Fabrication of spiral inter-digitated terminal (IDT) structure of electroplated gold on quartz substrate and progressive microplasma generation

Abstract

This paper discussed about the progressive microplasma generation in planar spiral inter-digitated terminal (IDT) structure. The IDT structures (with separation between two adjacent spiral electrodes varied progressively from 30 to 33 µm) are fabricated on quartz wafer by 5 µm thick gold electroplating. The onset of microplasma is witnessed around 580 V applied bias (Electric field: ~ 193 kV/cm). Initially, the microplasma is observed nearby the central area of the spiral IDT structure. Thereafter, the microplasma started spreading out other regions and finally engulfs the whole IDT with an intense glow. Although the bias is applied continuously, the microplasma generation in the spiral IDT structure is found to be discontinuous. It seems to be due to the discharge of the energy stored in the metal-air-metal capacitor (spiral IDT) during micro-plasma generation and thus reduces the resultant electric field below the threshold of microplasma generation. When the micro-plasma stops, the voltage at the IDT capacitors is again restored to its threshold value and microplasma is being observed again.