X-ray diffraction for powder samples is the most convenient and easiest method, for crystalline silicon you obtained one peak, many peak for polycrystalline and none for amorphous.

good luck

Dear Hafid,

thanks for your answer.

What about thin film layer?

In my opinion, the best and most convenient way to distuinguish between crystalline and amorphous silicon is Raman microscopy. However, it is very difficult to distinguish between multi and single crystalline Si. I remember, I have found only one paper about this. In this case I would suggest EBSD in order to extract the orientation of the grains you observe.

Dear Contantina,

I think the easiest method to classify silicon into momo poly and amorphous is to use chemical etching and microscopy either optical for the relatively larger grain sizes that can be resolved by it or  electron microscope  for the fine grained structures. We can make full use of the the geometrical features that made observable  after preferential etching. Preferential etching delineate the growth features and geometrical crystallographic defect  such as grain boundaries , stacking faults and dislocations. A solution of sodium hydroxide can be used for etching  or one can use a mixture of acetic acid, niteric acid and hydrofloric acid. You can find in the silicon etching literature the suitable mixing ratios.

From the principle point of view when you deposit silicon you adjust the deposition condition and the substrate to get certain degree of crystallinity. Practically the deposited layer is either single crystal or poly crystal having different grains according to the deposition condition.

Wish you success