In this work, effects of thermal annealing on the structural and optical properties of ZnO thin films grown on p-Si and GaN substrates using metalorganic chemical vapor deposition (MOCVD) are investigated. Annealing at 600 °C results in optimum crystal and optical qualities of the ZnO thin films on both substrates. Smaller lattice mismatch between grown ZnO epitaxial layer on GaN substrates results in better film morphology as compared to p-Si substrates. Higher annealing temperature along with a slower thermal ramp provides better crystal quality of ZnO thin films on both substrates. Annealing ZnO thin films at 700 °C with a slower thermal ramp results in better crystal quality as is evident from a 56% reduction in the full-width at half maximum (FWHM) of the (002) peak compared to the as-grown films. The optical quality also enhances with a slower annealing rate. The determination of the optimum annealing conditions for different substrates has important implications in fabricating optimized and efficient ZnO based electronics.

A hierarchy of nanostructured-ZnO was fabricated on the electrospun nanofibers by atomic layer deposition (ALD) and hydrothermal growth, subsequently. Firstly, we produced poly(acrylonitrile) (PAN) nanofibers via electrospinning, then ALD process provided a highly uniform and conformal coating of polycrystalline ZnO with a precise control on the thickness (50 nm). In the last step, this ZnO coating depicting dominant oxygen vacancies and significant grain boundaries was used as a seed on which single crystalline ZnO nanoneedles (average diameter and length of ∼25 nm and ∼600 nm, respectively) with high optical quality were hydrothermally grown. The detailed morphological and structural studies were performed on the resulting nanofibers, and the photocatalytic activity (PCA) was tested with reference to the degradation of methylene blue. The results of PCA were discussed in conjunction with photoluminescence response. The nanoneedle structures supported the vectorial transport of photo-charge carriers, which is crucial for high catalytic activity. The enhanced PCA, structural stability and reusability of the PAN/ZnO nanoneedles indicated that this hierarchical structure is a potential candidate for waste water treatment.

ZnO nanoparticles were prepared by a green electrochemical synthesis method applying low current densities followed by a thermal treatment. Sodium polystyrene sulphonate (PSS) was used as stabilizer in the electrolytic aqueous medium due to its biocompatibility and stability. The as-prepared nanocolloids were then annealed to improve their stability, and then converted via hydroxide species into stoichiometric oxide. Different calcination temperatures were studied. ZnO@PSS nanomaterials were deposited onto SiO2/Si substrates, in part in combination with an organic semiconductor layer to evaluate their influence on organic field effect transistors (OFETs). All nanomaterials and composite layers were characterized by morphological and spectroscopic techniques. Promising results regarding the use of ZnO@PSS in OFETs could be demonstrated.

We report, for the first time, effects of annealing of ZnO NWs grown on p-Si substrates. ZnO NWs are grown using metalorganic chemical vapor deposition (MOCVD) and thermal annealing was performed in situ under nitrogen ambient at different stages of the growth process. Increasing the annealing temperature of the ZnO seed epi-layer from 635 °C to 800 °C does not affect the morphology of the grown NWs. In contrast, annealing the NWs themselves at 800 °C results in a 48% decrease of the surface area to volume ratio of the grown NWs. The optical quality can be improved by annealing the seed layer at a higher temperature of 800 °C, although annealing the NWs themselves does not affect the defect density.

Methods of improving low-cost Cu2O|ZnO heterojunction diodes fabricated through galvanostatic deposition of Cu2O are presented. Improved processing parameters responsible for maximizing built-in voltage (Vbi) are determined. The relationship between pH, deposition current, temperature, and diode quality is analyzed and a process window for optimal Cu2O deposition on ZnO is obtained with a pH range between 12.0 and 12.1 and a current density range which is determined by the effect of both pH and deposition current (Jdep) on grain size. The pH window is found to be narrower than previously reported1 and much narrower than the processing window for the deposition of Cu2O films. A two-step approach deposition based on the use of different Jdep is presented for the first time. A Vbi of 0.6 V is achieved, which is the highest reported for cells produced using low temperature processing routes involving electrodeposition and reactive sputtering.

Due to the high surface area and good bio-compatibility of nano structured ZnO, it finds good utility in biosensor applications. In this work we have fabricated highly dense ZnO nano bundles with the assistance of self assembled poly methylsilisesquoxane (PMSSQ) matrix which has been realized in a carpet like configuration with implanted ZnO nano-seeds. Such high aspect ratio structures (∼50) with carpet like layout have been realized for the first time using solution chemistry. Nanoparticles of PMMSQ are mixed with a nano-assembler Poly-propylene glycol (PPG) and Zinc Oxide nanoseeds (5-15 nm). The PPG acts by assembling the PMSSQ nanoparticles and evaporates from this film thus creating the highly porous nano-assembly of PMMSQ nanoparticles with implanted Zinc Oxide seeds. Nano-wire bundles with a high overall surface roughness are grown over this template by a daylong incubation of an aqueous solution of hexamethylene tetra amine and Zinc nitrate. Characterization of the fabricated structures has been extensively performed using FESEM, EDAX, and XRD. We envision these films to have potential of highly dense immobilization platforms for antibodies in immunosensors. The principle advantage in our case is a high aspect ratio of the nano-bundles and a high level of roughness in overall surface topology of the carpet outgrowing the zinc-oxide nanowire bundles. Antibody immobilization has been performed by modifying the surface with protein-G followed by Goat anti salmonella antibody. Antibody activity has been characterized by using 3D profiler, Bio-Rad Protein assay and UV-Visible spectrophotometer.

A radio-frequency magnetron sputtering technique and subsequent rapid thermal annealing (RTA) at 600, 700, 800, and 900 °C were implemented to grow high-quality Ga-doped MgxZn1-xO (GMZO) epi-layers. The GMZO films were deposited using a radio-frequency magnetron sputtering system and a 4 inch ZnO/MgO/Ga2O3 (75/20/5 wt %) target. The Hall results, X-ray diffraction (XRD), and transmittance were determined and are reported in this paper. The Hall results indicated that the increase in mobility was likely caused by the improved crystallization in the GMZO films after thermal annealing. The XRD results revealed that MgxZn1-xO (111) and MgO2 (200) peaks were obtained in the GMZO films. The absorption edges of the as-grown and annealed GMZO films shifted toward the short wavelength of 373 nm at a transmittance of 90%. According to these results, GMZO films are feasible for forming transparent contact layers for near-ultraviolet light-emitting diodes.

Scanning electronic microscopy (SEM), X ray diffraction (XRD) and photoluminescence (PL) have been applied to the study of structural and optical properties of ZnO nanocrystals prepared by the ultrasonic spray pyrolysis (USP) at different temperatures. The variation of temperatures and times at the growth of ZnO films permits modifying the ZnO phase from the amorphous to crystalline, to change the size of ZnO nanocrystals (NCs), as well as to vary their photoluminescence spectra. The study has revealed three types of PL bands in ZnO NCs: defect related emission, the near-band-edge (NBE) PL, related to the LO phonon replica of free exciton (FE) recombination, and its second-order diffraction peaks. The PL bands, related to the LO phonon replica of FE, and its second-order diffraction in the room temperature Pl spectrum testify on the high quality of ZnO films prepared by the USP technology.

Oxide thin films of zinc and titanium materials were deposited by different deposition techniques, to be applied as sensitive layers of pH sensor – EGFET device. The deposition techniques tested were dip-coat, spin-coat, electrodeposition and spray-pyrolysis. The routine and the parameters of each technique were changed aiming optimized the procedures. The pHs buffer solutions tested ranged from 2 to 12. ZnO thin film shows sensitivity about 23 mV/pH, while TiO2 thin films shows only 13.8 mV/pH. The final purpose of this study is to optimize the parameters for each deposition technique for both oxide materials.

Due to the rapid advance of the emergence of resistant microorganisms to different antibiotics, there is a need to create new antimicrobial agents. It is possible that Nanotechnology has a great impact in this area since the nanoparticles can improve the antimicrobial effect of the antibiotics. In this study we used three different metal oxides nanoparticles, the MgO, ZnO and CuO. These nanoparticles were selected because their interactions leading to cell death and their optical properties. The aim of this study is to develop new methods that are more effective against resistance bacteria, developing antibacterial agents using different nanoparticles against Escherichia coli (ATCC 10536), Pseudomonas aeruginosa (ATCC 10145), and Staphylococcus aureus (ATCC BAA-1026). This study was conducted to evaluate the antibacterial effects of a combination of nanoparticles together with different concentrations of three antibiotics, Gentamicin, Cephalexin and Co-Trimoxazole. The results showed that some nanoparticles are effective to inhibit growth in these microorganisms by increasing the effectiveness of the antibiotic. Therefore, the present study indicates that the combination of the nanoparticles with antibiotics may be applicable as a new antimicrobial agent.

The effective incorporation of dopant species into ZnO host structure should induce changes in its physical and chemical properties enabling the establishment of novel multi-functional properties. Doping with transition metal ions and the subsequent exchange interaction between available spins of the magnetic species are expected to induce a ferromagnetic behavior. This ferromagnetic functionality will enable the application of this material in data storage and spintronics-based devices. The present research addresses the study of the effect of the oxidationstate of Fe species and the influence of the annealing atmosphere on the structural and functional properties of nanocrystalline ZnO-based powders.

Gold nanoparticles supported on ZnO nanostructures were prepared through a simple chemical-thermal method and characterized by SEM, TEM, XRD and photo luminescence (PL) spectroscopy. Effect of annealing temperature on catalytic activity of these Au/ZnO nanocatalysts were investigated by aerobic oxidation of benzyl alcohol. The results indicated that the catalyst with ZnO nanowire support annealed at 300 °C exhibited more activity than Au/ZnO catalyst supported on ZnO nanoparticles annealed at 600 °C. The Au/ZnO-nanowire achieved to increase the benzaldehyde selectivity and yield to 93.7 % and 85.6 %, respectively, at 60 °C whereas in Au/ZnO-nanoparticle the benzaldehyde selectivity and yield to 85.1 % and 69.9 %, respectively at 80 °C. The XRD and PL spectroscopy revealed that the supports have interstitial zinc (Zni), oxygen vacancy (Vo-2) defects definitely but there is no evidence for interstitial oxygen (Oi) and zinc vacancy (VZn) defects and single ionized charged oxygen vacancy (Vo-).

The present work focuses on the synthesis and evaluation of the antimicrobial activity of ZnxMg1-xO solid solutions. ZnxMg1-xO solid solutions were synthesized through the thermal decomposition of ZnMg-precursor synthesized in aqueous and ethanol solutions via a two-steps process. The antimicrobial activity of ZnxMg1-xO solid solution against E. coli was evaluated using the spread plate method in presence of ZnxMg1-xO powder of different contents of Zn species, ‘x’. The powder concentrations evaluated were 500, 1000, and 1500 ppm. Zn0.10Mg0.90O powders exhibited a bacterial growth inhibition between 38% and 100% when the powder concentration increased from 500 up to 1500 ppm, respectively. A decreasing trend was observed for x = 0.30 and above; the corresponding bacterial growth inhibition was 12%, 6%, and 5% when the particles concentration was, respectively, 500, 1000, and 1500 ppm. X-Ray diffraction analyses suggested the incorporation of Zn ions into the MgO lattice for ‘x’ values below 0.10, enhancing the antimicrobial activity; the formation of two isolated oxide phases observed at larger ‘x’ values (e.g. x = 0.30 and x = 0.50 Zn), could explain the detected inhibition of the corresponding antimicrobial activity.

Strontium titanate (SrTiO3) has novel properties, including a large temperature-dependent dielectric constant, and can be doped to make it metallic or even superconducting. The origin of conductivity observed at the SrTiO3/LaAlO3 interface is a topic of intense debate. In the present work, bulk single crystal SrTiO3 samples were heated at 1200°C, with the goal of producing cation vacancies. These thermally treated samples exhibited persistent photoconductivity (PPC) at room temperature. Upon exposure to sub-band-gap light (>2.9 eV), the free-electron density increases by over two orders of magnitude. This enhanced conductivity persists in the dark, at room temperature, for several days with essentially no decay. Light excites an electron from the vacancy to the conduction band, where it remains, due to a large recapture barrier. These observations highlight the importance of defects in determining the electrical properties of oxides and may point toward novel applications.

Ferroelectric epitaxial Pb(Zr,Ti)O3 (PZT) layers were grown by pulsed laser deposition on SrTiO3/GaAs templates fabricated by molecular beam epitaxy. The templates present an excellent structural quality and the SrTiO3/GaAs is abrupt at the atomic scale thanks to surface Ti pre-treatment. The PZT layers contain a- and c- domains, as shown by X-Ray diffraction analyses. Piezoforce microscopy experiments and macroscopic electrical characterizations indicate that PZT is ferroelectric. A relative dielectric permittivity of 164 is extracted from these measurements.

The BiFeO3 (BFO) / PbTiO3 (PT) multiferroic ceramic composites with multilayered structure were prepared from orderly laminated BFO and PT tapes by tape casting method. The dielectric constant εr, loss tanδ, remnant polarization Pr and field-induced strain of BFO/PT ceramic composites were 140 (1 kHz), 5% (1 kHz), 12 µC/cm2 (at 80 kV/cm) and 0.06% (at 80 kV/cm) respectively, which were comparable to those pure BFO ceramics and BFO-based solid solutions

The present work addresses the systematic evaluation of the influence of the incorporation of dopant species (Ca+2, Ag+1) on the structural and functional properties of bismuth ferrite (BFO) nanocrystalline powders and films. Pure and doped BFO powders and thin films were synthesized by a modified sol-gel method. The concentration of the doping species varied from 0 up to 7 at %. The development of the host BFO structure was confirmed by XRD analyses of samples annealed at 700°C for one hour in air and nitrogen atmosphere. Thicknesses of films varied between 80 and 200 nm, depending on the concentration of Ca+2 species. Doped BFO exhibited a magnetic behavior that turned from paramagnetic into ferrimagnetic with the increase of Ca+2 concentrations.

Magnetic nanoparticles have drawn much attention due to their potential in magnetic recording as well as many biological and medical applications such as magnetic separation, hyperthermia treatment, magnetic resonance contrast enhancement and drug delivery. The magnetic fields generated by these nanoparticles can be used for diagnostics in Magnetic Resonance Imaging (MRI) etc. Manganese doped tin dioxide (SnO2:Mn) possess interesting physical and chemical properties. The physical and chemical properties of the particles themselves like the size, shape, crystallinity and composition, will control the magnetic properties and response of the particles to magnetic fields. Our work is rooted to control the properties of the particles as well as tailor their magnetic properties for specific applications. In this study, SnO2: Mn films with different Mn doping concentrations (0-3 mol%) were deposited on the glass substrates by sol-gel dip coating technique. XRD patterns shows tetragonal structure for all the SnO2:Mn films and crystallite size decreased as Mn doping concentration increased from 0 - 3 mol%. The magnetic property shows that pure SnO2 film is diamagnetic and 1- 3 mol% SnO2:Mn films posses room temperature ferromagnetism. The optical properties of the films revealed that transmittance of the films decreased with increase in Mn doping concentration. The optical energy band gap values (3.55 eV-3.71 eV) increased with the increase in Mn doping concentrations. Such SnO2:Mn films with structural, optical and magnetic properties can be used as dilute magnetic semiconductors.

Effect of Gd substitution at Y-site on the structural and magnetic properties of Y1-xGdxMnO3 (x=0, 0.05) nanoparticles prepared by conventional solid state reaction method has been studied. The structural study using X-ray diffraction pattern indicates the hexagonal structure with P63cm space group for all the samples. The average particle size for all the samples lies in the range of 30-40 nm as confirmed by X-ray diffraction and transmission electron microscopy analysis. The change in a and c lattice parameters confirm the substitution of Gd at Y-site. Magnetization versus temperature measurements show enhanced magnetic moment and an increase in Neel temperature with Gd-doping. Spin glass behavior is observed at low temperature in all the samples. Exchange bias effect has been observed at 5 K after field cooling the samples which is ascribed to the formation of antiferromagnetic-ferromagnetic (AFM-FM) core-shell structure of the nanoparticles. A significant improvement in the dielectric properties of Gd-doped samples has also been observed.

As the need for smaller data storage devices in the market continues to grow, the study of new combinations of self-assembled magnetic nanoparticles/films is greatly needed. In this research, Fe50-Ni50 films were synthesized using a Pulsed Laser Deposition technique. The films were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM) and physical properties measurement system (PPMS). Films were deposited from Fe-Ni alloy target (50%-50% composition), deposition was conducted in vacuum, at substrate temperatures varying from liquid nitrogen temperature -196°C to 600°C. The films were annealed in a vacuum chamber at 600°C for 1 hour. The study reveals that the substrate temperature has significant effect on the structure of the films and their magnetic properties. It was shown that additional thermal treatment improved the quality of films in terms of narrow grain size distribution. Magnetic properties were also found to improve significantly after post annealing process.