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Optical manipulation of work function contrasts on metal thin films
Sai Kishore Ravi1, Wanxin Sun2, Dilip Krishna Nandakumar1
1Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117574, Singapore.
Science Advances
|March 8, 2018
Summary
Researchers discovered a new method to adjust the work function of metals using light intensity, not chemicals. This optical modulation technique offers a novel way to control charge transport in optoelectronic devices.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Optoelectronics
Background:
- Work function is critical for optoelectronic device performance.
- Limited stable conductive materials exist for specific work function ranges.
- Existing work function modulation methods are primarily chemical.
Purpose of the Study:
- Introduce a novel optical modulation approach for work function adjustment.
- Investigate light intensity-dependent work function changes in metal-semiconductor systems.
- Demonstrate a new phenomenon contradicting previous work function theories.
Main Methods:
- Coating metallic thin films (Au, Pt, W) onto n-type silicon (n-Si).
- Modulating the work function by varying light intensity.
- Testing the phenomenon in Au/n-Si, Pt/n-Si, and W/n-Si systems.
Main Results:
- Observed a light intensity-dependent change in work function, previously considered light-independent.
- Achieved a 0.22 eV work function shift in Pt/n-Si by tuning illumination from 0 to 18 mW/cm².
- Demonstrated continuous work function tuning and in-plane charge transport via selective illumination.
Conclusions:
- Optical modulation provides a viable alternative to chemical methods for work function control.
- This discovery enables precise tuning of work functions with limited materials.
- Selective illumination creates work function contrast, impacting optoelectronic device design and function, including directional photodetectors.
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