ULTRAVIOLET-LIGHT FROM POROUS SILICON BY A MICROSCOPIC DISCHARGE

We discovered that some porous silicon samples show a characteristic l ine spectrum in the near UV and violet spectral regions. The violet pa rt of the light can be clearly seen with the naked eye in the darkened laboratory at ambient pressure. The origin of this phenomenon is comp letely different from that of the known luminescence of this material in the visible region and the near IR. While visible luminescence star ts at voltages of some volts, UV line emission starts at a threshold v oltage of about 80 V. The UV spectrum emitted from porous silicon is i dentical to the spectrum of a low-pressure RF N-2 plasma (for the reso lution of the spectrograph), thus proving that a stable plasma dischar ge can be established in the pores of porous silicon. Especially at hi gher voltages, ozone is produced. In this paper we present some of the fundamental optical and electrical properties of the samples and sugg est a model for the origin of the plasma discharge.