tailieunhanh - Báo cáo hóa học: " Optical characterisation of silicon nanocrystals embedded in SiO2/Si3N4 hybrid matrix for third generation photovoltaics"

Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Optical characterisation of silicon nanocrystals embedded in SiO2/Si3N4 hybrid matrix for third generation photovoltaics | Di et al. Nanoscale Research Letters 2011 6 612 http content 6 1 612 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Optical characterisation of silicon nanocrystals embedded in SiO2 Si3N4 hybrid matrix for third generation photovoltaics Dawei Di Heli Xu Ivan Perez-Wurfl Martin A Green and Gavin Conibeer Abstract Silicon nanocrystals with an average size of approximately 4 nm dispersed in SiO2 Si3N4 hybrid matrix have been synthesised by magnetron sputtering followed by a high-temperature anneal. To gain understanding of the photon absorption and emission mechanisms of this material several samples are characterised optically via spectroscopy and photoluminescence measurements. The values of optical band gap are extracted from interference-minimised absorption and luminescence spectra. Measurement results suggest that these nanocrystals exhibit transitions of both direct and indirect types. Possible mechanisms of absorption and emission as well as an estimation of exciton binding energy are also discussed. Keywords silicon nanocrystals third generation photovoltaics absorption coefficient photoluminescence band gap extraction Background Self-assembled silicon nanocrystals Si NCs embedded in a dielectric matrix are believed to be a promising material for applications in optoelectronics 1-3 and photovoltaic solar cells 4-10 . One major advantage of Si nanocrystals over bulk Si is the freedom to engineer the material s effective band gap by varying the size of the Si NCs or by modifying the properties of the matrix material. A simple method of fabricating SiO SiO2 superlattice or Si NCs in SiO2 matrix was described by Zacharias et al. 11 . The optical absorption properties of this kind of superlattices were investigated by a number of groups 12-14 . Photovoltaic diodes fabricated using similar approaches have been demonstrated by some of the present authors 5 6 . Their limitations include high device resistivity .