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