The effect of annealing temperature on the electron emission characteristics of silicon tips coated with Ba_0.67Sr_0.33TiO₃ thin film

Electron emission from an array of silicon tips coated with Ba_0.67Sr_0.33TiO₃ (BST) ferroelectric thin film was systematically investigated by varying the sol-gel BST annealing temperature. It was found that the turn-on electric field of BST coated silicon tips decreases as the BST annealing temperature increases. Analysis of the emission data using Fowler-Nordhiem plots, suggested that a higher annealing temperature would result in lower effective work function. To better understand this effect, solid-state BST-silicon junction I-V measurements for different annealing temperatures were studied. The analysis suggests that the conduction mechanism of BST-silicon junction conforms to a space-charge limited injection current (SCLC) model with shallow and deep traps. The higher BST annealing temperature, the shallower the trap was found to be and the quasi-Fermi level was nearer to the conduction band. It can be deduced that higher annealing temperature results in higher activation of ionic conduction. This higher activation increases carrier concentration, raises the Fermi level toward the conduction band, thus reduces the effective work function, and thereby enhances field emission.