Study of structural, morphological, optical and electroluminescent properties of undoped ZnO nanorods grown by a simple chemical precipitation

Abstract

In this work, zinc oxide (ZnO) nanorods were obtained by a simple chemical precipitation method in the presence of capping agent: polyvinyl pyrrolidone (PVP) at room temperature. X-ray diffraction (XRD) result indicates that the synthesized undoped ZnO nanorods have hexagonal wurtzite structure without any impurities. It has been observed that the growth direction of the prepared ZnO nanorods is [1 0 1]. XRD analysis revealed that the nanorods have the crystallite size of 49 nm. Crystallite size is calculated by Debye-Scherrer formula and lattice strain is calculated by Williomson-Hall equation. Cell volume, Lorentz factor, Lorentz polarization factor, bond length, texture coefficient, lattice constants and dislocation density have also been studied. We also compared the interplanar spacings and relative peak intensities with their standard values at different angles. The scanning electron microscope (SEM) images confirmed the size and shape of these nanorods. It has been found that the diameter of the nanorods ranges from 1.52 µm to 1.61 µm and the length is about 4.89 µm. It has also been observed that at room temperature ultraviolet visible (UV-Vis) absorption band is around 355 nm (blue shifted as compared to the bulk). The average particle size has also been calculated by mathematical model of effective mass approximation equation, using UV-Vis absorption peak. Finally, the bandgap has been calculated using UV-absorption peak. Electroluminescence (EL) studies show that emission of light is possible at very small threshold voltage and it increases rapidly with increasing applied voltage. It is seen that smaller ZnO nanoparticles give higher electroluminescence brightness starting at lower threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

Effects of growth conditions on properties of CBD synthesized ZnO nanorods grown on ultrasonic spray pyrolysis deposited ZnO seed layers

“…All the peaks detected were matching with the standard bulk ZnO (COD 10 11 258) patterns. The mean crystalline sizes (D), strain (ε) and stress (σ) of ZnO nanorods were calculated using the following formulas [ 48 , 49 , 50 , 51 ]: where θ is Bragg's diffraction angle, β is Full Width at Half Maximum (FWHM), ƛ is the X-ray wavelength (1.5418 Å), c is the lattice parameter of the strained ZnO from the XRD and c o is the lattice parameter of the unstrained bulk ZnO (COD 10 11 258).

Figure 3 (a) XRD diffractograms; (b) FWHM and crystallite size graph; (c) Optical transmittance spectra; (d) Raman spectra of ZnO nanorods fabricated for 1.5 h–3.0 h.

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Structural and optical properties of ZnO films obtained on mesoporous Si substrates by the method of HF magnetron sputtering

“…The full width at half maximum (FWHM) of the peak (002) of the ZnO films is 0.73°. The average crystallite size can be calculated from the position of the peak (002) by the Scherrer equation [11]:…”

“…The value of microstresses ( ε) and the dislocation density ( δ) can be calculated by the following expressions [12]: ε = λ D cos θ − β × 1 tan θ and δ = 15ε Da . The length L of the Zn -O bond is defined as [11]:…”

Influence of Cu/in Ratios and the Growth Temperature on the Microstructural Parameters of Sprayed Cuinse2 Thin Films.

“…If the sample has a texture coefficient value equal the unity (TC (hkl) =1) then the crystallites of that sample were randomly oriented. While if the sample has TC >1, then its crystallites were oriented at a certain (hkl) direction [28][29][30][31]. The greater value of TC, the greater the number of crystallites that periodically oriented.…”

“…N is the total number of reflections and n is the number of diffraction peaks [29]. The calculated values of this coefficient for the three major diffraction lines were listed in Determination of the microstructural parameters:-For each investigated samples prepared of Cu/In ratios at different growth temperature, the estimated correct integral broadening (β) of the detected X-ray diffraction lines were calculated by the area under the beak divided by the maximum intensity (I o ).…”