Miniaturizing electronics has been one of the most important goals for experts in this field for decades. The idea of developing functional components at the molecular scale presents multiple challenges, and prototypes created so far have suffered serious limitations. However, a team of researchers at Columbia University has created a single-molecule diode with performance 50 times superior to that observed in previous designs.
A concept with deep roots
The first vacuum tube was born in 1904, and it was also the first thermionic diode. But the concept of the diode is even older. Karl Ferdinand Braun discovered the so-called "unidirectional conduction" of crystals, (which allowed him to patent the rectifier crystal 25 years later), and Frederick Guthrie explored the theory of the thermionic diode a year earlier. A little more than a century has passed, and I think none of those brilliant minds could have imagined the level of quality, precision, and performance that electronics would achieve. Nor is it necessary to go that far back: just by taking a smartphone thirty years into the past, we would have a supercomputer in our pocket. Today, experts are developing different methods to push the limits of miniaturization, which affect a huge number of elements, including Moore's Law and the creation of faster systems. However... the history of "modern" electronics began with a diode.
The new diode at Columbia
With that in mind, it is not surprising that the extraordinary advance of a group of researchers at Columbia University also focuses on a diode. The first aspect to highlight is that it is a diode formed by a single molecule. According to Latha Venkataraman, professor of applied physics, the creation of a functional molecular diode is a kind of Holy Grail that many have sought since the publication of the concept by Arieh Aviram and Mark Ratner in 1974. Asymmetry is a fundamental aspect for its construction, and previous molecular projects managed to mimic several properties, but they have always suffered from a fairly low rectification ratio. The Columbia researchers managed to change this completely, as their diode is capable of working with an electric current of 0.1 microamperes, a value 50 times better than previous molecular designs.
How they solved the asymmetry
With the help of the group led by Professor Luis Campos (also from Columbia) and the group of Jeffrey Neaton at UC Berkeley, the experts created an "environmental asymmetry" by wrapping the molecule in an ionic solution, and applied gold electrodes to connect it. What follows now? To study more closely the physics related to this diode, and to optimize the rectification ratio. We are still far from a commercial application, but the technology exists. Just give it time.
