Effect of stabilizer on optical and structural properties of MgO thin films prepared by sol–gel method

The effects of monoethanolamine (MEA) and acetylacetone (ACAC) addition as stabilizer on the crystallization behaviour, morphology and optical properties of magnesium oxide were investigated using thermogravimetry (TG/DTG), X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Visible, photoluminescence (PL) and Fourier transform infrared (FTIR) spectroscopy. Stabilizer addition reduces transparency of the films. MgO films prepared at 500 °C showed weak orientation of (200). However, the films prepared by addition of stabilizer are amorphous. MgO powders were prepared for exhibiting the structural properties. The patterns of MgO powders showed a preferred orientation of (200). The addition of stabilizer causes a reduction in grain size. SEM micrographs show that a homogenous and crack-free film can be prepared at 500 °C and addition of stabilizer causes an increase in packing density.     

Effect of solution concentration on the structural, optical and conductive properties of ZnO thin films prepared by sol–gel method

ZnO thin films with different solution concentrations (0.1–0.9 mol/L) were prepared by a simple sol–gel dip-coating technique. X-ray diffraction, ultraviolet–visible spectroscopy, Hall effect measurements and photoluminescence (PL) spectroscopy were employed to investigate the effect of solution concentration on the structural,optical and electrical conductive properties of the ZnO thin films. The results showed that the ZnO thin films preferentially oriented along the (002) direction at higher solution concentration. The careful study of the optical and electrical conductive properties showed that the resistivity decreased monotonously, while the transmittance increased first and then decreased when solution concentrations changed from 0.1 to 0.9 mol/L. Photoluminescence spectra indicated that the defect-related blue emission was increased with the enhancement of solution concentration. The mechanism of the blue emission, and the reasons why high solution concentration was favorable for forming high c-axis oriented ZnO thin films and obtaining low resistivity were also discussed in detail.     

Influence of annealing temperature on the structural,topographical and optical properties of sol–gel derived ZnO thin films

This investigation deals with the effect of annealing temperature on the structural, topographical and optical properties of Zinc Oxide thin films prepared by sol–gel method. The structural properties were studied using X-ray diffraction and the recorded patterns indicated that all the films had a preferred orientation along (002) plane and the crystallinity along with the grain size were augmented with annealing temperature. The topographical modification of the films due to heat treatment was probed by atomic force microscopy which revealed that annealing roughened the surface of the film. The optical properties were examined by a UV–visible spectrophotometer which exhibited that maximum transmittance reached nearly 90% and it diminished with increasing annealing temperature.     

Effect of Zn doping on structural,magnetic and dielectric properties of LaFeO3 synthesized through sol–gel auto-combustion process

We have studied the structural and dielectric properties of nano-crystalline LaFe_1−xZn_xO₃ (0 ≤ x ≤ 0.3) pervoskite samples synthesized through sol–gel auto-combustion technique. X-ray diffraction and FTIR spectroscopy are used to confirm the single phase characteristics. Microstructural features are investigated using scanning electron microscope and compositional analysis is performed through energy dispersive spectroscopy. The average grain sizes, calculated from the Scherrer formula, lie in the range below 30 nm. The hysteresis (M-H) curves display a weak magnetic order and a shift in the hysteresis loops. Dielectric response has been discussed, in the framework of “universal dielectric response” model. The value of dielectric constant (ɛ′) increases drastically on Zn doping. The dielectric loss factor (ɛ″) shows Debye like dipolar relaxation behavior. The observed peaks in loss factor (ɛ″) are attributed to the fact that a strong correlation between the conduction mechanism and the dielectric behavior exists in ferrites.     

Investigation of the iron doping on the structural,optical, and magnetic properties of Fe-doped ZnO nanoparticles synthesized by sol–gel method

Journal of Materials Science: Materials in Electronics - In this work, the compatibility of zinc oxide for spintronic applications motivated the development of single-phase Fe/ZnO nanostructures by...     

Post annealing effect on structural and optical properties of ZnO thin films derived by sol–gel route

Zinc oxide thin films have been spun coated on p-Si (100) substrates by sol–gel route. These films were annealed at different annealing temperatures from 300 to 1,000 °C in the oxygen ambient. In this way a suitable annealing temperature window for the sol–gel derived ZnO films exhibiting minimum defects (points and dislocations) and better quality (crystal and optical) was investigated. The structural and optical features of ZnO thin films have been examined by X-ray diffraction, atomic force microscopy, UV–Vis spectroscopy, and photoluminescence spectra. The results revealed that the crystallization in the films initiated at 300 °C, improved further with annealing. All the deposited films exhibited wurtzite phase with c-axis orientations. The variations in the position of characteristic (002) peak, stress, strain and lattice parameters are investigated as a function of annealing temperature. The optical band gap is not significantly affected with annealing as observed by UV–Vis transmission spectroscopy. The Photoluminescence spectra exhibited three luminescence centers. The near band edge esmission was observed in UV region which enhanced with the heat treatment, is an indication of improvement in the optical quality of films. The other two visible emissions are related to native defects in ZnO lattice were appeared only for higher annealing (≥700 °C).     

Effect of Zn doping on structure and ferroelectric properties of PST thin films prepared by sol–gel method

(Pb _y Sr_1−y )Zn _x Ti_1−x O_3−x thin films were prepared on ITO/glass substrate by sol–gel process using dip-coating method. The phase structure, morphology and ferroelectric property of the thin film were studied. All the thin films show the typical perovskite phase structure. Both the crystallinity and c/a ratio of the perovskite phase increases initially and then decreases gradually with doping Zn in the thin film. Ferroelectric properties of the Zn-doped PST thin films, including ferroelectric hysteresis-loop, remnant polarization and coercive force, decrease gradually with increasing Zn. And the effect of Zn on ferroelectric properties is more obvious in PST thin film with high content of Pb than that with low Pb although the high lead thin film exhibits high intrinsic ferroelectric properties.     

Effect of different solvents on the key structural,optical and electronic properties of sol–gel dip coated AZO nanostructured thin films for optoelectronic applications

Transparent conducting aluminum (i.e. 2 at.%) doped zinc oxide (AZO) thin films were prepared on glass substrates by sol–gel dip coating technique using different solvents. This inexpensive dip coating method involves dipping of substrate consecutively in zinc solution and tube furnace for required cycles. Prepared films were investigated by XRD, SEM, PL, Raman spectroscopy optical and electrical studies. From the XRD studies, it confirmed the incorporation of aluminum in ZnO lattice. The prepared samples are polycrystalline nature, and these films reveal hexagonal wurtzite arrangement with (002) direction. The structural parameters such as crystallite size, dislocation density, micro strain, texture coefficient and lattice constant were investigated. SEM study showed well defined smooth and uniformed ganglia shaped grains are regularly distributed on to the entire glass substrate without any pinholes and cracks, and the average grain size is 75 nm. From the optical studies, the observed highest transmittance is 93% in the visible range and the band gap (E_g) is 3.26 eV. Room temperature PL spectra exhibited strong UV emission peak located at 386 nm for all the films. The electrical properties of the AZO thin films were studied by Hall-Effect measurements and found as n-type conductivity with high carrier concentrations (n), 2.76?×?10¹⁹ cm^??3 and low resistivity (ρ), 7.56?×?10^??3 Ω cm for the film deposed using methanol as solvent.     

Effect of the Brij 30 porogen on the properties of sol–gel derived thin polymethylsilsesquioxane films

Thin polymethylsilsesquioxane films with Brij 30 porogen concentrations in the range ω_surf = 15.5–52.5 wt % have been produced by a sol–gel process. Their dielectric permittivity, refractive index, relative porosity, and shrinkage have been measured as functions of heat treatment temperature and porogen concentration.     

Investigations on the optical properties of sol–gel derived lanthanum doped lead titanate thin films

In the present work we studied the optical properties of undoped and La doped lead titanate thin films, and also demonstrated that the optical characterization of thin films can be used as an effective diagnostic tool to assess film quality. The optical properties of Pb_1−xLa_xTi_1−x/4O₃ [where x=0 (undoped), 10, 15, 20, 25 and 30 at.%] thin films were investigated using both transmission and reflection spectra in the 200–900-nm wavelength range. The refractive index (n), extinction coefficient (k) and the thickness of the film (d_f) were determined from the measured transmission spectra. The thickness of the film obtained from the interference fringes in transmission or reflection spectra matched well with those obtained from other methods. The appearance of interference fringes is an indication of the thickness uniformity of the film. The low value of extinction coefficient (in the order of 10⁻²) as observed in our films is a qualitative indication of excellent surface smoothness of the films. The densities of the films were estimated from their refractive indices using effective medium approximation. The average oscillator strength and its associated wavelength were estimated using a Sellmeier-type dispersion equation. Absorption coefficient (α) and the band-gap energy (E_g) were obtained for undoped and La doped films with varying La concentration. It was found that the refractive index and packing fraction values decrease with La doping. La doping was found to decrease the grain size of the films and increase the density of individual grains. Increased La content led to clustering of smaller grains. The observed variation of band-gap energy with La doping has been correlated to the observed microstructure of these films.     

Influence of Fe dopant concentration and annealing temperature on the structural and optical properties of ZnO thin films deposited by sol–gel method

Nanostructured Fe doped ZnO thin films were deposited onto glass substrates by sol–gel spin coating method. Influence of Fe doping concentration and annealing temperature on the structural, compositional, morphological and optical properties were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV–Vis spectroscopy and photoluminescence (PL) measurements. XRD analysis showed that all the films prepared in this work possessed a hexagonal wurtzite structure and were preferentially oriented along the c-axis. Pure ZnO thin films possessed extensive strain, whereas Fe doped films possessed compressive strain. In the doped films, least value of stress and strain was observed in the 0.5 at.% Fe doped thin film, annealed at 873 K. Average crystallite size was not significantly affected by Fe doping, but it increased from 15.57 to 17.79 nm with increase in annealing temperature from 673 to 873 K. Fe ions are present in +3 oxidation state as revealed by XPS analysis of the 0.5 at.% Fe doped film. Surface morphology is greatly affected by changes in Fe doping concentration and annealing temperature which is evident in the SEM images. The increase in optical band gap from 3.21 to 3.25 eV, with increase in dopant concentration was attributed to Moss–Burstein shift. But increase in annealing temperature from 673 to 873 K caused a decrease in band gap from 3.22 to 3.20 eV. PL spectra showed emissions due to excitonic combinations in the UV region and defect related emissions in the visible region in all the investigated films.     

Effect of annealing temperature on electrical and nano-structural properties of sol–gel derived ZnO thin films

Zinc oxide (ZnO) thin films have been prepared on silicon substrates by sol–gel spin coating technique with spinning speed of 3,000 rpm. The films were annealed at different temperatures from 200 to 500 °C and found that ZnO films exhibit different nanostructures at different annealing temperatures. The X-ray diffraction (XRD) results showed that the ZnO films convert from amorphous to polycrystalline phase after annealing at 400 °C. The metal oxide semiconductor (MOS) capacitors were fabricated using ZnO films deposited on pre-cleaned silicon (100) substrates and electrical properties such as current versus voltage (I–V) and capacitance versus voltage (C–V) characteristics were studied. The electrical resistivity decreased with increasing annealing temperature. The oxide capacitance was measured at different annealing temperatures and different signal frequencies. The dielectric constant and the loss factor (tanδ) were increased with increase of annealing temperature.     

Structural, optical, and electric properties of BNT–BT0.08 thin films processed by sol–gel technique

Thin films with the composition [(Bi_0.5Na_0.5)TiO₃]_0.92–[BaTiO₃]_0.08 (hereafter BNT–BT_0.08) were deposited on Pt–Si by spin-coating from a stable sol precursor. The BNT–BT_0.08 film, crystallized on the Bi_0.5Na_0.5TiO₃ rhombohedral lattice, was obtained after annealing the film-gel at 700 °C. The films have a smooth surface (Rms = 2.76 nm) and grains with ferroelectric domains. The film showed a bandgap of 3.25 eV and a refractive index of 2.20 at a wavelength of 630 nm. The dielectric characteristics of BNT–BT_0.08 thin films were measured at room temperature and 10 kHz the dielectric constant (ε _r) was 243 and the loss tangent (tanδ) was 0.38. The remnant polarization (P _r) was 0.87 μC/cm² and the coercive field (E _c) was 220 kV/cm at 10 kHz and room temperature. The current density was approximately 2.7 × 10⁻⁵ A/cm² at low electric fields (100 kV/cm). BNT–BT_0.08 thin films shown piezoelectric properties (d _33eff = 100 pm/V) comparable to those of PZT thin films.     

Effects of Mg doping on sol–gel derived nanocrystalline hydroxyapatite thin films

Abstract

Both pure and Mg doped thin films were fabricated by sol–gel dip coating. The films were sintered either at 800 or 1000°C. The average grain size of the films was significantly affected by Mg substitution in the hydroxyapatite (HA) structure and change in the sintering temperature. The grains were considerably larger in the films sintered at higher temperatures. In addition, Mg doped films contained significantly larger grains compared to undoped HA films. Mg doping also caused rodlike grains at 800°C, and led to whitlockite (β-TCP) formation at 1000°C. The ratio of the existing phases was estimated as β-TCP/HA=27 : 73. All the films had rough surfaces with high porosity. It was also observed that undoped films had higher surface roughness than Mg doped ones.