Structure and Properties of Heavily B and P Codoped Amorphous Silicon Quantum Dots

Abstract

Colloidal silicon quantum dots feature a number of outstanding properties, such as size and termination controlled band gap and photoluminescence, which, in combination with nontoxicity, make them suitable for biomedical applications. Because of the presence of structural disorder and experimental limitations, the atomic structure, especially of the small sub 2.5 nm dots, is not well known. We have developed computational techniques that allow us to model the atomic structures of the small dots and have applied them to heavily B and P codoped Si quantum dots and studied their structural, electronic, and vibrational properties. The study confirms that the structures of the smallest dots are fully amorphous with the onset of formation of a quasi-crystalline core in the larger ones. The models give insights into the dopant distribution in the dot. We find that the core morphology depends strongly on the chemical composition of the dot. Study of the electronic and vibrational properties gives insights into their localization properties and allows validation of the generated models by comparison with experiments. The degree of agreement of the properties of our simulated dots with those from experiments suggests that the fine details in preparation protocols may not critically affect their structure and properties.

Ab Initio Molecular Dynamics Simulation Study on Phosphorus/Boron Co-Doped Si Nanocrystals/SiO2 Core/Shell Structures

“…Ab initio molecular dynamics (AIMD) simulations are a powerful tool that can provide a viable complementary approach to experimental investigations and can effectively surmount the limitations encountered in conventional empirical methods . Several studies have reported on the molecular dynamics of Si NCs, including investigations into freestanding structures outside the encapsulation of hydrogen atoms, as well as models focusing on the encapsulation of N and O within the external environment of Si. − However, limited research has been conducted on the Si/SiO 2 structure of the core–shell model, which is constructed similarly to our model. Additionally, there has been minimal exploration into the mechanism of co-doping.…”