Optical emission spectral analysis of microplasma discharges in atomic and molecular gases at pressures up to 1.65 MPa

High Pressure microplasmas are potentially useful as high frequency microswitches due to their high electron densities and rapid switching characteristics. In the process of designing these high frequency microswitches, plasma temperatures are important in determining the lifetime of the microswitch materials. Pure gases and mixtures of He, Ar, H₂, and N₂ are tested for pressure ranges from 0.1 MPa to 1.65 MPa at electrode gap lengths ranging between 20 μm and 50 μm. Higher pressures allow for smaller discharge diameters with high current densities while still maintaining normal glow discharge characteristics. Optical emission spectra (OES) are collected as a non-intrusive diagnostic. Rotational and vibrational temperatures are measured for the different combinations using the 2nd positive system of N₂. Rotational temperatures increase with pressure and range from 500K to 3000K for various mixtures at 10 atm. In molecular gases a transition to vibrational-rotational equilibrium is observed at higher pressures. Normal glow discharge operating regimes are maintained at high pressures in all the gases. However instabilities are more likely to occur at high pressure when the system capacitance is high.