  Some instances of electron field emitters are characterized by
frequency-dependent hysteresis in their current-voltage characteristics. We
argue that such emitters can be classified as memristive systems and introduce
a general framework to describe their response. As a specific example of our
approach, we consider field emission from a carbon nanotube array. Our
experimental results demonstrate a low-field hysteresis, which is likely caused
by an electrostatic alignment of some of the nanotubes in the applied field. We
formulate a memristive model of such phenomenon whose results are in agreement
with the experimental results.
