I didn't fully understand the last part of your question, could you please elaborate a bit? You can determine the surface area of your film using scanning electron microscope (SEM). 

The specific surface area can be determined using a BET (Brunauer–Emmett–Teller) measurement system.  This relies on self-limiting gas adsorption of the sample surface. Typically the sample is cooled in the presence of a suitable gas, such as H2.  The gas supply is then removed and the gas released by the sample is measured as it is warmed.  This is proportional to the surface area.

Depending on the sample it could be encapsulated with a photoresist or a thin silicon nitride layer.

I have forget to say the sample is perovskite thin film(CH3NH3PbI3), I want to know the precise specific surface area.

Dear Kaicheng,

Specific surface area (SSA) describes the property of the material and determines the type and structure of the material. Practically this quantity shall analysis the reactions on surfaces, adsorption and heterogeneity of the sample . It is defined as,

                   SSA =  SAd  / vd  X (density)                         (1)

                   or                    

                            SSA =  6 X 103  / τ X ρ                           (2)

where in Eq.1, SSA is Surface Area per mass, Vd is domain volume and SAd is surface area and in Eq. 2, τ is the size of the particle and ρ is the density of the used experimental samples. From SEM you can easily find out the size of the particle.

[1] T.Theivasanthi, M.Alagar: Archives of Phy. Res. Vol.1, 112 (2010)

[2] T.Theivasanthi, M.Alagar: Nano Biomed. Eng., Vol.3, 161 (2011)

[3] J.Antony,J,Nutting, D.R.Baer, D.Meyer, A.Sharma,Y.Qiang: J. Nanomatel,Vol. 54961, 1 (2006)

[4] Jo-Yong Park, Yun-Jo Lee, Ki-Won Jun, Jin-Ook Baeg, D.J.Yim:  J. Ind. Eng Chem., Vol.12, 882 (2006)

With regards.

Thank all fo you very much!

Chapter 2.5 Specific Surface Area