Liquid metal-based synthesis of high performance monolayer SnS piezoelectric nanogenerators

Hareem Khan,Aaron Elbourne,Md Ataur Rahman,Salvy P Russo,Bao Yue Zhang,Vaishnavi Krishnamurthi,Nasir Mahmood,Ali Zavabeti,Yongxiang Li,Jiong Yang,Guolin Zheng,Torben Daeneke,Lan Wang,Anil R Ravindran,Mohammad B Ghasemian,Sumeet Walia,Kourosh Kalantar-Zadeh,Paul Atkin

doi:10.1038/s41467-020-17296-0

Hareem Khan, Aaron Elbourne + Show 16 more

Open Access

https://doi.org/10.1038/s41467-020-17296-0

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Abstract

The predicted strong piezoelectricity for monolayers of group IV monochalcogenides, together with their inherent flexibility, makes them likely candidates for developing flexible nanogenerators. Within this group, SnS is a potential choice for such nanogenerators due to its favourable semiconducting properties. To date, access to large-area and highly crystalline monolayer SnS has been challenging due to the presence of strong inter-layer interactions by the lone-pair electrons of S. Here we report single crystal across-the-plane and large-area monolayer SnS synthesis using a liquid metal-based technique. The characterisations confirm the formation of atomically thin SnS with a remarkable carrier mobility of ~35 cm2 V−1 s−1 and piezoelectric coefficient of ~26 pm V−1. Piezoelectric nanogenerators fabricated using the SnS monolayers demonstrate a peak output voltage of ~150 mV at 0.7% strain. The stable and flexible monolayer SnS can be implemented into a variety of systems for efficient energy harvesting.

Highlights

The predicted strong piezoelectricity for monolayers of group IV monochalcogenides, together with their inherent flexibility, makes them likely candidates for developing flexible nanogenerators
Despite the predictions of large piezoelectricity and ability to achieve the high conversion efficiency for nanogenerators made from monolayers of group IV monochalcogenides, their synthesis has so far been mostly limited to small scale surface coverage due to significant challenges, with a trade-off between lateral size and thickness and limited sliding effect between layers[14,15,16]
To synthesise the monolayer of SnS, we exposed a molten droplet of Sn to an anoxic atmosphere containing a sulphur source (50 ppm H2S gas in N2 background) at 350 °C in a custom-made setup (Fig. 1a and Supplementary Fig. 1)

Summary

Introduction

The predicted strong piezoelectricity for monolayers of group IV monochalcogenides, together with their inherent flexibility, makes them likely candidates for developing flexible nanogenerators. Despite the predictions of large piezoelectricity and ability to achieve the high conversion efficiency for nanogenerators made from monolayers of group IV monochalcogenides, their synthesis has so far been mostly limited to small scale surface coverage due to significant challenges, with a trade-off between lateral size and thickness and limited sliding effect between layers[14,15,16]. To make the matter more challenging, the formation of high quality monolayers of group IV monochalcogenides, SnS, using conventional exfoliation, has been suggested to be limited due to the strong inter-layer interactions by the lone-pair electrons of S, which are much stronger than the van der Waals forces between the layers[17,20]. Utilisation of a direct surface reaction for the synthesis enables the production of stable superior quality monolayer tin compounds with no competing impure species in the immediate environment that is used for developing PENG of exceptional performance

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Conclusion