wherein {TAIL ~ a thickness} of the Mg Ag layer is in a range of 170 Å to {HEAD ~ 200 Å}, 
wherein { TAIL ~ a thickness } of the Mg Ag layer is in a range of 170 Å to { HEAD ~ 200 Å } ,
OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH