CuxSnSx+1 (x = 2, 3) thin films grown by sulfurization of metallic precursors deposited by dc magnetron sputtering

摘要

We report the results of the growth of Cu-Sn-S ternarychalcogenide compounds by sulfurization of dc magnetronsputtered metallic precursors. Tetragonal Cu2SnS3forms for a maximum sulfurization temperature of 350 ºC.Cubic Cu2SnS3 is obtained at sulfurization temperaturesabove 400 ºC. These results are supported by XRDanalysis and Raman spectroscopy measurements. The latteranalysis shows peaks at 336 cm-1, 351 cm-1 fortetragonal Cu2SnS3, and 303 cm-1, 355 cm-1 for cubicCu2SnS3. Optical analysis shows that this phase changelowers the band gap from 1.35 eV to 0.98 eV. At highersulfurization temperatures increased loss of Sn is expectedin the sulphide form. As a consequence, higher Cucontent ternary compounds like Cu3SnS4 grow. In theseconditions, XRD and Raman analysis only detected orthorhombic(Pmn21) phase (petrukite). This compoundhas Raman peaks at 318 cm-1, 348 cm-1 and 295 cm-1. Fora sulfurization temperature of 450 ºC the samples presenta multi-phase structure mainly composed by cubicCu2SnS3 and orthorhombic (Pmn21) Cu3SnS4. For highertemperatures, the samples are single phase and constitutedby orthorhombic (Pmn21) Cu3SnS4. Transmittanceand reflectance measurements were used to estimate aband gap of 1.60 eV. For comparison we also include theresults for Cu2ZnSnS4 obtained using similar growth conditions.