Secondary electron emission (SEE) plays a crucial role in the gain performance of devices, such as electron multipliers and microchannel plates (MCPs). Gain performance could be improved by increasing the secondary electron yield (SEY) of device surface. Al₂O₃ coating is an ideal material for SEE, benefiting from its high SEY. The Al₂O₃ coating deposited on inner device walls by atomic layer deposition (ALD) can improve the gain performance of devices. In this study, the SEE characteristics of Al₂O₃ coatings were investigated experimentally. A series of Al₂O₃ coatings with thicknesses of 1-30 nm were prepared on Si substrate through the ALD method. Then, the SEY of the coatings were quantified as a function of primary electron energy in the range of 100∼1500 eV. Furthermore, an equation describing the true SEY as a function of thickness was established by applying theory of Dionne’s SEE model. This work presents potential approach for controlling the SEE level of Al₂O₃ coatings through thickness adjustment and is crucial for comprehending the SEE of composite materials.

Ti-6Al-4V, also called TC4, is an alpha–beta titanium alloy with high specific strength, low weight ratio, and excellent corrosion resistance, having wide applications in the biomechanical and aerospace industries.¹ In particular, the surface roughness of TC4 plays a critical role in metallic dental implants and affects the accumulation of plaque,² and it also determines the performance of functional components in aerospace applications.³ Moreover, other applications involving surface roughness include reduced frictional heating in moving parts, increased surface area for chemical etching, and improved fluid flow for biofluidic applications.^4,5 Therefore, achieving fine surface roughness on the selected region of TC4 is an extremely important challenge that needs to be overcome.