Density of electronic states in silicon nanocrystals embedded in a SiO2 matrix and passivated by hydrogen

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Subject of study. This study is devoted to the optical transitions and density of electron and hole states in silicon nanocrystals embedded in a SiO2 dielectric matrix and silicon nanocrystals passivated by hydrogen. Aim of study. The aim is to calculate the probability of optical transitions, density of electron and hole states, and absorption cross-section in silicon nanocrystals surrounded by different environments. Another goal is to adapt the tight-binding method for correct passivation of dangling bonds of silicon. Method. The calculations are performed using the variant of the tight-binding method that accounts for a large number of orbitals: s, p, d, and s∗. Main results. The local density of states of electrons and holes, probabilities of optical transitions, and absorption cross-sections of silicon nanocrystals passivated by hydrogen and nanocrystals embedded in a SiO2 matrix were calculated. It is shown that the electron and hole states in hydrogen-passivated silicon nanocrystals are localized within the crystal, and optical transitions occur at wavelengths in the range of 440–620 nm. The presence of the SiO2 matrix surrounding the nanocrystal increases the probability of optical transitions and leads to the appearance of the local density of states outside the nanocrystal, with radiative emission in the wavelength range of 410–620 nm. Practical significance. The results highlight the feasibility of utilizing silicon nanocrystals in photonics and photovoltaics. They are expected to contribute to the development of technology for creating silicon nanocrystals with specific optical properties.