A dilution gas for use at {TAIL ~ the time} of forming the surface layer is made of {HEAD ~ hydrogen} , argon or helium or the like 
A dilution gas for use at { TAIL ~ the time } of forming the surface layer is made of { HEAD ~ hydrogen } , argon or helium or the like
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH