Raman spectroscopy of thin films

Raman spectroscopy was used in conjunction with x-ray diffraction and x-ray photoelectron spectroscopy to elucidate structural and compositional information on a variety of samples. Raman was used on the unique La 2NiMnO6 mixed double perovskite which is a member of the LaMnO3 family of perovskites and has multiferroic properties. Raman was also used on nanodiamond films as well as some boron-doped carbon compounds. Finally, Raman was used to identify metal-dendrimer bonds that have previously been overlooked.;Vibrational modes for La2NiMnO6 were ascribed by comparing spectra with that for LaMnO3 bulk and thin film spectra. The two most prominent modes were labeled as an asymmetric stretch (A g) centered around 535 cm-1 and a symmetric stretch (B g) centered around 678 cm. The heteroepitaxial quality of La2NiMnO 6 films on SrTiO3 (100) and LaAlO3 (100) substrates were examined using the Raman microscope by way of depth profile experiments and by varying the thickness of the films. It was found that thin films (10 nm) had much greater strain on the LaAlO3 substrate than on the SrTiO3 substrate by examining the shifts of the Ag and the Bg modes from their bulk positions. Changes in the unit cell owing to the presence of oxygen defects were also monitored using Raman spectroscopy. It was found that the Ag and Bg modes shifted between samples formed with different oxygen partial pressures. These shifts could be correlated to changes in the symmetry of the manganese centers due to oxygen defects.;Raman spectroscopy was used to examine the structural and compositional characteristics of carbon materials. Nanocrystalline diamond coated cutting tools were examined using the Raman Microscope. Impact, abrasion, and depth profile experiments indicated that delamination was the primary cause of film failure in these systems. Boron doped material of interest as catalyst supports were also examined. Monitoring of the G-mode and intensities of the D- and G-modes indicated that boron was successfully introduced into both a bulk powder fabricated in a quartz furnace using a BCl3/C6H 6 precursor and for a thin film (30 nm) deposited in a vacuum chamber using d.c. magnetron cosputtering. In addition to Raman, x-ray diffraction and x-ray photoelectron spectroscopy were used to verify boron-doping of the materials.;Generation 4 Poly(amidoamine) dendrimers were used to form platinum and cobalt nanoparticles to form dendrimer-encapsulated nanoparticles (DENs). It was seen using both Raman and infrared spectroscopy that these metals bonded with the dendrimers after reduction. These studies highlight the efficacy of Raman in the study of a wide variety of materials to obtain both compositional and structural information.