Multifunctional Sulfur‐Hyperdoped Silicon Nanoparticles with Engineered Mid‐Infrared Sulfur‐Impurity and Free‐Carrier Absorption

Abstract

rather limited dangling-bond absorption of electromagnetic waves in amorphous nanosilicon, broadly variable free-carrier absorption (free-carrier concentration ≈10 17 cm −3 ) [4] in controllably doped silicon has recently brought another important modality to Si NPs, related to space-selective in situ anti-cancer hyperthermiabased therapies via near-and mid-infrared (IR) laser, or radiofrequency (RF) Joule heating. [4,6] However, to date strong Si-NP doping was realized only via minor introduction of gold, [7] since Si is rather immiscible material. [8] In contrast, n-hyperdoped Si was actively studied for the last decade as a material platform, supporting fabrication of mid-IR sensitizers for solar cells, [9] broadband active media for thin-film photovoltaics, [1] broad-band mid-IR nightvision and imaging devices for novel promising and emerging applications. The currently achieved strong (≈10 3 -10 4 cm −1 ) smooth [10][11][12][13][14] or band-engineered [15,16] mid-IR absorption in sulfur-(or selenium and tellurium [12] ) doped Si was suggested for raising solar-cell efficiency up to 49% through efficient harvesting of near-and mid-IR solar radiation. [17] Besides the donor-based band-to-band absorption, considerable free-carrier absorption via thermal ionization of shallow donor states was also reported in such Si nanoparticles (NPs), which are innovative promising light-harvesting components of thin-film solar cells and key-enabling biocompatible theranostic elements of infrared-laser and radiofrequency hyperthermia-based therapies of cancer cells in tumors and metastases, are significantly advanced in their near/mid-infrared band-to-band and free-carrier absorption via donor sulfur-hyperdoping during high-throughput facile femtosecond-laser ablative production in liquid carbon disulfide. High-resolution transmission electron microscopy and Raman microscopy reveal their mixed nanocrystalline/ amorphous structure, enabling the extraordinary sulfur content of a few atomic percents and very minor surface oxidation/carbonization characterized by energy-dispersive X-ray spectro scopy and X-ray photoelectron spectroscopy. A 200-nm thick layer of the nanoparticles exhibits near−mid-infrared absorbance, comparable to that of the initial 380-micron thick n-doped Si wafer (phosphordopant concentration ≈10 15 cm −3 ), with the corresponding extinction coefficient for the hyperdoped NPs being 4-7 orders higher over the broadband spectral range of 1-25 micrometers. Such ultimate, but potentially tunable mid-IR structured, multi-band absorption of various sulfur-impurity clusters and smooth free-carrier absorption are break through advances in mid-infrared (mid-IR) laser and radiofrequency (RF) hyperthermia-based therapies, as envisioned in the RF-heating tests, and in fabrication of higher-efficiency thin-film and bulk photovoltaic devices with ultra-broad (UV−mid-IR) spectral response.

Multigram-Scale Production of Hybrid Au-Si Nanomaterial by Laser Ablation in Liquid (LAL) for Temperature-Feedback Optical Nanosensing, Light-to-Heat Conversion, and Anticounterfeit Labeling

“…This provides a pathway for the preparation of nanomaterials with a wide range of morphologies, structures and compositions (including metastable and nonequilibrium phases) . Laser irradiation of LAL-generated dispersions can further expand the method functionality, allowing for the high-performance preparation of diverse hybrid nanomaterials for photovoltaics, , photothermal conversion, ,− catalysis, − nonlinear optics, sensing, − and medical applications. , …”

Hybrid Au-Si microspheres produced by laser ablation in liquid (LAL) for temperature-feedback optical nano-sensing and anti-counterfeit labeling

“…This provides a pathway for the preparation of nanomaterials with a wide range of morphology, structure and composition (including meta-stable and non-equilibrium phases). Laser irradiation of LAL-generated dispersions can further expand the method functionality, allowing for highperformance preparation of diverse hybrid nanomaterials for photovoltaics 17,18 , photothermal conversion 19,20 , catalysis [21][22][23] , nonlinear optics 24 , sensing [25][26][27][28] and medi-cal applications 29,30 . Gold, the most chemically stable plasmon-active metal, and silicon, an earth-abundant semiconductor widely applied for all-dielectric metasurface design, present an intriguing combination, in which the advantages of plasmonic and nanophotonic concepts can be merged within unified nanostructures.…”

Black Au-Decorated TiO2 Produced via Laser Ablation in Liquid

“…Laser ablation in liquids (LAL) has emerged as a promising high-performance and green approach for nanomaterial preparation. − When compared with wet-chemistry methods, LAL represents a simple and environmentally friendly technology that can be performed under normal environmental conditions without external stimuli. Intense pulsed laser radiation generates extremely high local pressures, temperatures, and quenching rates, thus providing experimental conditions for production of nanostructures with different phase composition (including unique metastable phases), , complex chemical composition, and morphology. − However, so far only a few studies reported on LAL-generated hybrid nanomaterials where plasmonic and dielectric counterparts were combined within practically relevant design, ,− yet without rigorous assessment of their nanophotonic properties and practical applications.…”