Effects of crystal shape on the energy levels of zero-dimensional PbS quantum dots

Nanometer-size PbS quantum dots have been made by electrodeposition on a Au(111) substrate. The deposited nanocrystals have a flattened cubic shape. We probed the single-electron energy-level spectrum of individual quantum dots by scanning tunneling spectroscopy and found that it deviates strongly from that of spherical PbS quantum dots. The measured energy-level spectrum is successfully explained by considering strong confinement in a flattened cubic box.