Diagnostics and analyses of decay process in laser produced tetrakis(dimethyl-amino)ethylene plasma

摘要

A large volume (hundreds of cm(3)) plasma is created by a 193 nm laser ionizing an organic vapor, tetrakis(dimethyl-amino)ethylene (TMAE). The plasma is characterized as high electron density (10(13)-10(12)cm(-3)) and low electron temperature (similar to0.1 eV). To investigate the plasma decay processes, a fast Langmuir probe technique is developed, including detailed considerations of probe structure, probe surface cleaning, shielding, frequency response of the detection system, physical processes in probe measurement, dummy probe corrections as well as noise analysis. The mechanisms for the plasma decay are studied and a delayed ionization process following the laser pulse is found to be important. This mechanism is also supported by optical emission measurements which show that nitrogen enhances the delayed emission from TMAE plasma. A model combining electron-ion recombination and delayed ionization is utilized together with experimental results to order the terms and calculate the relaxation times for delayed ionization. The relaxation times are longer for lower TMAE pressures and lower electron densities. (C) 2001 American Institute of Physics. [DOI: 10.1063/1.1329154]. [References: 41]