Transient characteristics of nitrogen gas-pulsed electron cyclotron resonance plasma

Transient optical emission characteristics of a nitrogen gas-pulsed electron cyclotron resonance (ECR) plasma have been investigated as a first step towards understanding the nature of a nitrogen gas-pulsed plasma. We observed different transient optical emission profiles for the first negative N+2, the second positive N2*, and the first positive N2* emission bands in nitrogen gas-pulsed ECR plasma that are closely related to the pressure changes in a discharge cavity of the plasma source. On the basis of the transient emission profiles, optical emission spectra over the wavelength range 300–700 nm were obtained for three specific time regions within the pulse. During the gas-pulsed injection period large ratios of N2*/N+2 (2.5–7.1) and low electron temperatures (1.2 eV) were observed. On the other hand, small ratios of N2*/N+2 (0.3) and high electron temperature (2.5 eV) were recorded 0.65 s after stopping the gas-pulsed injection. These observed N2*/N+2 ratios are interpreted in terms of different excitation processes and electron temperatures (Te) due to the surge of neutral N2 gas. The N2*/N+2 ratios in an ECR gas-pulsed plasma are 5–7 times higher than those in continuous wave plasma. Through timing optimization of the transient characteristics, nitrogen gas-pulsed ECR plasma is considered to be a useful candidate for high efficiency p-type high doping in Zn(Se,Te) semiconductors or for the plasma deposition of nitride films.