ИСТИНА

The significant progress in miniaturization of electronic components most likely will lead to development the fabrication technologies in atomic scale range. Presumably at this scale the new physical phenomena will take place as a basis for the future nanoelectronic devices. The effect of single-electron tunneling is one of them. The principal device based on this effect is a single-electron transistor (SET) [1]. Last decade there were published a number of original papers devoted to an electron transport through a single atoms and molecules in different devices [2-5]. Although this new research topic is actively developing at the moment, there are still many interesting effects in this field. In this work we would like to demonstrate our several experimental techniques for the fabrication of SETs based on single molecules and atoms. The single gold nanoparticles (2–4 nm), functionalized by octanethiol, were used for formation of an island for molecular transistor. The device electrodes were fabricated using a standard e-beam lithography (Carl Zeiss FESEM Supra 40 with Raith ELPHY-Quantum attachment) combined with an electromigration technique [6]. Nanoparticles were placed into 50-70 nm gap between electrodes from the toluene solution using a self-assembling techniques. A Coulomb diamonds on the stability diagrams clearly demonstrate a single-electron character of electron transport. The maximum measured value of a Coulomb blockade offset for the molecular transistors was near 300 mV. The electrical properties of the devices were investigated in 77–300 K temperature range. Obtained results are very important for high temperature applications of single-electron devices. Single As or P dopants act as an island in the single-atom SET. It consist of: 1) a silicon solid bridge connecting lead electrodes with a localized impurity atom, which plays the role of active charge center; 2) source and drain macroscopic lead electrodes with a higher dopant concentration; 3) gate electrode or electrodes, which are located near the bridge. We developed a technique for controllable fabrication of such few atom systems. It includes electron-beam lithography, reactive ion etching, thin layer controllable doping techniques. At the first step a silicon nanowire with the cross section about 30x55 nm was formed using a non-uniform doped silicon on insulator. Then the size of nanowire was reduced by several short sequential processes of isotropic reactive ion etching. The electrical characteristics of the structures were analyzed after each etching step. We have observed the intermediate states of the structures when the effective tunneling path in the bridge has been formed by several atomic scale charge centers. Finally it was obtained the structure which has all features of a single-atom single-electron transistor. Electronic transport properties of the fabricated transistors were studied by measuring the charge stability diagram. Subsequent digital processing clearly indicates the presence of correlated tunneling of charge carriers and the discreteness of the energy spectrum at the effective charge center. This work was supported by "Russian science foundation" (grant № 16-12-00072) [1] Likharev K K. "Single-electron devices and their applications." Proceedings of the IEEE 87.4 (1999): 606-632. [2] Presnov D. E., et al. “Arsenic dopant single-atom single-electron transistor.” In Book of Abstracts of Intenational Conference "Micro- and Nanoelectronics - 2014", ICMNE 2014, Zvenigorod, Russia, (October 6-10, 2014), P2–02 [3] Kaneko, Satoshi, et al. "Site selection in single-molecule junction for highly reproducible molecular electronics." Journal of the American Chemical Society 138.4 (2016), 1294–1300 [4] Moraru, Daniel, et al. "Atom devices based on single dopants in silicon nanostructures." Nanoscale research letters 6.1 (2011): 1-9. [5] Fuechsle, Martin, et al. "A single-atom transistor." Nature Nanotechnology 7.4 (2012): 242-246. [6] Dagesyan, S. A., et al. "Properties of Extremely Narrow Gaps Between Electrodes of a Molecular Transistor." Journal of Superconductivity and Novel Magnetism 28.3 (2015): 787-790.