An Insitu X-Ray-Diffraction Method For The Structure Of Amorphous Thin-Films Using Shallow Angles Of Incidence

A technique for the structural characterization of thin amorphous films employing synchrotron radiation parallel beam x-ray optics at grazing angles of incidence is detailed. At incident angles near to the critical angle for total external reflection, sampling of specimens may be achieved via the evanescent mode. The parallel beam geometry allows the use of a technique in which a 2-theta detector, incorporating a parallel plate collimator, scans diffraction data for a given incident angle. For a specified wavelength, the incident angle chosen will determine the penetration of the radiation into the sample (approximately 10-1000 angstrom). The data must be corrected for significant peak shifting resulting from x-ray refraction, as well as for the effects associated with conventional theta:2-theta scans. Preliminary data resulting from the first application of this technique to amorphous hydrogenated silicon:carbon thin films, deposited onto crystalline silicon substrates, will be presented and discussed. Conventional theta:2-theta powder diffraction data will also be presented as a comparative standard.