Improved electron emission properties of the porous silicon emitter by chemical surface modification

A new chemical dipping method using nickel chloride (NiCl₂) solution is proposed to improve the characteristics of an electron emitter based on porous silicon (PS). Two groups of PS samples were prepared, one group was then left untreated, while the other group was treated by the chemical dipping method. Energy dispersive x-ray (EDX) and x-ray photoemission spectroscopy (XPS) studies confirm the uniform filling of the reduced Ni and the formation of the SiO₂ in the chemically dipped sample. The gold electrode was sputtered on the modified PS surface and the study of J-V characteristics show that the modified samples have more favorable rectifying behavior and longer-term durability than the unmodified one. The measured results showed that the voltage threshold ∼8 V, PVCR value ∼1.08, emission current density ∼48 μ A cm⁻², emission efficiency ∼0.72%, and stable emission were achieved for the modified sample; most of these electron emission characteristics were better than those from the unmodified emitter. Such improvements are mainly due to the decrease of the contact barrier height between the PS and the gold electrode, as is evident from analyzing the logarithmic J-V characteristics. The chemical dipping method is therefore expected to be a valuable technique to enhance the electron emission characteristics of the PS emitter. (paper)