Conductivity of the Granular Metal Films Obtained by High Dose Ion Implantation into Pmma
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V.V.Bazarov, V.Yu.Petukhov, V.A.Zhikharev, I.B.Khaibullin, Zavoisky Physical Technical Institute of Russian Academy of Science, Sibirsky Trakt, 10/7, Kazan, 420029, Russian Federation
ABSTRACT Thin granular metal films in polymethylmethacrylate(PMMA) have been synthesized by 40 keV Fe', Ag+ or Pb+ ions implantation with fluencies up to 6* 1017 ion/cm 2. The resistivity of synthesized films was measured in the temperature range from 300K to 5K. The temperature dependence of the resistivity of PMMA implanted with Ag+, Pb+ and small fluence Fe' obeys the well known law lnR-(l/T) 1/2 . The samples implanted by high fluence Fe+ reveal rather a different behaviour. At low temperature (T101 7ion/cm 2 ) a considerable deviation from (1) takes place for temperatures lower than 100K. The curve ln(R(T)) is more gently sloping than ln(RIR()-(I/T)1/ 2 law. We suppose that such behaviour of resistivity is connected with morphology features of granular Fe-film obtained at a high dose implantation. This supposition is confirmed by TEM study of implanted PMMA samples. Typical electron micrographs for samples implanted by Ag and Fe are shown in Fig.2(a-c). As can be seen in Fig.2c the high dose Fe+ - implanted layer contains two well distinguished groups of particles (one group - with sizes up to I Onm and the other - with sizes of 60-70nm). It should be marked that large particles were arranged in the form of "lattice" in the layer plane. The space between big particles is sufficiently large and filled with small Fe particles. It is obvious that in the case of Ar+ implantation the conductivity is determined only by a carboneouse layer near the polymer surface. Such layers also exist in samples implanted by metal ions. We suppose that for the temperatures higher than 100K the conductivity of implanted
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24 22 Ar, Fe-1 -
20
1.2xl0Cion/cm
-
Pb, Ag, Fe-2 -
-I
pb+ [
16 o
4xl01 ion/cm£
-
0
--
Fe*- I
El
Pb
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+
Ag+
++
1 •j12_
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0.10
0.20
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Fig. 1. Temperature dependences of surface resistivities of PMMA
implanted by different ions
419
0.40
S:JOOnmn PMMA + Fe+, D = 4xl017ion/cm 2 . Fig.2. TEM micrographs of implanted PMMA.
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polymer is a sum of conductivity of the carboneouse layer and that of granular metal film. Because of the high resistivity of the carboneouse layer the resistivity of implanted samples at low (
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