Using a scanning tunneling microscope (STM), we assembled the dots atom-by-atom and relied on the atomically precise structure of an InAs(111)A surface to define a lattice of allowed atom positions. This approach enables an essentially error-free control of the quantum mechanical wave functions and the level structure in quantum dot assemblies or ‘quantum dot molecules’, an important requirement for technologies in which exact fidelity of quantum dot architectures is essential. In the example shown here, a quantum dot molecule with perfect three-fold rotational symmetry was created by assembling three indium adatom chains and the resulting orbital structure was revealed by scanning tunneling spectroscopy.
S. Fölsch, J. Martínez-Blanco, J. Yang, K. Kanisawa, S. C. Erwin, “Quantum dots with single-atom precision”, Nature Nanotechnology vol. 9 (2014), DOI: 10.1038/NNANO.2014.129