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