Iron doped Zinc Oxide (Fe 0.2 Zn 0.8 O) by sol-gel method and its Characterization. K. Peddanna By M.Sc. Nano Science Dept. of Physics OSMANIA UNIVERSITY

Introduction to Semiconductors & Its applications

INTRODUCTION TO SEMICONDUCTORS  The magic word semiconductor is composed of two words- Semi and Conductor.  Semi means not completely while conductor mean something, which can conduct electricity.  A semiconductor is a material that has intermediate conductivity between a conductor and an insulator. It means that it has unique physical properties somewhere in between a conductor like aluminum and an insulator like glass  The definition of a semiconductor is a material that is neither a good conductor or a good insulator but that conducts more electricity when heat, light or voltage is added.

Classification of semiconductors Elementalcompound Intrinsic semiconductors Extrinsic semiconductors III-V compoundII-VI compound Ex: Silicon, germanium A)n-type semiconductor B) P -type semiconductor GaN, GaP, GaAs, GaSb, InP, InAs, InSb ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe,ZnO

APPLICATIONS Semiconductors are the foundation of modern electronics, including radio, computers, and telephones. Semiconductor-based electronic components include transistors, solar cells, many kinds of diodes including the light-emitting diode (LED), the silicon controlled rectifier, photo-diodes, and digital and analog integrated circuits.

ZnO (Zinc oxide)

Crystal Structure Zinc Oxide Other names: Zinc white, Calamine, philosopher's wool, Chinese white, flowers of zinc Structure: Zinc oxide crystallizes in two main forms, hexagonal wurtzite and cubic zincblende.. Wurtzite structure A zincblende unit cell

Properties Physical properties The wurtzite structure is most stable at ambient conditions and thus most common. The zincblende form can be stabilized by growing ZnO on substrates with cubic lattice structure. In both cases, the zinc and oxide centers are tetrahedral. Hexagonal and zincblende polymorphs have no inversion symmetry. This and other lattice symmetry properties result in piezoelectricity of the hexagonal and zincblende ZnO, and pyroelectricity of hexagonal ZnO.

Chemical properties ZnO occurs as a white powder The mineral zincite usually contains manganese and other impurities. Crystalline zinc oxide is thermochromic, changing from white to yellow when heated and in air reverting to white on cooling. This color change is caused by a small loss of oxygen to the environment. Zinc oxide is nearly insoluble in water, but it is soluble in (degraded by) most acids, such as hydrochloric acid: ZnO + 2 HCl ZnCl 2 + H 2 O

Applications  1. Rubber manufacture  2. Ceramic industry  3. Concrete industry  4. Medical  5. Cigarette filters  6. Food additive  7. Pigment  8. Coatings

Why FeZnO is interesting? Widely used: medicinal purposes (colds, rashes, antiseptics, sunscreen lotions) used in manufacturing of rubber as rubber cure (or as filler) pigment for paints and coatings in electronics, used mainly in laser diodes, LED’s, transparent thin film coatings, and various piezoelectrics Bright future: shows promising signs in the field of nanotechnology, UV detecors, nanoscale detectors and actuators.

Synthesis methods Precipitating nano particles from a solution of chemical compounds can be classified into several major categories: 1) colloidal methods 2) sol-gel processing 3) hydro thermal synthesis 4) co-precipitation method 5)Ball-milling

Sol-gel Advantages - Inexpensive and low temperature operation. -Very thin films of metal oxides can be obtained. -Uniform distribution of components and porosity. -Easy dopant addition in ceramics processing. -Sol gel material can be obtained as bulks, thin films, (nano) powders. - Atomic level mixing of components(Precursors).

Flow chart for Sol-gel Processing Fe(NO 3 ) 2.6H 2 OZn(NO 3 ) 2.6H 2 O Weight and dissolved in the stoichiometric ratio Neutralized with NH3 Adding Ethylene glycol and heated for chemical burning Burning the obtained material using burner stirring Heating up to get the “gel” XRD, SEM Fe 0.2 Zn 0.8 O Nanomaterial Citric acid

Characterization Methods X –Ray Diffraction Scanning Electron Microscope

X-Ray Diffraction Principle : XRD Works on the Bragg’s Law n λ = 2 d sin θ Where n=order of the diffraction λ=Wavelength d=interplanar distance θ =Angle between the Incidenct ray and scattering planes

Scherrer’s Formula D = crystallite size K = constant dependent on crystallite shape = wavelength of x-rays. B = FWHM (full width at half max) or integral breadth  B = Bragg Angle

Average Crystallite Size = nm

Uses of XRD Phase Identification of a sample Average crystallite size Crystal Structure

Scanning Electron Microscopy (SEM)

Topography Morphology Composition Crystallographic Information Uses of SEM

FUTURE WORK  Conforming of composition of prepared samples using EDAX(SEM) examination.  Microstructure of the samples can be studied after getting images from SEM.  Dielectric constant of samples can be determined using LCR meter.  Comparison of pure ZnO and Iron doped ZnO can be studied.

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