X-ray investigation of porous silicon under angles of grazing incidence and exit

Abstract Porous silicon (PS) was prepared from p-type Si wafers (1–5Ωcm) by electrochemical etching at 50mA/cm 2 . The in-plane microstructure of PS was investigated by X-ray diffraction under grazing incidence and exit (GID). In the as-etched sample we find the shape of the (220) Bragg peak to consist of two components which have the same Bragg angles, both corresponding to the lattice parameter of crystalline Si. There is a very sharp reflection with a width of the instrumental resolution and a second peak which is about 30 times broader. In explanation of these features we propose a structural model for PS in which the Si particles have crystalline cores which are coherently connected to each other and to the Si substrate. After rapid thermal oxidation (RTO) of PS only the sharp line remains, showing that the coherent matrix of small particles survived the oxidation. From other investigations it is known that RTO PS still shows photoluminescence.