Solid solutions of M2−2xIn2xS3 (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. M_2−2xIn_2xS₃ (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 M_2−2xIn_2xS₃ 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 M_2−2xIn_2xS₃ (0 ≤ x ≤ 1) samples varies significantly with the changes in the indium mole fraction in the precursor mixture. Elemental mapping of the mixed samples M_2−2xIn_2xS₃ (0 ≤ x ≤ 1) shows uniform elemental distributions of M, In and S in every sample investigated. The estimated band gap energies of Bi_2−2xIn_2xS₃ films varies from 1.66 to 2.39 eV, while the band gap energies of Sb_2−2xIn_2xS₃ 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.