Diamonds are forever and they are a girl’s best friend. They are also among a class of materials known as ultrawide-bandgap semiconductors. These are seen as a key component of next-generation electronics as they can handle higher voltages, operate at higher frequencies, and are more efficient than traditional silicon designs. One issue, however, is that how electric charges and heat move in diamonds is poorly understood. Now, scientists have developed a laser-based microscope that allowed them to study this at an unprecedented scale.
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Diamonds and similar materials have the quality to be transparent in visible and infrared light. To study the motion of particles in them, a more energetic form of light was required: ultraviolet light. The team had to devise a way to build a tabletop deep ultraviolet laser that would deliver the required energy and precision. It needed to generate nanoscale heat patterns on a material surface without altering the material itself.
To do so, the team started with a near-infrared laser with a light wavelength of 800 nanometers (just at the edge of our vision). They shined it through non-linear crystals and changed its energy so that it reached shorter and shorter wavelengths, eventually getting to the deep ultraviolet (200 nanometers). The team had to go through a trial-and-error process of aligning light through three successive crystals, to achieve the hoped results.
“We brainstormed a new experiment to expand what our lab could study,” lead author Emma Nelson, from the University of Colorado Boulder, said in a statement. “It took a few years to get the experiment working during the pandemic, but once we had the setup, we could create patterns on a scale never before achieved on a tabletop.”
The team used two beams to create a diffraction grating on the surface of the material. The wavelength is so small that it gives the nanoscale precision needed for the observations. They were indeed able to measure how heat, electrons, and mechanical waves move through materials like gold and diamonds, verifying the observations with computer simulations.
“Seeing the experiment work and align with the models we created was a relief and an exciting milestone,” Nelson added.
The team discovered that at the nanoscale heat transportation is not a smooth continuous flow, but it can be ballistic behavior or have some hydrodynamic effects. This means that it can move in a straight line without scattering or spreading like water flowing through channels.
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The team is now planning to improve the laser microscope further and study even more material that might feature in the next-generation electronics.
The study is published in Physical Review Applied.
Source Link: Powerful Ultraviolet Laser Reveals How Particles Move Through Diamonds
