The impact of post-deposition annealing durations on the formation of Tb4O7 passivation layer on silicon substrate

Abstract

In this study, we have effectively utilized radio frequency (RF) sputtering to sputter the Tb4O7 passivation layer on an n-type silicon (Si) substrate in an argon (Ar) ambient. Various characterization approaches were used to investigate the impact of varying annealing durations on structural, morphological, compositional, and optical properties. The grazing incidence X-ray diffraction (GIXRD) pattern confirmed that all investigated Tb4O7 passivation layers (as grown) and annealed at (15, 30, and 45 min) showed a crystalline structure, respectively. As observed, the sample annealed for 30 min attained the highest crystallinity, around 39.51 nm. Surface morphology analysis revealed different surface structures in response to different annealing durations when observed using the field emission scanning electron microscopy (FESEM) technique. Atomic force microscopy (AFM) was utilized to investigate the top surface of the examined samples, and a higher surface roughness of around 2.37 nm was obtained for the sample annealed for 30 min. The band gap energies (Eg) were estimated by applying the Kubelka-Munk (KM) approach for all the investigated samples, and the obtained values were within a range between (1.94–3.07 eV) earlier reported in the literature. Previous studies have shown that the Tb4O7 passivation layer deposited onto Si substrates using RF sputtering and then annealed for 5 min at 900 °C in an Ar atmosphere, resulted in the formation of a highly crystalline passivation layer. However, there is a lack of a clear explanation for the observation, and the authors mainly concentrated on the electrical properties of the Tb4O7 material. This inspired us to carry out this study to investigate the impact of various annealing durations on the formation of Tb4O7 passivation layers, focusing on their structure, composition, morphology, and optical properties.