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The interaction of active molybdenum field emission microcathode arrays with oxygen, water, carbon dioxide, methane, hydrogen and helium gases was studied. Experiments were setup to measure the emission characteristics as a function of gas exposures. The resulting changes in the surface work function of the tips were determined from the Fowler-Nordheim plots. The kinetics of the FEA-gas interaction were studied by observing the ion species originating from the array during and after gas exposures with a high resolution quadrupole mass spectrometer. With the work function data and the mass spectrometry information, the mechanisms responsible for emission degradation and subsequent device recovery after exposures have been determined. The data obtained was used in estimating the device lifetimes under various vacuum environments. Also it was found that the gas exposure effects are similar in dc and pulsed modes of operation of the arrays, thus permitting the use of dc mode testing as an effective acceleration method in establishing the device lifetimes under various vacuum conditions. The vacuum conditions required for the long term emission current stability and reliability of vacuum microelectronic devices employing FEAs are established. Exposure of Mo field emitter arrays to oxygen bearing species like oxygen, water and carbon dioxide resulted in serious emission current degradation. Whereas, exposure to methane and hydrogen caused a significant increase in emission current. The control of residual gases like 02, C02 and H20 in the vacuum envelope is essential for the emission current stability and long term reliability of vacuum microelectronic devices employing field emission microcathode technology.

This study addressed five key applications of paper spray mass spectrometry (PS-MS): (i) comparative analysis of the microporous substrate with the cellulose-based substrate in drug detection; (ii) detection of more than 190 fentanyl analogs with their fragmentation pattern can be implemented in the future reference for quicker, accurate and sensitive determination; (iii) exploring sweat in a fingerprint to be considered an alternate method to recognize non-invasive markers of metabolites, lipids, narcotics, and explosive residues that can be used in forensic testing applications; (iv) extending and improving better, cost-effective and quick real-time monitoring of the diseased stage using biofluid samples to obtain vastly different lipid information in viral infection such as COVID-19; and (v) mass spectral detection in chemical warfare agent (CWA) stimulant gas exposure with microporous structure absorbency capabilities in air quality monitoring. This novel synthetic material is known as Teslin® (PPG Industries), consisting of a microporous polyolefin single-layered silica matrix, can be used for precise, sensitive, selective, and rapid sample analysis with PS-MS. The Teslin® substrate provided longer activation time for samples and an active signal with a higher concentration of ion formation and mobility compared to cellulose-based papers. Direct analysis of multiple samples showed that, besides being more sensitive to the study and highly efficient with less sample size and spray solvent needed, Teslin® had less interaction with paper source molecules. For less than 60 seconds of processing time, PS-MS can be used as a rapid detection tool, with limited sample preparation requiring less than one microgram of the sample. Overall, the data in this analysis indicate the capacity of the PS-MS as an alternative approach for direct chemical analysis in many applications. Specifically, the waterproof and microporosity characteristics of Teslin® have proven its usefulness in detecting a variety of chemical components in liquid, solid, and gaseous phases without requiring any chemical treatment or substrate alteration.