A nanotube forming method includes growing a plurality of nanotubes to an
intermediate length that is deterministic of nanotube intrinsic
conductivity. Individual nanotubes exhibit an effective conductivity,
which varies among the plurality of nanotubes. The method includes
completing growth of nanotubes exhibiting effective conductivities inside
a selected range without completing growth of nanotubes exhibiting
effective conductivities outside the selected range. Before completing
nanotube growth, the method may further include stopping nanotube growth
and screening out nanotubes exhibiting conductivities outside the
selected range. The screening out of nanotubes may include deforming or
masking nanotubes exhibiting conductivities outside the selected range.
Deforming nanotubes may include applying a potential.