Nano characterization of porous silicon by transmission electron microscopy

Abstract

Although the exact origin of luminescence is still controversial, the proposed mechanisms prevalent in the literature are centred around the quantum size effects in very small silicon crystallites which constitute the porous silicon skeleton. To date Luminescent Porous Silicon (LPS) is known to be a very disordered material containing both crystalline and non crystalline domains and networs of pores. Preparation conditions (in particular the porosity level) greatly influence the proportion of crystalline / non crystalline phase ratio. In all cases crystallite with size at the nanometer scale (< 100 Å) are observed. Although no direct correlation has been established so far between the microstructure and the luminescence properties of LPS it is generally accepted that the crystallites features (dimensions, densities ...) play a vital role in luminescence and should be characterized at the nanometer scale.