Origin of Noise in Structures with Tuned Nanoconstrictions V.Sydoruk Peter Gruenberg Institute Forschungszentrum Juelich Juelich, Germany 1 current Institute: Institute of Bio- and Geosciences L.K.Vandamme Eindhoven University of Technology Eindhoven 5600MB, Netherlands M.Petrychuk Radiophysical Faculty Taras Shevchenko National University Kiev, Ukraine S.Pud, J.Li, D.Mayer, S.Vitusevich* Peter Gruenberg Institute Forschungszentrum Juelich Juelich, Germany * s.vitusevich@fz-juelich.de Abstract— Thin conducting gold films with nanoconstriction are characterized by noise spectroscopy with and without a single 1,4-benzenedithiol (BDT) molecule between the contacts. The low frequency noise spectral density demonstrates the 1/f α type behavior with a factor, α, near to 1. It is shown, that the normalized noise spectral density is proportional to the resistance R in power 3/2 for the case without a molecule as well as with a molecule. The experimental findings are in good agreement with theoretically predicted results. The results obtained are interpreted in terms of the fine tuning and evolution of structures with a nanoconstriction region. Structures with a single molecule demonstrate a lower noise level compared with the structures without it. Our results are promising for the development of nanostructures for future molecular electronics, functioning at room temperature. Keywords—single molecule, nanoconstriction, flicker noise, tunneling, transport properties I. INTRODUCTION Currently, transport phenomena in nanostructures are increasingly attracting the attention of researchers not only to identify new applications [1], but also to find ways to change the transport mechanism in new regimes as well as- to utilize novel approaches of transport formation in complex systems with the single-molecule participating in the structure transport phenomena [2]. This will allow conditions to be achieved for an important new stage of the design and development of molecular electronics. Structures with thin regions in the range of tens of nanometers, whose geometry can be tuned, represent unique systems for studying noise properties at the nanoscale. Noise spectroscopy is one of the methods for comprehensively studying transport processes in nanostructures, and analyzing transport regimes and also identifying the transition regions from one type of regime to another. Recently, the authors of Ref. [3] showed, that- in tunable break junctions (TBJ) noise is caused by resistance fluctuations and as a function of resistance this noise demonstrates different power dependencies for low-ohmic and high-ohmic junctions. Such behavior was explained by the transition from diffusive to ballistic transport using simple estimations of characteristic length change of the junction constriction. It was suggested that even in the smallest junctions flicker noise scales with the total number of channels proportional to the junction area. In the case where a layer of molecules self-assembled between two large-area gold electrodes forming metal-molecule-metal junctions, noise spectra show 1/f-noise, random telegraph noise, and shot noise components due to localized defects, which may be unintentionally introduced into the molecular layer [4]. However, a detailed analysis of noise as a function of resistance of metal-molecule-metal junction was not performed. In our work, we analyzed the transport and noise properties of gold nanostructures with nanoconstrictions, the geometry of which can be scaled down to a single gold atom. Moreover, after breaking the gold constriction and bonding the electrode with a single organic molecule, the structure demonstrated unique behavior with respect to molecule transport and noise properties. II. EXPERIMENTAL DETAILS Highly-stable TBJ structures were fabricated using advanced technology to study noise and transport properties. Stability of the structures was especially important for noise measurements. TBJ chips were fabricated on the basis of spring steel substrates with a length of 44 mm, a width of 12 mm and a thickness of 0.2 mm. First, a polyimide (HD-4100, HD ICNF2013 978-1-4799-0671-0/13/$31.00 ©2013 IEEE