Effect of SiO 2 Mixing on Structural Properties of ZnO Thin Films Prepared by Pulsed Laser Deposition ( PLD ) Technique

In this paper ,ZnO was mixed by various concentrations (5,10,15,20,25) w% SiO2.The mixture was deposited on glass substrate by laser pulse deposition at room temperature. X-ray results showed that there was a decrease in the peaks of zinc oxide with gradual peaks of the zinc silicate compound at angles 2Ө 2 ) due to the increase in silicon oxide concentrations rates. The infrared spectrometer Fourier transform was used to study all prepared films and gave good results about the chemical bonds of the composite and their locations and correspond to the standard results of the zinc silicate compound . The results of the Atomic Force Microscope showed that all of prepared films were having Nano scale size and there was an increase in square root roughness index.


Introduction:
Thin film technology is one of the most important technologies that contributed to the development of the semiconductor study and its properties.Thin films are used in many different fields.They are used in the manufacturing of various components of microelectronic devices, reagents, magnetic storage equipment, inverter filters, inverter and inverter coatings.
They are also used in the manufacture of micro circuits, electrical circuits for electronic microscopes and in the manufacture of capacitors and rectifiers.Because of their small size and light weight, they are used in digital computers [1].Zn 2 SiO 4 (willemite) is a long known material which still retains its place among the best inorganic phosphors [2].Having different crystal phases and being sensitive to doping by transition metals and rare earths, it can emit light at different wavelengths in the visible and near IR range.In the past years there were successful attempts to synthesize nano-phase of Zn 2 SiO 4 using both solid state techniques [3,4] and wet chemistry aimed at the development of novel low voltage phosphors having high efficiency and chemical stability.One of the advanced methods for solid state synthesis of nanoparticles is ion implantation with subsequent annealing, which allows creation of nanoparticle-host matrix composites with high chemical stability.Many research groups have studied the ZnO nanostructure formation in SiO 2 matrices using ion beam synthesis and thermal oxidation [5].

Experiment part:
Zinc oxide powder was mixed with silicon oxide powder according to (5, 10, 15, 20, 25)% wt.respectively.The proportions of the powders were weighed using a sensitive electronic balance Sensitive 10 -4 .The powders were then mixed into mixing machine Type of Spex mixer for (5) minutes and then the powders were blended by hydraulic press.And sintering the tablets in a tube electric furnace at a temperature of C) for two hours and after the process of sintering left the tablets to cool.The process of deposition was accomplished within a vacuum chamber in the laser system under pressure 10 -3 torr and the laser energy was 1000 mJ, which is the appropriate energy for deposition.Nd: YAG laser pulse used at (1000 mJ) and frequency (6Hz) for prepared thin film.

Results and discussion:
A. X-ray diffraction : X-ray diffraction used to characterize obtained films crystalline.The ( d, h k l ) spacing between crystal planes can be calculated using Bragg's law [6].
Where (θ) is diffraction angle and (λ) is the used XRD wavelength.Debay Scherrer equation, formula used to calculate crystalline size utilize the peaks broadening [7].
Where(λ) is the x-ray wavelength for kα transition from Cu target .Å) B is full width at half maximum and (θ) is the angle of diffraction.Before the process of annealing, we observe from Fig. 1 that there are peaks showing that the original composite (ZnO) is clearly present with the presence of some unclear peaks of the silicon oxide and after annealing in Fig. 2, The peaks of the zinc silicate complex begin to appear with the reduction of the zinc oxide peaks by increasing the doping ratio with the increasing temperature of the annealing which reveals that crystallization of the membranes is improving, as it can be seen that the height of the peaks increases with the increase of the doping ratio indicating an increase in the crystallization rate.It is also possible to observe that the width of the peaks decreases with an increase in the percentage of doping, which indicates an increase in particle size, where the particle size is inversely proportional to the width of the top, this corresponds to the results in the literature [8][9] .Is a technique which is used to obtain an infrared spectrum of absorption or emission of a solid, liquid or gas.An FTIR spectrometer simultaneously collects high spectral resolution data over a wide spectral range.This confers a significant advantage over a dispersive spectrometer, which measures intensity over a narrow range of wavelengths at a time.The term Fourier transform infrared spectroscopy originates from the fact that a Fourier transform (a mathematical process) is required to convert the raw data into the actual spectrum [10].The FTIR spectroscopy was employed at room temperature in the range of (400 -4000) cm -1 as shown in Fig. 3 and Table 1 where the sample inhibits the presence of composite symmetric stretching in (~880 cm -1 ), composite stretching in (~1100cm -1 ), Composite bending stretching in (~510 cm -1 ).Similar study was reported by [11][12].

C. Atomic Force Microscope AFM :
In this study, the use of an atomic force microscope type ((Scanning probe microscope type AA3000 equipped from (Angstrom Advanced Company), it is characterized by the ability of the high amount of analysis (0. runs under normal atmospheric pressure without the need to unload high as it is in electronic microscopes.this machine gives analytical images of two-dimensional (2D) and threedimensional (3D) to the surfaces of (ZnO-SiO 2 ) films.Its provide us some calculations on the form of grain size, rate of surface roughness and root mean square by computer program prepared from manufacturer [13].From Figs. (4)(5) and Table 2, We note that the increase in the ratio of mixing and the temperature of the annealing lead to an increase in particle size and decrease the surface roughness and mean square root value due to good crystalline uniformity and high surface homogeneity of the particles composed of the films material.As for the fifth and sixth samples, the granular size decreases and the surface roughness And the average square root value due to the large diameter of the zinc oxide atom relative to the radius of the silicon oxide atom before annealing and after annealing, this corresponds to the results in the literature [14][15].