Formation of gold particles at a functional LB film/gold interface leading to Coulomb blockade phenomena

A few monolayer Langmuir-Blodgett (LB) films of a polymer that contains mercapto functions in the hydrophilic head group region were deposited on microstructured gold electrodes. Upon evaporation of a gold top contact, junctions without ohmic behaviour were obtained. In some cases the current-voltage (I–V) characteristics displayed a step-like behaviour that is interpreted as the Coulomb blockade effect. To determine the nature and origin of the charged islands, cross-sectional specimens with a top gold electrode were prepared for transmission electron microscopy (TEM) investigations. The TEM images revealed the formation of small gold particles with diameters ranging from 2 to 6 nm located close to the top contact. These particles together with the surrounding polymeric matrix are expected to constitute a double-barrier tunnel structure and to be responsible for the observed single-electron tunnelling phenomena.