Porous silicon and siloxene: Vibrational and structural properties

Using Raman and infrared transmission spectroscopy, the vibrational properties of siloxene (${\mathrm{Si}}_6$ ${\mathrm{O}}_3$ ${\mathrm{H}}_6$) and its derivatives are investigated and interpreted in terms of various structural modifications of siloxene which have been proposed in the past. On the basis of experimental and theoretical investigations siloxene is found to be a mixture of ${\mathrm{Si}}_6$ rings and/or linear Si chains interconnected by oxygen, and Si planes terminated by H and OH. The influence of thermal annealing, chemical treatment, and laser irradiation on the structure of siloxene is discussed in terms of the corresponding changes of the vibrational spectra and the x-ray-diffraction patterns. The vibrational properties of siloxene are very similar to those of electrochemically anodized porous Si. Raman, infrared transmission, and photoluminescence measurements of the two classes of materials are compared and a possible mechanism for the efficient luminescence in porous Si is discussed in light of the similarities between siloxene and porous Si.