Physicists from the University of Bath in the United Kingdom has uncovered a new way of rearranging 2D materials into 3D shapes, altering energy landscapes and paving the way for the development of new materials.
The idea of a multiverse existing in other dimensions parallel to ours has always been a curious conjecture to physicians. And they aren’t alone. Science fiction novels, movies and the like have also entertained this concept by depicting parallel universes and cross-dimensional adventure and romance. One such work is Edwin Abbott’s 1884 novel, Flatland: A Romance in Many Dimensions, which tells of a 2D world and its geometric inhabitants.
The reality of 2D worlds, however, may not be so fantastical. Its physics would more closely bear semblance to modern 2D materials like graphene or transition metal dichalcogenides such as tungsten disulphide (WS2), tungsten diselenide (WSe2), molybdenum disulphide (MoS2) and molybdenum diselenide (MoSe2)). Modern 2D materials are made up of single-atom layers on which electrons can move in 2 dimensions, but not 3. This restriction causes these materials to gain amplified optical and electronic properties which may serve as invaluable features necessary to develop futuristic ultrathin devices for usage in fields like energy, communication, imaging and quantum computing.
As their name suggests, 2D materials are visualised as extremely thin, flat-lying layers, which proves to be as advantageous as they are detrimental. One particular shortcoming is highlighted upon illumination. Being incredibly narrow, light is only able to interact with the material over a very small width, hence restricting its practicality.
In mission to resolve this obstacle, researchers have begun experimenting the different ways in which 2D materials can be folded into complex 3D shapes to improve its issue on thickness. In Sci-fi terms, this scenario is akin to reconstructing our “universe” in such a way that parallel worlds, supposedly never to cross paths, meet.
One group of physicists at the University of Bath in the UK has discovered a way to rearrange 2D sheets of tungsten disulphide (WS2) into a 3D configuration, while also significantly modifying their energy landscape. The 3D version of WS2, also known as “nanomesh”, is a webwork of densely-packed, randomly dispersed stacks which constitute of twisted and/or merged sheets of WS2.
Professor Ventsislav Valev, who spearheaded the research, explained that their altered version of WS2 sheets have finite dimensions and irregular edges, with some oxygen atoms having been replaced by sulphur. But more importantly, because these sheets converge, merge, and twist on top of each other, the energy landscape of the materials is altered. In geometrical terms, energy landscape refers to energy as a function of the configuration space of the system. It allows the illustration of different possible states of a system. For the inhabitants of the micro-universe of WS2, it would not be an understatement to say that converting 2D WS2 into 3D means to quite literally bend the laws of the universe.
Their study has also demonstrated a promising outlook on materials research as it was evident that making rearrangements to these 2D materials can give rise to new, versatile materials that are easily fine-tuned for various applications.
Dr Adelina Ilie, who constructed the new material together with her former PhD student and post-doc Zichen Liu, explained, "The modified energy landscape is a key point for our study. It is proof that assembling 2D materials into a 3D arrangement does not just result in 'thicker' 2D materials - it produces entirely new materials. Our nanomesh is technologically simple to produce, and it offers tunable material properties to meet the demands of future applications."
The nanomesh was proved to possess powerful nonlinear optical properties, capable of efficiently transforming one colour of laser into another over a wide range of colours. Evidently, this recent discovery has unlocked new doors in materials development, and an exciting quest for more breakthroughs has only just begun. Professor Valev provided an outline of their next goal, which is to use their novel findings on Si waveguides to advance the rapidly-emerging field of quantum optical communications.
PhD student Alexander Murphy, also part of the research, added, "In order to reveal the modified energy landscape, we devised new characterisation methods and I look forward to applying these to other materials. Who knows what else we could discover?”