Copper(I) tert-butylthiolato clusters as single-source precursors for high-quality chalcocite thin films: Film growth and microstructure control

摘要

Soluble cluster compounds of polymeric ((CuSBu)-Bu-t)(infinity) (1), such as the trialkylphosphine adducts [((CuSBu)-Bu-t)(4)(PR3)(2)] (R = Me (2a), Et (2b)) or the mixed ligand cluster Cu-7((SBu)-Bu-t)(4)(hfa)(3)(PMe3)(3) (3, hfa = CH(COCF3)(2)), can be used as single-source precursors for chalcocite (alpha-Cu2S) film growth. Toluene or tetrahydrofuran solutions of 2a, 2b, or 3 afford high-quality chalcocite thin films on glass by aerosol-assisted chemical vapor deposition (AACVD). The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, optical spectroscopy, and Hall effect electrical measurements. Surface morphologies were analyzed by scanning electron microscopy and atomic force microscopy. Phase-pure Cu2S films grown with 2a/b consist of large micrometer-scale plates, which lie flat on the substrate surface, resulting in an extraordinarily strong < 00l > preferential orientation with respect to the hexagonal high-chalcocite substructure. The film morphologies as grown with precursor 3 suggest competing diketonate versus thiolate coordination at the {100} growth sites offering ligand-assisted film microstructural growth control.