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