Seeing Nanoscale Objects in 3-D: Is It Possible?

A new imaging technique could serve as the foundation for the next generation of optical devices.

Kristopher Sturgis

The ability to image objects in three dimension at the nanoscale level could help researchers understand how light interacts on the microscale. This has been unattainable through traditional imaging techniques because, the smaller an object gets, the lower the resolution becomes in 3-D.

Engineers from Stanford University, however, have developed a technique that they believe will make it possible to visualize the optical properties of objects several thousandths the size of a grain of sand. The work, which was accomplished in tandem with researchers from a lab in the Netherlands, was devised to improve how we observe light interactions at the nanoscale level, according to the university.

The method involves a combination of two technologies, cathodoluminescence and tomography, which enable the generation of 3-D maps that detail the optical landscape of objects. A concept that was tested by imaging a gold-coated crescent 250 nm in diameter -- several hundred times as thin as a human hair.

In an attempt to study the optical properties of the crescent, the group first imaged it using a modified scanning electron microscope. As the focused electron beam passed through the crescent, it excited the object energetically, causing it to emit photons in a process known as cathodoluminescence. By scanning the beam back and forth over the object, the engineers were able to create a 2-D image of these optical properties.

This 2-D cathodoluminescence spectral imaging technique pioneered by the team, revealed the characteristic ways in which light interacts with this nanometer-scale object. However, the group revealed that interpreting the 2-D image can still be quite limiting. So in an effort to push the technique into the third dimension, the engineers began tilting the nanocrescent, rescanning it and collecting 2-D emission data at a number of different angles.

The group was eventually able to combine this tilt-series of 2-D images to create a 3-D map of the object's optical properties, much like how 2-D x-ray images of a human body are stitched together to produce a 3-D CT image. Until now, techniques that image light-matter interactions have been limited to two dimensions. The group believes that their proof-of-concept could enable a new era of 3-D imaging with nanometer-scale spatial and spectral resolution.

Last year researchers from Rice University created one of thinnest ever imaging platforms through the use of copper indium selenide.

The efforts of the Rice and Stanford scientists could also help us improve the way we image, study, and understand biological systems at the molecular level.

While the proof-of-concept is encouraging, the prospect of imaging and scaling nanometer-sized objects in 3-D with high resolution is still more of a goal. Potential applications could range from improving solar panel and LED technology to enhancing medical imaging.

Kristopher Sturgis is a contributor to Qmed and MPMN.

Like what you're reading? Subscribe to our daily e-newsletter.