A logic-controllable array of high-density microplasmas

Summary form given only. Previously we have demonstrated the technique of generating arrays of microplasmas in small gaps between the ends of microwave resonators and reference electrodes. These arrays are fabricated using micro-milling of standard microwave substrates and typically operated in atmospheric-pressure argon. Here we demonstrate circuits where individual microplasmas can be switched on or off by low-voltage logic signals. Such switchable microplasmas could be of interest as components in novel circuitry and sensing devices or as patterning elements in atmospheric-pressure deposition of thin films. The switches are implemented as diodes connecting the reference electrodes to a ground plane. Reverse-biasing a diode prevents microwave current from flowing through, causing the reference electrode to float and reducing the voltage across the discharge gap below the level that can sustain a microplasma. Inductors act as a microwave block to isolate the logic control from the microwave power. We use an analytical transmission-line model to examine the behavior of the combined resonant and logic circuits, and to estimate the effects of microplasma formation on circuit behavior. This model and experimental evidence suggest the importance of minimizing stray capacitance to ensure full microplasma suppression. The microplasmas themselves are characterized using spectroscopic techniques. Stark broadening measurements show that microplasmas with electron densities in excess of 10¹⁴ cm^-3 can be fully controlled by logic voltages of +2 / -5 V. In addition, plasma switching speeds are estimated through time-resolved photography using an ICCD camera.