Photonic high-entropy alloy nanocomposites made by pulsed laser deposition

Photoluminescent quantum dots (QDs) have become popular for sensing chemo- and bio-species and ultraviolet (UV) radiation. Improvement of sensitivity is achieved by surrounding QDs with plasmonic metal nanoparticles (NPs) via the localized surface plasmon polariton (LSPP) resonance effect. Fine tuning of LSPP resonance can be potentially achieved by making the NPs of plasmonic high entropy alloys (HEAs). We describe our efforts to make HEA NPs using the concurrent multi-beam multi-target pulsed laser deposition (CMBMT-PLD). A vacuum system for such a process included permanent magnets under the PLD targets and the substrate. The magnets narrowed down the plasma plumes from the targets. HEA films of up to six metals (Au, Ag, Cu, Al. Ti, and W) were deposited on Cu, Al, Ni, and Fe substrates. Scanning electron microscopy and X-ray diffraction analysis indicated that the films were the aggregates of crystalline NPs of individual metals and double-metal alloys. Substrate heating and applying magnetic field resulted in the formation of a wider variety of double-alloy NPs. HEA films amplified the photoluminescence of perovskite (CsPbBr3) QDs deposited on the top 6 to 16 times due to LSPP resonance and Purcell effect. These results might be useful for the applications in optical sensing.