Many electronic devices today rely on semiconductor logic circuits based on switches hard-wired to perform predefined logic functions. Physicists from the National University of Singapore (NUS) and an international team of researchers have created a novel molecular memristor, or electronic memory device, with exceptional memory reconfigurability.
The molecular device, unlike hard-wired standard circuits, can be reconfigured using voltage to embed different computational tasks. The new energy-efficient technology, which has increased computational power and speed, has the potential to be used in edge computing, as well as handheld devices and applications with limited power resources.
“This work represents a significant step forward in our quest to create low-energy computing. The concept of using multiple switching in a single element is inspired by how the brain works and fundamentally reimagines the logic circuit design strategy “The research was led by Associate Professor Ariando of the NUS Department of Physics.
Many electronic devices today are dependent on semiconductor logic circuits based on switches hard-wired to perform predefined logic functions. Physicists developed a novel molecular memristor, or an electronic memory device, that has exceptional memory reconfigurability.
The research was first published in the journal Nature on 1 September 2021 and carried out in collaboration with the Indian Association for the Cultivation of Science, Hewlett Packard Enterprise, the University of Limerick, the University of Oklahoma, and Texas A&M University.
Brain-inspired technology
“This new discovery can contribute to edge computing developments as a sophisticated in-memory computing approach to overcome the von Neumann bottleneck, a delay in computational processing seen in many digital technologies due to the physical separation of memory storage from a device’s processor,” Assoc Prof Ariando said. The new molecular device may also help to design next-generation processing chips with increased computational power and speed.
“Our memory device, like the connections in the human brain, can be reconfigured on the fly for different computational tasks by simply changing the applied voltages. Furthermore, similar to how nerve cells store memories, the same device can store information for future retrieval and processing “Dr. Sreetosh Goswami, Research Fellow in the Department of Physics at NUS, is the study’s first author.
Dr. Sreebrata Goswami, a Senior Research Scientist at NUS and a former Professor at the Indian Association for the Cultivation of Science, conceptualized and designed a molecular system from the chemical family of phenyl azo pyridines, which have a central metal atom bound to organic molecules known as ligands. “These molecules act as electron sponges, allowing up to six electron transfers to occur, resulting in five different molecular states. The interconnectedness of these states is the key to the device’s reconfigurability “Dr. Sreebrata Goswami elaborated.
Dr. Sreetosh Goswami designed a tiny electrical circuit that included a 40-nanometer layer of molecular film sandwiched between a top layer of gold and a bottom layer of gold-infused nanodisc and indium tin oxide. When he applied a negative voltage to the device, he observed an unprecedented current-voltage profile. Unlike conventional metal-oxide memristors, which can only be switched on and off at a single fixed voltage, these organic molecular devices can switch between on and off states at multiple discrete sequential voltages.
To explain the multiple transitions, spectral signatures in the vibrational motion of the organic molecule were observed using an imaging technique called Raman spectroscopy. “Sweeping the negative voltage triggered the ligands on the molecule to undergo a series of reduction, or electron-gaining, which caused the molecule to transition between off and on states,” Dr. Sreebrata Goswami explained.
In contrast to the traditional approach of using basic physics-based equations, the researchers described the behavior of the molecules using a decision tree algorithm with “if-then-else” statements, which is used in the coding of several computer programs, particularly digital games.
New possibilities for energy-efficient devices
Using their research as a foundation, the team used molecular memory devices to run programs for various real-world computational tasks. The team demonstrated as a proof of concept that their technology could perform complex computations in a single step and then be reprogrammed to perform another task in the next instant. A single molecular memory device could perform the same computational functions as thousands of transistors, making the technology more powerful and energy-efficient.
“The technology could first be used in handheld devices such as cell phones and sensors, as well as other applications where power is limited,” Assoc Prof Ariando added. The team is in the process of developing new electronic devices that incorporate their innovation, as well as working with collaborators to conduct simulations and benchmarking of existing technologies.
