Quantum dot solids, a term for crystals fabricated from crystals may be the next thing after silicon wafers to bring about major changes in the field of electronics. Just as wafers constructed from single silicon crystals changed the tools of communication technology about half a century ago, a team of scientists in Cornell University working on quantum dot solids expects to transform this field further.

Larger structures from nanocrystals

The scientists grew larger crystals from nanocrystals of lead selenium. They then shaped square 2D superlattice structures by the process of fusion, taking care to maintain the atomic coherence. The atomic coherent lattice ensures that the atoms are directly connected to each other. There is no other intervening substance. As a result, these superstructures have superior electrical properties compared to those of existing nanocrystals of semiconductors. The researchers anticipate that this would aid absorption of energy and emission of light.

Tobias Hanrath, associate professor in Robert Frederick Smith School of Engineering, along with graduate student Kevin Whitham has led the study. The research findings have been published in Nature Materials.

Hanrath stresses upon the fact that the building blocks making up the superstructure have been designed with a degree of accuracy that matches with atomic scale precision. He goes on to say it would be reasonable to assume that the structures are as perfect as possible.

The current work is based on an earlier research done by the group, details of which have been brought out in a paper in Nano Letters in 2013. The study had dealt with new technique for bonding quantum dots. This involved monitored displacement or shift of ligands, which are connector molecules.

Tweaking the structure

Electronic coupling of each quantum dot or connecting the dots, as the paper has termed the process was considered a significant challenge. The new research appears to have resolved this problem. Compared to the previous structure consisting of nanocrystal solids linked with ligands, the new superstructure is vastly superior as it allows an ample scope for modifications. The nanocrystals undergo extremely strong coupling, which brings about energy band formation. Scientists can manipulate the bands according to the structure of the crystals. The researchers say that this maneuvering could lead to the development of new artificial materials with adaptable electronic structure and properties.

From lab to industry

Whitham does concede that a lot of work has to be done before starting production of these crystals on an industrial scale. The superlattice conceived by the group has several sources of flaws. This is principally because the nanocrystals making up the lattice are not exactly identical. The defects reduce the possibilities to which the electronic structure can be controlled. He points out furthermore, that the understanding of the structures formed by connecting the quantum dots is not yet complete and that this knowledge is essential for improving the results.

Whitham says that he expects that other scientists will further the work done by his team and improve upon the superlattice structure by removing the existing flaws. He is confident that additional research on the subject could lead to game changing techniques in the field of communication technology.