Tailoring Photoluminescence from Si-Based Nanocrystals Prepared by Pulsed Laser Ablation in He-N 2 Gas Mixtures

• Published in: Molecules (Basel, Switzerland) Vol. 25; no. 3
• Main Authors: Fronya, Anastasiya A, Antonenko, Sergey V, Kharin, Alexander Yu, Muratov, Andrei V, Aleschenko, Yury A, Derzhavin, Sergey I, Karpov, Nikita V, Dombrovska, Yaroslava I, Garmash, Alexander A, Kargin, Nikolay I, Klimentov, Sergey M, Timoshenko, Victor Yu, Kabashin, Andrei V
• Format: Journal Article
• Language: English
• Published: Switzerland 01.02.2020
• Subjects: Helium - chemistry; Lasers; Luminescent Measurements; Nanoparticles - chemistry; Nanoparticles - ultrastructure; Nitrogen - chemistry; Pressure; Silicon - chemistry; Spectroscopy, Fourier Transform Infrared; Spectrum Analysis, Raman; silicon nanoparticles; photoluminescence; pulsed laser deposition; silicon quantum dots; bioimaging; quantum confinement; silicon oxynitride; pulsed laser ablation in gases
• ISSN: 1420-3049
• DOI: 10.3390/molecules25030440

Using methods of pulsed laser ablation from a silicon target in helium (He)-nitrogen (N ) gas mixtures maintained at reduced pressures (0.5-5 Torr), we fabricated substrate-supported silicon (Si) nanocrystal-based films exhibiting a strong photoluminescence (PL) emission, which depended on the He/N ratio. We show that, in the case of ablation in pure He gas, Si nanocrystals exhibit PL bands centered in the "red - near infrared" (maximum at 760 nm) and "green" (centered at 550 nm) spectral regions, which can be attributed to quantum-confined excitonic states in small Si nanocrystals and to local electronic states in amorphous silicon suboxide (a-SiO ) coating, respectively, while the addition of N leads to the generation of an intense "green-yellow" PL band centered at 580 nm. The origin of the latter band is attributed to a radiative recombination in amorphous oxynitride (a-SiN O ) coating of Si nanocrystals. PL transients of Si nanocrystals with SiO and a-SiN O coatings demonstrate nonexponential decays in the micro- and submicrosecond time scales with rates depending on nitrogen content in the mixture. After milling by ultrasound and dispersing in water, Si nanocrystals can be used as efficient non-toxic markers for bioimaging, while the observed spectral tailoring effect makes possible an adjustment of the PL emission of such markers to a concrete bioimaging task.