NBu2Sn(SnBu)2 and nBu3SnEnBu (E = S or Se) – effective single source precursors for the CVD of SnS and SnSe thermoelectric thin films. Issue 14 (28th June 2021)

• Record Type: Journal Article
• Authors: Robinson, Fred; Curran, Peter J.; de Groot, C. H. (Kees); Hardie, Duncan; Hector, Andrew L.; Holloway, Katherine; Huang, Ruomeng; Newbrook, Daniel; Reid, Gillian
• Is Part Of: Materials advances. Volume 2:Issue 14(2021)
• Page Start: 4814
• Page End: 4823
• Publication Date: 2021-06-28
• Subjects: 620.11
• DOI: 10.1039/d1ma00331c
• Languages: English
• ISSNs: 2633-5409

Abstract

Abstract : LPCVD with the title compounds produces S-deficient SnS, or stoichiometric, semiconducting, resistive SnS or SnSe films with large positive Seebeck coefficients and an SnSe power factor of 0.4 μW cm −1 K −2 at 425 K. Abstract : The use of single source precursors offers a convenient option for the chemical vapour deposition of thin film semiconductor materials with good stoichiometric control and precursor efficiency. Here we show that reaction of n Bu3 SnCl with NaS n Bu or LiSe n Bu, or n Bu2 SnCl2 with 2 mol equiv. of NaS n Bu, gives the molecular alkyltin chalcogenolate precursors, n Bu3 SnE n Bu (E = S (1 ), Se (3 )) and n Bu2 Sn(S n Bu)2 (2 ), respectively, in good yield as colourless (S) or yellow/orange (Se) oils. These were characterised by 1 H, 13 C{ 1 H}, 77 Se{ 1 H} and 119 Sn{ 1 H} NMR spectroscopy, microanalysis and thermogravimetric analysis. Low pressure CVD experiments using these precursors showed that (1 ) gave S-deficient SnS thin films, whereas using (2 ) and implementing short deposition times and low precursor loadings, gave stoichiometric SnS films. Stoichiometric SnSe films were also obtained using (3 ) and confirmed by grazing incidence XRD analysis, which revealed the films adopt the orthorhombic Pnma structure. SEM and EDX analysis, together with Raman spectroscopic data, were also used to identify the films deposited and to correlate with the deposition conditions employed. Variable temperature Seebeck and Hall effect characterisation confirm that the stoichiometric SnS and SnSe films are semiconducting and highly resistive, giving large positive Seebeck coefficients, with the overall power factor ranging from 0.017 at 300 K to 0.049 μW cm −1 K −2 at 450 K for SnS and increasing from 0.06 at 300 K to 0.4 μW cm −1 K −2 at 425 K for SnSe.