Does that mean that if you used something that wouldn't boil away, such
as silicone, the two pieces of glass would not stick together in a
vacuum? Has it been tried?


If the silicone molecules inter-attract with the silicon dioxide molecules
more strongly than they intra-attract amongst themselves, no. The plates
would stick through wetting of the glass. They may be easy to separate and
that is a way of finding the strength of the interactions.

As to whether anyone has done it, I dunno.

Agkistrodon