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Time-dependent second-harmonic generation from the Si-SiO(2) interface induced by charge transfer
Optics Letters
|October 29, 2009
Summary
The second-harmonic signal from oxidized silicon varies over seconds due to third-harmonic light absorption. This absorption causes charge transfer and trapping in the oxide layer, with detrapping taking minutes.
Area of Science:
- Solid-state physics
- Surface science
- Optoelectronics
Background:
- Oxidized silicon (Si-SiO2) is a fundamental material in semiconductor technology.
- Second-harmonic generation (SHG) is a sensitive probe of surface and interface properties.
- Understanding charge dynamics at the Si-SiO2 interface is crucial for device performance.
Purpose of the Study:
- To investigate the temporal dynamics of the second-harmonic signal from oxidized Si(001).
- To elucidate the underlying physical mechanisms responsible for the observed signal variations.
- To characterize the charge transfer and trapping processes at the Si-SiO2 interface.
Main Methods:
- Time-resolved second-harmonic generation (SHG) measurements.
- Utilized ultrashort laser pulses (770 nm, 110 fs, 76 MHz).
- Investigated the influence of weak third-harmonic light generated in situ.
Main Results:
- Observed temporal variations in the SHG signal on a timescale of seconds.
- Identified absorption of weak third-harmonic light as the cause of these variations.
- Determined that charge transfer and trapping in the oxide layer induce the signal change, with detrapping requiring minutes.
Conclusions:
- The temporal behavior of SHG from oxidized Si(001) is linked to photoinduced charge dynamics.
- Third-harmonic generation, even at low power, significantly impacts interfacial charge states.
- The Si-SiO2 interface exhibits slow charge trapping and detrapping dynamics relevant to optical measurements.
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