Prospects of non-linear optical behaviour of PZT/ZnO heterostructures

PZT and ZnO heterostructures were fabricated by using the sol-gel spin-coating method on two different substrates, viz., ITO-coated glass and Corning glass. UV–Vis spectroscopy of these heterostructures showed 80% transparency in the visible region of the electromagnetic spectrum, which is desirable for optical device applications. Tauc's relation was used to calculate the energy bandgap, which was found to be blue shifted to 3.96 eV in the case of the heterostructure on ITO-coated glass and 3.9 eV for that on Corning glass, indicating a difference of ΔE = 0.06 eV due to the change in substrate. The refractive index (n), extinction coefficient (k), and the real and imaginary parts of the dielectric constant (ε ₁ and ε ₂) of the heterostructures were estimated. The second order non-linear refractive index (n ₂) and the third order non-linear optical susceptibility (χ ⁽³⁾) were determined by generalized Miller's rule in the photon energy range of 0.5–6.5 eV by using the UV–Vis spectroscopic data. The respective values of χ ⁽¹⁾ and χ ⁽³⁾ values were found to be in the range 0.10–0.45 and 3.88 × 10 ⁻¹³–6.0 × 10 ⁻¹². The optical and structural studies established that the nanocrystalline PZT-ZnO heterostructure on ITO-coated glass was more optically transparent and had better non-linear properties as compared to that on the corning glass substrate. These properties are advantageous for optoelectronic device applications.