Formation of Paramagnetic Defects in the Synthesis of Silicon Carbide.

Silicon carbide (SiC) is a very promising platform for quantum information processing, as it can host room temperature solid state defect quantum bits. These room temperature quantum bits are realized by paramagnetic silicon vacancy and divacancy defects in SiC that are typically introduced by irradiation techniques. However, irradiation techniques often introduce unwanted defects near the target quantum bit defects that can be detrimental for the operation of quantum bits. Here, we demonstrate that by adding aluminum precursor to the silicon and carbon sources, quantum bit defects are created in the synthesis of SiC without any post treatments. We optimized the synthesis parameters to maximize the paramagnetic defect concentrations-including already established defect quantum bits-monitored by electron spin resonance spectroscopy.

Amino-Termination of Silicon Carbide Nanoparticles.

Silicon carbide nanoparticles (SiC NPs) are promising inorganic molecular-sized fluorescent biomarkers. It is imperative to develop methods to functionalize SiC NPs for certain biological applications. One possible route is to form amino groups on the surface, which can be readily used to attach target biomolecules. Here, we report direct amino-termination of aqueous SiC NPs. We demonstrate the applicability of the amino-terminated SiC NPs by attaching bovine serum albumin as a model for functionalization. We monitor the optical properties of the SiC NPs in this process and find that the fluorescence intensity is very sensitive to surface termination. Our finding may have implications for a few nanometers sized SiC NPs containing paramagnetic color centers with optically read electron spins.

Measurements of the negative refractive index of sub-diffraction waves propagating in an indefinite permittivity medium.

An indefinite permittivity medium (IPM) has been fabricated and optically characterized in mid-infrared spectral range (10.7 µm-11.3 µm). Phase and amplitude transmission measurements reveal two remarkable properties of IPMs: (i) transmission of sub-diffraction waves (as short as λ/4) can exceed those of diffraction-limited ones, and (ii) sub-diffraction waves can propagate with negative refractive index. We describe a novel double-detector optical technique relying on the interference between sub-diffraction and diffraction-limited waves for accurate measurement of the transmission amplitude and phase of the former.

High Piezoelectric Conversion Properties of Axial InGaN/GaN Nanowires.

We demonstrate for the first time the efficient mechanical-electrical conversion properties of InGaN/GaN nanowires (NWs). Using an atomic force microscope equipped with a modified Resiscope module, we analyse the piezoelectric energy generation of GaN NWs and demonstrate an important enhancement when integrating in their volume a thick In-rich InGaN insertion. The piezoelectric response of InGaN/GaN NWs can be tuned as a function of the InGaN insertion thickness and position in the NW volume. The energy harvesting is favoured by the presence of a PtSi/GaN Schottky diode which allows to efficiently collect the piezo-charges generated by InGaN/GaN NWs. Average output voltages up to 330 ± 70 mV and a maximum value of 470 mV per NW has been measured for nanostructures integrating 70 nm-thick InGaN insertion capped with a thin GaN top layer. This latter value establishes an increase of about 35% of the piezo-conversion capacity in comparison with binary p-doped GaN NWs. Based on the measured output signals, we estimate that one layer of dense InGaN/GaN-based NW can generate a maximum output power density of about 3.3 W/cm². These results settle the new state-of-the-art for piezo-generation from GaN-based NWs and offer a promising perspective for extending the performances of the piezoelectric sources.