Modern miracle materials

A solution to a modern affliction affecting almost all of us has been discovered by researchers at Queen's University Belfast, UK, working with colleagues at Stanford University, University of California, California State University in the USA and a team at the National Institute for Materials Science in Japan. They have discovered a new material that could finally put paid to cracked screens on our tablets and smart phones. [Santos et al., ACS Nano (2017); DOI: 10.1021/acsnano.7b00551]

The team has turned to the darling of 1990s materials science, buckminsterfullerene, the so-called "buckyball", [60]fullerene and combined it with today's miracle materials, graphene and hexagonal boron nitride (hBN) to make a tough and inexpensive composite, a van der Waals solid. Such materials do not exist in nature, as far as we know, but their unique stability and photo-electronic properties open up the potential to creating a new type of display device, solar panels and other components.

Team leader Elton Santos explains: "Our findings show that this new 'miracle material' has similar physical properties to silicon but it has improved chemical stability, lightness and flexibility, which could potentially be used in smart devices and would be much less likely to break." He adds that, "The material might also mean that devices use less energy than before because of the device architecture so could have improved battery life."

The researchers explain that charge transfer at the interface between different types of material is often at the heart of electronic and photovoltaic devices. They have investigated the molecular orientation, electronic structure, and local charge transfer at the interface region of [60]fullerene deposited on a graphene layer, either in the presence of or absence of a supporting substrate, such as hexagonal boron nitride. The team used ab initio density functional theory with van der Waals interactions and also characterized in the laboratory the interface between the materials using high-resolution transmission electron microscopy and electronic transport.

They found that charge transfer between [60]fullerene and graphene is sensitive to the nature of the underlying supporting substrate and to the crystallinity and local orientation of the [60]fullerene. Moreover, even at room temperature, the fullerene molecules interface with graphene and are essentially locked in their orientation. The fact that the hybrid material has shows high electron and hole mobility could be exploited in organic high-mobility field-effect devices.

One important issue yet to be addressed is that the architecture of the new hybrid material means it does not actually have an electronic band gap, despite its putatively useful structural properties. Endowing the material with a band gap will be essential to giving it on-off switching capacity and allow it to be used for a range of operations required by electronic devices. The team is currently investigating whether transition metal dichalcogenides (TMDs) might be the answer to this sticky problem.

"We are currently looking for other materials to replace graphene in order to create a new transistor using the same device architecture," Santos told Materials Today. For example, C60-new material-hBN wherein "new material" currently refers to different kinds of 2D materials, such as transition metal dichalcogenides, which have electronic band gaps that rival silicon for electronic and optoelectronic properties.

David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom" you can see his ever-growing gallery of birds on his Imaging Storm website here.