{HEAD ~ The carbon nanotubes} may extend across the entire channel region or {TAIL ~ a portion} of the channel region 
extend across
{ HEAD ~ The carbon nanotubes } may extend across the entire channel region or { TAIL ~ a portion } of the channel region
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH