Photoluminescence of spark-processed metals Original Research Article

The photoluminescence (PL) properties of spark-processed (sp) metals were systematically investigated. It was found that spark-processing of Cr, Cu, Fe, Mg, and Mn essentially yielded no PL at room temperature in the visible spectral range. In contrast, sp-Ti, Ta, Al, Ni, Mo, and Zn showed strong PL, which is in many respects comparable to sp-Si. It was further found that the PL intensity of the sp metals depends exponentially on the nitrogen concentration, which is contained in the spark-processing ambient (along with oxygen). This behavior was also found for sp-Si. In contrast, the PL intensities for native oxides (containing essentially no nitrogen) is several orders of magnitude smaller than those for sp-metals and the respective PL peaks are situated at higher energies. The results are discussed in the light of the self-trapped exciton model.