Plasma-etching fabrication and properties of black silicon by using sputtered silver nanoparticles as micromasks

A nanohill structure has been fabricated on a silicon surface via a micromask formed by a radio-frequency magnetron sputtering deposition of silver nanoparticles and a following dry etching under SF6 plasma. The proposed technique does not rely on oxygen gas to eliminate the damages from oxygen plasma and to increase the lifetime of the silicon crystal. The experiments indicate that the morphology and particle size distribution of silver nanoparticles determine the reflectivity of the textured silicon wafer. Interestingly, the nanohill structure exhibits a stronger light confinement ability than the columnar one, leading to a lower reflectivity. A longer minority carrier lifetime is obtained in such nanohill structures with a lower defect concentration on the surface. This work provides a pathway to fabricating black silicon of excellent light confinement structure, which may have potential for applications in some localized surface plasmons-relevant areas.