January 27, 2020 by Sam Holland
Nanotechnology marks a new era of electrical engineering. Electronic devices, after all, continue to revolve around the minimisation of both their components and their level of circuit complexity.
Accordingly, we look at a major part of electronics miniaturisation: component fabrication, and the university research involved.
Indeed the very question, of how small an electronic component can be fabricated is now more than ever a major topic in itself. Consider, in particular, Tokyo Institute of Technology (Tokyo Tech) and University of Tsukuba’s project, which is set to revolutionise the nanotechnology sciences, in which polymers (i.e. substances that have a molecular structure that consists chiefly, or entirely, of many similar units bonded together) play an elementary role in fabricating single-molecule electronic devices.
In fact, as Tokyo Tech’s research lead Tomoaki Nishino (pictured below) explains, it is by scrutinising polymers, that research, such as this ongoing joint university project, is intended to achieve the ultimate goal of developing smaller electronic components.
Left to right: Tokyo Institute of Technology’s Tomoaki Nishino, associate professor; and Takanori Harashima, a doctoral student. Image Credit: Tokyo Institute of Technology.
Nishino demonstrated that, to achieve the minimal parameters of electronic device sizes, “a single molecule is [to be] utilised as a functional element”. (Fabricating electronic devices from a single molecule is nevertheless a very difficult task, given how complex it is to create such an atomic structure.)
The researchers, keeping in mind the previous experimental reports, deduced that, instead of using smaller molecules, the formation of polymers—based on the use of a long chain of singular molecules, known as monomers—would produce better results.
Such a technique, which is known as ‘scanning tunnelling microscopy (STM),’ became the chosen approach of experimentation. The researchers’ application of STM involved them using a metallic tip—ending in a single atom—for the measurement of both extremely small currents and their fluctuations.
When the tip creates an electrical contact (namely a junction—see the next image and caption) with the atom(s) of the target surface, fluctuations effectively take place.
As per the above figure, the junctions were created by the team through scanning tunnelling microscopy. Upon analysing and measuring the junctions’ conductive properties, the researchers gleaned that polymers can indeed be essential for the development and fabrication of single-molecule electronic devices.
A computer-generated rendition of single-molecule junctions, composed of a scanning tunnelling microscope (STM) tip and a polymer, both of which are needed to study single-molecule devices. The current that flows through the STM tip is ultimately analysed to gauge the target molecule’s functional applications in single-molecule electronics. Image Credit: Tokyo Institute of Technology.
To help them in both their analysis and general research progress, the team developed an algorithm that allowed them to take out the required current signal measurements obtained during the STM process.
Put more specifically, the researchers’ algorithm was used for the detection and counting of small plateaus (recorded periods of signal consistency) that were measured over time in the current signal (which, to reiterate, came from the STM tip to the target surface). A stable conducting junction—developed between the STM tip and the target surface’s single molecule—was indicated by the said plateaus.
The research team ultimately analysed the results, which were not only gathered from the junctions obtained from the polymer, but also its said counterpart, monomer.
From the researchers’ chosen approach, the following was deduced: in terms of their suitability to electronic devices, the properties of polymers are significantly better than that of monomers. As Nishino puts it: “[The] probability of junction formation, one of the most important properties for future practical applications, was much higher for the polymer junction”.
In addition to this, the research has also suggested that polymer junctions exhibit higher lifetimes and carry more stable current when it flows through them. The scientists concluded their research on the note that polymers play an important role in electronics and are the fundamental units when it comes to both the minimisation of components and the complexity of their circuits.
All in all, therefore, polymers are set to push the boundaries in terms of what nanotechnology and nano-sciences can accomplish. After all, single-molecule devices are highly attractive to such fields—and now, Tokyo Institute of Technology and the University of Tsukuba’s success in evidencing the effectiveness of polymers (particularly over monomers) shows all the more promise for the world of nano-scale electronics.
