SC Grown in Optical Fiber

An international science team has added new electronic capabilities to optical fibers by growing a single-crystal semiconductor inside the tunnel of a hollow fiber, work that could boost the performance of optical fibers used in medicine, computing, and telecommunications.

Optical fibers, used in a wide range of technologies that employ light, are considered an ideal media for transmitting many types of signals, but their performance in electronic devices is usually degraded by the interface connecting the fiber to the device. By building a single-crystal semiconductor in an optical fiber, the team said it has created a new type of device that will work better in electronics applications.

Illustration of single-crystal semiconductor wires integrated into microstructured optical wires. (Image courtesy Penn State University)

The development of the single-crystal device by researchers from Pennsylvania State University and the University of Southampton in England builds on work they reported in 2006, when they first created an optical fiber with electronic characteristics by combining the fibers with polycrystalline and amorphous semiconductor materials. The group said its latest work is expected to lead to even further improvements in the characteristics of optical fibers used in many areas of science and technology.

"For most applications, single-crystal semiconductor materials have better performance than polycrystalline and amorphous materials," said John Badding, associate professor of chemistry at Penn State. "We have now shown that our technique of encasing a single-crystal semiconductor within an optical fiber results in greater functionality of the optical fiber, as well."

The team used a high-pressure fluid-liquid-solid approach to build the crystal inside the fiber. First, the scientists deposited a tiny plug of gold inside the fiber by exposing a gold compound to laser light. Next, they introduced silane, a compound of silicon and hydrogen, in a stream of high-pressure helium. When the fiber was heated, the gold acted as a catalyst, decomposing the silane and allowing silicon to deposit as a single crystal behind the moving gold catalyst particle, forming a single-crystal wire inside the fiber.

"The key to joining two technologies lies not only in the materials, but also in how the functions are built in," said Pier Sazio, senior research fellow in the Optoelectronics Research Centre at the University of Southampton. "We were able to embed a nanostructured crystal into the hollow tube of an optical fiber to create a completely new type of composite device."

The researchers said there is potential to carry the application to the next level. "At present, we still have electrical switches at both ends of the optical fiber," Badding said. "If we can get to the point where the electrical signal never leaves the fiber, it will be faster and more efficient."

The team received financial support from the National Science Foundation, the Penn State Materials Research Science and Engineering Center, and the Penn State-Lehigh Center for Optical Technologies.

A paper on the research will be published later this month in the journal Advanced Materials.

For more information, visit: www.science.psu.edu