Abstract
The model of Forouhi and Bloomer (FB) for the optical properties of amorphous semiconductors is modified in order to describe more accurately the dispersion of the optical constants observed for amorphous carbon (a-C) and amorphous hydrogenated carbon (a-C:H) thin films. The FB model represents the optical absorption as the product of a lineshape function and a joint density of states function, which is derived by assuming the condition and valence bands to be parabolic and separated by an energy gap within which there are no allowed electronic states. Two modifications to this model are discussed to address the cases of non-parabolic bands and/or electron energy levels in the energy gap. These modified parametric models are then fit to a large number of a-C and a-C:H film optical constant spectra, and results are presented which indicate that non-parabolicity of the conduction and valence bands is the most important correction to the standard FB model required to describe a-C:H thin films. The modified model incorporating non-parabolic bands is shown to fit a broad range of both a-C and a-C:H spectra very well, and provides useful information about the optical absorption process and physical properties of the films.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 57-61 |
| Number of pages | 5 |
| Journal | Thin Solid Films |
| Volume | 253 |
| Issue number | 1-2 |
| DOIs | |
| State | Published - Dec 15 1994 |
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Keywords
- Carbon
- Ellipsometry
- Hydrocarbons
- Optical properties
ASJC Scopus subject areas
- Surfaces, Coatings and Films
- Condensed Matter Physics
- Surfaces and Interfaces
Cite this
Modified Forouhi and Bloomer dispersion model for the optical constants of amorphous hydrogenated carbon thin films. / McGahan, William A.; Makovicka, Tim; Hale, Jeffrey; Woollam, John A.
In: Thin Solid Films, Vol. 253, No. 1-2, 15.12.1994, p. 57-61.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Modified Forouhi and Bloomer dispersion model for the optical constants of amorphous hydrogenated carbon thin films
AU - McGahan, William A.
AU - Makovicka, Tim
AU - Hale, Jeffrey
AU - Woollam, John A
PY - 1994/12/15
Y1 - 1994/12/15
N2 - The model of Forouhi and Bloomer (FB) for the optical properties of amorphous semiconductors is modified in order to describe more accurately the dispersion of the optical constants observed for amorphous carbon (a-C) and amorphous hydrogenated carbon (a-C:H) thin films. The FB model represents the optical absorption as the product of a lineshape function and a joint density of states function, which is derived by assuming the condition and valence bands to be parabolic and separated by an energy gap within which there are no allowed electronic states. Two modifications to this model are discussed to address the cases of non-parabolic bands and/or electron energy levels in the energy gap. These modified parametric models are then fit to a large number of a-C and a-C:H film optical constant spectra, and results are presented which indicate that non-parabolicity of the conduction and valence bands is the most important correction to the standard FB model required to describe a-C:H thin films. The modified model incorporating non-parabolic bands is shown to fit a broad range of both a-C and a-C:H spectra very well, and provides useful information about the optical absorption process and physical properties of the films.
AB - The model of Forouhi and Bloomer (FB) for the optical properties of amorphous semiconductors is modified in order to describe more accurately the dispersion of the optical constants observed for amorphous carbon (a-C) and amorphous hydrogenated carbon (a-C:H) thin films. The FB model represents the optical absorption as the product of a lineshape function and a joint density of states function, which is derived by assuming the condition and valence bands to be parabolic and separated by an energy gap within which there are no allowed electronic states. Two modifications to this model are discussed to address the cases of non-parabolic bands and/or electron energy levels in the energy gap. These modified parametric models are then fit to a large number of a-C and a-C:H film optical constant spectra, and results are presented which indicate that non-parabolicity of the conduction and valence bands is the most important correction to the standard FB model required to describe a-C:H thin films. The modified model incorporating non-parabolic bands is shown to fit a broad range of both a-C and a-C:H spectra very well, and provides useful information about the optical absorption process and physical properties of the films.
KW - Carbon
KW - Ellipsometry
KW - Hydrocarbons
KW - Optical properties
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UR - http://www.scopus.com/inward/citedby.url?scp=0028757676&partnerID=8YFLogxK
U2 - 10.1016/0040-6090(94)90294-1
DO - 10.1016/0040-6090(94)90294-1
M3 - Article
VL - 253
SP - 57
EP - 61
JO - Thin Solid Films
JF - Thin Solid Films
SN - 0040-6090
IS - 1-2
ER -