As the second diffused region, {HEAD ~ a solid phase diffusion source} such as {TAIL ~ an impurity doped silicate glass} is used 
As the second diffused region , { HEAD ~ a solid phase diffusion source } such as { TAIL ~ an impurity doped silicate glass } is used
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH