Speaker
Description
This study examined the structural, chemical and electrical behaviour of silicon nanoparticles produced by high-energy milling, with the goal of understanding how milling conditions, material type and ageing influence their surface stability and electrical activity. The powders, derived from metallurgical and n-type silicon, consistently formed nanocrystalline particles with crystallite sizes of 30-50 nm, surrounded by strained and partially amorphous outer layers that readily incorporated oxygen. Despite long-term exposure to air, the particles did not develop a thick insulating oxide; instead, X-ray photoelectron spectroscopy revealed a thin, graded SiOₓ shell dominated by sub-oxide states (Si⁺, Si²⁺, Si³⁺), with only a small Si⁴⁺ contribution. The net SiO₂ capping was found to be extremely small, between 0.1 - 0.3 nm in one-year-old powders and not more than about 0.8 nm in three-year-old samples, corresponding to an approximate oxide growth rate of 0.1 nm per year, confirming that the nanoparticles remain surface-stable over time. Photoluminescence measurements further supported this interpretation by revealing three defect-related emission bands at 550 nm, 590 - 600 nm and 660 - 670 nm, characteristic of oxygen-related centers within the SiOₓ shell. The presence of these defect states was consistent with the activation energy of approximately 0.2 eV extracted from impedance spectroscopy, which showed that electrical transport in printed films occurs through trap-assisted hopping across the Si/SiOₓ interfaces. Because the oxide shell is thin and discontinuous, the nanoparticles retain measurable conductivity even after years of storage. The combined findings demonstrate that high-energy milling produces electrically active, chemically stable silicon nanoparticles with a defect-rich but ultrathin oxide interface, making them promising for low-temperature printed electronics, flexible sensors, and other silicon-based functional materials.
| Apply for student award at which level: | MSc |
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| Consent on use of personal information: Abstract Submission | Yes, I ACCEPT |