Papers by Keyword: Femtosecond Laser Processing

Abstract: This paper investigates the influence of different number of laser pulses on contact behavior and conductivity of the surface layer of femtosecond laser microstructured, sulfur-doped silicon. Single shot laser processed silicon (Pink Silicon) is characterized by low surface roughness, whereas five shot laser processed silicon (Grey Silicon) has an elevated sulfur content with a surface roughness low enough to maintain good contacting. To laterally confine the laser induced pn-junction part of the Grey Silicon sample surface is etched off. The etching depth is confirmed to be sufficient to completely remove the active n-type sulfur layer. While Pink Silicon shows little or no lateral conductivity within the laser processed layer, Grey Silicon offers acceptable conductivity, just as expected by the fact of having incorporated a higher sulfur dopant content. Recombination dominates the irradiated regions of Pink Silicon and suppresses excess charge carrier collection. Grey Silicon, while showing sufficient lateral conductivity, still shows regions of lower conductivity, most likely dominated by the laser irradiation-induced formation of dislocations. According to our results, the optimum laser pulse number for electrical and structural properties is expected to be in the range between one and five laser pulses.

Abstract: We modify optical and wetting properties of solids using a femtosecond laser surface nanostructuring technique. We demonstrate that this technique allows creating black and color metals. Absorptance of black titanium created in our study is measured to be about 90-97% over a broad wavelength range from the ultraviolet to infrared. Moreover, our technique can be also used for modifying wetting properties of solids. Here, we create a novel surface structure that transforms regular silicon to superwicking. This surface structure makes water run vertically uphill in a gravity defying way. Our study of the liquid motion shows that the extraordinarily strong self-propelling motion of water is due to a capillary effect from the surface structures we created.