Abstract
Extraordinary low-temperature vapor-phase synthesis of SnS thin films from single molecular precursors is attractive over conventional high-temperature solid-state methods. Molecular-level processing of functional materials is accompanied by several intrinsic advantages such as precise control over stoichiometry, phase selective synthesis, and uniform substrate coverage. We report here on the synthesis of a new heteroleptic molecular precursor containing (i) a thiolate ligand forming a direct Sn-S bond, and (ii) a chelating O^N^N-donor ligand introducing a “launch vehicle”-effect into the synthesized compound, thus remarkably increasing its volatility. The newly synthesized tin compound [Sn(SBut)(tfb-dmeda)] 1 was characterized by single-crystal X-ray diffraction analysis that verified the desired Sn:S ratio in the molecule, which was demonstrated in the direct conversion of the molecular complex into SnS thin films. The multi-nuclei (1H, 13C, 19F, and 119Sn) and variable-temperature 1D and 2D NMR studies indicate retention of the overall solid-state structure of 1 in the solution and suggest the presence of a dynamic conformational equilibrium. The fragmentation behavior of 1 was analyzed by mass spectrometry and compared with those of homoleptic tin tertiary butyl thiolates [Sn(SBut)2] and [Sn(SBut)4]. The precursor 1 was then used to deposit SnS thin films on different substrates (FTO, Mo-coated soda-lime glass) by CVD and film growth rates at different temperatures (300–450 °C) and times (15–60 min), film thickness, crystalline quality, and surface morphology were investigated.
Highlights
The monochalcogenide material SnS, which is isostructural to black phosphorous [1], has recently gained much attention due to its unique semiconductor and optoelectronic properties, as well as its low toxicity and the earth-abundant character of tin and sulfur [2,3,4,5]
This temperature (Tp) for 1 was maintained between Tp = 90–130 °C and substrate temperatures chosen in this study were Ts = 300–450 °C that resulted in crystalline deposits of homogeneous SnS films
We report here a new heteroleptic precursor [Sn(SBut )(tfb-dmeda)] 1, which was characterized thorougly in the solution- and solid-phase by multi-nuclei NMR and single crystal
Summary
The monochalcogenide material SnS, which is isostructural to black phosphorous [1], has recently gained much attention due to its unique semiconductor and optoelectronic properties, as well as its low toxicity and the earth-abundant character of tin and sulfur [2,3,4,5]. The MSP approach requires at least two components possessing different properties like vapor pressure and stability in the gas phase and often uses hazardous co-reagent like H2 S. Some of these drawbacks can be overcome by the single-source precursor (SSP) approach, which enables a predefined stoichiometry and phase control already at the molecular level. [SnBun 3 (SBun )] were employed in low pressure (LP)-MOCVD for the deposition of phase pure SnS in the temperature range between 375 and 530 ◦ C [24]. N or O in the final products) makes it an ideal “launch vehicle” to deliver Sn and S atoms on the substrate surface during the CVD process
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