For some embodiments, {HEAD ~ the carbon nanotubes} may be concentrated near {TAIL ~ the source/drain regions} 
For some embodiments , { HEAD ~ the carbon nanotubes } may be concentrated near { TAIL ~ the source / drain regions }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL