I want to deposit silver nanoparticles on glass substrate by thermal evaporation technique.what values of the parameter (accostic impedence,density,thickness) i should take.
The values of the parameter (accostic impedence,density,thickness) that you are talking about is for the digital thickness monitor, to measure in-situ thickness of the evaporated film. The thickness monitor you are using should have the reference manual where these parameters are given in table form for all targets to be deposited.
These parameters are important to measure the film thickness and rate of deposition in-situ.
For Ag, the density value you can set to 10.5 and Acoustic Impedance to 16.68 (refer to attached pdf).
The thickness of the Ag film you deposit is a parameter of your own choice, you can play with this parameter. Try 1nm to 5nm thickness, but thicker the Ag film bigger the size of the nano-crystals. So it is generally better to keep 1-2nm thickness of Ag film. You cannot deposit nano-crystals or nano particles as such but you have to deposit a thin film, 1-2nm, and then anneal it at some temperature to agglomerate the film to form nano-crystals. You can google it and get many papers on what temperature range you can choose for anneal step.
Also the thickness of Ag you choose depends on your Evaporator System and you may need to do few optimization runs before you get desired size of nano-crystals.