Ions with a specific mass to charge {HEAD ~ ratio} may selectively pass through {TAIL ~ the duct} and impinge on the substrate surface 
Ions with a specific mass to charge { HEAD ~ ratio } may selectively pass through { TAIL ~ the duct } and impinge on the substrate surface
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH