We present initial results on the modification of silicon surfaces via the combination of ion-beam implantation and subsequent ultrafast-laser irradiation. Femtosecond laser pulses provide a qualitatively different laser-material interaction than is obtained with longer laser pulses. In particular, a much more deterministic surface modification threshold behavior is achieved. A number of avenues are being pursued in this thrust. The dependence of the single-shot laser ablation threshold of Si on the ion irradiation fluence is being investigated. Experiments on the damage and potential annealing effects from multiple sub-damage-threshold laser pulses on pristine and ion-irradiated samples are also a part of this study. In addition, ultrashort laser pulses have been shown to generate sub-wavelength coherent nanostructures (see e.g., [1]), and we plan to determine the effects of ion implantation on this mechanism of nanostructuring. In a broader context of surface texturing, we will use femtosecond laser irradiation in conjunction with ion implantation to alter the optical absorption and emission properties of silicon surfaces. Initial results have shown an effect and we aim to greatly extend the parameter space of these experiments. Finally, through transmission electron microscopy investigations of focused ion beam prepared cross-sectional specimens, we plan to study the final state of a variety of irradiated samples. The authors would like to acknowledge NSERC for financial support.

[1] T. H. R. Crawford, G. A. Botton and H. K. Haugen, Crystalline orientation effects on conical structure formation in femtosecond laser irradiation of silicon and germanium, Appl. Surf. Sci. 256, 1749 (2010)