The cathodoluminescence from porous or thermally oxidized porous material was investigated by using X-ray spectroscopic and photoluminescence techniques. Two predominant cathodoluminescence bands were observed, at 460nm (2.7eV) and 650nm (1.9eV), respectively. These were not observed in the photoluminescence spectrum. It was found that electron-beam irradiation caused degradation and/or an increase in luminescence; with the 2 bands exhibiting differing variations. It was concluded that electron-beam excitation occurred mainly in amorphous SiO2, and that the 2 bands were caused by various defects in amorphous SiO2 which covered the porous Si.

T.Suzuki, T.Sakai, L.Zhang, Y.Nishiyama: Applied Physics Letters, 1995, 66[2], 215-7