Highly luminescent, stable, and biocompatible 3C-SiC quantum dots (QDs) with no protective shells have been applied for fluorescence imaging of biological living cells. Structural and luminescent properties of the 3C-SiC QDs are described. Marking of the living cells with such QDs highlights the penetration, accumulation, and heterogeneous distribution of the QDs inside the intracellular space.
We show how the height dispersion of self-organized InAs/InP(001) quantum islands emitting at 1.55 μm was reduced by optimizing the epitaxial growth parameters. Low height dispersion was obtained when the InAs deposit thickness was much greater than the critical thickness for two-dimensional/three-dimensional growth mode transition, and when adatom surface diffusion was favored by increasing the growth temperature or reducing the arsenic pressure during the InAs growth. When these growth conditions are not respected, the multicomponent photoluminescence spectrum obtained is explained through the common interpretation of island height varying with monolayer fluctuation. In optimized growth conditions, the multicomponent spectrum obtained is interpreted as emission from fundamental and excited levels of InAs islands with low height dispersion. Transmission electron microscopy (TEM) imaging shows that these InAs islands are stick-like, 50–100 nm in length and 22±1.2 nm in width. Cross-sectional TEM reveals flat islands, shaped like truncated pyramids, with a very homogeneous height measured at 2.4 nm. A fundamental level linewidth of 22 meV at 8 K is associated to this very narrow height distribution. Such low photoluminescence linewidth values are believed to be mainly due to the propensity of the InAs/InP(001) system to produce flat InAs islands with discrete height fluctuation.
The fabrication of microcavities by a sol–gel process and their optical properties are described. The cavities are constituted of an Eu3+-doped SiO2 active layer inserted between two Bragg mirrors, fabricated by stacking alternatiely undoped TiO2 and SiO2 sol–gel thin films. Eu3+ luminescence modification due to the cavity effect, intensity enhancement and modification of the line shape has been observed, and shows a cavity quality factor of 1200. The reflectivity factor of the associated Bragg mirrors reaches 99.8% for seven alternate SiO2/TiO2 layers.
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