What is the mechanism of APTES mono-layer formation on glass substrates? The reagent APTES is a fairly common "ink" for microcontact printing, a technique that forms covalent bonds between the silanols found on the surface of the glass and the silane in the the APTES. It's also been demonstrated that the mono-layer then polymerizes somewhat, forming bonds between neighboring silanols.


What is the mechanism by which the printing and polymerization occur? 
What is the reason for using APTES instead of a more reactive trichlorosilane?
Here's two links (1, 2) that show the simple scheme on forming monolayers. The essential figure is also shown here. 



For the second part of your question... I can only point out this article that describes which properties change, if you make the molecules more bulky or add chloride, etc. I would guess that APTES has well known properties and they are "neutral" regarding common applications.