Tin(iv) chalcogenoether complexes as single source precursors for the chemical vapour deposition of SnE2 and SnE (E = S, Se) thin films

Abstract

The molecular Sn(IV) complexes, [SnCl₄{ⁿBuS(CH₂)₃SⁿBu}] (2), [SnCl₄(ⁿBu₂S)₂] (3) and [SnCl₄(ⁿBu₂Se)₂] (4) have been prepared in good yield from reaction of SnCl₄ with the appropriate chalcogenoether ligand in anhydrous hexane and, together with the known [SnCl₄{ⁿBuSe(CH₂)₃SeⁿBu}] (1), employed as single source precursors for the low pressure chemical vapour deposition of the corresponding tin dichalcogenide thin films. At elevated temperatures the bidentate ligand precursors, (1) and (2), also form the tin monochalcogenides, SnSe and SnS, respectively. In contrast, (3) gave a mixture of phases, SnS₂, Sn₂S₃ and SnS and (4) gave SnSe₂ only. The morphologies, elemental compositions and crystal structures of the resulting films have been determined by scanning electron microscopy, energy dispersive X-ray spectroscopy, grazing incidence X-ray diffraction and Raman spectroscopy. Van der Pauw measurements on the SnS₂, SnS and SnSe₂ films confirm their resistivities to be 2.9(9), 266(3) and 4.4(3) Ω cm, respectively.