A team of physicists and chemists has discovered a previously unknown way in which light interacts with matter. The discovery could lead to advances in solar power systems, light-emitting diodes, semiconductor lasers, and other technologies.
Harintsev other. They discovered that when photons are confined to nanometer-scale spaces within silicon, they can gain significant momentum, similar to electrons in solid materials. Image credit: Kharintsev other.
“Silicon is the second most abundant element on Earth and is the backbone of modern electronics,” said Dr. Dmitry Fishman, a chemist at the University of California, Irvine.
“However, as an indirect semiconductor, its use in optoelectronics has been hampered by poor optical properties.”
“Silicon does not spontaneously emit light in its bulk state, but the porous, nanostructured silicon produces detectable light after being exposed to visible light.”
Scientists have been aware of this phenomenon for decades, but the exact origins of illumination have been the subject of debate.
“In 1923, Arthur Compton discovered that gamma photons have enough momentum to interact strongly with free or bound electrons,” Dr. Fishman said.
“This helped prove that light has both wave and particle properties, a discovery for which Compton was awarded the Nobel Prize in Physics in 1927.”
“Our experiments showed that the momentum of visible light confined in nanoscale silicon crystals causes similar optical interactions within semiconductors.”
To understand the origins of interaction, we need to go back once more to the early 20th century.
Indian physicist CV Raman, who won the Nobel Prize in Physics in 1930, attempted to recreate the Compton experiment in 1928 using visible light.
However, they encountered a formidable obstacle: the large difference between the momentum of an electron and the momentum of a visible photon.
Despite this setback, Raman studies of inelastic scattering in liquids and gases have led to the elucidation of what is now recognized as the vibrational Raman effect, and spectroscopy, an important method for the spectroscopic study of materials, has been linked to Raman scattering. became known as.
“The discovery of photon momentum in disordered silicon is due to a type of electron Raman scattering,” said Professor Eric Potoma of the University of California, Irvine.
“However, unlike traditional vibrational Raman, electronic Raman involves different initial and final states of the electron, a phenomenon that has previously only been observed in metals.”
For the experiment, the researchers created silicon glass samples in the lab that ranged in transparency from amorphous to crystalline.
They illuminated a 300-nm-thick silicon film with a tightly focused continuous-wave laser beam and scanned it to write an array of straight lines.
In regions where the temperature did not exceed 500 degrees Celsius, this procedure resulted in the formation of homogeneous cross-linked glasses.
In the region where the temperature exceeded 500 degrees Celsius, a non-uniform semiconductor glass was formed.
This lightly foamed film allowed scientists to observe how electronic, optical, and thermal properties change on the nanometer scale.
“This study challenges our understanding of light-matter interactions and highlights the important role of photon momentum,” Dr. Fishman said.
“In disordered systems, the matching of electron and photon momentums amplifies the interaction, which was previously associated only with high-energy gamma photons in classical Compton scattering.”
“Ultimately, our work moves traditional optical spectroscopy, such as conventional vibrational Raman spectroscopy, beyond its typical use in chemical analysis to the realm of structural studies, where it can be closely linked to the momentum of photons. This opens the door to expanding the information that is needed.”
“This newly realized optical property will definitely open up new areas of application in optoelectronics,” Professor Potoma said.
“This phenomenon will increase the efficiency of solar energy conversion devices and light-emitting materials, including materials that were previously considered unsuitable for emitting light.”
Regarding this research, paper in a diary ACS nano.
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Sergey S. Harintsev other. 2024. Electron Raman scattering using photon momentum in silicon glass. ACS Nano 18 (13): 9557-9565
Source: www.sci.news
