Surface Modification of Silicon with Picosecond Laser Pulses in Air

We report the observation of laser-induced surface modification of silicon in air using Nd: YAG picosecond ( ps ) pulsed laser irradiation. The n-type (100) silicon wafers exposed to laser fluence levels of 1 to 5 J/cm2. Below the laser fluence level of 1.3 J/cm2 no significant change in the surface morphology is observed. The formation of microstructures occurs at high number of laser pulses (~5000) at laser fluence of 1.3-1.5 J/cm2. The microstructures are cones which grew toward the laser beam and surrounded by deep holes. The ps-formed microstructures are roughly 10 μm tall and separated by 5 μm in the center of the irradiation spot. Nanocolumns (or Nanodroplets) are formed on top of every cone of the laser-induced microstructures surface, reaching a height of ~1 μm and diameter of 100−250 nm. At higher applied laser fluence levels (above 1.5 J/cm2), no conical spikes formed and ablated hole with smooth surface is obtained. We will discuss on the possible mechanism underlying these experimental observations.

کلیدواژه ها:

Surface modification of solids ، conical microstructure ، picosecond pulse ، silicon