Infrared Imaging Using Thermally Stable HgTe/CdS Nanocrystals.

Transferring nanocrystals (NCs) from the laboratory environment toward practical applications has raised new challenges. HgTe appears as the most spectrally tunable infrared colloidal platform. Its low-temperature synthesis reduces the growth energy cost yet also favors sintering. Once coupled to a read-out circuit, the Joule effect aggregates the particles, leading to a poorly defined optical edge and large dark current. Here, we demonstrate that CdS shells bring the expected thermal stability (no redshift upon annealing, reduced tendency to form amalgams, and preservation of photoconduction after an atomic layer deposition process). The electronic structure of these confined particles is unveiled using k.p self-consistent simulations showing a significant exciton binding energy of ∼200 meV. After shelling, the material displays a p-type behavior that favors the generation of photoconductive gain. The latter is then used to increase the external quantum efficiency of an infrared imager, which now reaches 40% while presenting long-term stability.

250 DPI at 1000 Hz acquisition rate S0 lamb wave digitizing pen.

This paper presents an active stylus (X, Y) flat digitizing tablet (AST). The tablet features an acquisition rate of 1000 pts/s with 0.1 mm resolution. The cordless stylus incorporates a 1-mA low-power pulse generator. Precision is limited by diffraction to about ±0.3 mm on a 57 x 57 mm region of a 71 x 71 x 1 mm digitizing plate. Selective generation and detection of the S(0) Lamb mode with a precessing tip is the key feature of this tablet. We first highlight the ultrasonic propagation inside the stylus tip and stability of Lamb wave generation when the stylus is inclined, rotated, and slid. Then, modeling of the limitations imposed by diffraction of a 1-MHz burst S(0) plane Lamb wave packet is carried out. The model takes into account high-order zero crossing detection as well as reflections and shear horizontal (SH) conversions of the S(0) Lamb mode at free edges of a glass plate. Reflection and transmission through an isotropic PZT bar are also calculated. Finally, localization precision by time difference of arrival (TDOA) is calculated and experimentally verified near the borders of the plate, taking into account the angular sensitivity of the precessing tip.

Ultraviolet illumination thermoreflectance for the temperature mapping of integrated circuits.

Noncontact optical methods such as thermoreflectance, which measure temperature-induced optical reflectivity changes, are particularly suitable for obtaining high-resolution temperature mappings on integrated circuits. Unfortunately, the coefficient linking the variations of temperature and reflectivity depends on the nature of the material and can be modified when optical interferences occur in the Si3N4-based encapsulation layers protecting the circuits. We show that taking advantage of the deep UV absorption of encapsulation layers yields temperature mapping that is independent of the underlying materials. A single calibration is therefore enough to yield the temperature on any point of the uniform and thermally thin encapsulation layer. This simplification and its potential for high resolution should make UV thermoreflectance more attractive to the semiconductor industry.