Optical and electrical properties of silicon nanoparticles

For the fabrication of optoelectronic devices based on silicon nanoparticles (Si-NPs), it is very important to understand their optical and electrical behavior. In this paper, we present the optical and electrical properties of Si-NPs. We demonstrate that the optical properties of Si-NPs depend on their size as well as their surface chemistry. The size of Si-NPs was finely tuned by etching them in a mixture of hydrofluoric acid (HF) and nitric acid (HNO₃) for different times. The resulting Si- NPs exhibit bright luminescence across the visible spectrum. In order to stabilize the optical emission, the surface of freshly etched Si-NPs was successfully functionalized with organic molecules.As the surface chemistry is also expected to strongly influence the electrical transport between Si-NPs and therefore the electrical properties of Si-NP ensembles, the conductivity of pellets consisting of Si-NPs was measured using impedance spectroscopy. The surface oxide of Si-NPs was removed by etching them with HF acid. The freshly etched Si-NPs showed much higher conductivity compared to as-prepared samples. The surface functionalization of freshly etched Si-NPs slightly decreases their conductivity. However, it was observed that the conductivity was still much higher compared to as-prepared samples.