Proof-of-Concept Vacuum Microelectronic NOR Gate Fabricated Using Microelectromechanical Systems and Carbon Nanotube Field Emitters.

This paper demonstrates a fully integrated vacuum microelectronic NOR logic gate fabricated using microfabricated polysilicon panels oriented perpendicular to the device substrate with integrated carbon nanotube (CNT) field emission cathodes. The vacuum microelectronic NOR logic gate consists of two parallel vacuum tetrodes fabricated using the polysilicon Multi-User MEMS Processes (polyMUMPs). Each tetrode of the vacuum microelectronic NOR gate demonstrated transistor-like performance but with a low transconductance of 7.6 × 10-9 S as current saturation was not achieved due to a coupling effect between the anode voltage and cathode current. With both tetrodes working in parallel, the NOR logic capabilities were demonstrated. However, the device exhibited asymmetric performance due to differences in the CNT emitter performance in each tetrode. Because vacuum microelectronic devices are attractive for use in high radiation environments, to test the radiation survivability of this device platform, we demonstrated the function of a simplified diode device structure during exposure to gamma radiation at a rate of 45.6 rad(Si)/second. These devices represent a proof-of-concept for a platform that can be used to build intricate vacuum microelectronic logic devices for use in high-radiation environments.

Detection and Analysis of Uncharged Particles Using Consumer-grade CCDs.

In the current climate of increased global terrorism, the threat of a radiological incident is becoming more realistic than ever, and as such, the necessity of early-warning detection is paramount to national security. To assist with this need, we have investigated the detection of uncharged particle emissions from radiological sources using charged-coupled devices (CCDs), which are contained within a variety of products, including consumer cellphones and traffic cameras. Because the CCD is intrinsically sensitive to charge accumulation as a result of linear energy transfer by the incident particles, each event can be counted and quantified using video-image processing and an estimated energy band assessed by the properties of the pixels. In an effort to make this process applicable to the widest possible range of CCDs available, this experiment was conducted using low-quality CCDs contained within consumer-grade, budget web cameras. Within a Pu-Be neutron howitzer, particles were detected using several camera models: Gigaware X76, Z76 and Logitech C170, C270. Particle detection events were counted by post-processing with Matlab, and an efficiency for each CCD was determined relative to both a theoretical flux model and a calibrated He tube detector. The relative detection efficiencies for the cameras tested fell within the range 14-18% and showed a linear correlation between incident energy and pixel response.