Carbon Nanotube Vacuum Gauges With Wide Dynamic Range

Carbon-nanotube-based vacuum gauges have been developed and characterized, which primarily utilize the thermal conductivity principle. The vacuum gauges, comprising 5- to 10-mu m-long single-walled nanotubes contacted on either end with Au/Cr electrodes, have been shown to operate at low power (nanowatts to microwatts) and exhibit a wide dynamic range from 760 to 10^-6 torr. Pressure sensitivity was found to increase rapidly as the bias power was increased. In addition, by etching part of the thermal SiO ₂ beneath the tubes and minimizing heat conduction through the substrate, pressure sensitivity was extended toward higher vacuums. Results are compared to a conventional thin-film meander resistor, which was fabricated and whose pressure response was also measured for comparative purposes.