Growth and characterization of Bi12SiO20films by metalorganic chemical vapor deposition

The metalorganic chemical vapor deposition (MOCVD) technique was applied to the epitaxial growth of Bi
12
SiO
20
films. The growth was carried out in an atmospheric and low pressure reactor using Bi(CH
3
)
3
and Si (OCH
3
)
4
(or Si(OC
2
H
5
)
4
) as metal sources, and O
2
or N
2
O gas as an oxidizing gas. The single crystal films have been grown over a wide composition range of 5.5 < Bi
2
O
3
/SiO
2
< 8. The lattice constants of the films increase in proportion with Si deficiencies. Films with good compositional uniformity were obtained using the N
2
O gas as an oxidizing gas. For these epitaxial films, it was found that the photoconductivity was ten to fifteen times as large as that of bulk crystals and there was a strong relationship between the film composition and the photoconductivity spectral response.