Volume Charge Distribution Measurement in Thin Dielectrics

ABSTRACT: An instrument measuring volume charges in thin dielectric films is proposed. The instrument utilizes an enhanced Pulsed Electro-Acoustic (PEA) technique and delivers submicron spatial and at least 0.1 micro-Coulombs per cubic centimeter resolutions of the charge density. Traditional PEA instruments suffer from significant signal loss due to acoustic mismatches between the testing material and piezoelectric sensors but conventional acoustic-layer matching techniques have limited efficiency for pressure-pulse measurements. Our proprietary solid-state capacitive pressure sensor approach alleviates the problems of acoustic matching between the tested material and the sensing element. In addition, a submicron-thick sensing element provides greater voltage response to the pressure wave than a piezoelectric layer having similar thickness. Further proposed improvements include the use of (1) acoustic delay lines to reduce electromagnetic noise, (2) sensing rosettes providing differential signal measurements, (3) extending pulse detection rates into the picosecond regime, (4) operating temperature range matching the tested material, and (5) operation in open-face configurations. All of these improvements will result in increased sensitivity, finer spatial resolution, operation in space and extends the use of PEA techniques to a number of application areas that are currently out of reach of existing technology. BENEFIT: A wide range of applications will benefit from enhanced capabilities in measuring volume charge distribution. The direct goal for this project is the measurement of charge distribution within realistic spacecraft dielectric insulators generated by space-like radiation energies. After its implementation, the new instrument can be used for testing existing materials, to provide data for improving models for charge generation and accumulation, and to develop procedures for a better spacecraft protection. With increased spatial resolution and signal sensitivity more applications, both civilian and military, will emerge. Immediate candidates for such applications are flexible electronics, solar cells, biology, surface chemistry, and microelectronics. The higher the spatial resolution in thinner materials becomes, the more application areas will emerge. The goal of this project is to achieve submicron spatial and at least 0.1 micro-Coulombs per cubic centimeter resolutions of the volume charge density. In addition it outlines a roadmap for resolution improvements for at least on another order of magnitude.