Me. Rincon et Pk. Nair, LOW-TEMPERATURE VAPOR-PHASE DEPOSITION OF BISMUTH SULFIDE FILMS, Semiconductor science and technology, 12(4), 1997, pp. 467-474
A nearly stoichiometric bismuth sulphide precipitate obtained as a by-
product of the chemical deposition technique is used as a source in lo
w-temperature vapour phase deposition of Bi2S3 thin films. At relative
ly low deposition temperatures (250 degrees C < T < 380 degrees C) hig
hly polycrystalline Bi2S3 films are formed on glass substrates, while
very thin films are obtained at lower temperatures (95-250 degrees C).
The highest photocurrent (I-ph similar to 10(-4) A) is found in the f
irst group while the highest photosensitivity (S = 56) is found in the
amorphous or too thin films. XRD patterns of bismuth sulphide powder
before and after 5 h deposition show its enrichment in Si due to the e
nrichment in S and sulphur-rich bismuth sulphide species (BiS2)(n) of
the vapour phase. For films deposited at temperatures in the range of
290-380 degrees C, the change in composition of the source causes diff
erent deposition rates and preferential growth of some of the bismuthi
nite planes (2 theta < 25 degrees for as-deposited powder and 2 theta
> 25 degrees for bismuth-rich sources), compositional changes in the f
ilms (stratification) does not seem to be relevant at these temperatur
es. The bandgap (E-g) of the films decreases as the deposition tempera
ture increases from E-g = 2 eV at T-dep = 95-205 degrees C to 1-1.3 eV
at T-dep = 290-380 degrees C. Similar results were obtained with diff
erent sources, which indicates the stronger dependence of E-g with res
pect to substrate temperature than with respect to the type of source.