Aerospace Arsenal Includes Powerful Microscope

They say that good things come in small packages.

But what if those good things are so small you can't see them with the naked eye, or even an average microscope?

Aerospace, in its typical problem-solving manner, has an answer for that, in the form of its transmission electron microscope (TEM), which is located in the Physical Sciences Laboratories of the Engineering and Technology Group.

"This microscope is capable of imaging with sub-angstrom spatial resolution and quantitative chemical mapping of device structures with sub-nanometer precision," said Dr. Brendan Foran, laboratory manager in the Microelectronics Technology Department.

To put this in perspective, a nanometer is one-billionth of a meter and an angstrom is one ten-billionth of a meter. Angstroms and nanometers are used to measure atoms, molecules, and similar-sized objects.

Foran leads the team of scientists who use the TEM and other related microscopes to investigate space system component anomalies and conduct reliability assessments for a wide range of customers throughout the Aerospace community.

"More and more often, we find that the critical functionality of materials and devices depends on features in the nanoscale range (10-7 to 10-10 m)," he said. "With our TEM, we have looked at the smallest transistors found in modern microelectronics, and we can see and measure artifacts that often the vendors and contractors can't see so accurately."

This instrument has played a significant role in a large number of component anomaly resolutions, and has helped with "root cause failure investigations and reliability studies for a broad range of microelectronic and optoelectronic devices as well as structural materials, composites and energy storage materials," Foran said.

The TEM is a handy tool in Aerospace's bag of tricks. But what is a transmission electron microscope, anyway?

Many people may be more familiar with a light microscope, in which light shines upon a specimen. A transmission electron microscope works in a similar manner, but electrons are transmitted through the specimen instead of light. Because electrons have a smaller wavelength than light, it is possible to view much smaller objects, and because of the way electrons interact with atoms, as they pass through a sample, it is possible to interrogate the chemical makeup of these very small objects at the same time as imaging them.

Although the microscope is powerful, it is also flexible, which comes in handy when studying different types of materials.

"While initially designed for highest resolution using 300 keV electrons, recent reconfiguration has enabled lower energies (80 and 100 keV) for analysis of beam-sensitive materials such as carbon nanotubes and graphene, and this instrument has supported several recent IR&D projects directed towards carbon-based electronics following a recent initiative of the Aerospace Research and Program Development Office," Foran said.

The JEOL 3100F was a top-of-its-class instrument when purchased in 2006 for $2.4 million, and it has been continuously upgraded and improved to provide more detailed characterizations of mission-critical components.

"We have recently begun electron holography measurements to characterize critical distributions of strain, electrostatic potential, and magnetism at the nanoscale," Foran said. "Further, we have a current IR&D (led by Dr. Matthew Mecklenburg, a recent hire into Foran's group) focused on a quantitative analysis of electrons' time-dependent signals. This analysis could provide an important tool for measuring atomic scale temperatures and lead to a new characterization tool for certain device and component failures."

So the microscope continues to be a useful tool at Aerospace. The TEM, providing information for failure investigations and research assignments, is just one of the many instruments Aerospace uses to support its customers in its dedication to mission success.

Contact Pam Keeton, 703-812-0648 or Pamela.V.Keeton@aero.org.