J Supercond Nov Magn DOI 10.1007/s10948-014-2875-7 ORIGINAL PAPER Properties of Extremely Narrow Gaps Between Electrodes of a Molecular Transistor S. A. Dagesyan · A. S. Stepanov · E. S. Soldatov · O. V. Snigirev Received: 11 June 2014 / Accepted: 24 October 2014 © Springer Science+Business Media New York 2014 Abstract An electron transport through the extremely small gaps (1–5 nm wide) formed in narrow and thin gold nanowires by the electromigration method is studied in this work at various temperatures. A careful investigation of the final stage of a gap formation has shown a quantum char- acter of a nanowire conductivity on this stage. Analysis of the electron transport characteristics through the resulting gaps was carried out. It shows that regimes of both a direct tunneling between electrodes and a “cold” emission into a barrier region were realized. Significant reduction of elec- tron work function for gold electrodes of prepared gaps is revealed. Keywords Molecular electronics · Electromigration · Single electronics 1 Introduction Despite of the undoubted success of the modern nanotech- nological industry, its possibilities (nowadays the minimal element size is about 14 nm [1]) is still not enough to resolve the fundamental challenge to create the basic electronic ele- ments based on single molecules and even atoms [2, 3]. At the same time a number of experimental techniques S. A. Dagesyan · E. S. Soldatov · O. V. Snigirev () Faculty of Physics, Lomonosov Moscow State University, 119991 Moscow, Russia e-mail: oleg.snigirev@phys.msu.ru S. A. Dagesyan e-mail: dagesyan@physics.msu.ru A. S. Stepanov D.V. Skobeltsyn Institute of Nuclear Physics of Moscow State University, 119991 Moscow, Russia providing a creation of even smaller structures were devel- oped during the last two decades [4]. It provided the real possibilities to create the molecular scale electronic ele- ments [5] and to experimentally study an electron transport through the single molecules [6, 7]. It should be taken into account that in such elements not only a molecule is a quantum object, but also a nanogap between electrodes is a quantum object due to extremely small size. That is why the own properties of such extremely small nanogaps must be carefully investigated. It is necessary both for a proper molecule selection for a future device and for correct interpretation of experimental data. One of the most conve- nient laboratory methods of nanometer scale gaps creation is the electromigration method [8]. In this work we stud- ied the characteristics of the electron transport through the extremely small (1–5 nm) nanogaps obtained by breaking of gold nanowires using the electromigration method. 2 Sample Preparation Our technology of a sample preparation consists of the following main stages: Thin and narrow gold nanowires were formed using electron-beam lithography on the insu- lated substrate. Then a system of micrometer-sized wires was formed using photolithography to provide a connec- tion of the created nanostructures to measuring instruments. Then the nanowires were broken by the algorithm we have developed based on the electromigration effect. A3 × 3-mm chip made of standard silicon wafer was the substrate for the samples. Silicon was insulated by a 400- nm SiO 2 film. Then the chip was spin coated by PMMA for electron-beam lithography. After resist exposure and devel- opment, a 14-nm gold film with a thin Al 2 O 3 buffer layer was thermally evaporated on the substrate. An aluminium