UV light exposure can enhance the field emission performance of nano vacuum devices

Nano vacuum devices are the modern, compact version of early vacuum tubes. While vacuum-tube transistors, due to bulkiness and high voltage requirements, have long been replaced by semiconductor technology, up-and-coming nano vacuum devices can eliminate these disadvantages while retaining the resilience to high temperature and intense radiation environments. Consequently, these nano vacuum tubes may find applications in satellites or nuclear reactors.

Silicon gated field emission arrays (Si-GFEAs) are essential components of these devices. Bhattacharya et al. tested the performance of Si-GFEAs before and after ultraviolet light exposure. They monitored how environmental gases, especially water molecules, interact and affect field emission and the leakage current between the gate and the emitter.

Current-voltage characterization of the Si-GFEA showed that the gate current reduced by over a factor of 10, and the emission current increased by a similar factor after 70-minutes of UV exposure. The changes happen in parallel with water desorption from the GFEA during the UV exposure, as indicated by residual gas analyzer measurements. The gate and emission currents eventually returned to their pre-exposed values after three days in ambient atmospheric conditions, but subsequent UV exposure would return the currents to their enhanced levels.

The results are consistent with previous high-temperature experiments that also showed water desorption to affect field emission array performance.

“We introduce a simple yet effective, no contact, non-invasive method to desorb residual gases, primarily water from the dielectric surfaces of silicon field emitter arrays without a high-temperature bakeout. High-temperature bakeout can be complex and sometimes difficult to carry out,” said author Ranajoy Bhattacharya. “This simple yet effective water desorption method can be applied to enhance the performance of nano vacuum channel transistors for harsh environment electronics.”

Source: “Ultraviolet light stimulated water desorption effect on emission performance of gated field emitter array,” by Ranajoy Bhattacharya, Nedeljko Karaulac, Winston Chern, Akintunde Ibitayo Akinwande, and Jim Browning, Journal of Vacuum Science & Technology B (2021). The article can be accessed at http://doi.org/10.1116/6.0001036 .