Multi-Technique Study of Porous Silicon Membranes by Raman Scattering, Ftir, Xps, Aes and Sims

Abstract

Optical and surface analytical techniques of Raman scattering, Fourier transform infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy, Auger electron spectroscopy and secondary ion mass spectrometry have been used to study porous Si membranes with visible light emission. The Raman features from porous Si membranes are markedly distinct from that of crystalline, microcrystalline and amorphous Si. Their anomalous Raman-temperature behavior is explained by the quantum wire model and strain effects. Their FTIR spectra show a large number of infrared active modes due to the oxidized and organized surfaces of the pores. Surface analyses reveal the main components of surface layers to be Si02 plus Si clusters and some contamination elements. The depth distributions of these impurities over the entire 200 [xm thick membrane are determined. The combination of surface and optical analyses offers a better understanding of the properties of porous Si.

Compositional characterisation of metallurgical grade silicon and porous silicon nanosponge particles

“…These peaks are similar to previous XPS analysis of PS. 29 Feng et al has shown that 200 mm thick PS membranes showed similar peak positions to those observed here for the PS and Si particles. 29 Quantification of elements from XPS analysis is given in Table 2 with relative percentage concentrations of F at 2%, C at 28.6%, Si at 60.2%, and O at 9.2% for 2E-100.…”

“…9. The features between 900-1000 cm 21 indicate second order optical modes, 29 as seen in both samples 2E-100 and 2E-60. It has also been shown that surface strain or stress in PS can also contribute to a downshift in the Raman peak as is observed from 2E-bulk Si to 2E-100 in Fig.…”

“…These quantum confined features come from the smallest pore wall structures but particularly from the high density of small ,5 nm crystallites seen by STEM, as outlined in section 3.3. These core Si values do not correlate directly with Si or PS substrates with typical Raman peaks around 521 cm 21 but are more closely linked to the PS membranes studied by Feng et al 29 In that work, Raman spectra of PS membranes removed from anodically oxidised p-type ,100. Si substrates, showed dominant Raman shifts between 502 and 512 cm 21 .…”

“…29,32 A typical Raman spectrum for crystalline Si usually consists of a symmetric first order transverse optical phonon centred at y521 cm…”

“…Si substrates, showed dominant Raman shifts between 502 and 512 cm 21 . 29 The bands located near 300 cm 21 correspond to an acoustic phonon (2TA). These values correlate directly to what is observed for sample 2E-100 in Fig.…”