Effect of N doping on the Optical and Electrical properties of Thermal Spray pyrolysed ZnO Thin Films

Abstract

Nitrogen doped ZnO (ZnO:N), thin films have been deposited on glass substrate at the temperature of 350ºC by low cost homemade thermal spray pyrolysis (TSP) technique at a normal environmental conditions. In this study the average reflectance, transmittance and absorbance were measured (20%), (35%), and (45%), respectively. Absorption coefficient is 3.5x10⁴cm^-1 for N doped ZnO. Direct bandgap energy varies from 3.08-2.99eV and indirect band gap energy varies from 2.86-2.67eV for N doped ZnO. XRD analysis shows the (002) plane is present of samples and the average grain size decrease with increasing N concentration. Surface morphology of N doped ZnO films is studied by Scanning Electron Microscopy (SEM). It is seen that hexagonal crystal grains few voids are present for N doped ZnO samples. The surface exhibits more or less uniform surface morphology with some clusters on the whole surface. Hall Effect study confirms that Nitrogen doped ZnO (ZnO:N), thin films using Vander pauws method were made at room temperature at a constant field of 9.75 KG. Experimentally (1, 2, 3, and 4) % N doped ZnO thin films have shown in negative Hall Constant (R_H). Which exhibited n-type characteristics. Hall Constant (R_H), and Hall concentration (n), increases with increasing N doping concentration. Initially Hall mobility (μ_H), increases linearly for (1-2) % N doping concentration then it decreases for the rest of the doping concentration. We also found that the resistivity (ρ) decreases and the conductivity (s) increases with increasing N doping concentration which exhibits the semiconducting nature.