Researchers from Los Alamos National Laboratory found that asymmetrical strain in quantum dots provides non-fluctuating single-dot emission of light
A team of researchers from Department of Energy’s Los Alamos National Laboratory found that dots capable of stable light emission can be achieved by intentionally squashing colloidal quantum dots during chemical synthesis. Moreover, the squashed dots are fully comparable with the light produced by dots made with more complex processes and emit spectrally narrow light with a highly stable intensity and a non-fluctuating emission energy. The team suggests that the strained colloidal quantum dots are a practical alternative to presently employed nano-scale light sources and can be used as single-particle, nano-scale light sources for optical quantum circuits, ultrasensitive sensors, and medical diagnostics.
Victor Klimov, lead Los Alamos researcher on the project stated that these new strained dots are capable of offering unparalleled flexibility in manipulating the emission color. Moreover, the squashed dots also demonstrate compatibility several substrate or embedding medium along with various chemical and biological environments. In the new colloidal processing techniques, it is possible to prepare a virtually ideal quantum-dot emitters that offer around 100% emission quantum yields for a wide range of visible, infrared, and ultraviolet wavelengths.
Colloidal quantum dots as single-particle, nanoscale light sources would require particles with highly stable and non-fluctuating spectral characteristics. Although considerable progress in eliminating random variations in emission intensity has been achieved by protecting a small emitting core with an especially thick outer layer, these thick-shell structures still show strong fluctuations in emission spectra. The team demonstrated that spectral fluctuations in single-dot emission can be nearly completely suppressed with the help of a new method of ‘strain engineering.’ The major step in the process includes combining a core/shell motif two semiconductors with directionally asymmetric lattice mismatch for an anisotropic compression of the emitting core. This alters the structures of electronic states of a quantum dot along with its light emitting properties. Moreover the modified electronic structures also results in drastic narrowing of the emission linewidth that becomes smaller than the room-temperature thermal energy. The research was published in the journal Nature Materials on January 7, 2019.