Scientists have developed a micrometer-wide thermometer that can measure tiny amounts of heat generated by light electron beams in real time. The device can be applied in photo-thermal cancer treatment as well as in advanced research on crystals, optical light harvesting, etc.

The miniaturised system with a nanoscale heat source and detector is essential for future development of next-generation transistors that will be employed in designing new nanoscale devices. The device developed by scientists at Tokyo Institute of Technology in Japan consists of a gold and nickel thermocouple on a silicon nitride membrane and is miniaturised to the extent that the electrodes are only 2.5 micrometres wide and the membrane is just 30 nanometres thick.

A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming electrical junctions at differing temperatures. It produces a temperature-dependent voltage, which can be interpreted to measure temperature. For such a system to be used as a thermometer, it must show sensitivity to temperature change. The developed micro-thermocouple exhibited high responsiveness to heat generated by a laser and an electron beam.
Tiny temperature changes were measured by the developed thermocouple for both types of heating.

To prepare the micro-thermocouple a cross pattern of metal stripes with widths of a few micrometers is created. Researchers used this technique to create a pattern on a nano-thin silicon nitride membrane, which enhanced the device sensitivity and enabled it to respond faster. Through this approach, a thermometer that could measure fast and small temperature changes was successfully produced, with the measurements being performed through the nano-thin silicon nitride membrane. The system can be regarded as a new ‘toolbox’ for investigating heat transport behaviour on the micro- and nano-scales, with many important applications in a wide range of fields, researchers said.