Researchers have found a way of sandwiching organic molecules between silicon and metal that could allow the creation of electronic switches made from individual molecules. Using molecules as switches carries the promise of even smaller electronic components that can be produced cheaply in huge numbers, perform faster than their larger silicon brethren, and use only a fraction of their energy.
Although the idea of using molecules as switches has been around for years and there has been progress in creating the switching molecules themselves, the overall concept has been hampered in large part because organic molecules are delicate and tend to be damaged irreparably when subjected to the particularly stressful step of the chip-building process that attaches them to electrical contacts.
Metal forms many of these contacts in chip circuits, but getting metal onto a chip involves heating it until it evaporates, then allowing it to condense on the silicon. The fragile organic switching molecules can’t withstand the heat involved in this process, but the research team made up of scientists from the National Institute of Standards and Technology (NIST) and the University of Maryland have found a way to cool the kitchen.
They covered a surface with a non-stick material before condensing gold on top of it, allowing the metal to cool to an ultra-smooth surface. They then laminated the gold surface with the plastic used in overhead transparencies. The non-stick layer allows them to remove the laminated gold from the surface as easily as peeling off plastic wrap. Adding the organic molecules was then a comparatively simple matter of attaching the molecules to the gold and then flipping the whole assembly onto a silicon base, with the organic molecules sandwiched neatly inside – and intact.
Scientists have attempted to make sandwiches of this sort before, but the researchers' use of an imprinting machine, which allows three layers to be pressed together so the organic molecules contact both the silicon and gold without smashing or otherwise degrading them, finally made it possible to assemble the ingredients effectively.
The researchers have dubbed the process 'flip-chip lamination' and say it could lead to applications beyond chip design, including biosensors, which depend on the organic and electronic worlds interacting.