Chemical vapour deposition of antimony chalcogenides with positional and orientational control: precursor design and substrate selectivity

Abstract

A series of alkylchalcogenostibines, Me₂SbSeⁿBu, MeSb(SeⁿBu)₂, Sb(SeⁿBu)₃ and MeSb(TeⁿBu)₂, have been designed and synthesised as potential precursors for chemical vapour deposition (CVD) by reaction of ⁿBuELi (E = Se, Te) with the appropriate halostibine, Me_3−nSbCl_n (n = 1, 2, 3), and characterised by ¹H, ¹³C{¹H} and ⁷⁷Se{¹H} or ¹²⁵Te{¹H} NMR spectroscopy as appropriate. MeSb(SeⁿBu)₂ and MeSb(TeⁿBu)₂ are very effective single source precursors for the low pressure CVD of high quality crystalline thin films of Sb₂Se₃ and Sb₂Te₃, respectively, confirmed by scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy and thin film X-ray diffraction. Hall conductivity, carrier mobility, carrier density and, in the case of Sb₂Te₃, Seebeck coefficient measurements reveal electronic characteristics comparable with Sb₂E₃ deposited by atomic layer deposition or molecular beam epitaxy, suggesting materials quality and performance suitable for incorporation into electronic device structures. Choice of substrate and deposition conditions were found to significantly affect the morphology and preferred orientation of Sb₂Te₃ crystallites, enabling deposition of films with either 〈1 1 0〉 or 〈0 0 1〉 alignment. Use of micro-patterned substrates allowed selective deposition of crystalline 2D micro-arrays of Sb₂Te₃ onto exposed TiN surfaces only.