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