Fabrication of single-phase SnS film by H2 annealing of amorphous SnSx prepared by atomic layer deposition

Abstract

This study evaluated a simple and novel route to fabricate single-phase SnS thin films, consisting of the growth of smooth amorphous SnS2 films by atomic layer deposition at very low temperature using tetrakis(dimethylamino)tin {TDMASn, [(CH3)2N]4Sn} and hydrogen sulfide followed by H2 annealing at controlled higher temperatures. The properties of the SnS films fabricated by subjecting the amorphous as-grown SnS2 films deposited at 100 °C to post-H2 annealing at 360 °C were superior to those of the as-grown SnS films deposited at 200 °C in terms of their phase purity, optical band gap, adhesion, and surface roughness. Raman spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, and atomic force microscopy consistently showed that single-phase, stoichiometric crystalline (orthorhombic structure) SnS films (Sn/S ratio: ∼1), without any incorporated sulfur-rich tin sulfides, could be fabricated with a very low surface roughness [root mean square (RMS) roughness: ∼7 nm] using the proposed scheme. On the other hand, the as-grown SnS film at 200 °C still contained a small amount of SnS2 phase and its RMS surface roughness was as high as 16 nm. The optical band gap of the as-grown SnS film was 1.85 eV, whereas that of the annealed SnS film was ∼1.2 eV, confirming the latter's improved phase purity. The SnS film fabricated by H2 annealing was a p-type semiconductor with a carrier concentration of ∼2.3 × 1016/cm3 and a hole mobility of ∼15 cm2/V s. The present scheme to prepare high-quality SnS films might be useful for fabricating photovoltaic or solar conversion devices.

Enhanced activity of highly conformal and layered tin sulfide (SnSx) prepared by atomic layer deposition (ALD) on 3D metal scaffold towards high performance supercapacitor electrode

“…The interlayer spacing (d-spacing) of SnS grown at 180 and 160 °C corresponding to the strongest XRD peak at 2θ = 31.8 and 15.7°, is found to be 0.28 and 0.59 nm respectively. Previous studies 35 have also demonstrated that SnS film is predominantly formed above 180 °C, whereas the single phase of SnS 2 film is formed at a slightly lower deposition temperature of 160 °C. These findings suggest that the formation of SnS is more favourable at high temperatures, as compared to relatively low temperatures.…”

“…The first Raman peak at 56 ± 2 cm −1 [B 2g (LO)-A g (TO)] and last peak at approximately 313.4 cm −1 [A g (TO) + A g (LO2)], can be assigned to the second order multiple phonons scattering process. In addition, the observed Raman active peak at 56 ± 2 cm −1 belongs to the vibrational mode of SnS phase, whereas the specific Raman peak at 313.4 cm −1 (only can be seen in the SnS x -160 sample) is associated with optical phonon mode of 2H-SnS 2 poly-type with a hexagonal symmetry, and is related to Sn-S bonding in the a-c plane 18,35 . Moreover, the Raman spectra obtained from SnS x @NF (Fig.…”

“…High purity argon (Ar) gas (99.999%) was supplied at a flow rate of 100 sccm as a carrier gas, which facilitated the appropriate transfer of the precursor to the chamber. The following experimental protocol was applied for the SnS x films deposition to guarantee the self-limiting film growth from the previous study 35 : 1 s pulsing of the TDMASn precursor, 10 s of Ar purging, 1 s pulsing of the H 2 S reactant gas, and 10 s of Ar gas purging. One ALD cycle consisted of four steps and by repeating ALD cycles, the film with a desirable thickness could be prepared precisely.…”

“…Therefore, these studies truly suggest the potential of this method in developing the thin films of metal sulfides for direct fabrication of supercapacitor electrodes without any additional treatment. In this study, we prepared SnS or SnS 2 predominant SnS x films by controlling the deposition temperature 35,39,40 in order to comparatively investigate their supercapacitor’s performances. For the first time, two kinds of ALD-SnS x films were directly grown on NF, and then the composites of ALD-SnS x @NF were tested as active electrodes without any additional treatment.…”

Atomic Layer Deposition of Two-Dimensional Layered Materials: Processes, Growth Mechanisms, and Characteristics

“…43 Another example is the production of 2D SnS, in which SnS 2 is deposited first via ALD and then reduced in H 2 into 2D SnS at high temperature. 44 This R3 route has also been used for h-BN, where a polymer was first deposited via ALD at low temperature and then converted into h-BN in NH 3 at high temperature. 45,46 This route has multiple benefits: (1) ease of generalization for more 2D materials;…”