Intense blue-light emission from carbon-plasma-implanted porous silicon

We have investigated the room-temperature photoluminescence (PL) characteristics of porous-silicon plasma implanted with carbon. Before implantation, the porous silicon made by anodizing emits intense orange light. After carbon-plasma-immersion ion implantation, the orange light disappears and blue light appears. Furthermore, intense blue light is obtained after annealing at 400 °C for 30 min. Analytical results show that the quenching of orange light and appearance of blue light are due to the reduction of the size of nanocrystallites caused by implantation. The effects of different annealing temperature on the light-emission properties of the implanted porous silicon are also studied. The intensity decreases with increased temperature from 600 to 1000 °C, but the PL intensity increases drastically again after annealing at 1250 °C due to the formation of a substance.