M. Senthilkumar

Reactive electron beam evaporation of gadolinium oxide optical thin films for ultraviolet and deep ultraviolet laser wavelengths

Availability of ultraviolet optical thin film materials, especially high index refractory oxides that transmit down to deep ultraviolet (approx. 0.2 mm) is very much limited. The present article discusses some of the research optimization studies on gadolinium oxide (Gd O ), a novel lanthanide sesquioxide material, for such challenging spectral requirements. Optical and 23 topographical properties of single layer films have been studied using phase modulated spectroscopic ellipsometry, spectrophotometry and multimode atomic force microscopy. Films deposited at lower substrate temperatures have shown higher band gaps and higher substrate temperatures yielded higher refractive indices. Multilayer high reflection filters have been developed for ultraviolet laser wavelengths such as ArF (193 nm), KrCl (222 nm), KrF (248 nm) and Nd-Yag-III (355 nm), using this material at lower substrate temperature conditions and successfully tested for their performances. 2003 Elsevier Science B.V. All rights reserved.

Correlation of optical and microstructural properties of Gd2O3 thin films through phase-modulated ellipsometry and multi-mode atomic force microscopy

Gadolinium oxide thin films have been prepared by electron beam evaporation with different reactive oxygen pressures at low ambient substrate temperature. These thin films have been analyzed with phase-modulated spectroscopic ellipsometry and multi-mode atomic force microscopy (AFM). The distinct influences of oxygen pressure on surface topographies, microstructures and refractive indices of the thin films have been observed from the results of these advanced measurements. Both these techniques have displayed very strong co-relationships in the characterisation results acquired through respective modes of measurements and data analysis. Unequivocally, these two techniques indicated an optimum value of the oxygen pressure leading to best optical and structural properties of such a novel optical coating material.

Surface roughness and interface diffusion studies on thin Mo and W films and Mo/Si and W/Si interfaces

Single layers of Mo and W thin films and Mo/Si/Mo and W/Si/W tri-layers have been deposited by r.f. sputtering on c-Si substrates as precursor to the fabrication of Mo/Si and W/Si multilayer X-ray mirrors. The single layer thin films have been characterized primarily by phase modulated spectroscopic ellipsometry (SE) and information have been derived regarding the thickness and volume fraction of voids present in the layers. The results obtained by fitting the SE data have been verified by complementary techniques, viz. grazing-incidence X-ray reflectivity, Rutherford back-scattering and atomic force microscopy. With the optimized values of the sputtering parameters, Mo/Si/Mo and W/Si/W tri-layer structures have been deposited on c-Si substrates and have been characterized by secondary ion mass spectrometry (SIMS) technique using sputtering by a Cs þ ion source. The depth profile data obtained from the SIMS measurements have been analyzed to get the inter-diffusion at the metal‐ Si interfaces. Efforts have been given to correlate the interface diffusion at the interfaces to the thickness of the surface layers of the metal films. # 2003 Elsevier Science B.V. All rights reserved.