared by excimer laser annealing of sol–gel derived precursor films

Indium gallium zinc oxide (IGZO) transparent semiconductor thin films were prepared by KrF excimer laser annealing of sol–gel derived precursor films. Each as-coated film was dried at 150 °C in air and then annealed using excimer laser irradiation. The influence of laser irradiation energy density on surface conditions, optical transmittances, and electrical properties of laser annealed IGZO thin films were investigated, and the physical properties of the excimer laser annealed (ELA) and the thermally annealed (TA) thin films were compared. Experimental results showed that two kinds of surface morphology resulted from excimer laser annealing. Irradiation with a lower energy density (≤250 mJ cm⁻²) produced wavy and irregular surfaces, while irradiation with a higher energy density (≥350 mJ cm⁻²) produced flat and dense surfaces consisting of uniform nano-sized amorphous particles. The explanation for the differences in surface features and film quality is that using laser irradiation energy to form IGZO thin films improves the film density and removes organic constituents. The dried IGZO sol–gel films irradiated with a laser energy density of 350 mJ/cm² had the best physical properties of all the ELA IGZO thin films. The mean resistivity of the ELA 350 thin films (4.48 × 10³ Ω cm) was lower than that of TA thin films (1.39 × 10⁴ Ω cm), and the average optical transmittance in the visible range (90.2%) of the ELA 350 thin films was slightly higher than that of TA thin films (89.7%).     

Low temperature synthesis of sol–gel derived Al-doped ZnO thin films with rapid thermal annealing process

A series of sol–gel derived Al-doped ZnO (AZO) thin films with rapid thermal annealing process at low temperature were studied to examine the influence of annealing temperature and the Al doping concentration on their microstructure, electrical and optical transport properties. Crystalline AZO thin films were obtained following an annealing process at temperatures between 400 and 600 °C for 10 min in argon gas ambient. AZO thin films with Al doping of 1 at% were oriented more preferentially along the (002) direction, and have larger grain size and lower electrical resistivity, while the highest average optical transmittances of 92% were observed in AZO films with Al doping of 2 at%. With the annealing temperature increasing from 400 to 600 °C, the grain size of AZO films increased, the optical transmittance became higher, and the electrical resistivity decreased to a lowest value of 1.2 × 10⁻⁴ Ω cm resulting from the increase of the carrier concentration and the mobility.     

Effect of annealing atmosphere (Ar vs. air) and temperature on the electrical and optical properties of spin-coated colloidal indium tin oxide films

Colloidal indium tin oxide (ITO) ~6 nm nanoparticles synthesized in-house were deposited by spin coating on fused silica substrates, resulting in high resistivity films due to the presence of passivating organics. These films were annealed at various temperatures ranging from 150 to 750 °C in air and argon atmospheres. The films are very transparent in the as-coated form, and they retain high transparency upon annealing, except the films annealed at 300 °C in argon, which became brown due to incomplete pyrolysis of the organics. Thermogravimetric analysis and Raman characterization showed that the removal of organics increases with an increase in the annealing temperature, and that this removal is more efficient in the oxidizing atmosphere of air, especially in the 300–450 °C temperature range than in Ar. Although ITO defect chemistry suggests that argon annealing should result in higher carrier concentration than air annealing, the faster removal of insulating organics upon annealing in air resulted in significantly lower film resistivity at intermediate annealing temperatures for films annealed in air than in Ar. At higher annealing temperatures, both Ar and air annealing, resulted in comparable film resistivities (the lowest achieved was ~10⁰ Ω cm).     

Effect of post-deposition annealing on phase formation and properties of RF magnetron sputtered PLZT thin films

In this work, we report the preparation of lanthanum-modified lead zirconate titanate (PLZT) thin films by RF magnetron sputtering on platinized silicon (Pt/Ti/SiO₂/Si) substrate. Sputtering was done in pure argon at 100 W RF power without external substrate heating. X-ray diffraction studies were performed on the films to study the effect of post-deposition furnace annealing temperature and time on the perovskite phase formation of PLZT. Annealing at 650 °C for 2 h was found to be optimum for the preparation of PLZT films in pure perovskite phase. The effect of different annealing conditions on surface morphology of the films was examined using AFM. The dielectric, ferroelectric and electrical properties of these films were also investigated in detail as a function of different annealing conditions. The pure perovskite film exhibits better properties than the other films which have some fraction of unwanted pyrochlore phase. The remanent polarization for pure perovskite film was found to be ∼29 μC/cm² which is almost double compared to the films having mixed phases. The dc resistivity of the pure perovskite film was found to be 7.7 × 10¹⁰ Ω cm at the electric field of ∼80 kV/cm.     

Temperature measurements in the pulsed laser heating of metals

The results of an investigation of the temperature dynamics of certain metals, measured by a photoemission method with a time resolution of 1 μsec, when they are heated in air and in an argon medium by millisecond laser radiation (λ = 1.06 μm) with energy densities of 75–140 J/cm² are presented.     

Determination of hydrogen concentration in a-Si and a-Ge layers by elastic recoil detection analysis

In this work we have studied the individual a-Si and a-Ge hydrogenated layers prepared by RF sputtering on Si (100) substrates using Ar and H₂ gas mixture. The absolute value of atomic content of the H was determined by Elastic Recoil Detection Analysis (ERDA) with 1.6 MeV 4He⁺ beam. The dynamics of the out diffusion was investigated by annealing in high purity (99.999%) argon atmosphere at 350 °C for several hours. It was clearly shown that hydrogen can diffuse out faster from Ge film than from the Si one during annealing of the samples.     

Effect of annealing atmosphere on microstructure,optical and electronic properties of spray-pyrolysed In-doped Zn(O,S) thin films

Spray-pyrolysed zinc oxy-sulphide Zn(O,S) has been doped with varying concentrations of indium (In) to improve its electrical and optical properties for possible application as buffer layer in thin film solar cells. The In-doping in Zn(O,S) is found to change the electron carrier concentration from \(10^{19}\) to \(10^{18}\,\hbox {cm}^{-3}\) and a subsequent annealing in argon atmosphere is found to improve its electrical conductivity. Moreover, annealing in air atmosphere reduces the carrier concentration to a range of \(10^{13}\)–\(10^{15}\,\hbox {cm}^{-3}\) making it useful as a buffer layer. The reduction in degeneracy of In-doped Zn(O,S) is desirable for its application as buffer material, whereas annealing in argon makes it suitable as electron membrane (window layer) in thin film solar cell.     

Electrical conductivity of copper nanoparticle thin films annealed at low temperature

Copper nanoparticles with a mean diameter of 20 nm were used to prepare electrical conductive films at low temperature. After dispersal in an organic solvent, the copper nanoparticle pastes were coated onto a glass substrate, which was then annealed under various conditions to investigate the effects of various atmospheric conditions, such as air, nitrogen gas or hydrogen gas, as well as different annealing temperatures. Two-step annealing, which first involves oxidation in air followed by reduction, is effective in the preparation of high electrical conductive copper nanoparticle films. The copper nanoparticle films that were calcined in air for 1 h and then hydrogen gas for 1 h at a low temperature of 200 °C showed a low resistivity of 2 × 10^-5 Ω cm.     

The electrical and optical properties of indium zinc tin oxide thin films with different Sn/Zn ratio

Indium zinc tin oxide (IZTO) thin films with two different chemical compositions, i.e. IZTO15 and IZTO25, where In content was fixed at 60 at.% and Sn content was 15 and 25 at.%, respectively, were deposited onto alkaline-free glass substrate at temperature from 37 °C to 600 °C. The deposition process was carried out in argon using an RF magnetron sputter. After deposition, the films were annealed in argon atmosphere at 450 °C for 30 min. The effect of substrate temperature and annealing treatment was investigated, and the minimum resistivity value of 3.44 × 10^− 4Ω.cm was obtained from the film deposited at 400 °C using IZTO25 target followed by rapid thermal annealing at 450 °C for 30 min. The average optical transmittance was kept fairly high over 80%. It was proven that both substrate temperature and thermal annealing were important parameters in lowering the electrical resistivity without deteriorating optical properties.     

Structural, electrical and optical studies of SILAR deposited cadmium oxide thin films: Annealing effect

Successive ionic layer adsorption and reaction (SILAR) method has been successfully employed for the deposition of cadmium oxide (CdO) thin films. The films were annealed at 623 K for 2 h in an air and changes in the structural, electrical and optical properties were studied. From the X-ray diffraction patterns, it was found that after annealing, H₂O vapors from as-deposited Cd(O₂)_0.88(OH)_0.24 were removed and pure cubic cadmium oxide was obtained. The as-deposited film consists of nanocrystalline grains of average diameter about 20-30 nm with uniform coverage of the substrate surface, whereas for the annealed film randomly oriented morphology with slight increase in the crystallite size has been observed. The electrical resistivity showed the semiconducting nature with room temperature electrical resistivity decreased from 10⁻² to 10⁻³ Ω cm after annealing. The decrease in the band gap energy from 3.3 to 2.7 eV was observed after the annealing.     

Role of oxygen in enhancing N-type conductivity of CuInS2 thin films

Post-growth treatments in air atmosphere were performed on CuInS₂ films prepared by the single-source thermal evaporation method. Their effect on the structural, optical and electrical properties of the films was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), optical reflection and transmission and resistance measurements. The films were annealed from 100 to 350 °C in air. The stability of the observed N-type conductivity after annealing depends strongly on the annealing temperature. Indeed it is shown that for annealing temperatures above 200 °C the N-type conductivity is stable. The resistance of the N-CuInS₂ thin films correlates well with the corresponding annealing temperature. The samples after annealing have direct bandgap energies of 1.45-1.50 eV.     

Microstructure and properties of Al-doped ZnO thin films by nonreactive DC magnetron sputtering at room temperature following rapid thermal annealing

A series of Al-doped ZnO (AZO) thin films deposited by nonreactive DC magnetron sputtering at room temperature following rapid thermal annealing was studied to examine the influence of these Al doping concentration, sputtering power and annealing temperature on their microstructure, electrical and optical transport properties. AZO thin films with Al dopant of 3 wt% were oriented more preferentially along the (002) direction, bigger grain size and lower electrical resistivity The resistivity of AZO films decreases with the increase of Al content from 1 to 3 wt%, sputtering power from 60 to 100 W and the annealing temperature from 50 to 250 °C. Sputtering power and annealing had some effect on the average transmittance of AZO thin films. For AZO thin films with Al doping level of 3 wt%, the lowest electrical resistivity of 5.3 × 10⁻⁴ Ω cm and the highest optical transmittance of 88.7% could gain when the sputtering power was 100 W and the annealing temperature was 200 °C or above.