In the early ’80s, Alexey Ekimov and Louis E. Brus independently researched semiconductor clusters, leading to the discovery of quantum dots (QDs). QDs are nanoscale semiconductor particles with unique optical and electronic properties. In 1993, Moungi Bawendi improved quantum dot production, making them nearly perfect for various applications.
By the late ’90s and early 2000s, quantum dots found uses in fields like biology, displays, photovoltaics, and lasers. Throughout the 2010s, quantum dot technology advanced. In 2015, Philips introduced a quantum dot computer monitor with brilliant color. Quantum dots became integrated into displays, enhancing color accuracy and energy efficiency, especially in high-quality LCD TVs and monitors. The term “quantum dots” became mainstream [1].
In 2023, the Nobel Prize in Chemistry was awarded to Bawendi, Brus, and Ekimov for their work in discovering and synthesizing quantum dots.
Quantum dots are miniature crystals, typically composed of 1 000 to 100 000 atoms, ranging from one to a few dozen nanometers in size. Their small size allows them to exhibit quantum behaviors like individual atoms. When excited with electricity or light, electrons move to higher energy levels, emitting light upon returning to their lowest energy state. The wavelength of this emitted light depends on factors such as the crystal’s size, composition, and shape. Smaller crystals emit light toward the blue end of the spectrum, while larger ones exhibit a noticeable shift towards the visible spectrum, near-infrared, and even further into the mid-infrared range [2].
Bruker provides several solutions for photo-luminesce (PL) studies of QDs. For NIR PL the easy to use PLII module is available. It can be attached to the right-hand side of VERTEX or INVENIO FT-IR R&D spectrometers equipped with suitable optical components.
For conducting MIR PL measurements, more advanced methods are needed due to interference from atmospheric and thermal backgrounds. To avoid interference from water vapor and CO2, vacuum spectrometers like the VERTEX 70v or VERTEX 80v are required. The well-established approach is using Amplitude-modulated Step-Scan PL Measurements.
QDs have a strong reputation as highly promising materials suitable for MIR detectors. In Bruker, we provide multiple solutions not only for the analysis of detector materials but also for characterizing the completed detector devices.
References
[1] https://nexdot.fr/en/history-of-quantum-dots/ [2] F. P. García de Arquer, D. V. Talapin, V. I. Klimov, Y. Arakawa, M. Bayer, E. H. Sargent, Semiconductor quantum dots: Technological progress and future challenges, Science 373, 640 (2021).
