Multiphoton Excited Singlet/Triplet Mixed Self-Trapped Exciton Emission: Experimental Details

Experimental Section

Sample Preparation

Samples were prepared by chemical vapor deposition (CVD) growth on Si(100) substrates. For experimental purposes, samples were divided into two groups: untreated and heat-treated. Heat treatment was conducted in a nitrogen atmosphere at 700ﾰC for 30 minutes.

Laser System

A tunable Ti:Sapphire laser system was employed, operating at a wavelength of 800 nm with a pulse width of 150 fs and a repetition rate of 1 kHz.

Spectroscopic Measurements

The laser beam was focused onto the sample using an optical system. The excitation intensity was 2ￗ10^13 W/cm^2. Emitted light from the sample was collected and dispersed using a grating before being detected by a photodiode detector.

Time-Resolved Spectroscopy

Time-resolved spectroscopy was performed using a modified liquid nitrogen-cooled CCD camera. The laser beam was focused onto the sample using an optical system. The excitation intensity was 2ￗ10^13 W/cm^2. Emitted light from the sample was collected and dispersed using a grating before being detected by the camera. The camera has a time resolution of 150 fs.

Results

Multiphoton excited self-trapped exciton emission was observed. In untreated samples, both singlet and triplet emission peaks were detected. In heat-treated samples, only singlet emission peaks were observed. Time-resolved spectroscopic measurements revealed a full width at half maximum (FWHM) of approximately 200 fs for the emission peaks, indicating a short lifetime for the self-trapped excitons.

Conclusion

This study successfully observed multiphoton excited self-trapped exciton emission and identified both singlet and triplet emissions. The presence of only singlet emission in heat-treated samples suggests that heat treatment can reduce the production of triplet states. Time-resolved spectroscopic measurements indicate a short lifetime for the self-trapped excitons. These findings have significant implications for furthering our understanding of the behavior and applications of multiphoton excited self-trapped excitons.