Organic electronics are being lauded for their flexibility and ability to be printed on a variety of form factors. However, inorganic electronics still hold large leads in most important component parameters for digital circuits, over mass-producible organic electronics. Unfortunately, they couldn't be printed.
Well chalk up another victory to nanotechnology -- printable inorganic semiconductor circuits may soon be on their way thanks to a new high-tech ink which uses nanoclusters.
Zachary L. Mensinger, a doctoral student in the lab of University of Oregon, and chemist Darren W. Johnson led the research which discovered a way to produce large amounts of nanocluster ink, rapidly, for the first time.
The process produced perhaps the first heterometallic gallium-indium hydroxide nanocluster. It took advantage of a trick in which nitrosobutylamine replaced nitrosobenzene as an additive in a key step in the bottom up approach. Mr. Mensinger identified the replacement compound through extensive screening of possible candidates. The additive compounds optimize and speed crystallization, allowing for reaction yields of up to 95 percent. Traditional techniques to produce the compound require far more caustic chemicals and take months or even years, while producing only low yields.
Professor Johnson describes, "The benefit is that we can predictably control the ratio of gallium and indium in these structures at molecular levels, which can result in the same control in the fabrication of semiconductor thin films. We can tailor the properties for specific applications or for different performance levels."
The results of the research will be reported in the Angewandte Chemie (Applied Chemistry) International journal. College football rivals Oregon State and University of Oregon collaborated on the paper, part of the pair's nanotechnology efforts, driven by the Oregon Nanoscience and Microtechnologies Institute (ONAMI), which both schools are involved with. Six authors from the two schools appear in the paper.
The research is breathtaking, explains Johnson. He adds, "Researchers working in the solid-state materials community are looking at these kinds of nanoclusters as precursors for thin films and other advanced materials, but you typically cannot get them in high enough yields. Our synthesis, however, allows for gram-scale quantities."
Research in Johnson's lab revolved around low temperature production of the nanoclusters. A nanocluster consists of 13 metal atoms in a framework, which contains two different types of metals. This framework has special properties useful to electronics. The cluster described in the paper was Ga7In6 hydroxide, a composite of the elements gallium and indium.
Mr. Mesinger describes his work, stating, "We're starting from a bottom-up approach, in that we can make these with the ratios we desire already built in. Using this nitroso compound, we get a higher yield and at a larger scale. I screened several of these compounds to narrow down the best choice. We can also re-use the nitroso compound. It is still present at the end of the reaction, so we can remove it and use it in future reactions."
Not only does the nitrosobutylamine produce large quantities of the nanoclusters, but it is also reusable in later reactions. The only downside is that it is still relatively toxic. Professor Johnson says the team is exploring greener alternatives.
So what can the new nanocluster inks be used for? Perhaps the first high-performance printed electronics. Co-author Douglas A. Keszler reports, "We now have new methods for pushing printed inorganic electronics to higher levels of performance within a useful class of materials."
With the new nanoclusters, the dream of wearing a high-speed circuit, such as a CPU, may finally be realizable.