Standord researchers have created a technique that could be used to develop high-efficiency solar cells. Source: YouTube/Stanford
Engineers have developed a technique that allows them to visualize the optical properties of objects smaller than a mere grain of sand – in 3D. What`s even more impressive: the images are in nanometer-scale resolution. This technique, called cathodoluminescence topography, could lead to the development of high-efficiency solar cells.
The researchers at Stanford and AMOLF (a research laboratory in the Netherlands) relied on two technologies: cathodoluminescence and tomograph. The engineers tested their technique on a 250-nanometer gold-coated crescent, which was significantly thinner than human hair. The team initially used a modified scanning electron microscope. The cathodoluminescence process occurred once the electron beam passed through the object and energetically excited the crescent, which in turn led it to emit photons.
Creating a 2D image
The photons` intensity and wavelength varied depending on which part of the object was excited by the electron beam. For instance, the gold shell at the base emitted different photons than the tip of the crescent. The engineers were able to create a 2D image by continuously scanning the beam over the object. This technique allowed the researchers to understand the ways in which light interacted with the nanometer-scale object.
"Interpreting a 2-D image, however, can be quite limiting," researcher Ashwin Atre said in a statement. "It's like trying to recognize a person by their shadow. We really wanted to improve upon that with our work."
Re-scanning the nanocrescent
In order to create a 3D image, Atre and his team tilted the nanocrescent and then rescanned it. They did this in order to obtain 2D emission data at multiple angles, thus allowing them to hone in on the approximate optical signal location. The process is similar to the way 2D x-ray images transform into 3D CT images.
The engineers ultimately succeeded at creating a 3D map of the object`s optical properties. "This work could enable a new era of 3D optical imaging with nanometer-scale spatial and spectral resolution," said Jennifer Dionne, an assistant professor of materials science and engineering at Stanford.
The researchers say their technique has many applications. "It has applications for testing various types of engineered and natural materials," Atre explained. "For instance, it could be used in manufacturing LEDs to optimize the way light is emitted, or in solar panels to improve the absorption of light by the active materials."
Source: Stanford