The detection of UV photons is becoming increasingly important in particle physics experiments. New detector materials are needed to directly detect UV photons and/or absorb them by emitting light in the visible spectrum, which can be measured using existing photon detectors without requiring an active cooling system. Silicon nanoparticles are sensitive to UV light. Depending on the nanoparticle size, they absorb UV light and re-emit it at visible wavelengths. The size of silicon nanoparticles can vary depending on the technological parameters of laser ablation. Therefore, it is essential to effectively control the laser ablation process in order to obtain nanoparticles of desired sizes. In this project, we plan to form colloidal solutions of Si nanoparticles having different sizes via silicon target laser ablation and to use them for modification of charge-coupled device photodetectors, thereby increasing their sensitivity to < 400 nm wavelength light.
Project funding:
KTU Research and Innovation Fund
Project results:
Silicon nanoparticles were produced using pulsed laser ablation in a styrene solution. Firstly, through precise control of the laser scanning speed during synthesis, we successfully modulated the size distribution of the Si NP. This parameter-driven size control allowed us to tailor the Si NP dimensions, with the optimal conditions identified at a scanning speed of 3000 mm/s, resulting in Si NP with an average diameter of ~4 nm and PDI of 0.811. The Raman spectra exhibited a hypsochromic shift in the peak position and a decrease in intensity compared to the pristine silicon target. Si NP colloidal dispersion excited at 330 nm unveiled a broad PL spectrum covering a wide visible wavelength range with a peak position at 416.5 nm. The Si NP colloidal dispersion exhibited a crystal blue color with color space coordinates of X: 1.0708, Y: 1.1785, and Z: 2.7970 in the CIE chromaticity diagram. PL decay analysis demonstrated a bi-exponential decay behavior, indicating the existence of multiple radiative recombination pathways within the nanoscale structure. Fabricated free-standing thin films containing Si NPs exhibited slightly different photophysical properties as compared to Si NP colloidal dispersions. The emission peak in the broad PL spectrum shifted to the lower wavelength from 416.5 nm to 379.2 nm, with the emission color change to Jordy blue. Additionally, free-standing thin films containing Si NP exhibited a slightly slower radiative recombination rate with lifetimes of ?1 = 2.23 ns and ?2 = 13.75 ns. Furthermore, we extended the practical use of Si NP by utilizing them as passive filters for CCD detectors. This practical example leveraged the wavelength-shifting properties of Si NP to enable non-sensitive CCD detectors to detect UV light. The overall efficiency of the CCD detector with the Si NP passive filter was determined to be 67 ± 2%. The transformation of UV light into visible light through Si NP-induced wavelength shifting showcased the versatility of Si NP in enhancing the functionality of existing technologies. These findings not only advance our fundamental understanding of Si NP but also pave the way for innovative applications in optoelectronics and related fields. As Si NPs continue to evolve as a key nanomaterial, their unique properties, including quantum confinement effects, hold promise for transformative advancements in diverse scientific and technological domains.
Period of project implementation: 2023-04-11 - 2023-12-31
Project partners: Lithuanian Energy Institute
