In the work, Professor Kaustav Banerjee and his team used a focused electron beam to fabricate a large-scale quantum dot superlattice on which each quantum dot has a specific pre-determined size and precise location on a sheet molybdenum disulphide (MoS2). When the focused electron beam interacts with the MoS2 monolayer, that area changes from semiconducting to metallic. According to the team, the quantum dots can be placed less than 4nm apart, becoming a 2D material in which the band gap can be specified to order in the range from 1.8 to 1.4eV.
The process not only creates several quantum dots, but can also be applied directly to large-scale fabrication of 2D quantum dot superlattices. “We can, therefore, change the overall properties of the 2D crystal,” Prof Banerjee said. “Using this technique, we can engineer the band gap to match the application.”
The quantum dot is theoretically an artificial atom. The developed technique makes design and tuning possible by enabling top-down control of the size and the position of the artificial atoms at large scale.
“When you change the dose of the electron beam, you can change the size of the quantum dot in the local region and, once you do that, you can control the band gap of the 2D material,” Prof Banerjee continued. “If you say you want a band gap of 1.6eV, I can give it to you. If you want 1.5eV, I can do that too, starting with the same material.”
