hi there...to start with mostly the laser wavelengths are 488, 515 or 633nm...whatever the wavelength try to use low power (say 25% ) single iteration for a standard sample like silicon single crystal. notch filter is used  mostly...for range you need to know that from an earlier published data, like Si will have a peak at 520cm-1...once you know the range decide a slower scan rate to get the spectra...

What instrument do you have access to? This normally limits your choices. The materials should be transparent in the visible, so laser power should not be a major issue. However, if you are looking for a monolayer on the surface, it may be very tricky to detect, and you may need maximum power. You should use the shortest wavelength available, and the shortest focal length objective. Ideally if you have a confocal instrument, close the hole to the minimum recommended  to try to limit your detection as much as possible to the surface. It still might be difficult, however!

Concering the silane you can confirm the reaction by montiitoring the vibrational bands at around 620 cm-1. 

Article Analysis of silanes and of siloxanes formation by Raman spectroscopy

Thanks Michael I wont be able to characterize my sample for a while but I will tell if it worked.

Will I get the same signature analyzing the silane attached to the glass slide?