Spectroscopic ellipsometry studies of nanocrystalline carbon thin films deposited by HFCVD

Citation
S. Gupta et al., Spectroscopic ellipsometry studies of nanocrystalline carbon thin films deposited by HFCVD, DIAM RELAT, 10(11), 2001, pp. 1968-1972
Citations number
19
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science","Material Science & Engineering
Journal title
DIAMOND AND RELATED MATERIALS
ISSN journal
09259635 → ACNP
Volume
10
Issue
11
Year of publication
2001
Pages
1968 - 1972
Database
ISI
SICI code
0925-9635(200111)10:11<1968:SESONC>2.0.ZU;2-M
Abstract
Nanocrystalline carbon thin films were grown by hot-filament chemical vapor deposition (HFCVD) using a relatively high concentration of methane in hyd rogen. The films were deposited on molybdenum substrates at 900 degreesC, a nd under various substrate-biasing conditions. The optical properties were examined ex situ using spectroscopic phase-modulated ellipsometry (SPME) fr om the near IR to the near UV region (1.5-5.0 eV). The ellipsometry data [p si(lambda (i)), Delta(lambda (i))] were modeled using Bruggeman effective-m edium approximation (EMA) and the dispersion relation for the amorphous sem iconductor (Forouhi and Bloomer Model Phys. Rev. B 34, 7018, 1986). We perf ormed these simulations by least-square regression analysis (LRA) and obtai ned the true dielectric function of our nanocrystalline carbon material and the energy band-gap (E-g), along with the film thickness, bulk void fracti on and roughness layer. We discuss the possible physical meaning of the fiv e parameters in the amorphous dispersion model applied to the case of nanoc rystalline carbon. Micro-Raman spectroscopy and profilometry were used to g uide and validate the simulations. (C) 2001 Elsevier Science B.V. All right s reserved.