Henning Richter

Radio Frequency Carbon Nanotube Thin-Film Bolometer

A radio frequency bolometer was realized using a thermistor fabricated from a carbon nanotube thin-film deposited on a sapphire substrate. Power detection performance was characterized at room and liquid nitrogen temperatures. With the thermistor held at a temperature of 15 °C, the bolometer’s sensitivity of 915-MHz test signals was found to be 0.36 mV/mW, and power levels as low as −45 dBm could be detected with a 20-s integration time constant. The sensitivity increased to 2.3 mV/mW when the thermistor was cooled to −193 °C. Experiments over the temperature range of 15 °C–240 °C indicate that internanotube mechanisms dominate power detection at temperatures below a value of approximately 200 °C and that intrananotube mechanisms (primarily Joule-heating) dominate at higher temperatures.

Uncooled radio frequency bolometer based on carbon nanotube thin films

Carbon nanotube thin films deposited on sapphire substrates have been used to realize a microwave power sensor that operates at and above room temperature. The detector includes a power-sensitive resistor that has been incorporated into a voltage divider circuit. Using lock-in detection, experiments were performed with 915 MHz test signals that showed detection down to -45 dBm. A sensitivity of 0.36mV/mW was achieved with the device held at a temperature of 15°C. Additional experiments (which included static and pulsed current versus voltage measurements) indicate that the primary physical mechanism responsible for power detection near room temperature is Joule heating.