Abstract
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.
Highlights
Vacuum tubes emerged in the early 20th century and were the central of the original electronic devices [1]
The emission current of a multiwalled carbon nanotube (CNT) electron emitter is measured repeatedly with collector electrodes applied with 50 V and gate electrode vacant
As the collecting voltage is fixed at 50 V and electric field at the surface of the CNT is almost unchanged during the measurements, electron emission is not governed Electronics 2b0y22e, 1l1e,cxtFrOicRfiPEeElRd.RETVhIEeWelectron emission from a Joule-heated CNT is attributed to thermionic5 of 10 emission mechanism with non-thermal equilibrium electron distribution [20,21]
Summary
Vacuum tubes emerged in the early 20th century and were the central of the original electronic devices [1]. Solid-state devices took over their roles in most areas in the past 60 years because of the advantages of integrability, miniaturization, lower power consumption, reduced costs, etc. Vacuum as a medium for electron transport is more immune to radiation damage than conventional semiconductors. Vacuum devices are more reliable and efficient than solid-state devices for high-power and high-frequency devices [3]. Combining vacuum triodes and microfabrication technologies leads to the creation of a new area called “vacuum transistors”, which is expected to possess the advantages of both conventional vacuum devices and solid-state devices, such as high carrier velocity, reliable performances in high temperature and extreme environment, miniaturization and easy integration [7]
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