Optical properties and structure of amorphous silicon films prepared by CVD

doi:10.1016/0165-1633(79)90053-4

Solar Energy Materials

Volume 1, Issues 1–2, February 1979, Pages 11-27

https://doi.org/10.1016/0165-1633(79)90053-4 Get rights and content

Abstract

Silicon films were deposited by pyrolytic decomposition of silane on substrates held at various temperatures, $T_{s}$ , in the range 550 to 800°C. The absorption coefficient, refractive index, anf X-ray diffraction pattern of these films were determined. The films deposited at temperatures, $T_{s} ≤660°C$ are amorphous, and their absorption profile resembles that reported in the literature for sputtered or evaporated amorphous films after long-time anneal. Films deposited on substrates at or above 670°C are partially crystallized, with particle size increasing gradually with substrate temperature. When the amorphous films are annealed, the resulting changes depend on length and temperature of the anneal. After a temperature-dependent induction period, the samples crystallize rapidly. The volume shrinks by ≈3% as determined from the decrease in film thickness. The onset of crystallization is indicated first by a red shift of the absorption edge, which after further anneal is overcompensated by a blue shift. The results demonstrate that the superior solar absorptance of amorphous silicon can be utilized in photothermal solar energy converters of sufficient stability without sacrificing the advantages of CVD fabrication.

References (53)

F. Schwidefsky
Thin Solid Films
(1973)
T.I. Kamins et al.
Thin Solid Films
(1973)
L.H. Hall et al.
Thin Solid Films
(1973)
N.A. Blum et al.
J. Non-Cryst. Solids
(1972)
A.J. Mountvala et al.
Vacuum
(1965)
D. Turnbull et al.
J. Non-Cryst. Solids
(1972)
D.E. Polk
J. Non-Cryst. Solids
(1971)
B.O. Seraphin
Thin Solid Films
(1976)
M.H. Brodsky et al.
J. Non-Cryst. Solids
(1972)
M. Paesler

H. Fritzsche

R.F. Adamsky et al.

J. Vac. Sci. Technol.

(1969)

J.D. Finegan et al.

M.L. Theye

Structural Effects in the Optical Properties of Tetrahedrally Bonded Amorphous Semiconductors

T.I. Kamins

IEEE Trans. PHP

(1974)

A. Emmanuel et al.

J. Electrochem. Soc.

(1973)

R.M. Anderson

J. Electrochem. Soc.

(1973)

C. Kühl et al.

J. Electrochem. Soc.

(1974)

N. Nagasima et al.

Jpn. J. Appl. Phys.

(1975)

N. Nagasima et al.

J. Vac. Sci. Technol.

(1977)

J.Y.W. Seto

J. Electrochem. Soc.

(1975)

M.E. Cowher et al.

J. Electrochem. Soc.

(1972)

M. Hirose et al.

M.H. Brodsky

J. Vac. Sci. Technol.

(1971)

M.H. Brodsky et al.

Phys Rev. B

(1970)

S.C. Moss et al.

Phys. Rev. Lett.

(1969)

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^☆: Work supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract ER-78-S-02-4899.

^∗∗: Present address: Kulicke & Soffa Industries, Inc., 507 Prudential Road, Horsham, PA 19044, USA.

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Optical properties and structure of amorphous silicon films prepared by CVD☆

Abstract

Thin Solid Films

Thin Solid Films

Thin Solid Films

J. Non-Cryst. Solids

Vacuum

J. Non-Cryst. Solids

J. Non-Cryst. Solids

Thin Solid Films

J. Non-Cryst. Solids

J. Vac. Sci. Technol.

Structural Effects in the Optical Properties of Tetrahedrally Bonded Amorphous Semiconductors

IEEE Trans. PHP

J. Electrochem. Soc.

J. Electrochem. Soc.

J. Electrochem. Soc.

Jpn. J. Appl. Phys.

J. Vac. Sci. Technol.

J. Electrochem. Soc.

J. Electrochem. Soc.

J. Vac. Sci. Technol.

Phys Rev. B

Phys. Rev. Lett.