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Title: Analysis of dielectric constants to determine sp³/sp² ratio and effect of substrate bias on spectroscopic ellipsometric studies of tetrahedral amorphous carbon films grown using an S bend filtered cathodic vacuum arc process
Authors: Panwar, O S
Khan, Mohd Alim
Basu, A
Kumar, Satyendra
Kumar, Sushil
Keywords: Spectroscopic ellipsometry;Optical constants;FCVA, sp³/sp²;ta-C;Substrate bias
Issue Date: Feb-2009
Publisher: CSIR
Abstract: The carbon bonding ratio and optical properties have been studied by spectroscopic ellipsometry of as grown tetrahedral amorphous carbon (ta-C) films, deposited using an S bend filtered cathodic vacuum arc (FCVA) process. First, the carbon bonding ratio in ta-C films has been estimated from imaginary part of dielectric constant (Ɛ₂) spectra obtained by spectroscopy ellipsometry. A method has been developed to find out the fractions of sp³ and sp² bonded carbon atoms from the Wemple-Didomenico plot. Second, the effect of varying negative substrate bias on the optical properties and sp³/sp² ratio of as-grown ta-C films has been made. The values of the optical constants evaluated are found to increase with the increase of the negative substrate bias in the as-grown ta-C films but the values of sp³/sp² ratio and the optical band gap (Eg) evaluated increase up to -200 V substrate bias and beyond -200 V substrate bias the values of sp³/sp² ratio and Eg decrease. Application of substrate bias is, thus, found to increase the sp³ bonding and Eg up to -200V substrate bias and beyond -200V substrate bias there is reversal of the trend.
Page(s): 141-148
ISSN: 0019-5596
Appears in Collections:IJPAP Vol.47(02) [February 2009]

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