ISSN 1063-7397, Russian Microelectronics, 2016, Vol. 45, No. 1, pp. 26–32. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © R.Yu. Rozanov, V.A. Kondrashov, V.K. Nevolin, Yu.A. Chaplygin, 2016, published in Mikroelektronika, 2016, Vol. 45, No. 1, pp. 29–35.
Characteristics of Chloride Memristors Based
on Nanothick Metal Films
R. Yu. Rozanov, V. A. Kondrashov, V. K. Nevolin, and Yu. A. Chaplygin
National Research University of Electronic Technology (MIET), Zelenograd, Russia
Received April 3, 2015
Abstract⎯Memristors based on films of Cu and Cr, as well as their chlorides, which provide better charac-
teristics of electronic components compared to the commonly used ones, are investigated.
Memristors—passive two-terminal electronic
components—can be regarded as resistors with vari-
able resistance. The conduction state of such a com-
ponent depends on the magnitude and direction of the
current flowing through it. The current value of the
memristor conductivity remains unchanged over a
long period of time, even when there are no external
energy sources. This effect allows one to use memris-
tors as cells of nonvolatile resistive random-access
memory (ReRAM) [1–3] or as a neuron model for the
hardware implementation of neural networks [4, 5].
Memristors are fabricated based on thin films of an
active layer, which is sandwiched between two highly
conductive electrodes and in which the variation in the
resistance occurs. A number of compounds that
exhibit the memristor effect are presently known.
Among these are many oxides [6, 7] and other binary
metal compounds [8–11].
The purpose of this work is to find new materials
that exhibit the memristor effect, thus providing better
characteristics of electronic components.
IDEA OF SEARCHING
In most modern theories of resistive switching, the
change of the conduction state in electronic compo-
nents based on thin films of metal compounds is
related, in one way or another, to the physical migra-
tion of ions. Therefore, the magnitude of the memris-
tor switching effect depends on the distance to which
ions migrate. The thickness of the active layer can be
regarded as such a distance, which generally does not
exceed 100 nm. The ion mobility also makes a consid-
erable contribution to the switching effect. The mobil-
ity of ions depends on their charge, as well as ionic
radius, and depends only slightly on the electric field
applied. If the coefficient of ionic diffusion in solids is
is the diffusion factor, Q is the activation
energy, R is the gas constant, and T is the absolute
temperature, then it is believed that a twofold decrease
in the ion charge (for example, when oxygen ions O
are replaced by chloride ions Cl
) results in a consid-
erable decrease in the activation energy. In this case,
the diffusion coefficient will grow, along with the
mobility (other factors being equal), and, at least, the
state switching frequency of the memristor will
increase. However, it is not all that simple. The radius
of chloride ions is 1.34 times larger than that of oxygen
ions , which hinders the diffusion of chloride ions.
Nevertheless, it can be assumed that the exponential
factor will prove to be more significant, which is con-
firmed by the experiments described below.
The first samples of memristors were fabricated
based on titanium oxide, one of the most widely inves-
tigated compounds [13–21]. Based on these publica-
tions, the technology for fabricating and investigating
such memristors has been developed.
Having the developed technology for memristor
fabrication and a method for showing the memristor
effect, we decided to search for new materials, which
exhibit such an effect, in the class of nonoxide materi-
als, which is now being less investigated. As active lay-
ers, we use copper chloride and chromium chloride.
In the experiments, single-crystal silicon wafers
(KDB 7.5 grade), which have orientation (100), are
used as substrates for samples. The thickness of the
substrates is 380 um. On the silicon surface, there is a
layer of native oxide about 10 nm in thickness. A layer
exp( ),DD QRT=−