The structure is then etched in {HEAD ~ a suitable etching solution} to form {TAIL ~ porous silicon} in the boron doped region of the silicon substrate 80 
to form
The structure is then etched in { HEAD ~ a suitable etching solution } to form { TAIL ~ porous silicon } in the boron doped region of the silicon substrate 80
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH