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Giant Flexoelectricity in Bent Semiconductor Thinfilm
Ya-Xun Wang1,2, Jian-Gao Li1,2, Gotthard Seifert3
1College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875, P.R. China.
Nano Letters
|December 26, 2023
Summary
We discovered a new flexoelectric effect in semiconductors like Silicon and Germanium under high strain. This effect, driven by band gap closure, leads to significant polarization and has potential for new electronic applications.
Area of Science:
- Solid State Physics
- Materials Science
- Semiconductor Physics
Background:
- Flexoelectricity in semiconductors is not well understood, especially under high strain gradients.
- Existing models do not fully explain the observed phenomena in bent semiconductor thin films.
Purpose of the Study:
- To elucidate the mechanism of flexoelectricity in semiconductors under high strain gradients.
- To investigate the role of strain-gradient-induced band gap changes on semiconductor flexoelectricity.
Main Methods:
- Utilized the generalized Bloch theorem to model semiconductor behavior.
- Analyzed thin films of Silicon (Si) and Germanium (Ge) under bending conditions.
Main Results:
- Uncovered a strong flexoelectric-like effect in bent Si and Ge films due to band gap closure induced by high strain gradients.
- Observed an unusual type-II band alignment between compressed and elongated film regions.
- Demonstrated electron transfer from compressed to elongated sides, causing significant polarization changes along the film thickness.
- Reported unexpectedly high transverse flexoelectric coefficients with a quadratic dependence on film thickness.
Conclusions:
- The study reveals a novel mechanism for flexoelectricity in semiconductors driven by strain-gradient-induced band gap closure.
- This mechanism is applicable to other semiconductor materials with moderate energy gaps.
- Findings have significant implications for developing novel semiconductor-based flexoelectric devices.
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