Polycrystalline diamond coatings are grown on Si (100) substrate by hot filament CVD technique. We investigate here the effect of substrate roughening on the substrate temperature and methane concentration required to maintain high quality, high growth rate and faceted morphology of the diamond coatings. It has been shown that as we increase the substrate roughness from 0.05 𝜇m to 0.91 𝜇m (centre line average or CLA) there is enhancement in deposited film quality (Raman peak intensity ratio of 𝑠𝑝³ to non-𝑠𝑝³ content increases from 1.65 to 7.13) and the substrate temperature can be brought down to 640°C without any additional substrate heating. The coatings grown at adverse conditions for 𝑠𝑝³ deposition has cauliflower morphology with nanocrystalline grains and coatings grown under favourable 𝑠𝑝³ condition gives clear faceted grains.

We report the optimization and usage of surfactantless, water dispersible Ag and Au-coated 𝛾 –Fe₂O₃ nanoparticles for applications in surface-enhanced Raman scattering (SERS). These nanoparticles, with plasmonic as well as super paramagnetic properties exhibit Raman enhancement factors of the order of 10⁶ (10⁵) for Ag (Au) coating, which are on par with the conventional Ag and Au nanoparticles. Raman markers like 2-naphthalenethiol, rhodamine-B and rhodamine-6G have been adsorbed to these nanoparticles and tested for nonresonant SERS at low concentrations. Further, to confirm the robustness of Ag-coated nanoparticles, we have performed temperaturedependent SERS in the temperature range of 77–473 K. The adsorbed molecules exhibit stable SERS spectra except at temperatures >323 K, where the thermal desorption of test molecule (naphthalenethiol) were evident. The magnetic properties of these nanoparticles combined with SERS provide a wide range of applications.