Measurement and control of absolute nitrogen atom density in an electron-beam-excited plasma using vacuum ultraviolet absorption spectroscopy

The absolute nitrogen (N) atom density in an electron-beam-excited plasma ( EBEP) operating at an ultralow pressure has been investigated by vacuum ult raviolet absorption spectroscopy, employing a microdischarge hollow-cathode lamp. The measured N atom density was estimated to be around 6x10(11) cm(- 3), and the dissociation fraction was 4.9% at a N-2 pressure of 0.05 Pa, an electron-beam current of 10 A, and an electron-beam acceleration voltage o f 120 V. The EBEP potentially enables us to control the electron density an d electron energy independently with the electron-beam current and electron -beam acceleration voltages, respectively. It was found that N atom densiti es increased with increasing electron-beam current and electron acceleratio n voltage under low-pressure conditions. The EBEP shows great promise as a N atom source operating at an ultralow pressure. (C) 2000 American Institut e of Physics. [S0021-8979(00)01616-9].