X-ray absorption spectroscopy on light emitting porous silicon by XEOL and TEY

Abstract

This paper presents an experimental investigation of the local structure of porous silicon based on X-ray absorption fine structure by two different techniques: Total electron yield (TEY) and X-ray excited optical luminescence (XEOL). The influence of the main parameters of sample preparation on both the photoluminescence and the local structure around Si atoms has been investigated. The dependence of the optical emission energy on the current density shows a saturation limit. The analysis of both the optical emission and the short range order (up to the third coordination shell) confirms the presence of crystalline cores on a scale of a few nanometers in freshly prepared porous silicon samples. Although the local structural parameters obtained by TEY are similar to those reported in recent X-ray absorption studies, a direct connection between optical emission energy and short range order has not always been found. In particular, while the role of HF concentration in determining optical and microstructural properties is clear, a change of current density affects the energy shift of the X-ray excited optical band but not the short range order properties monitored by TEY.