We have deposited silicon carbide on carbon substrate using one PVD technique. Due to amorphous behavior of SiC at low deposition temperature, we performed heat treatment of those films at elevated temperatures in an inert environment. Following peaks (Blue and red) emerged and potentially belongs to Crystalline SiC. These peaks somehow matched with Moissanite (one of crystalline form of hexagonal SiC) but characteristic peak (with most intensity) didn't emerge in my spectrum. We have tried different software like Jade and X'pert HighScore and also consulted literature but didn't find exact XRD phase and PDF card no. Any suggestion or recommendation of journal article related to these peaks will be appreciated.
Regards.
Dear Nisar Ahmed ,
Since the sample's origin is a PVD deposition, it is necessary to consider a textured sample (with an epitaxial relationship with the substrate).
SiC has several descriptions in the literature trigonal, hexagonal, among others. There are several CIF files available in the COD (Crystallographic Open Database), freely available, naturally with no texture as the sample in question.
I'm attaching 5 CIF files from which you have access to the publication inside the CIF; open it with a text editor.
Check with the supplier for the original substrate orientation. If not amorphous, the substrate's diffraction alone determines the polishment direction. If not mismatched higher than 5-8% in the lattice parameters (some structures admit even higher mismatch), the SiC deposition by PVD will follow the same orientation.
Best regards,
WNM
I strongly recommend to make yourself familiar with the systematics of the diffraction effects generated from polytypes if you deal with such a problem. Dealing with PDF cards may helps to get a rapid but possible incorrect or incomplete answer. PDF cards is not science! Look at "sic polytypes diffraction" in google scholar. Looking at the cif files sent by Wagner Da Nova Mussel try to discover which similarities exist between the diffraction patterns of the different polytypes and which differences exist. By this you will learn to distinguish polytypes in a systematic fashion and not by trial and error.
I believe the reason why X-ray diffraction of SiC deposited by PVD (or most other thin film deposition methods for that matter) is three-fold:
1) the covalent nature of SiC makes it difficult to obtain films with good crystallinity and very high annealing temperatures are necessary.
2) SiC crystallizes in multiple polytypes (2H, 4H, and 6H for example)
3) SiC contains a lot of stacking faults due to the layered nature of its crystal structure which is closely related to its polytypes
4) the deposition on a substrate will cause severe texture and preferred orientation
All of these aspects combined are making it very difficult to obtain high-quality powder diffraction patterns and can lead to reflections that are very broad or with a intensity that is seemingly too low. Therefore, it is not easy to identify the correct polytype. You might actually be looking at an intergrowth or mixture of many polytypes. That doesn't mean that your interpretation is necessarily wrong (or right), it simply means that a sample like yours is not well suited for powder X-ray diffraction and phase identification via PDF cards.
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