Prude University West Lafayette, IN 47907 USA

Researchers at Prude University West Lafayette, IN 47907 USA, have used a thin film of titanium nitride into transporting plasmons. Plasmons are tiny electron excitations coupled to light that can direct and manipulate optical signals on the nanoscale. According to researchers, titanium nitride's addition to the short list of surface-plasmon-supporting materials, formerly comprised only of metals, could pave the way to a new class of optoelectronic devices with unprecedented speed and efficiency. "We have found that titanium nitride is a promising candidate for an entirely new class of technologies based on plasmonics and metamaterials," said Alexandra Boltasseva, researcher, Purdue and an author on a paper published today in the Optical Society's (OSA) open-access journal Optical Materials Express. Metals carry electricity with ease, but normally do nothing to transmit light waves. Surface plasmons, unusual light-coupled oscillations that form on the surface of metallic materials, are the exception to that rule. When excited on the surface of metals by light waves of specific frequencies, plasmons are able to retain that same frequency, but with wavelengths that are orders-of-magnitude smaller, cramming visible and near-infrared light into the realm of the nanoscale. Gold and silver are the best candidates for plasmonic materials, but they are not compatible with silicon manufacturing technologies, limiting their use in commercial products. 

 

In an effort to overcome these drawbacks, Boltasseva and her team chose titanium nitride—a ceramic material that is commonly used as a barrier metal in microelectronics and to coat metal surfaces such as medical implants or machine tooling parts. It also could be easily integrated into silicon products, and grown crystal-by-crystal, forming highly uniform, ultrathin films—properties that metals do not share. The researchers deposited a very thin film of titanium nitride on a sapphire surface and observed that the material supported the propagation of surface plasmons almost as efficiently as gold. Currently, the researchers are now looking into a manufacturing method known as molecular beam epitaxy to further improve the performance of titanium nitride. This method would enable them to grow the films and layered structures known as superlattices crystal-by-crystal. The researchers also speculate that titanium nitride may have applications in metamaterials. Recently proposed applications of metamaterials include invisibility cloaks, optical black holes, nanoscale optics, data storage, and quantum information processing. "Plasmonics is an important technology for nanoscale optical circuits, sensing, and data storage because it can focus light down to nanoscale," noted Boltasseva. "Titanium nitride is a promising candidate in the near-infrared and visible wavelength ranges. Unlike gold and silver, titanium nitride is compatible with standard semiconductor manufacturing technology and provides many advantages in its nanofabrication and integration."

Source: EE Times