A Planar CMOS Field-Emission Vacuum Magnetic Sensor
We have fabricated a CMOS vacuum magnetic sensor that exploits the deflection of an electron beam produced by field emission by a perpendicular magnetic field. The device is planar and fabricated by conventional lithography and etching processes. An extremely high magnetic field sensitivity of 4times103%/T is reported.
Homogeneous Field Emission Cathodes With Precisely Adjustable Geometry Fabricated by Silicon Technology
Silicon-based cathodes with precisely aligned field emitter arrays of sharp tips applicable for miniaturized electron sources were successfully fabricated and characterized. This was made possible by an improved fabrication process using wet thermal oxidation, wet etching, and reactive-ion etching steps with adjustable anisotropy. As substrate materials, both p-doped silicon and n-doped silicon were used. The cathode chips contain about 3 × 105 Si tips/cm2 in a triangular array with tip heights of 2.5 μm, tip radii of less than 30 nm, and spacing of 20 μm. Well-aligned field emission (FE) and excellent homogeneity from all tips (i.e., 100% efficiency) and maximum stable currents of typically 0.1 μA (0.6 μA) for p (n)-type Si were reproducibly achieved. The current-voltage characteristics of the p-Si tips exhibit the expected saturation at around 10 nA with around ten times better current stability, whereas the n-Si tips show the usual Fowler-Nordheim behavior. Additional coating of the Si tips with 5-nm Cr and 10-nm Au layers resulted in improved stability and at least five times higher average FE current limits (about 3 μA) at about 30% higher operation voltage.
Simulation study of high power microwave generation by virtual cathode oscillation in coaxial vircator
Summary form only given, as follows. We have numerically simulated the high power microwave generation by virtual cathode oscillation in a coaxial vircator with 3 dimensional PIC code Magic. It is noted that the coaxial vircator has the advantage of an enhancement of power efficiency and gaining of narrow bandwidth frequency. The study is focused on the design of a diode structure for a coaxial vircator suitable for Chundoong IREB pulser (Max. 600 kV, 85 kA, 60 ns). It consists of a center annular cathode, a cylindrical meshed-anode and a reflector. The simulation results showed that the coaxial vircator can indeed be operated at the selected frequency with the narrow bandwidth and the microwave output power strongly depends on the position and geometry of the reflector. From this simulation results we expect that the maximum microwave output power will be obtained by the reflector of 4 cm in width and also 4 cm in distance away from the IREB, where the resonant frequency of microwave from coaxial vircator is simulated to be 6.577 GHz.