Resonant-cavity-enhanced mid-infrared photodetector on a silicon platform

In this paper, we demonstrate high optical quantum efficiency (90%) resonant-cavity-enhanced mid-infrared photodetectors fabricated monolithically on a silicon platform. High quality photoconductive polycrystalline PbTe film is thermally evaporated, oxygen-sensitized at room temperature and acts as the infrared absorber. The cavity-enhanced detector operates in the critical coupling regime and shows a peak responsivity of 100 V/W at the resonant wavelength of 3.5 μm, 13.4 times higher compared to blanket PbTe film of the same thickness. Detectivity as high as 0.72 × 10[superscript 9] cmHz[superscript 1/2]W[superscript −1] has been measured, comparable with commercial polycrystalline mid-infrared photodetectors. As low temperature processing (< 160 °C) is implemented in the entire fabrication process, our detector is promising for monolithic integration with Si readout integrated circuits

Solution-Processable Near-IR Photodetectors Based on Electron Transfer from PbS Nanocrystals to Fullerene Derivatives

Nanocrystal/fullerene derivative inorganic-organic hybrid photodetectors exhibiting high detectivity for near-IR wavelengths and a linear power dependence are produced. The ultrafast electron transfer from the PbS crystals to the fullerene opens a new route to obtaining efficient photodetectors that are appealing, cost-effective alternatives to the currently available technology

Large-Area Ordered Superlattices from Magnetic W\"ustite/Cobalt Ferrite Core/Shell Nanocrystals by Doctor Blade Casting

Although a large diversity of single-component and binary superlattices from colloidal nanocrystals have been demonstrated, applications of such ordered nanocrystal assemblies are still hampered due to a lack of control over the self-assembly processes over large areas. A reel-to-reel compatible large-area coating technique for solutions is given by doctor blade casting, which is applied here to deposit colloidal nanocrystals onto various substrates. The self-assembly process is demonstrated for magnetic nanocrystals, having a high potential for applications in magnetic memory devices. Shape-controlled (spherical and cubic) and monodisperse nanocrystals with a Wustite core and a cobalt ferrite shell are used in particular. Doctor blade casting of these colloidal nanocrystals results in films exhibiting hexagonally closely packed arrangements, which are formed by a top-down growth, as is evidenced by cross sectional transmission electron microscopy. The ordering in the topmost layer extends over large areas, although some defects and irregularities are found. The degree and quality of self-assembly is quantified by analyzing plan view images of the assemblies by means of the decay of their autocorrelation function. This analysis reveals that the degree of ordering obtained by doctor blade casting outperforms those provided by alternative deposition techniques such as inkjet printing or drop casting. The results for the coherent lengths deduced from the autocorrelation analysis are shown to be consistent with those from grazing-incidence small-angle X-ray scattering, giving coherence length on the order of 1000 nm

Prospects of Nanoscience with Nanocrystals

International audienceColloidal nanocrystals (NCs, i.e., crystalline nanoparticles) have become an important class of materials with great potential for applications ranging from medicine to electronic and optoelectronic devices. Todays strong research focus on NCs has been prompted by the tremendous progress in their synthesis. Impressively narrow size distributions of just a few percent, rational shape-engineering, compositional modulation, electronic doping, and tailored surface chemistries are now feasible for a broad range of inorganic compounds. The performance of inorganic NC-based photovoltaic and light-emitting devices has become competitive to other state-of-the-art materials. Semiconductor NCs hold unique promise for near- and mid-infrared technologies, where very few semiconductor materials are available. On a purely fundamental side, new insights into NC growth, chemical transformations, and self-organization can be gained from rapidly progressing in situ characterization and direct imaging techniques. New phenomena are constantly being discovered in the photophysics of NCs and in the electronic properties of NC solids. In this Nano Focus, we review the state of the art in research on colloidal NCs focusing on the most recent works published in the last 2 years