We have used a superconducting single-electron transistor as a DC-electrometer that is strongly coupled to the metal island of another transistor. With this set-up, it is possible to directly measure the charge distribution on this island. The strong capacitive coupling was achieved by a multilayer fabrication technique that allowed us to make the coupling capacitance bigger than the junction capacitances. Simulations of this system were done using orthodox theory of single-electron tunnelling and showed excellent agreement with the measurements.
@article{arxiv.cond-mat/0105263,
title = {Charge spectrometry with a strongly coupled superconducting single-electron transistor},
author = {C. P. Heij and P. Hadley and J. E. Mooij},
journal= {arXiv preprint arXiv:cond-mat/0105263},
year = {2009}
}