Ramsey Research GroupThe University of North Carolina at Chapel Hill

Department of Chemistry

Ion Source Development


Develop a low-power, voltage gatable, and compact ionization source capable of operating at >1 Torr in conjunction with an array of miniaturized cylindrical ion traps (CIT).


Replace the traditional thermionic emitter used for electron impact ionization (EI) with a semiconductor-based, cold cathode of novel design. Since the electron flux is not dependent upon heating, the microionizer can be placed in very close proximity to the CIT, reducing the electron beam path length. This minimizes collisional effects associated with higher pressures improving the ionization efficiency compared with traditional sources. The microionizer is etched in silicon on insulator (SOI).  A modest voltage (≈ 30 V) applied across the silicon electrodes results in large electric fields (> 105 V/cm).  These fields induce electron field emission at the sharp features distributed around the circumference of the interface.

The bottom left image is an SEM of one of the 16 multi-feature arrays (highlighted in red the image above). The bottom right image is an SEM image of an individual element of the array.