The electron field emission properties of the nanodiamond films were examined using scanning tunneling microscopic sSTMd technique. Current image tunneling spectroscopic measurements reveal the direct dependence of electron tunneling/field emission behavior of the films on the
proportion of grain boundaries present. Local tunneling current-voltage sIt–Vd measurements show that incorporation of boron species insignificantly alters the occupied state, but markedly modifies
the empty state of the diamond films, viz. it induces the presence of impurity states for the films heavily doped with borons, resulting in smaller emission energy gap for the samples. Such a characteristic improves both the local electron field emission behavior of the diamond films measured by STM and the average electron field emission properties measured by conventional
parallel plate setup. These results infer clearly that the presence of impurity states due to boron doping is a prime factor improving the field emission properties for these boron-doped nanodiamond films.