Effects of zinc capping layers and annealing on the properties of porous silicon

Porous silicon (PS) was prepared by using electrochemical anodization. Ultra-thin zinc layers were deposited on the PS by using plasma-assisted molecular beam epitaxy (PA-MBE). The effects of the zinc capping layers and annealing on the properties of the PS were investigated by using scanning electron microscopy (SEM) and photoluminescence (PL). The as-prepared PS has fissure-like pores over the entire surface. The irregular and randomly distributed nanosized pores became circular after deposition of zinc layers with a thickness of 120 Å. As the annealing temperature was increased to 600 °C, the diameter of the circular shaped pores increased. However, the contours of the circularshaped pores on the surface of the PS capped with the ultra-thin zinc layers (ZPS) became blurred slightly by further increases in the annealing temperature. The ZPS exhibited a higher intensity and an enhanced photostability of the red emission peak compared with conventional PS. The size and the number of the circular-shaped pores on the surface of the ZPS were increased by annealing, leading to increases in the intensities and the full width at half maximums and the redshifts of the emission peaks. Moreover, the annealing temperature of 600 °C was the most suitable for enhancing the luminescent intensity of the ZPS.