  A power efficient and stable field emission (FE) has been reported here from
Nickel Oxide nanostructures. Modification in device geometry and surface micro-
(nano-) structure has been found helpful in addressing the bottlenecks in
achieving an efficient FE . In terms of threshold and turn on fields, three
orders of magnitude better electron FE has been observed in the nickel oxide
nanopetals (NiO-NPs) fabricated using simple hydrothermal technique. Uniform
and vertically aligned NiO-NPs structures, grown on very flat conducting
surface (FTO coated glass), show sharp needles like structures on the top edges
of the flakes. These ultrafine structures play the main role in field emission
to start at such a low turn on fields. The FE data (J-E plot) has been fitted
with Fowler-Nordheim (FN) equation to estimate threshold field value and field
enhancement factor which are found to be 3 V/mm and $\sim$ 5 $\times$ 10$^6$
respectively.
