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Advisor(s)
Abstract(s)
We report the results of the growth of Cu-Sn-S ternary
chalcogenide compounds by sulfurization of dc magnetron
sputtered metallic precursors. Tetragonal Cu2SnS3
forms for a maximum sulfurization temperature of 350 ºC.
Cubic Cu2SnS3 is obtained at sulfurization temperatures
above 400 ºC. These results are supported by XRD
analysis and Raman spectroscopy measurements. The latter
analysis shows peaks at 336 cm-1, 351 cm-1 for
tetragonal Cu2SnS3, and 303 cm-1, 355 cm-1 for cubic
Cu2SnS3. Optical analysis shows that this phase change
lowers the band gap from 1.35 eV to 0.98 eV. At higher
sulfurization temperatures increased loss of Sn is expected
in the sulphide form. As a consequence, higher Cu
content ternary compounds like Cu3SnS4 grow. In these
conditions, XRD and Raman analysis only detected orthorhombic
(Pmn21) phase (petrukite). This compound
has Raman peaks at 318 cm-1, 348 cm-1 and 295 cm-1. For
a sulfurization temperature of 450 ºC the samples present
a multi-phase structure mainly composed by cubic
Cu2SnS3 and orthorhombic (Pmn21) Cu3SnS4. For higher
temperatures, the samples are single phase and constituted
by orthorhombic (Pmn21) Cu3SnS4. Transmittance
and reflectance measurements were used to estimate a
band gap of 1.60 eV. For comparison we also include the
results for Cu2ZnSnS4 obtained using similar growth conditions.