Charge-state investigations of single adsorbates on ultrathin insulating films have revealed fundamental charging properties. For example, charge-state determination and control of adatoms (1) and molecules (2,3) on bilayer NaCl as well as the charge-distribution mapping within a molecule (4) was demonstrated. However, multilayered insulating films are necessary to efficiently confine charges at the surface – requiring better understanding of adsorbate charging and their quantification on thicker films.
Here, we exhibit the essential steps towards exploring stable charge states of single molecules. First, we demonstrate reversible charge-state manipulation, leading to a tip-induced lateral single-electron transfer between molecules (5). Second, we present a novel approach based on single-electron detection using an atomic force microscope that allows tunneling spectroscopy measurements of a single molecule on an insulator. This culminates in the characterization of a fundamental property of the molecule/surrounding system, the reorganization energy.
(1) J. Repp et al, Science 305, 493 (2004)
(2) T. Leoni et al, Physical Review Letters 106, 216103 (2011)
(3) I. Swart et al, Nano Letters 11, 1580 (2011)
(4) F. Mohn et al, Nature Nanotechnology 7, 227 (2012)
(5) W. Steurer et al, Nature Communications 6, 8353 (2015)