NEAR INFRARED PHOTOLUMINESCENCE OF THE HYDROGENATED AMORPHOUS SILICON THIN FILMS WITH IN-SITU EMBEDDED SILICON NANOPARTICLES

Abstract

The intrinsic hydrogenated silicone layers with embedded silicon nanoparticles were grown in-situ at 250°C on glass substrates by the radio frequency plasma enhanced chemical vapor deposition (CVD) from silane highly diluted in hydrogen. The changes in the optical absorption coefficient were detected by the photothemal deflection spectroscopy (PDS). The transition from amorphous to crystalline phase for samples deposited at 5−6% silane concentration correlates to the crystalline volume fraction about 50% as detected by Raman spectroscopy and the high resolution transmission electron microscopy (HRTEM). The room temperature photo-luminescence increases significantly with increased crystallinity volume fraction but diminishes abruptly when crystallinity volume fraction exceeds above 80%. The photoluminescence intensity strongly correlates with the presence of isolated silicon nanoparticles in the mixed amorphous and crystalline phase. The strongest photoluminescence was found in the sample with mixed phase of amorphous matrix and isolated silicon nanoparticles and the crystalline volume fraction about 50%.

Keywords

• Amorphous silicon
• Chemical vapor deposition
• Photothermal deflection spectroscopy