Effect of annealing temperature on the electron emission characteristics of silicon tips coated with Ba0.67Sr0.33TiO3 thin film

Electron emission from an array of silicon tips coated With Ba0.67Sr0.33TiO3 (BST) ferroelectric thin film was systematically investigated by varying the sol-gel BST annealing temperature from 650 to 800 degreesC. It was found that the turn-on electric field of BST-coated silicon tips tend to decrease as the BST annealing temperature increases, except for the 750 degreesC annealing temperature case that has a considerably lower turn-on field than that of 800 degreesC. Analysis of the emission data using Fowler-Nordheim plots suggested that a higher annealing temperature would result in lower effective work function. To better understand this effect, solid-state BST-silicon junction current-voltage measurements for different annealing temperatures were also studied. The analysis suggests that the conduction mechanism of BST-silicon junction conforms to a space-charge limited injection current 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 a 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. In addition, it was found that the BST film annealed at 750 degreesC has relatively lower electron trap density than other cases. Lower electron trap density may be responsible for its relatively high emission efficiency. (C) 2003 American Vacuum Society.