Analytical Techniques
Raman Spectroscopy
Raman spectra were recorded using a HORIBA Jobin-Yvon confocal LabRAM ARAMIS micro-Raman system equipped with a multichannel charge-coupled device (CCD) detector, operated by Labspec5 software. The light source was the internal laser Diode pumped solid-state laser of 532 nm with a nominal output power of 50 mW. The sample was focused to a diameter of approximately 2 µm using an Olympus 100x lens. Raman spectra were obtained at room conditions. The following analytical conditions were used: 100 μm hole, 100 μm slit, grating of 1800 grooves per millimeter during 20 sec, and data accumulated over one cycle. The Raman spectrometer was calibrated by adjusting the peak (frequency of 520.7 cm-1) position for silicon metal. A Gaussian curve-fitting technique was applied for the precise frequency determination of the Raman bands.
Transmitted Electron Microscopy (TEM)
Selected areas were removed from thin sections to be Ar-ion-beam thinned. These thinned specimens were examined by imaging and diffraction in a Philips EM430 TEM operated at 300 kV, with minerals identified using diffraction supplemented by X-ray spectra from an EDAX thin-window energy-dispersive spectrometer mounted on the TEM.