Influence of power and duration on RF sputtering for the formation of terbium oxide passivation layers via the argon ambient

In this study, we have successfully used radio-frequency (RF) sputtering to sputter the Tb₄O₇ passivation layers on silicon (Si) substrates. The impact of different RF powers and durations on structural, morphological, compositional, and optical characteristics was investigated via different characterization systems. The grazing incidence X-ray diffraction (GIXRD) analysis has verified the formation of all the studied samples (A, B, C, and D) sputtered at A (80 W/30 min and then raised to 100 W/15 min), B (80 W/30 min and then raised to 100 W/35 min), C (80 W/30 min and then raised to 100 W/55 min), and D (100 W/45 min), respectively. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to analyze the surface morphology of the investigated samples. Sample (C) exhibited larger grain sizes and higher surface roughness of 2.33 nm. The band gap energy (E^D) values were evaluated by applying the Kubelka–Munk (KM) approach for all the studied samples, and the obtained values were within a range between 2.29 and 2.53 eV. Previous research has shown that the Tb₄O₇ thin film sputtered on a Si substrate for 45 min using the RF power (110 W) and annealed for 900 °C in argon (Ar) ambient resulted in the formation of crystalline Tb₄O₇ phase without clear explanation. This motivated us to conduct this study to observe the influence of different RF power and durations as well as determine the best RF power for the formation of the best Tb₄O₇ passivation layer.