Analysis of the Thickness of Multilayered Porous Silicon in the Cold Emission Property

This work aims to investigate the influence of thickness of multilayered porous silicon (MPS) on its cold emission properties. The MPS layer with different thicknesses was prepared by adjusting the charge quantity Q ( $\text{mA}\cdot \text{min}$ ) in the pulsed electrochemical etching process and oxidized through rapid thermal oxidation (RTO). The microstructure of the oxidized MPS was characterized by the scanning electron microscope (SEM) and the cold emission performance of the MPS-based emitters were also measured in vacuum. The studies show that, to fully utilize the advantages of a multilayered structure, it is essential to use the appropriate thickness and achieve sufficient oxidation for the MPS in this electron emitter fabrication. The optimal electron emission performance, with a stable efficiency of nearly 1%, a high current density of about 300 $\mu$ A/cm $^{\text{2}}$ , and an emission current fluctuation of only 9.8% can be achieved with a 5.5- $\mu$ m thickness in the present MPS configuration and RTO condition at the operating voltage of 20 V. This work helps explore the intrinsic relationship between multilayered structures and the cold emission property of PS-based cathodes, facilitating their application in vacuum microelectronic devices.