CUED Publications database

Analysis of amorphous carbon thin films by spectroscopic ellipsometry

Lee, J and Collins, RW and Veerasamy, VS and Robertson, J (1998) Analysis of amorphous carbon thin films by spectroscopic ellipsometry. Journal of Non-Crystalline Solids, 227-23. pp. 617-621. ISSN 0022-3093

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Using spectroscopic ellipsometry (SE), we have measured the optical properties of amorphous carbon (a-C) films ∼ 10-30 nm thick prepared using a filtered beam of C + ions from a cathodic arc. Such films exhibit a wide range of sp 3 -bonded carbon contents from 20 to 76 at.% as measured by electron energy loss spectroscopy (EELS), and a range of optical gaps from 0.65 eV (20 at.% sp 3 C) to 2.25 eV (76 at.% sp 3 C) as measured by SE. SE data from 1.5 to 5 eV have been analyzed by applying the most widely used effective medium theory (EMT) namely that of Bruggeman with isotropic screening, assuming a model of the material as a composite with sp 2 C and sp 3 C components. Although the atomic fractions of sp 3 C deduced by SE with the Bruggeman EMT correlate monotonically with those obtained by EELS, the SE results range from 10 to 25 at.% higher. The possible origins of this discrepancy are discussed within the framework of an optical composite. Improved agreement between SE and EELS is obtained by employing a simple form for the EMT, in which the effective dielectric function is determined as a volume-fraction-weighted average of the dielectric functions of the two components. © 1998 Elsevier Science B.V. All rights reserved.

Item Type: Article
Divisions: Div B > Solid State Electronics and Nanoscale Science
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:32
Last Modified: 08 Feb 2018 01:31