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 SiO2 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.