Techniques for microfluidic channel fabrication in soda-lime glass and fused quartz using femtosecond laser ablation and ablation in conjunction with polymer coating for surface roughness improvement were tested. Systematic experiments were done to characterize how process variables (laser fluence, scanning speed and focus spot overlap, and material properties) affect the machining feature size and quality. Laser fluence and focus spot overlap showed the strongest influence on channel depth and roughness. At high fluence, the surface roughness was measured to be between 395 nm and 731 nm RMS. At low fluence, roughness decreased to 100 nm-350 nm RMS and showed a greater dependence on overlap. The surface roughness of laser ablation was also dependent on the material properties. For the same laser ablation parameters, soda-lime glass surfaces were smoother than fused quartz. For some applications, especially those using quartz, smoother channels are desired. A hydroxyethyl methacrylate (HEMA) polymer coating was applied and the roughness of the coated channels was improved to 10-50 nm RMS.

By operating the field emitter triode in the collector-assisted field emission mode, a strong dependency of the collector current as a function of emitter-to-collector distance is obtained. This property can be used in the construction of displacement and/or pressure sensors. Experimental results are presented for a silicon emitter array. These include displacement measurements under DC and AC conditions, sensitivity, and temperature dependency from room temperature to 200 degrees C. From experimental data, model parameters for the Fowler-Nordheim equation are deduced. These parameters can then be used to calculate the performance of the device as a function of gate and collector voltages and of deflection.

No abstract

No abstract

No abstract

No abstract

Several concepts have been proposed in the literature on how to use field emitter devices as pressure sensors [l]. These range from diode structures in which the

The scaling of emission currents and of their corresponding current fluctuations of ensembles of gated, monocrystalline silicon emitters ranging from n=1 to n=20 800 emitters have been investigated. For randomly selected ensembles, the current scales approximately with n and the fluctuation with n−0.16. For selected ensembles of identical emission behavior, the current scales with n and the fluctuations with n−0.5 as is expected from theory. The discrepancy in the exponent for the scaling of the current fluctuations is caused by the poor participation of the emitters within an ensemble. Only a few emitters per ensemble contribute to the total current. The scaling behavior can thus be used as a diagnostic tool to evaluate a given process. The measurements were performed at room temperature and at pressures of approximately 1×10−8 Torr.