INFRARED-SPECTROSCOPY AND SECONDARY-ION MASS-SPECTROMETRY OF LUMINESCENT, NONLUMINESCENT, AND METAL QUENCHED POROUS SILICON

Porous silicon with varying optical properties (luminescent, nonluminescent, and metal quenched) is investigated by transmission infrared (IR) spectroscopy and secondary ion mass spectrometry (SIMS). SIMS and transmission IR data are presented which show a lack of correlation between the optical properties of similarly prepared luminescent and nonluminescent porous silicon samples and the concentrations of the chemical elements and bonds detected therein. Similar results are obtained for a comparison of IR spectra before and after dissolving the topmost layers (approximately 2000 angstrom) of a luminescent sample in a KOH solution, exposing the nonluminescent porous material below. Finally, IR and SIMS results for luminescent porous silicon quenched by metal ion solutions show a large increase in oxygen after quenching, but it is argued that the increased oxygen is unlikely to be directly responsible for the quenching of luminescence.