Assessing, surface morphology, optical, and electrical performance of ZnO thin film using ALD technique

In this study, we focus on the influence of the deposition process of ZnO thin films with a thickness of 250 nm—grown on glass and silicon substrates by atomic layer deposition (ALD) technique—on morphology, optical properties, AC conductivity, and dielectric properties. The atomic structure of the ZnO film was analyzed using scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX), and incident X-ray diffraction pattern (XRD). The XRD pattern confirms the presence of a crystalline phase, which is clearly observed in the SEM image. The crystallite size value was found to be equal to 35.41 nm. Transparency study was performed by UV-vis spectroscopy. A key element of this study was to prove that it is impossible to attribute the optical energy gap (Eg) and refractive index (n) dependence to any typical thin film material because these parameters depend on the deposition condition and growth temperature. The values of the optical energy gap and the refractive index estimated from the absorption spectrum (Eg = 3.32eV, n = 2.29) were compared with those obtained from the transmittance and reflectance measurements (Eg = 3.36, n = 2.272). A new relation has been proposed based on the best fit for calculating the refractive index, which has been determined and compared with the values estimated by different researchers, showing excellent agreement. Electrical parameters such as dielectric characteristics and AC conductivity were also estimated at different temperatures ranging from 303 to 413 K versus the frequency ranging from 1 kHz to 1 MHz. AC conductivity behavior was studied to explore the mechanism of conduction. Further analysis revealed that the correlated barrier hopping (CBH) model is the predominant theoretical model for elucidating the conduction mechanism existing in our ZnO thin film. This article contains recent advances in the modified ZnO metal oxide prepared by ALD, which is an efficient approach for sensor device fabrication, mainly depending on the estimated parameters.