Enhancement of emission characteristics for field-emitter arrays by optimizing the etched feature of the gate electrode

Abstract

The etched features of thin chromium (Cr) films deposited on SiO2–Si substrate were investigated as a function of the substrate temperature during rf sputtering deposition. In this work, the changes of both the grain structures and crystallographic orientations of sputtered Cr films as a function of substrate temperature were examined, and we found that the tapering angle θt of thin Cr film after reactive ion etching depends on the deposition condition, especially the substrate temperature during the rf sputtering process. Based on the obtained results, we fabricated two kinds of Cr-grated Mo-tip field-emitter arrays (FEAs): the first kind is a FEA with tapered-gate electrode (tapered-gated FEA, θt⩽90°) and the second kind is a FEA with taper-free gate electrode (nontapered-gated FEA, θt=90°). We obtained more emission current than that of tapered-gated FEAs, whereas the gate leakage current of nontapered-gated FEAs was almost the same value as compared to that of tapered-gated FEAs. Because of the optimized etched shape of the gated electrode, the field conversion factor β of the nontapered-gated FEAs increased to 32% more than that of tapered-gated FEAs. Furthermore, the total transconductance Gm of nontapered-gated FEAs increased to 20% without increasing the packing density of FEAs.