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Giant and Controllable Photoplasticity and Photoelasticity in Compound Semiconductors
Jiahao Dong1, Yifei Li1, Yuying Zhou1,2
1Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Physical Review Letters
|August 26, 2022
Summary
Wide-band gap semiconductors like ZnO exhibit significant photoplastic and photoelastic effects due to point defects. Illumination dramatically alters their mechanical properties, offering tunable optomechanical applications.
Area of Science:
- Materials Science
- Solid State Physics
- Optomechanics
Background:
- Wide-band gap compound semiconductors (ZnO, ZnS, CdS) are crucial in various electronic and optical applications.
- Existing research on semiconductor optomechanics is limited, particularly concerning defect-mediated effects on mechanical properties.
Purpose of the Study:
- To investigate and quantify the photoplastic and photoelastic effects in ZnO, ZnS, and CdS.
- To elucidate the role of point defects in mediating these optomechanical phenomena.
- To develop a theoretical framework for understanding defect ionization's impact on semiconductor elasticity.
Main Methods:
- Nanoindentation was used to measure mechanical properties (elasticity, plasticity) of semiconductor ceramics and single crystals.
- Variable illumination conditions (band-gap, sub-band gap, UV light) were applied to assess their influence.
- Density functional theory (DFT) calculations were employed to model point defect ionization and its effect on elastic tensors.
Main Results:
- ZnO, ZnS, and CdS demonstrate substantial photoplastic and photoelastic responses to illumination.
- Elastic stiffness of ZnO increased by over 40% under blue light (1.4 mW/cm²).
- Optomechanical effects were tunable via materials processing, linked to point defect equilibrium.
Conclusions:
- Point defects are key mediators of large photoplastic and photoelastic effects in wide-band gap semiconductors.
- A new theoretical framework using DFT successfully explains photoelastic effects driven by point defect ionization.
- These findings advance semiconductor optomechanics and suggest novel applications.
