Because their atomic structures can be precisely engineered, molecules could enable computing, sensing, photonic, and quantum devices that are smaller, faster, and more efficient than today’s silicon-based technology. But there is a problem standing in the way — while we are capable of designing the molecules that we need, there is no practical way to integrate them into electronic devices without destroying them during fabrication.
Researchers at MIT believe they have solved that problem with a new manufacturing technique that combines conventional semiconductor fabrication with molecular self-assembly. Rather than trying to get fragile molecular materials to survive the harsh chemicals and processing steps used to manufacture chips, the team builds almost the entire device first and introduces the molecules only at the final stage.
In a test of the process, the team fabricated metal electrodes using standard semiconductor manufacturing techniques. The electrodes are separated by an extremely small gap, and a molecular layer is deposited onto their surfaces. As the liquid containing the molecules evaporates, naturally occurring capillary forces gently pull the upper electrode into position. Once the electrodes meet, van der Waals forces hold the completed structure together, creating a pristine electrical connection without exposing the molecules to damaging fabrication steps.
A look at one of the chips produced by the team (📷: S. Spector et al.)
Unlike many research projects, this approach has been shown to be both scalable and reliable. The team has already fabricated more than 1,000 electrically active metal-molecule-metal devices using molecular layers thinner than one nanometer. Manufacturing yields reached as high as 99%, with an average yield of about 96% across the fabricated chips. The devices also remained stable through more than 100,000 electrical measurement cycles, while in situ Raman spectroscopy confirmed that the molecules themselves remained undamaged throughout the assembly process.
To demonstrate the possibilities, the team assembled arrays of self-rectifying molecular memory devices arranged in a crossbar architecture and successfully ran vector-matrix multiplication operations, one of the core mathematical operations used in neuromorphic computing systems designed to mimic certain aspects of the human brain.
While there is still plenty of work to be done before molecule-based electronics become commonplace, this research addresses one of the field’s biggest roadblocks. By combining established semiconductor manufacturing with a self-assembly process that protects fragile molecular materials, the technique provides a practical path toward building devices that were previously difficult or impossible to manufacture. If the approach continues to prove itself, it could help bring molecular electronics out of the laboratory and into future computing, sensing, photonic, and quantum technologies.
