Ultraviolet emission intensity, visible luminance, and electrical characteristics of small arrays of Al∕Al2O3 microcavity plasma devices operating in Ar∕N2 or Ne at high-power loadings

Abstract

Small arrays (3×3→10×10) of microcavity plasma devices, having a two-stage structure comprising multilayer stacks of nanostructured Al2O3 grown on Al foil with cylindrical microcavities 100–300μm in diameter, produce intense ultraviolet (UV) and visible emission when operated in Ar∕3% N2 gas mixtures or Ne and excited by a sinusoidal ac voltage wave form. Near-UV (300–400nm) intensities emitted into a solid angle of ∼10−2sr above 30 mW per cm2 of radiating area are measured for Ar∕N2 gas mixture pressures of 400–800Torr, an excitation frequency of 15kHz, and an average current ⩾20mA (rms). Two or more conjoined cylindrical microcavities of differing diameters allow for the confinement of the plasma to progressively smaller volumes as the power deposited is increased (thereby decreasing the Debye length and the spatial extent of the cathode fall region) and provides a convenient tool with which the luminosity of an array can be modulated. The transition of a microplasma from confinement in a 200-μm-diam cavity into an adjacent 100-μm-diam microcavity is accompanied by an order-of-magnitude increase in the luminance of Ne plasmas in a 3×3 array as the rms current is increased by ∼1mA.