3 research outputs found
Electronic transport in quasi-one-dimensional arrays of gold nanocrystals
We report on the fabrication and current-voltage (IV) characteristics of very
narrow, strip-like arrays of metal nanoparticles. The arrays were formed from
gold nanocrystals self-assembled between in-plane electrodes. Local
cross-linking of the ligands by exposure to a focused electron beam and
subsequent removal of the unexposed regions produced arrays as narrow as four
particles wide and sixty particles long, with high degree of structural
ordering. Remarkably, even for such quasi-one-dimensional strips, we find
nonlinear, power-law IV characteristics similar to that of much wider
two-dimensional (2D) arrays. However, in contrast to the robust behavior of 2D
arrays, the shape of the IV characteristics is much more sensitive to
temperature changes and temperature cycling. Furthermore, at low temperatures
we observe pronounced two-level current fluctuations, indicative of discrete
rearrangements in the current paths. We associate this behavior with the
inherent high sensitivity of single electron tunneling to the polarization
caused by the quenched offset charges in the underlying substrate.Comment: 5 pages, 4 figure
Percolating through networks of random thresholds: Finite temperature electron tunneling in metal nanocrystal arrays
We investigate how temperature affects transport through large networks of
nonlinear conductances with distributed thresholds. In monolayers of
weakly-coupled gold nanocrystals, quenched charge disorder produces a range of
local thresholds for the onset of electron tunneling. Our measurements
delineate two regimes separated by a cross-over temperature . Up to
the nonlinear zero-temperature shape of the current-voltage curves survives,
but with a threshold voltage for conduction that decreases linearly with
temperature. Above the threshold vanishes and the low-bias conductance
increases rapidly with temperature. We develop a model that accounts for these
findings and predicts .Comment: 5 pages including 3 figures; replaced 3/30/04: minor changes; final
versio
A model for the onset of transport in systems with distributed thresholds for conduction
We present a model supported by simulation to explain the effect of
temperature on the conduction threshold in disordered systems. Arrays with
randomly distributed local thresholds for conduction occur in systems ranging
from superconductors to metal nanocrystal arrays. Thermal fluctuations provide
the energy to overcome some of the local thresholds, effectively erasing them
as far as the global conduction threshold for the array is concerned. We
augment this thermal energy reasoning with percolation theory to predict the
temperature at which the global threshold reaches zero. We also study the
effect of capacitive nearest-neighbor interactions on the effective charging
energy. Finally, we present results from Monte Carlo simulations that find the
lowest-cost path across an array as a function of temperature. The main result
of the paper is the linear decrease of conduction threshold with increasing
temperature: , where is an
effective charging energy that depends on the particle radius and interparticle
distance, and is the percolation threshold of the underlying lattice. The
predictions of this theory compare well to experiments in one- and
two-dimensional systems.Comment: 14 pages, 10 figures, submitted to PR