Effects of Gas Exposure on Silicon Gated Field Emitter Arrays

Adsorption effects of gasses such as N 2 , Ar, He and H 2 O on field emission performance of Silicon Gated Field Emitter Arrays (Si-GFEAs) are of importance. In this work, Si-GFEAs with 1000×1000 tips 1 have been exposed to these gasses after cleaning with ultraviolet light (UV) to remove water vapor 2 . The collector voltage was fixed at 200 V DC, and the gate was held at 40 V for all measurements. Three different partial pressures, 5×10 -6 Torr, 5×10 -5 Torr and 5×10 -4 Torr were used. A residual gas analyzer (RGA) was used to monitor the partial pressure. It was observed that for a gate voltage of 40 V, the collector current decrease for N 2 was 41% at 5×10 -4 torr; whereas Ar had a 65% drop at 5×10 -4 torr. Each test took ≈ 10 minutes. After the exposure, vacuum was restored and the I-V sweep was repeated. After pump down, observed collector current was restored to pre-exposure conditions, though not completely (within 10-15%) . A subsequent UV exposure restored the pre-exposure collector current completely. It was hypothesized that the exposed gasses were adsorbed by emitter tips which increased the work function. However, the RGA also showed that a large percentage of the gas (1%) introduced into the chamber was H 2 O which might have a large impact on work function. Further study is ongoing.