Zohra Nazir Kayani

Fabrication and properties of zinc oxide thin film prepared by sol-gel dip coating method

Abstract ZnO thin films were deposited on a glass substrate by dip coating technique using a solution of zinc acetate, ethanol and distilled water. Optical constants, such as refractive index n and extinction coefficient k. were determined from transmittance spectrum in the ultraviolet-visible-near infrared (UV-Vis-NIR) regions using envelope methods. The films were found to exhibit high transmittance, low absorbance and low reflectance in the visible regions. Absorption coefficient α and the thickness of the film t were calculated from interference of transmittance spectra. The direct optical band gap of the films was in the range of 3.98 to 3.54 eV and the thickness of the films was evaluated in the range of 173 to 323 nm, while the refractive index slightly varied in the range of 1.515 to 1.622 with an increase in withdrawal speed from 100 to 250 mm/s. The crystallographic structure of the films was analyzed with X-ray diffractometer. The films were amorphous in nature.

Structural, Optical, and Magnetic Properties of Cobalt-Doped Dip Coated ZnO Films

Co-doped zinc oxide thin films (ZnCoO) have been deposited on glass substrates by sol-gel dip coating deposition method. X-ray diffractometer patterns for these thin films prove crystalline behavior with wurtzite structure. The films have lattice parameters similar to that of ZnO. When Zn is replaced by Co, more impurity levels are produced within the bandgap, and more defects are developed. However, Co-doping does not alter the wurzite structure. The bandgap of the films tends to decrease with increasing withdrawal speed. These transparent thin films possess bandgap in the ultra-violet (3.86-3.45 eV) and high transparency throughout the visible spectral region. Ellipsometry also show the same trend for bandgaps (3.83-3.45). Morphological analysis by scanning electron microscope shows surface with porous structure. Magnetic property studied shows the ferromagnetic behavior. Chemical composition of these Co-doped ZnO thin films was investigated through Fourier transform infrared analysis.

In vitro evaluation of bioactivity of SiO2-CaO-P2O5-Na2O-CaF2-ZnO glass-ceramics

Zinc is an essential trace element that stimulates bone formation but it is also known as an inhibitor of apatite crystal growth. In this work addition of ZnO to SiO2-CaO-P2O5-Na2O-CaF2 glass-ceramic system was made by conventional melt-quenching technique. DSC curves showed that the addition of ZnO moved the endothermic and exothermic peaks to lower temperatures. X-ray diffraction analysis did not reveal any additional phase caused by ZnO addition and showed the presence of wollastonite and hydroxyapatite crystalline phases only in all the glass-ceramic samples. As bio-implant apatite forming ability is an essential condition, the surface reactivity of the prepared glass-ceramic specimens was studied in vitro in Kokubo’s simulated body fluid (SBF) [1] with ion concentration nearly equal to human blood plasma for 30 days at 37 °C under static condition. Atomic absorption spectroscopy (AAS) was used to study the changes in element concentrations in soaking solutions and XRD, FT-IR and SEM were used to elucidate surface properties of prepared glass-ceramics, which confirmed the formation of HCAp on the surface of all glass-ceramics. It was found that the addition of ZnO had a positive effect on bioactivity of glass-ceramics and made it a potential candidate for restoration of damaged bones.

Synthesis of Iron Oxide Nanoparticles by Sol–Gel Technique and Their Characterization

Fe2O3 nanoparticles are synthesized chemically by sol-gel method. The nanoparticles have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), thermo gravimetric analysis/differential thermal analysis-differential scanning calorimetry (TGA/DTA-DSC), and vibrating sample magnetometer (VSM). XRD results identify hematite phase of iron oxide nanoparticles. The average crystalline size of the nanoparticles increased from 34 to 36.7 nm when the annealing temperature increased from 400 °C to 1000 °C. FTIR technique also confirmed XRD results. Phase transformation temperatures were determined by DSC-TGA. The exothermic peak at 720.2 °C is attributed to the phase change from y Fe2O3 (low temperature phase) to α Fe2O3 (high temperature phase). The annealing temperature also affects the optical properties since the measured band gap increased from 2.4 to 2.7 eV when the annealing temperature increased from 400 to 1000 °C.

Effect of Bi/Fe Ratio on the Structural and Magnetic Properties of BiFeO 3 Thin Films by Sol-Gel

Bismuth iron oxide (BiFeO3) is amongst the class of multiferroic materials that has attracted worlds attraction because of its high antiferromagnetic Neel temperature and high ferroelectric Curie temperature of 643 and 1103 K, respectively. However, synthesis of phase pure BiFeO3 is extremely difficult due to the volatile nature of Bi2O3 that results in formation of bismuth deficient and/or rich phases. Most of the previous research is based on obtaining pure BiFeO3 phase with variation in annealing/calcination temperature in the range 400 °C-700 °C. However, very little consideration is given to change Bi/Fe ratio during synthesis. Here, we report preparation of phase pure BiFeO3 thin films using cost effective sol-gel and spin coating method. Bismuth nitrate and iron nitrate are used as precursors whereas ethylene glycol is used as solvent. Molar ratio of Bi/Fe is varied as 0.9, 0.95, 1.0, 1.05, 1.1, and 1.20. Films are annealed at 300 °C for 60 mins in the presence of vacuum under 500 Oe applied magnetic field. X-ray diffraction results indicate formation of phase pure BiFeO3 thin films for Bi/Fe ratio of 1.0-1.1. However, both high (1.2) and low (0.9-0.95) Bi/Fe molar ratios result in the appearance of impurity phases. In addition, bismuth iron oxide shows ferromagnetic behavior as opposed to the antiferromagnetic nature of bulk BiFeO3. Strong ferromagnetic behavior, for Bi/Fe ratios of 1.0 and 1.05, can be explained on the basis of suppression of helical spin structure as the crystallite size reduces to ~30 nm, which is well below the cycloidal spin arrangement of BiFeO3 (62 nm).

STRUCTURAL AND MAGNETIC PROPERTIES OF THIN FILM OF IRON NITRIDE

The nano-crystalline iron nitride films with a mixture of γ-Fe4N, eFe3N and αFe2N phases were synthesized on copper substrate by sol–gel technology. The structure, morphology and magnetic properties of the samples were characterized using X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. The films are ferromagnetic at room temperature. Magnetic properties such as coercive forces and saturation magnetization were found to be 398 Oestered and 32.92 emu/cm3, respectively.

Study of Nickel Nitride Thin Films Deposited by Sol–Gel Route

A solution phase route to synthesize films of nickel nitride is presented here. The use of controlled amounts of amine results in sols; these can be coated onto copper substrates via a spin coating method. Pyrolysis of these films leads to nickel nitride. The annealing temperature has a strong influence both on the phase formation as well as on the degree of crystallinity of the thin films deposited. The structural properties and the grain size of films are determined by X-ray diffractometer. Magnetic characterization is performed using vibrating sample magnetometer. The surface morphology is investigated using scanning electron microscope.

Structural And Magnetic Properties Of The Thin Film Of Cobalt Nitride

Cobalt nitride has been prepared and studied for magnetic memory applications. Sol–gel technique is used to prepare thin films of cobalt nitride. The films were deposited onto Cu substrates by spin coating at 3000 rpm for 30 s. The films were then air dried and heated at 300°C for 120 min. As-deposited and heated samples were characterized for their structural and magnetic properties using X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM) techniques. The grain size was in the range of 22.7–30.10 nm. Their surface was studied by scanning electron microscopy (SEM). Orthorhombic structure can be seen in SEM micrographs. This orthorhombic structure is also confirmed by XRD.

Growth and Characterization of Iron Oxide Nanocrystalline Thin Films via Sol-Gel Dip Coating Method

In this paper, iron (III) oxide thin films are deposited on glass substrate via sol-gel dip coating by increasing withdrawal speeds in the range 100-250 mms^-1. Prepared thin films were characterized by UV-VIS spectrophotometer, spectroscopic ellipsometry (SE), X-ray diffraction (XRD), scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and Fourier transform infrared (FTIR) spectroscopy. UV-VIS spectrum and SE show decrease in bandgap energy from 2.8 to 1.6 eV with increased withdrawal speed. FTIR results indicate formation of α-Fe₂O₃ (hematite) phase of iron oxide with preferred orientation along (104) plane. From SEM studies, it is observed that the developed α-Fe₂O₃ films are nanocrystalline with small grain size. The surface of α-Fe₂O₃ films is smooth and homogenous, which also supports the XRD results. VSM results show that α-Fe₂O₃ thin films have ferromagnetic behavior.

Probe of ZrTiO 2 thin films with TiO 2 -ZrO 2 binary oxides deposited by dip coating technique

Zirconium Titanium dioxide (TiO2: Zr) thin films were synthesized on glass substrates by the dip coating technique. The structural, optical, magnetic, photo-catalytic and antibacterial properties were explored for the films synthesized with zirconium concentration 10, 15, 20, 25 and 30 at.%. X-ray diffraction (XRD) revealed that the thin films contain anatase-rutile-brookite TiO2 and cubic-ZrO2 phases. Moreover, it was noticed that ZrO2 retarded the anatase-to-rutile transformation at high Zr doping percentage.The crystallite size of ZrO2 phase was in the range of 10.93-18.22 nm, whereas it was in the range of 13.5-21.59 nm for TiO2 phase for same Zr doping percentage. The band gap of films was in the range of 2.99-3.17 eV. The band gap value decreased with increase in Zr-doping percentage due to the creation localized levels near the conduction band providing a large number of electrons to reach the conduction band. Films showed room temperature ferro-magnetism due to the defects produced by Zr in TiO2 lattice. The antibacterial efficiency of ZrTiO2 thin films was investigated by utilizing disc diffusion method. Band gap was quite low, then pure TiO2 in the range 2.99-3.14 eV with Zr percentage 10-30% atom. The ZrTiO2 thin films with 20 and 25% Zr showed better antibacterial activity against Escherichia coli than 10, 15 and 30% Zr. It was found that ZrTiO2 thin films were effective solar light photo-catalyst.