Allows the study of thin polycrystalline or amorphous films; the grazing angle geometry (small angle of incidence) allows suppressing the contribution from the substrate. This can generally be used on samples tens of nanometers thick, and can identify multiple layers of different phases. Crystallite size information will be available from this diffraction data.

Pore size information will generally be available using Small Angle X-Ray Scattering (SAXS) technique. Personally if I need information of 'surface atomic detail' I use XPS (X-Ray Photoelectron Spectroscopy). Would need to have a more detailed understanding of your characterisation problems to fully understand if GIXRD can assist in this part 

We have typically used it for detecting the surface properties and in case if the object under investigation was polycrystalling.

Allows the study of thin polycrystalline or amorphous films; the grazing angle geometry (small angle of incidence) allows suppressing the contribution from the substrate. This can generally be used on samples tens of nanometers thick, and can identify multiple layers of different phases. Crystallite size information will be available from this diffraction data.

Pore size information will generally be available using Small Angle X-Ray Scattering (SAXS) technique. Personally if I need information of 'surface atomic detail' I use XPS (X-Ray Photoelectron Spectroscopy). Would need to have a more detailed understanding of your characterisation problems to fully understand if GIXRD can assist in this part 

Yes, the basic principle of GIXRD is the same as usual XRD.

Thanks all for clarifying my doubts. Please could you tell me which will be more useful for studying surface/ porous natures either GIXRD or GISAXS?

Definately GISAXS. See for example the attached link as one of many examples in this area.

http://www.hecus.at/pdf/3_porosity_thin_films_gisaxs.pdf

Thank you very much for your reply and provided link Dr.Timothy I. Hyde.