Self Aligned Gated Tip Arrays for Efficient Ionization of Gases and Electron Emission

Applications

Ion source in: 

  • Compact neutron generators
  • Oil well logging 
  • Atom beam microscopes 
  • Portable mass spectrometer

Problem Addressed

When a high electric field lowers and narrows the potential barrier in a molecule, it allows an electron to tunnel out of the gas molecule and create a positive ion. This process, known as field ionization (FI), creates ions with minimal fragmentation and at orders-of-magnitude higher pressure compared with other means of ionization of gases, e.g., electron impact ionization. The current challenge in state-of-the-art field ionization devices is achieving a miniaturized, stable, and low cost ion source that is capable of producing large ion fluxes at a low bias voltage. 

Technology

This technology defines the design, fabrication, and characterization of a gas field ionizer made from large arrays of resilient, self-aligned gated nano scale tips. These tips are capable of field ionizing helium (the hardest gas to field ionize) at voltages as low as 150 V, and can generate ion fluxes exceeding 1.76 ×10^(10) cm^(-2) s^(-1), with long term (> 104 s) stable characteristics at pressures as high as 1 Torr.

Advantages

  • Threefold reduction in ionization voltage of helium (i.e. 150 V) 
  • Demonstrated ion flux generation exceeding 1.76 × 10^(10) cm^(-2) s^(-1) and long term stable characteristics of over 2.5  hours at pressures up to 1 Torr
  • High-yield fabrication process to produce massive arrays of self aligned gated tips