In one embodiment, the first sub portions are formed by {HEAD ~ ion implantation} at a dose about {TAIL ~ E13 cm−2} at an energy level about 25 80 
In one embodiment , the first sub portions are formed by { HEAD ~ ion implantation } at a dose about { TAIL ~ E13 cm−2 } at an energy level about 25 80
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH