Syracuse Sun

With grant funding from the Department of Energy, Professor Mathew Maye and his collaborators will manufacture and test a new generation of Quantum dots.

Tiny but powerful semiconductors named Quantum dots (Qdots) could someday drive hyper-powerful computers. Qdots are crystals confined in a space just a few nanometers in diameter. They are currently used in products such as solar cells or LEDs and work by either absorbing or emitting light with high efficiency. The amount or color of the light is fine-tuned by Qdot dimension, chemical composition, and crystal structure, which is designed by chemists in the lab or at the factory.

These applications rely on the excitation or relaxation of an electron in what is called “quantized” energy levels. However, “the future of Qdots is not about bright colors or how much electricity they produce,” says Mathew Maye, professor and department chair of chemistry at Syracuse University.

Instead, the future involves measuring or manipulating the electron’s spin while in those energy levels in new ways. Each electron in an atom has one of two spin states, “up” or “down,” which describes its orbit. Spins can then be “paired,” where a spin-up electron is combined with a spin-down one, or un-paired when a single electron is left either spin-up or down. The amount of un-paired electrons affects a material’s magnetic property. When a single electron is excited in a Qdot, it should maintain the same spin, but there may be ways to engineer or flip its spin in the future.

Such capabilities could provide new pathways in communications and information storage, leading to powerful quantum computers and important cryptographies that use spin states to store information instead of traditional binary bits.

Images show Quantum dots – or “Qdots.” Cell “a” displays photographs of Qdots with different compositions emitting light at tailored energies (i.e., colors). Cells “b-e” show transmission electron microscopy images of three different Qdot morphologies.

To achieve this goal, Maye is partnering with Brookhaven National Laboratory and its Center for Functional Nanomaterials on a grant from the U.S. Department of Energy (DOE) to manufacture and test this new generation of Qdots.

“We proposed to design new alloy and magnetic Qdots whose composition or dimension allow the electron to be more easily measured or manipulated by external stimuli,” says Maye. “This requires thinking about how to induce polarization or which energy levels to add in order to trap, manipulate or transfer the electron during excitation.”

However, synthesizing such Qdots presents challenges because electron excitation and transfer occur very quickly—on the order of pico- (10^-12) to nano-seconds (10^-9)—and measuring spin requires low temperatures, magnetic fields, and high-precision instruments.

Scientists at Brookhaven play an essential role by designing, building, and acquiring such "ultrafast" instruments that enable researchers to measure these processes. “We will be collaborating closely with experts there,” says Maye.

This project will provide research opportunities for Syracuse students in materials chemistry, lithography, and quantum computing.

“I’m excited to train our undergraduate students and graduate trainees to not only use our chemistry to design and make these new Qdots but also travel with them to Brookhaven to do their own state-of-the-art measurements,” says Maye.

Story by John H. Tibbetts