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