Reflectance measurements on clean surfaces for the determination of optical constants of silicon in the extreme ultraviolet-soft-x-ray region
- Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, California 94720 (United States)
The refractive index n=1{minus}{delta}+i{beta} of Si in the energy range 50{endash}180 eV is investigated with angle-dependent reflectance measurements. The optical constants {delta} and {beta} are both determined by fitting to the Fresnel equations. The results of this method are compared with the values in the atomic tables derived from experimental data for {beta} and implementation of the Kramers-Kronig relations for {delta}. The samples were prepared by UV irradiation and HF:ethanol dipping to H passivate the surface. It is found that the values of {delta} in the atomic tables are 8{endash}15{percent} too high in the region 50{endash}90 eV. This is attributed to missing oscillator strength in the tabulated absorption coefficient for Si. The measured values of {beta} for crystalline Si exhibit structure below the L{sub 2,3} edge (99.8 eV), as was previously observed in transmission measurements of Si(111). It is also found that the method of least-squares fitting reflectance data to obtain optical constants is most effective for energies well below the edge, where {delta}{gt}{beta}, while for a range of energies around and above the edge, where {delta}{lt}{beta}, the optical constants are determined with large uncertainties. This behavior is not unique to the Si L{sub 2,3} edge. {copyright} 1997 Optical Society of America
- Research Organization:
- Lawrence Berkeley National Laboratory
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 543738
- Journal Information:
- Applied Optics, Journal Name: Applied Optics Journal Issue: 22 Vol. 36; ISSN 0003-6935; ISSN APOPAI
- Country of Publication:
- United States
- Language:
- English
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