Solid solutions of M2-2 xIn2 xS3 (M = Bi or Sb) by solventless thermolysis

Abstract

Tris(O-ethylxanthato)bismuth(iii) [Bi(S2COEt)3], tris(O-ethylxanthato)antimony(iii) [Sb(S2COEt)3] and tris(O-ethylxanthato)indium(iii) [In(S2COEt)3] were synthesized and employed for the preparation of Bi-In-S and Sb-In-S solid solutions by solventless thermolysis. M2-2xIn2xS3 (where M = Bi or Sb) alloys were obtained using a mixture of In(S2COEt)3 and M(S2COEt)3 molecular precursors, with different mole fractions of indium x (0 ≤ x ≤ 1) at 300 °C. The structural, compositional, optical and morphological properties of the synthesized M2-2xIn2xS3 samples were characterized using a range of techniques including powder X-ray diffraction (p-XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Raman spectroscopy and UV-Vis absorption spectroscopy. The p-XRD data suggest that the incorporation of mole fractions of indium up to x ≤ 0.4 into M2S3 does not alter the orthorhombic crystal structure of M2S3. Higher quantities of indium (x ≥ 0.6) change the crystal structure to cubic M2S3. The elemental compositions from EDX data are in line with the stoichiometric ratios expected. SEM images reveal that the morphology of the M2-2xIn2xS3 (0 ≤ x ≤ 1) samples varies significantly with the changes in the indium mole fraction in the precursor mixture. Elemental mapping of the mixed samples M2-2xIn2xS3 (0 ≤ x ≤ 1) shows uniform elemental distributions of M, In and S in every sample investigated. The estimated band gap energies of Bi2-2xIn2xS3 films varies from 1.66 to 2.39 eV, while the band gap energies of Sb2-2xIn2xS3 films are in the range of 2.19-2.9 eV, and in both cases the energy can be tuned by variation of the indium content.