Credit: Institute of Industrial Science, The University of Tokyo
Researchers from Japan have developed a novel microscopy technique that utilizes evanescent waves to reveal details on an object's surface. The technique can reveal details such as the lattice and electron temperature of a material with nanoscale precision.
Evanescent waves do not transport energy and can be created when light interacts with the surface or they can be thermally generated. Localized heat fluctuations can also be used to create evanescent waves and the passive detection of these waves is key to the new microscopy technique.
“Scanning near-field optical microscopy, using scattered electromagnetic radiation, is one of the most commonly used techniques for examining material properties at the nanoscale level,” said lead author Ryoko Sakuma. “Our new technique uses passive detection of the radiation emitted by the object itself, so the surface doesn’t need any illumination.”
In the research, published in Scientific Reports, the researchers examined the thermally generated evanescent waves of aluminum nitride and gallium nitride. The weak scattering of the waves was visible within an absorption band called the Reststrahlen band, this was the first time this phenomenon was visible without light exposure. Their analysis showed that only the polariton waves exist in the Restshrahlen band, despite the previous belief that large amounts of thermal fluctuations would accompany the polariton waves.
“Our instrument is the only one in the world capable of observing nanoscale temperature distributions on surfaces using terahertz wavelengths.” said senior author Yusuke Kajihara. “This microscope technology is completely new, so we’re still learning specifically how and where it can be applied.”