Publications

The design, simulation, fabrication, packaging, electrical characterization and testing analysis of a microfabricated a cylindrical ion trap ({mu}CIT) array is presented. Several versions of microfabricated cylindrical ion traps were designed and fabricated. The final design of the individual trap array element consisted of two end cap electrodes, one ring electrode, and a detector plate, fabricated in seven tungsten metal layers by molding tungsten around silicon dioxide (SiO{sub 2}) features. Each layer of tungsten is then polished back in damascene fashion. The SiO{sub 2} was removed using a standard release processes to realize a free-hung structure. Five different sized traps were fabricated with inner radii of 1, 1.5, 2, 5 and 10 {micro}m and heights ranging from 3-24 {micro}m. Simulations examined the effects of ion and neutral temperature, the pressure and nature of cooling gas, ion mass, trap voltage and frequency, space-charge, fabrication defects, and other parameters on the ability of micrometer-sized traps to store ions. The electrical characteristics of the ion trap arrays were determined. The capacitance was 2-500 pF for the various sized traps and arrays. The resistance was in the order of 1-2 {Omega}. The inductance of the arrays was calculated to be 10-1500 pH, depending on the trap and array sizes. The ion traps' field emission characteristics were assessed. It was determined that the traps could be operated up to 125 V while maintaining field emission currents below 1 x 10{sup -15} A. The testing focused on using the 5-{micro}m CITs to trap toluene (C{sub 7}H{sub 8}). Ion ejection from the traps was induced by termination of the RF voltage applied to the ring electrode and current measured on the collector electrode suggested trapping of ions in 1-10% of the traps. Improvements to the to the design of the traps were defined to minimize voltage drop to the substrate, thereby increasing trapping voltage applied to the ring electrode, and to allow for electron injection into, ion ejection from, and optical access to the trapping region.

Abstract not provided.

This work describes the design, simulation, fabrication and characterization of a microfabricated thermal conductivity detector to be used as an extension of the {micro}ChemLab{trademark}. The device geometry was optimized by simulating the heat transfer in the device, utilizing a boundary element algorithm. In particular it is shown that within microfabrication constraints, a micro-TCD optimized for sensitivity can be readily calculated. Two flow patterns were proposed and were subsequently fabricated into nine-promising geometries. The microfabricated detector consists of a slender metal film, supported by a suspended thin dielectric film over a pyramidal or trapezoidal silicon channel. It was demonstrated that the perpendicular flow, where the gas directly impinges on the membrane, creates a device that is 3 times more sensitive than the parallel flow, where the gas passed over the membrane. This resulted in validation of the functionality of a microfabricated TCD as a trace-level detector, utilizing low power. the detector shows a consistent linear response to concentration and they are easily able to detect 100-ppm levels of CO in He. Comparison of noise levels for this analysis indicates that sub part per million (ppm) levels are achievable with the selection of the right set of conditions for the detector to operate under. This detector was originally proposed as part of a high-speed detection system for the petrochemical gas industry. This system was to be utilized as a process monitor to detect reactor ''upset'' conditions before a run away condition could occur (faster than current full-scale monitoring systems were able to achieve). Further outlining of requirements indicated that the detection levels likely achievable with a TCD detector would not be sufficient to meet the process condition needs. Therefore the designed and fabricated detector was integrated into a detection system to showcase some technologies that could further the development of components for the current gas phase {micro}ChemLab as well as future modifications for process monitoring work such as: pressurized connections, gas sampling procedures, and packed columns. Component integration of a microfabricated planar pre-concentrator, gas-chromatograph column and TCD in the separation/detection of hydrocarbons, such as benzene, toluene and xylene (BTX) was also demonstrated with this system.