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doi:10.1038/nindia.2017.63 Published online 5 June 2017

Stanene, graphene’s wonder cousin

Biplab Das

Researchers (clockwise from left): Raghavendra P. Chaudhary, Shobha Shukla & Sumit Saxena

Tin is set to become the next wonder material. Like graphene, the humble anti-corrosive metal can act as a conductor by forming a one-atom thick film called stanene. Theoretically, stanene could even allow electrons to flow without any resistance.

Using ultrafast laser material interactions1, an Indian research team, led by Sumit Saxena from the Indian Institute of Technology, Bombay, synthesized a few layers of free-standing stanene to explore its  potential.

“This study is the first ever reported synthesis of free-standing stanene,” says Shobha Shukla, one of the team. “It also experimentally proves that stanene has a low buckled armchair-shaped honeycomb structure.”

In 2013, physicists theoretically predicted the existence and potential of stanene and suggested it could function as a topological insulator through which electrons could not travel. Instead, electrons travel on the surface at very high speeds without colliding with other electrons and atoms as they do in most materials. This should allow stanene film to conduct electricity without dissipating energy as waste heat.

This property is potentially useful in fabricating electronic and photonic devices using stanene, according to Shukla and her colleagues.

But to make topological insulators from stanene, physicists need to synthesize and understand its structure and properties. The scientists made the free-standing stanene by shining ultrafast femto-second laser pulses on to a tin target in a liquid medium. This triggered a phase change, converting tetragonal structure of tin into hexagonal stanene.  

Using sophisticated imaging techniques, they found that the sheets of stanene had extremely narrow interlayer spacing with weak interlayer interactions like graphene. The stanene exhibited strong absorption in the ultraviolet region. During such absorption, it showed electron movement which is also observed in graphene2.

Physicists doing research on stanene hail the synthesis of free-standing stanene. “This study shows that free-standing stanene sheet can be synthesized with any support. This is a promising approach in terms of synthesis,” says Biswarup Pathak from the Indian Institute of Technology, Indore.

Such development in synthesizing stanene will certainly put India on the map for producing and utilizing stanene as a topological insulator, Pathak adds.   

Experimentally validating the two-dimensional structure of stanene is valuable work which backs the previous theoretical predictions on its structure and properties, says Chiranjib Majumder from the Bhabha Atomic Research Centre, Mumbai.


References

1. Saxena, S. et al. Stanene: atomically thick freestanding layer of 2D hexagonal tin. Sci. Rep. 6, 31073 (2016)

2. Chaudhary, R. P. et al. Optical properties of stanene. Nanotechnology. 27, 495701 (2016)