Plan view of VACNT-column arrays with square (a), triangular (b), and hexagonal (c) symmetries, respectively, and (d) 2D contour plot of the electric field distribution at the top surfaces of the VACNT columns in a square array with the pitch-to-height ratio of 0.5 and height-to-diameter ratio of 1.
Electric field distribution along the respective cut lines in Figs. 1(a)–1(c) for (a) square, (b) triangular, and (c) hexagonal VACNT-column arrays with 0.5 pitch-to-height ratio and identical column diameter. Position on the cut line is defined from bottom to top.
Plan-view SEM images of fabricated VACNT-column arrays. The identical diameter for all VACNT columns is , and the respective pitch distances are 400, 650, and for square, triangular, and hexagonal geometries.
Current density vs applied field curves (a) and the corresponding FN plots (b) of VACNT-column arrays of square, triangular, and hexagonal symmetries. The diameter of and pitch of were identical for three VACNT-column arrays, and the respective heights were 423, 403, and for the square, hexagonal, and triangular VACNT-column arrays.
Temporal variation in the emission current density at the dc electric field of from a hexagonal VACNT-column array. The net current after the stabilization was about .
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