{HEAD ~ The precursor reacts} under {TAIL ~ the second conditions} to form the desired material, and at least some of the desired material forms a layer on the substrate 
under
{ HEAD ~ The precursor reacts } under { TAIL ~ the second conditions } to form the desired material , and at least some of the desired material forms a layer on the substrate
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH