  Nanocomposites based on graphene and carbon nanotubes dispersed in
polypyrrole or poly(3,4ethylenedioxy)thiophene have been prepared and their
performance as cold cathodes for field emission has been evaluated. It was
found that the polymer matrix will degrade during the field emission process
and result in unstable performance. Electropolymerization of the composites
results in significantly better field emission performance, but the stability
is still a major problem. Deposition of composites onto a stable membrane was
proposed as a strategy for improving the performance of electrodes. The field
emission data indicates that composites deposited on the surface of a membrane
can limit the emission surface and result in lower maximum emission and higher
Turn-On voltage. The lower emission current and consequently lower heat
generation, in addition to the possible heat dissipation by the AAO membrane,
can reduce the rate of the thermal degradation of the polymer. The membrane can
also act as a physical barrier that holds nanotubes in place and allows
electrons through. Thus, it can prevent shorting of the field emission cell. In
this way higher emission and longer life time can be achieved.
