Molecular clusters as a basis of single-molecule SET nanosystems
E. S. Soldatova, S. P. Gubinb, P. Johanssonc, G. B. Khomutov*, a, V. V. Kolesovd, A. Yu. Obydenova, V. V. Shorokhova, and K. S. Sulaimankulove
aFaculty of Physics, M.V. Lomonosov Moscow State University, 119899, Moscow, Russia bN.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 119991, Moscow, Russia cDivision of Solid State Theory, Lund University, Solvegatan 14 A, S-223 62 LUND, Sweden dInstitute of Radioengineering & Electronics, Russian Academy of Sciences, 103907, Moscow, Russia eInstitute of Chemistry & Chemical Technology, National Academy of Sciences, 720071, Bishkek, Republic of Kirgistan
The single-electron (correlated) tunneling (SET) effect in the systems based on the single organometallic nanocluster molecules is studied experimentaly and theoreticaly. Using Langmuir-Blodgett technology for deposition and Scanning Tunneling Microscope (STM) - technique for topography and electron transfer characteristic measurements a wide spectrum of different cluster molecules was investigated. The technique that allows to create nanostructures with preset characteristics (separate clusters, one-dimensional chains of clusters, two-dimensional regular arrays of clusters) was developed. Clusters with nonspherical shape are shown to be better for this technology. A molecular single-electron transistor on the base of a single cluster molecule operating at room temperature was realized. I-V curves and control curves of such transistors with various molecules as a central electrode was studied. The atomic and electronic structure of nanoclusters, containing in the core from 3 to 23 metal atoms, were shown to have no crucial importance for the realization of the transistor effect in itself. An analysis of influence of HOMO - LUMO gap and ionization potential of the molecule on the shape of transistor characteristics shows that these parameters determine only common shape of I-V curves. The peculiarities of I-V curves are conditioned apparently by other area of states of the multielectronic cluster molecule which is a set of levels corresponding to the states with a similar energy, delocalized through the whole molecule and easily polarized, similar to that of pseudo-metal state of nano-granules. The charge sensitivity of the systems at room temperature was of about 10-4 e/Hz1/2 which is close to the typical values for traditional thin-film low-temperature single-electron systems. I-V curves of molecular SET transistor are simulated based on a modified theory of single-electronics that accounts for the discretness of the energy spectrum of the molecule. This simulation was performed including for the first time the effects of energy relaxation of the electrons in the molecule for two limiting cases of fast and slow relaxation, and for two types of the molecule energy spectrum. A comparison of the simulated I-V curves with the experimental ones provide the unambiguious interpretation of the experimental data and allow to conclude that the experimental conditions correspond to the slow energy relaxation case.
This work was supported in part by INTAS-99-00864, RFBR (99-03-32218), the Russian Program on the Prospective Technologies for Nanoelectronics and the Russian Program on the Physics of Nanostructures (99-1143).