UNIVERSITY PARK, Pa. — Newly achieved precise control over light emitted from incredibly tiny sources, a few nanometers in size, embedded in two-dimensional (2D) materials could lead to remarkably high-resolution monitors and advances in ultra-fast quantum computing, according to an international team led by researchers at Penn State and Université Paris-Saclay.
In a recent study, published in ACS Photonics, scientists worked together to show how the light emitted from 2D materials can be modulated by embedding a second 2D material inside them — like a tiny island of a few nanometers in size — called a nanodot. The team described how they achieved the confinement of nanodots in two dimensions and demonstrated that, by controlling the nanodot size, they could change the color and frequency of the emitted light.
"If you have the opportunity to have localized light emission from these materials that are relevant in quantum technologies and electronics, it's very exciting,” said Nasim Alem, Penn State associate professor of materials science and engineering and co-corresponding author on the study. “Envision getting light from a zero-dimensional point in your field, like a dot in space, and not only that, but you can also control it. You can control the frequency. You can also control the wavelength where it comes from."
The researchers embedded nanodots made of a 2D material called molybdenum diselenide inside another 2D material, tungsten diselenide, and then aimed a beam of electrons at the structure to make it emit light. This technique, called cathodoluminescence, allowed the team to study how individual nanodots in the material emit light at high resolution.
“By combining a light detection tool with a transmission electron microscope, which is a powerful microscope that uses electrons to image samples, you can see much finer details than with other techniques,” said Saiphaneendra Bachu, first author who served as the primary doctoral student on the study before earning a doctorate from Penn State in 2023 and is now a TEM analysis engineer at Samsung Austin Semiconductor. “Electrons have tiny wavelengths, so the resolution is incredibly high, letting you detect light from one tiny dot separately from another nearby dot."
They found that larger dots give off one type of glow, while smaller dots produce another. When the dots are extremely tiny — less than 10 nanometers wide, which is about the size of 11 hydrogen atoms arranged in a line — they behave in a unique way, trapping energy and emitting light with higher frequency, which equates to a smaller wavelength.