56 R&DMagazine October 2013 www.rdmag.com
The Heat is On
Nanoprobes and nanoindenters have dramatically improved physical measurements at the
nanoscale. Now, researchers want faster testing under a wider array of conditions.
The effort to better understand nanoscale properties has produced large-scale government and industrial research organizations, such as the National Nanotechnology Initiative (NNI) and the Nanoelectronics Research Initiative (NRI). These efforts, each
funded in the billion-dollar range, depend on the ability of researchers
from around the world to effectively use the analytical tools at their disposal to learn as much as possible about the properties of materials at
The difficulty, however, is that answers often generate new questions.
As imaging and mechanical testing technologies have improved, so has
the desire by researchers to understand how materials act at the smallest,
most fundamental levels. By doing this, a set of knowledge could be
generated that would allow engineers to understand or even construct
materials from the most basic of building blocks: atoms.
This race to discover more about nanoscale materials has generated a
number of highly sophisticated technologies, many of which have, over
the years, earned R&D 100 Awards. 2013 is no different. Three R&D 100
Awards address specific nanoscale measurement challenges: electrical
behavior, thermal changes and throughput. And each of them also represents an effort to improve the return of reproducible results.
Probe techniques charge forward
Scanning probes are among the most useful tools at the disposal of a
researcher working with nanoscale materials. The development of highly
precise and sensitive piezoelectric actuators has allowed a wide variety
of techniques, or modes, to be developed that can acquire physical,
electrical, magnetic and sometimes even chemical information. Dozens
of microscopy techniques rely on the use of scanning probes, including
atomic force microscopy (AFM) and scanning tunneling microscopy
Laboratory researchers are always on the hunt for more information,
which has prompted instrument developers to combine as many of these
methods as possible. Modern scanning probe-based instrumentation can
involve the use of several scanning probes, a plethora of optics and various
detector technologies. The 2013 R&D 100 Award-winning LT Nanoprobe
from Oxford Instruments Omicron NanoScience, Taunusstein, Germany, offers a good example of how far these instrument platforms have
progressed to fulfill the needs of today’s nanotechnologists.
Designed to bring a new level of precision to nanoscale electrical
transport measurements, the LT Nanoprobe offers the ability to analyze
samples under vacuum at very low temperatures of less than 5 K. This
is a key capability, because it provides fundamental electrical information about sample materials without the need for integrating nanoscale
structures with larger-scale electrical circuits for test purposes. This saves
considerably and accelerates research into molecular electronics and
To achieve a flexible platform for comprehensive electrical testing
at such small scales, Oxford Instruments’ LT Nanoprobe combines
four individual-controlled scanning probes with a scanning electron
microscope (SEM). According to Andreas Frank, marketing manager at
Oxford Instruments, the availability of several probes means they can be
navigated to any region of interest within the measurement range.
With this setup, he says, “nanostructures of any geometrical structure can be analyzed. Furthermore, it is possible to analyze only some
regions of interests of the nanostructure. Another advantage of their
independence is that we can use each probe module like a conventional
However, uniting the four nanoprobes with the SEM while still permitting low-temperature analyses created a design challenge for Oxford
Instruments’ developers, says Frank. They first had to design both the
scanning probe and the thermal shield compartment in as little space as
possible to obtain a small working distance for the SEM. This distance,
which falls between the front end of the SEM column and sample surface, is essential for achieving optimal resolution, but means little sepa-ratation from a room-temperature environment from 5 K.
This created two points of potential thermal weakness: the aperture in
the shield compartment that allows the SEM electron beam to enter the
shield compartment and the sample-clamping mechanism.
The solution, says Frank, was “to make the access port for the SEM as
small as possible in order to reduce the thermal radiation onto the sample so that the sample temperature is below 5 K during illumination of
the sample with the electron beam.”
In addition to allowing researchers to study nanoscale structures in real
time, Nanomechanics Inc.’s InSEM HT can prove a heated tip and sample
evironment up to 500 C in vacuum. Image: Nanomechanics Inc.