ISSN 1063-7397, Russian Microelectronics, 2007, Vol. 36, No. 6, pp. 353–357. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © O.A. Ageev, B.G. Konoplev, V.V. Polyakov, A.M. Svetlichnyi, V.A. Smirnov, 2007, published in Mikroelektronika, 2007, Vol. 36, No. 6, pp. 403–408.
The emergence of quantum nanodevices  may be
seen as a forerunner of a second quantum revolution in
technology, but their fabrication still faces the chal-
lenge of ensuring lithographic reproducibility on the
Currently, nanolithography relies on extreme-ultra-
violet (EUV) radiation, x rays, electron beams, or scan-
ning probes [1–3] to produce nanodevices based on
quantum-conﬁned structures with a two-dimensional
electron gas and on nanoscale metallic elements [1–4].
On the other hand, the above approaches suffer from
some disadvantages. The resolution of x-ray and elec-
tron-beam techniques is degraded by scattering in the
material being processed . EUV lithography faces
the problem of focusing at an operating wavelength of
13.4 nm. With a very limited choice of transparent
materials in this spectral region, one has to employ
costly catoptric devices that must satisfy stringent
requirements [1, 2].
Scanning-probe nanolithography is free from those
limitations. It offers a way to assemble devices by
manipulation of individual nanoscale objects such as
carbon nanotubes, fullerenes, or nanoclusters [2–5].
One promising method in this ﬁeld is tip-induced
local anodic oxidation [2–5]. However, it entails solv-
ing the problem of unstable transport of charge and
mass across the tip–substrate gap due to local variations
in the properties of the material, a factor that degrades
the lithographic resolution and reproducibility [6, 7].
Ageev et al.  proposed introducing an activating
agent, such as ultraviolet (UV) radiation, into the tip–
substrate gap that would dominate the oxidation to
reduce the inﬂuence of the above-mentioned variations.
In general, photoassisted oxidation is known to
allow some control over the kinetics of oxidation and
the properties of the oxide [9, 10]. Yet the underlying
mechanism is not well understood despite its being dis-
cussed by quite a few authors.
This article reports on an experimental investigation
into the inﬂuence of UV or infrared (IR) irradiation on
nanolithography by tip-induced local anodic oxidation
as applied to titanium ﬁlms. Geometric parameters of
test nanostructures are deduced from measurements
and subjected to statistical data analysis.
Local anodic oxidation was carried out by dynamic-
mode atomic-force microscopy (AFM) using a Solver
P47 Pro scanning probe microscope (SPM) from
NT-MDT (Russia), together with the software, attach-
ments, and materials supplied with the instrument.
The process was carried out on a titanium ﬁlm about
5 nm thick, which was formed on a silicon substrate by
a pulsed-plasma method.
We used the Nova RC1 control program (version
1.0.26.097) and DSP-20 cantilevers with a conducting
diamond coating, the voltage amplitude and scanning
rate being 8 V and 2
m/s, respectively. The relative air
humidity was measured with an Oregon Scientiﬁc
ETHG913R digital meter; it was
1%. The resulting
oxidation reaction, involving the moisture adsorbed on
the specimen surface, produced nanoscale structures of
titanium oxide according to a preformed mask.
To investigate the effect of UV or IR stimulation on
the local anodic oxidation, the oxidation region was
irradiated with a 395-nm CREE light-emitting diode
(LED), designed in the United States, or with a 900-nm
AL-103A LED, respectively. In addition, reference
nanostructures were fabricated without irradiation.
The test structure was chosen to be an array of a suit-
ably large number of nanosized oxide dots to allow reli-
able statistical processing of experimental results.
Indeed, arrays of scattering centers with controlled
topology and parameters are widely used in nanoelec-
tronics, e.g., as part of ballistic rectiﬁers [5, 11].
Photoassisted Scanning-Probe Nanolithography on Ti Films
O. A. Ageev, B. G. Konoplev, V. V. Polyakov, A. M. Svetlichnyi, and V. A. Smirnov
Taganrog State University of Radioengineering, Taganrog, Russia
Received September 12, 2006
—An experimental investigation is reported on the inﬂuence of UV or IR incoherent irradiation on
nanolithography by tip-induced local anodic oxidation as applied to titanium ﬁlms. Both forms of irradiation
are found to increase the uniformity of feature sizes and to improve the resolution of the lithographic technique.
It is also shown that UV irradiation makes it possible to produce a conducting channel 11 nm wide.