We
report a tunneling diode enabling efficient and dense electron
emission from SiO2 with low poisoning sensitivity. Benefiting
from the shallow SiO2 channel exposed to vacuum and the
low electron affinity of SiO2 (0.9 eV), hot electrons tunneling
into the SiO2 channel from the cathode of the diode are
efficiently emitted into vacuum with much less restriction in both
space and energy than those in previous tunneling electron sources.
Monte Carlo simulations on the device performance show an emission
efficiency as high as 87.0% and an emission density up to 3.0 ×
105 A/cm2. By construction of a tunneling diode
based on Si conducting filaments in electroformed SiO2,
an emission efficiency up to 83.7% and an emission density up to 4.4
× 105 A/cm2 are experimentally realized.
Electron emission from the devices is demonstrated to be independent
of vacuum pressure from 10–4 to 10–1 Pa without poisoning.
Vacuum triodes have been scaled down to the microscale on a chip by microfabrication technologies to be vacuum transistors. Most of the reported devices are based on field electron emission, which suffer from the problems of unstable electron emission, poor uniformity, and high requirement for operating vacuum. Here, to overcome these problems, a vacuum transistor based on field−assisted thermionic emission from individual carbon nanotubes is proposed and fabricated using microfabrication technologies. The carbon nanotube vacuum transistor exhibits an ON/OFF current ratio as high as 104 and a subthreshold slope of ~4 V·dec−1. The gate controllability is found to be strongly dependent on the distance between the collector electrodes and electron emitter, and a device with the distance of 1.5 μm shows a better gate controllability than that with the distance of 0.5 μm. Benefiting from field−assisted thermionic emission mechanism, electric field required in our devices is about one order of magnitude smaller than that in the devices based on field electron emission, and the surface of the emitters shows much less gas molecule absorption than cold field emitters. These are expected to be helpful for improving the stability and uniformity of the devices.
Surface waves (SWs) are of great importance in terahertz (THz) photonics applications, due to their subwavelength properties. Hence, it is crucial to develop surface wavefronts shaping techniques, which is urgent...
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