Electron spectroscopy of porous silicon layers. Indirect detection of hydrogen by elastic peak electron spectroscopy

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Abstract
Efficient visible luminescence from porous Si (PSi) layers is associated with the quantum size and the presence of hydrogen as a passivaant on the inner surface. The increase of the amount of H was performed by wet chemical etching in HF, producing the increase of photoluminescence intensity. The detection of H is not possible by AES or XPS and is difficult even with EELS. Elastic peak electron spectroscopy (EPES) showed a large decrease of the elastic reflection coefficient re appearing in the elastic peak, and measured with a retarding field analyser (RFA). The effective elastic backscattering coefficients of a monolayer of H, Si, O were calculated for the RFA angular window and resulted in reasonable agreement with literature data available. They were completed for the 50–100 eV range. Experiments on a Si(111) wafer verified calculations. A dramatic decrease of re was found on HF‐etched PSi (a factor of 3–10) in the 50–100 eV range. Above 200 eV, effects are shadowed by the contribution of deeper layers of the substrate and reduced attenuation of the H adlayer. This indicates the formation of high H coverage on the porous inner surface. Experiments are interpreted by multiple elastic reflection and attenuation of electrons by the H‐covered porous surface. Detailed AES and EELS studies made with a hemispherical analyser resulted in Si and SiO2 bond on the surface.