Effect of the TiN-coating-layer properties on the electron emission of volcano-structured silicon field emitter arrays

Volcano-structured field emitter arrays (FEAs) have gained attention due to their excellent electron beam-focusing properties. While we have demonstrated high-current operation of FEAs by coating silicon tips with a titanium nitride (TiN) layer, the influence of TiN properties on emission characteristics remains unclear. In this study, we formed TiN coating layers on FEAs using reactive sputtering with a titanium target and varying Ar/N2 gas ratios and evaluated their emission characteristics. The operational voltage decreased significantly with increasing N2 gas ratio (RN2, N2/(Ar + N2)) with the lowest operational voltage observed at RN2 = 1.00. Electron emission began at a gate voltage of 20 V, and the emission current reached 1 mA at 60 V using 1027 tips. This behavior is likely attributed to a reduction in the work function of the TiN layer, corresponding to decreased oxygen concentration in TiN with increasing RN2 as confirmed by x-ray photoelectron spectroscopy analysis. Theoretical calculations also indicate a decrease in the work function of TiN-coated FEAs with increasing RN2, consistent with the experimental results. These findings may be broadly applicable to the development of microscale electron sources with TiN-coated emitters.