ISSN 1068-3356, Bulletin of the Lebedev Physics Institute, 2007, Vol. 34, No. 8, pp. 219–222. c  Allerton Press, Inc., 2007. Original Russian Text c  A.P. Boltaev, L.S. Podlesnykh, F.A. Pudonin, 2007, published in Kratkie Soobshcheniya po Fizike, 2007, Vol. 34, No. 8, pp. 3–9. Anomalously High Effective Permittivity of a System of FeNi Metal Nanoislands A. P. Boltaev, L. S. Podlesnykh, and F. A. Pudonin Received January 23, 2007 Abstract—The low-frequency effective permittivity of a system of FeNi metal nanoislands was studied. It was found that the effective permittivity of the structures under study is anomalously high, 10 7 − 10 8 . The nature of the high permittivity of films is caused by structural parameters (topography) of island films and is associated with the polarization of the dipoles of charged metal nanoislands. DOI: 10.3103/S1068335607080015 Nanostructures based on granular or island metal films have a number of unique properties. Electron and photon emission in an external electric field [1] and photoconductivity in visible and infrared spectral ranges [2] are observed in such structures. At not too high densities of metal islands, the mode of thermally activated conduction [3–7] is realized in such structures. Moreover, a significant change in the differential conductance of island metal films, depending on a weak electric field at temperatures up to 300 K, is observed [8]. There are a number of models pretending to explanation of the mechanism of current flow in films with a system of metal nanoislands [4, 7, 9]. It is considered as an established fact that the conduction mechanism in granular systems and, in particular, in island metal films is associated with tunneling transitions of charge carriers between metal grains or metal islands. It is clear that metal nanoislands surrounded by insulator will be polarized in an electric field. Polarized nanoislands can contribute to the film permittivity, which can significantly affect the low-frequency conductivity of the film. In this study, the temperature dependences of the differential conductance and susceptance of the system of FeNi metal nanoislands were measured. These measurements were performed simultaneously with the study of the dependences of the conductance and susceptance of island films on the electric field. The film permittivity was determined by analyzing the film susceptance. Thin island FeNi films were grown by HF sputtering in argon onto insulating substrates. Details of the method for growing such films are given in [2]. For measurements, multilayer FeNi nanoisland structures consisting of ten layers were selected. The effective thickness of each FeNi layer was d =7 ˚ A; between FeNi layers, Al 2 O 3 layers with effective thickness d = 20 ˚ A were deposited. The effective thickness of metal and insulating layers was determined by the film deposition time (the FeNi and Al 2 O 3 film deposition rates were determined in advance). Rectangular samples 0.5–1.5 mm wide and 2–3.5 mm long were fabricated from the structures. Ohmic contacts were made by deposition of narrow indium strips onto the surface of the metal island film along opposite rectangle sides. When studying the differential conductance and susceptance of the structures based on island metal films, the voltage U = U 0 + U 1 cos(ωt) was applied to the sample. The ac voltage amplitude was U 1 = 10 -2 V. The dc voltage U 0 was varied from U 0 =0 V to U 0 ≈ 15 V (the electric field in samples varied from F =0 V/cm to F ≈ 60 V/cm). The differential conductance was measured at the external electric field frequency f = ω/2π = 12 kHz. This frequency was optimum for separate measurements of the active and reactive (capacitive) components of the structure impedance using phase-sensitive detection, since these impedance components are close in order of magnitude at this frequency. The structure resistance at Т = 300 К was R =7.7 · 10 4 Ω, the capacitance was C =3.3 · 10 -11 F. It should be emphasized that the capacitance of the insulating substrate of area S =1 cm 2 in air medium is C s ≈ 5 · 10 -14 F. The conductance and capacitance measurement error for the system of FeNi nanoislands was ∼ 5%. 219