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

摘要

A series of alkylchalcogenostibines, (Me2SbSeBu)-Bu-n, MeSb((SeBu)-Bu-n)(2), Sb((SeBu)-Bu-n)(3) and MeSb((TeBu)-Bu-n)(2), have been designed and synthesised as potential precursors for chemical vapour deposition (CVD) by reaction of (BuELI)-Bu-n (E = Se, Te) with the appropriate halostibine, Me3-nSbCln (n = 1, 2, 3), and characterised by H-1, C-13{H-1} and Se-77{H-1} or Te-125{H-1} NMR spectroscopy as appropriate. MeSb((SeBu)-Bu-n)(2) and MeSb((TeBu)-Bu-n)(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.