Synopsis

Semiconductors in the Spotlight

Physics 15, s102
A new model suggests that lattice defects are responsible for the way some semiconductors become harder under illumination.
J. Dong/MIT

Understanding how semiconductors respond to illumination has been crucial to the development of photovoltaics and optical sensors. But some light-induced behaviors have been less thoroughly investigated. For example, when some semiconductors are illuminated, their mechanical properties can change drastically, a phenomenon known as photoelasticity. Photoelastic materials could be useful in the development of flexible electronics, but researchers do not understand in detail the mechanism behind the effect. Now, based on experiments and simulations, Rafael Jaramillo of the Massachusetts Institute of Technology and colleagues present a new theoretical framework that explains photoelasticity in terms of lattice defects [1].

The researchers used a diamond-tipped probe to make nanometer-scale indentations in samples of zinc oxide, zinc sulfide, and cadmium sulfide—first in the dark, and then under a range of visible and ultraviolet wavelengths. All three materials hardened to varying degrees when illuminated, with cadmium sulfide showing the largest and most consistent response. For every sample, the effect increased as the photon energy increased toward the material’s band gap.

The team then modeled multiple unit cells of each material, looking specifically at the effect of lattice vacancy defects. These defects make the material softer, as they cause atoms in the lattice to experience, on average, less repulsion from their neighbors. Upon illumination, however, atoms around the vacancy site become excited, increasing their mutual repulsion and causing the material to stiffen. Jaramillo and colleagues found that they could tune a material’s illumination response by varying the number of defects in the lattice. They say that their discovery could lead to the identification of materials whose photoelasticity is more pronounced or more easily manipulated.

–Sophia Chen

Sophia Chen is a freelance science writer based in Columbus, Ohio.

References

  1. J. Dong et al., “Giant and controllable photoplasticity and photoelasticity in compound semiconductors,” Phys. Rev. Lett. 129, 065501 (2022).

Subject Areas

Condensed Matter PhysicsMaterials ScienceSemiconductor Physics

Related Articles

Thermal Conductivity Not Too Hot to Handle
Materials Science

Thermal Conductivity Not Too Hot to Handle

A radiometry technique directly measures thermal conductivity in molten metals and confirms the relationship with electrical resistivity. Read More »

Probing Liquid Water’s Structure with Attosecond X-Ray Pulses
Condensed Matter Physics

Probing Liquid Water’s Structure with Attosecond X-Ray Pulses

Using an ultrafast technique, researchers shed light on how the hydrogen-bonded structure of water is reflected in its x-ray spectrum. Read More »

A Counterintuitive Set of Tunneling Effects Observed at Last
Particles and Fields

A Counterintuitive Set of Tunneling Effects Observed at Last

Graphene is the setting for the first demonstration of relativistic electrons’ paradoxical ability to whiz through a barrier, provided the barrier is high enough. Read More »

More Articles