We demonstrate experimentally bipolar (electrons and holes) current injection into silicon nanocrystals in thin nanocrystalline-$\text{Si}/{\text{SiO}}_2$ multilayers. These light emitting devices have power efficiency of 0.17% and turn-on voltage of 1.7 V. The high electroluminescence efficiency and low onset voltages are attributed to the radiative recombination of excitons formed by both electron and hole injection into silicon nanocrystals via the direct tunneling mechanism. To confirm the bipolar character, different devices were grown, with and without a thick silicon oxide barrier at the multilayer contact electrodes. A transition from bipolar tunneling to unipolar Fowler–Nordheim tunneling is thus observed.

We report on the investigation on the resolution of optical sensors exploiting Bloch surface waves sustained by one dimensional photonic crystals. A figure of merit is introduced to quantitatively assess the performance of such sensors and its dependency on the geometry and materials of the photonic crystal. We show that the figure of merit and the resolution can be improved by adopting a full ellipsometric phase-sensitive approach. The theoretical predictions are confirmed by experiments in which, for the first time, such type of sensors are operated in the full ellipsometric scheme.

Recent measurements have suggested that the antiplasticizing effect of glycerol on trehalose can significantly increase the preservation times of proteins stored in this type of preservative formulation. In order to better understand the physical origin of this phenomenon, we examine the nature of antiplasticization in trehalose-glycerol mixtures by dielectric spectroscopy. These measurements cover a broad frequency range between $40\mathrm{Hz}\text{to}18\mathrm{GHz}$ (covering the secondary relaxation range of the fragile glass-former trehalose and the primary relaxation range of the strong glass-former glycerol) and a temperature $\left(T\right)$ range bracketing room temperature $\left(220\mathrm{K}\text{to}350\mathrm{K}\right)$. The Havriliak-Negami function precisely fits our relaxation data and allows us to determine the temperature and composition dependence of the relaxation time $\tau$ describing a relative fast dielectric relaxation process appropriate to the characterization of antiplasticization. We observe that increasing the glycerol concentration at fixed $T$ increases $\tau$ (i.e., the extent of antiplasticization) until a temperature dependent critical “plasticization concentration” $x_{wp}$ is reached. At a fixed concentration, we find a temperature at which antiplasticization first occurs upon cooling and we designate this as the “antiplasticization temperature,” $T_{\mathit{ant}}$. The ratio of the $\tau$ values for the mixture and pure trehalose is found to provide a useful measure of the extent of antiplasticization, and we explore other potential measures of antiplasticization relating to the dielectric strength.

Silicon nanocrystals (Si-nc) is an enabling material for silicon photonics, which is no longer an emerging field of research but an available technology with the first commercial products available on the market. In this paper, properties and applications of Si-nc in silicon photonics are reviewed. After a brief history of silicon photonics, the limitations of silicon as a light emitter are discussed and the strategies to overcome them are briefly treated, with particular attention to the recent achievements. Emphasis is given to the visible optical gain properties of Si-nc and to its sensitization effect on Er ions to achieve infrared light amplification. The state of the art of Si-nc applied in a few photonic components is reviewed and discussed. The possibility to exploit Si-nc for solar cells is also presented. In addition, nonlinear optical effects, which enable fast all-optical switches, are described.

We report on the design, fabrication, and characterization of optical sensors based on Bloch surface waves propagating at the truncation edge of one-dimensional photonic crystals. The sensors can be simultaneously operated in both a label-free mode, where small refractive index changes at the surface are detected, and a fluorescence mode, where the fluorescence from a novel heptamethyne dye label in the proximity of the surface is collected. The two modes operate in the near-infrared spectral range with the same configuration of the optical reading apparatus. The limit of detection is shown to be smaller than that of equivalent surface plasmon sensors and the fluorescence collection efficiency is such that it can be efficiently analyzed by the same camera sensor used for label-free operation.