Scientists Create New Methods to Overcome Limits in Electronic Miniaturization

electronic miniaturization breakthroughs

Researchers at the University of Illinois have made significant strides in molecular electronics by developing stable, shape-persistent molecules with controlled conductance. Their innovative synthesis approach sets the stage for creating more dependable, miniaturized electronic devices.

As electronics continue to shrink in size, physical limitations are beginning to challenge the long-standing trend of increasing transistor density on silicon-based microchips, a principle known as Moore’s law.

Molecular electronics, which relies on individual molecules as the fundamental building blocks of electronic devices, offers a compelling solution for further reducing the scale of modern electronics.

For molecular electronics to function optimally, precise regulation of electrical current flow is crucial. However, the inherent dynamic behavior of these single-molecule components often affects device performance and undermines reproducibility.

In response to this challenge, researchers at the University of Illinois Urbana-Champaign have unveiled a novel method for controlling molecular conductance.

By utilizing molecules with rigid, ladder-like backbones—known for their shape-persistent properties—they’ve achieved remarkable stability in molecular conductance.

Additionally, they’ve introduced a simplified, “one-pot” synthesis method to produce these molecules. This technique was successfully applied to create a butterfly-shaped molecule, further showcasing its versatility in controlling molecular conductance.

The research, led by Charles Schroeder, the James Economy Professor of Materials Science and Engineering, alongside postdoctoral researcher Xiaolin Liu and graduate student Hao Yang, has been published in Nature Chemistry.

The Role of Molecular Rigidity

“In molecular electronics, you must account for the flexibility and movement of molecules, as these factors significantly influence their functional properties,” notes Schroeder.

“Our approach to addressing this issue was to develop molecules with rigid backbones, ensuring consistent conductivity regardless of molecular conformation.”

A key obstacle in molecular electronics is the flexibility of many organic molecules, which can adopt various conformations—each potentially exhibiting different electrical conductance levels.

Liu explains, “Molecules with multiple conformations can vary in conductance by up to 1,000 times. We opted for ladder-type molecules, known for their rigidity, which allowed us to achieve stable and robust conductance in molecular junctions.”

Ladder-type molecules are characterized by a continuous sequence of chemical rings, with at least two atoms shared between adjacent rings, effectively “locking” the molecule into a specific shape. This structural rigidity minimizes rotational movement and reduces variations in conductance.

Overcoming Barriers in Molecular Electronics

Achieving consistent conductance is vital when molecular electronics are intended for real-world devices, which require billions of components with identical electronic properties.

Yang highlights, “The variation in conductance has been a major barrier to the commercialization of molecular electronic devices. If we can precisely control molecular conductance, it will drive the development of much smaller, more efficient electronic devices.”

To control conductance in shape-persistent molecules, the team employed a unique one-pot synthesis strategy, which produced a variety of chemically diverse, charged ladder molecules.

Traditional synthesis methods rely on expensive starting materials and often involve two-component reactions, limiting the diversity of products.

In contrast, the one-pot multicomponent strategy uses simpler, commercially available materials, enabling the creation of a wide range of product molecules suitable for molecular electronics, as Liu explains.

Building on their success with ladder-type molecules, Liu and Yang further demonstrated the broad applicability of shape persistence by designing, synthesizing, and characterizing a butterfly-shaped molecule.

Like ladder molecules, these butterfly structures feature a locked backbone and restricted rotation, promising to advance the design of functional materials and ultimately lead to more reliable, efficient electronic devices.

Reference

This pioneering research, titled “Shape-persistent ladder molecules exhibit nanogap-independent conductance in single-molecule junctions,” was published on August 26, 2024, in Nature Chemistry. The study was supported by the U.S. Department of Energy’s Office of Science.

DOI: 10.1038/s41557-024-01619-5

electronic miniaturization breakthroughs