Quantum dots power nano sensors

Piezoelectric effects enables the translation of mechanical motion into electricity and vice versa, energizing electronic transducer applications and promising to cut power consumption in MEMS devices. McGill University researchers are harnessing the piezoelectric effect in quantum dots, targeting nanoscale sensors and power supplies that will translate vibration into a usable signal.

The research program, led by Patanjali Kambhampati, has already discovered a method for producing a large electrical field in cadmium selenide quantum dots by assembling an electronic charge around their exterior. Because of the dots' small size of only 10 to 50 atoms—or about 10nm in diameter—the internal electric field can be enormous, producing immediate expansion and contractions cycles in under a trillionth of a second, according to the researchers.

Migration of charges to the surface of a quantum dot produces a piezoelectric force, causing the dot to vibrate. The higher the number of charges going to the surface, the higher the amplitude of vibration.

The team currently is learning to control the frequency and size of the induced vibration, with an eye toward controlling the switching time of future electronic devices based on the effect. Once control of the vibrations is achieved, the researchers plan to try reversing the effect, hoping to produce a relatively large voltage from a tiny, environmentally induced compression.

Applications could include measuring the pressure in a fluid noninvasively by adding piezoelectric quantum dots, energizing them with a laser and then measuring the piezoelectrically induced vibrations.

The research team includes doctoral candidate Pooja Tyagi. Funding agencies include the Canada Foundation for Innovation, the Natural Sciences and Engineering Research Council of Canada and Fonds Québécois de la Recherche sur la Nature et les Technologies.

- R. Colin Johnson
EE Times