Low-cost nebulizer spray deposited conduction mechanism of thin film ZnO nanoparticles

Abstract

The Zinc Oxide (ZnO) thin films have been deposited on glass substrate at different temperature from 300 to 500 o C by nebulizer spray pyrolysis technique. The prepared films were characterized by X-Ray diffraction (XRD), High resolution scanning electron microscope (HRSEM), Energy dispersive analysis by X-rays (EDAX), Photoluminescence (PL), UV-Vis-NIR spectrometer and impedance spectroscopy, respectively. The XRD confirms that the films are polycrystalline in nature with hexagonal wurtzite crystal structure with (002) plane as preferential orientation. The various parameters such as crystallite size, micro strain, and dislocation density were calculated from X-ray diffraction. HR-SEM images show smooth, tiny grains and dense morphology. The PL studies exhibits two emission peaks one at 389 nm corresponding to band gap excitonic emission and another located at 490 nm due to the presence of singly ionized oxygen vacancies. The UV-Vis-NIR spectrometer confirms the possibility of good transparent ZnO films with an average transmission of about ~85-95% in the visible region and optical band gap shifted from 3.37 eV to 3.2 eV with increase in temperature and which is supported by PL study. The semiconductor bahaviour and activation energy of these films have been confirmed by impedance spectroscopy measurements.

Temperature Dependence on Structural Properties of Liquid Phase Synthesized ZnO

“…The increase in crystalline size values with an increase in temperature is attributed to the enlargement of grain sizes and a decrease in the micro strain while increase in dislocation density [8]. This could also be linked to an increase in crystal growth rate as a result of volume expansion and a decrease in system supersaturation at high temperatures [14].…”

“…where D is the particle size in nm, k is a constant of value 0.9, λ is the X-ray wavelength in nm, θ is the Bragg's angle in radians, and β is the full width at half maximum of the peak in radians [12], [17], [23]. The dislocation density (δ), which is the number of defects in the sample is calculated using equation 8 [7], [8], [14], [24];…”

“…Due to its non-toxicity, it is a bio-safe and a bio-compatible material and consequently is being used for numerous biomedical applications such as biomedical implants, drug carriers, cosmetics and fillings in medical materials and several wide range medical applications [5], [6]. The importance of ZnO is owed to its unique chemical stability, physical, mechanical and thermal properties, highly efficient UV emission, high excitation binding energy of 60 MeV, high optical transparency in the visible region, low electrical resistivity, eco-friendly nature and above all its low cost make it a prospective candidate for industrial and other technological applications [7], [8], [5]. ZnO also stands out from other materials because of its ability to operate in tremendous conditions such as found in nuclear reactors and in space, due to its superior radiation hardness and high thermal conductivity than the majority of other materials [5].…”

“…ZnO also stands out from other materials because of its ability to operate in tremendous conditions such as found in nuclear reactors and in space, due to its superior radiation hardness and high thermal conductivity than the majority of other materials [5]. Interesting applications of ZnO includes transparent electrodes, thin-film transistors, light-emitting diodes, ultraviolet laser diodes and photodetectors, solar cells, gas sensors, piezoelectric nanogenerators, spintronic devices and surface acoustic wave device [9], [8], [3]. In the advent of nanotechnology, several methods have been developed for the preparation of nanomaterials (particularly ZnO) [7], [8], [3] [10].…”

“…Interesting applications of ZnO includes transparent electrodes, thin-film transistors, light-emitting diodes, ultraviolet laser diodes and photodetectors, solar cells, gas sensors, piezoelectric nanogenerators, spintronic devices and surface acoustic wave device [9], [8], [3]. In the advent of nanotechnology, several methods have been developed for the preparation of nanomaterials (particularly ZnO) [7], [8], [3] [10]. These are classified according to the medium of preparation as solution or liquid phase, solid phase and vapour phase methods [6].…”