Real-Time Spectro-Ellipsometry Study of the Growth of Thin Film Diamond and Hydrogenated Amorphous Carbon.
Real time spectroscopic ellipsometry (RTSE) has been developed to study the nucleation and growth of vacuum deposited thin films for the first time--specifically, chemical vapor deposition (CVD) diamond and ion beam-deposited hydrogenated amorphous carbon (a-C:H) thin films. A rotating polarizer ellipsometer with an optical multichannel analyzer (OMA) detection system is coupled with a deposition chamber to obtain spectra from 1.5 eV to 4.5 eV during thin film growth typically at a time resolution of 3.2 s and a repetition period of 15 s. Comprehensive optical characterization of the a-C:H thin films by direct ion beam deposition technique has been carried out. The bulk dielectric function of a-C:H and an approximate dielectric function for the interface layer has been deduced. As a result, the optical gap of a-C:H has been determined, representing the first such determination from real-time data. Finally, the time evolution of the bulk and interface layer thicknesses have also been obtained. Quantitative information of optical quality diamond thin films has been deduced from high accuracy ex situ spectroscopic ellipsometry (SE) measurements. The optical functions of CVD diamond film and its sp^2 C bonding defects are determined. RTSE was also applied to monitor surface modification of optical quality diamond films during exposure to low energy Ar and H ion beams, and atomic H. Monolayer sensitivity to optically absorbing sp^2 C bonding at the diamond surface is attained even in the presence of surface roughness. The feasibility of ion beam surface densification and smoothing is also demonstrated. Finally, RTSE is applied to study the processes occurring in the initial nucleation of thin film diamond by heated-filament assisted CVD. These studies reveal that an accurate measurement of the true temperature of the substrate-surface can be obtained from the energy position of critical points in the c-Si band structure. For the diamond nucleation and growth, the evolution of the diamond film mass thickness has been deduced from RTSE analysis. The results of final film mass thickness and film thickness from SE analysis are found to be in good agreement with those from scanning electron microscopy.
- Pub Date:
- Physics: Condensed Matter