Failed to generate mesh for subdomain

Hello everyone,

I have a metal nanoparticle (radius = 100nm) next to an emitter embedded in glass ( n = 1.5). The computational domain around the metal nanoparticle and the emitter is also spherical and it is 650nm in diameter (PML layer).

I measure the emission from the emitter in terms of Power and it works really great. The parameter for the mesh was:
'max element size' = 3.5e-9 and 'growth rate' = 1.25

I start to have a problem with mesh for the glass subdomain once I increase the size of the nanoparticle and the computational domain.

The computer i am using has 64 GB RAM and 16 processors. The error i get everytime is the following...

Failed to generate mesh for subdomain...

Coordinate of a point in 3D

I have tried to change the 'max element size' and 'growth rate' values but it does not help at all.

I would be grateful to anyone who could help me figure this out.

Looking forward to getting replies. :)

Thanks in advance,
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