ISSN 10637397, Russian Microelectronics, 2012, Vol. 41, No. 7, pp. 431–436. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © A.N. Belov, S.A. Gavrilov, M.Yu. Nazarkin, V.I. Shevyakov, S.V. Lemeshko, 2011, published in Izvestiya Vysshikh Uchebnykh Zavedenii. Elektronika,
2011, No. 3, pp. 75–81.
Scanning probe microscopy (SPM) provides the
study of the morphology and the modification of sur
face properties of solid bodies with a nanosized resolu
tion [1, 2]. Scanning electricalconductivity micros
copy (SECM) is one of the SPM methods that use
conducting cantilevers and allow one to study electri
cal properties of nanoobjects [2–4]. It employs the
regime of the atomic force microscopy (AFM) in the
contact mode and implements superposed measure
ments of the topography and the study of ground cur
rents on the same conducting surface patch of the
sample under study. However, SECM is not widely
used in Russia or abroad.
The purpose of this paper is to investigate the capa
bilities of the method which support its significance
among methods of scanning probe microscopy.
THE SECM TECHNIQUE
The sample under study is placed on the piezocer
amic scanner of the microscope and tightened by the
electric contact. Then, the sample is brought to the
conducting cantilever, and a surface patch is scanned
in the semicontact mode of the AFM. Further, an area
of interest is chosen for scanning in the contact mode,
which is accompanied by supplying positive voltage of
up to 10 V per sample. When scanning, measurements
of the resulting current flowing in the conducting can
tilever–conducting surface system are carried out and,
at the same time, data on the surface geometry are
obtained. Thus, the AFM image of the surface and the
picture of the current spreading on the surface patch
The analysis of circuit schematics applied in
SECM measurements showed that twometer current
circuits are generally used in SECM .
In the case of problems that involve measuring the
absolute magnitude of the current flow, a circuit with a
linear current amplifier can be applied (Fig. 1a).
This circuit resembles a typical AFM circuit that
uses the laser and the 4section photodiode as an optical
system for obtaining the topographical representation
of the surface and maintaining the constant force of
pressing the needle to the surface. The circuit has an
additional part for measuring the current. The current is
supplied on the current amplifier, and a certain poten
tial, which is specified and can be changed in the pro
cess of scanning by means of a program, is fed on the
sample. In forming an ohmic contact, the current
begins to flow between the conducting needle and the
conducting surface at a nonzero potential difference.
The maximal magnitude of the current flowing in the
needle–sample system will depend on the resistance of
the conducting cantilever–conducting surface system.
When scanning in the contact mode, the current’s mag
nitude is measured in each halftone dot. Current mag
nitudes measured along a certain line form the distribu
tion profile of the ground current when scanning along
a single line, while the collection of corresponding cur
rent profiles over an arbitrary field gives the picture of
the current spreading on the surface under study.
The circuitas schematic (see Fig. 1a) complies with
the quantitative analysis of current magnitudes. By
applying this circuit one can measure currents in the
range from noises of the current amplifier to 1 mA.
However, when measuring highly conductive sam
ples or samples involving areas of high conductivity, the
flow of currents of magnitudes over 100
A is often pos
sible; these are sizeable quantities in terms of current
densities for actual areas of cantilevers–surface contacts
and can result in damaging both the conducting coating
on the cantilever’s nib and the conducting sample.
Peculiarities of Measurements
in Scanning ElectricalConductivity Microscopy
A. N. Belov
, S. A. Gavrilov
, M. Yu. Nazarkin
, V. I. Shevyakov
, and S. V. Lemeshko
National Research University of Electronic Technology MIET, Moscow, Russia
ZAO Nanotekhnologiya MDT, Moscow, Russia
Received September 21, 2010
—Functional capabilities of the scanning electricalconductivity microscopy (SECM) in determin
ing the electrical conductivity of nanosized elements, studying the nanostructure of conductive coating
materials, and evaluating the conductivity of nanoobjects are described. The applicability of the SECM to
finding imperfections in the multilevel metallization of integrated circuits with a nanosized topology is dem