The intercalation of layered compounds opens up a vast space of new host–guest hybrids, providing new routes for tuning the properties of materials. Here, it is shown that uniform and continuous layers of copper can be intercalated within the van der Waals gap of bulk MoS2 resulting in a unique Cu–MoS2 hybrid. The new Cu–MoS2 hybrid, which remains semiconducting, possesses a unique plasmon resonance at an energy of ≈1eV, giving rise to enhanced optoelectronic activity. Compared with high‐performance MoS2 photodetectors, copper‐enhanced devices are superior in their spectral response, which extends into the infrared, and also in their total responsivity, which exceeds 104 A W−1. The Cu–MoS2 hybrids hold promise for supplanting current night‐vision technology with compact, advanced multicolor night vision.

Among the phase-change materials, Ge-rich GeSbTe (GST) alloys are of considerable interest as they offer a much higher thermal stability than their congruent contenders, a desirable characteristic for embedded digital memories and neuromorphic devices. Up to now, the mechanisms by which such alloys crystallize and progressively switch from one resistivity state to the other remain unclear and very controversial. Using in situ synchrotron X-ray diffraction during isothermal annealing and advanced transmission electron microscopy techniques, we solve this riddle and unveil the mechanisms leading to the overall crystallization of such alloys. During annealing at 310 °C, the initially homogeneous and amorphous material undergoes a progressive phase separation, leading to the formation of Ge-rich regions of different compositions. During this decomposition, the first formed GeTe embryos crystallize and trigger the heterogeneous crystallization of the Ge cubic phase. As the phase separation proceeds, these embryos dissolve and the Ge phase gradually builds up through the nucleation of small grains. Only when this Ge cubic phase is largely formed, the remaining amorphous matrix may locally reach the Ge 2 Sb 2 Te 5 composition at which it can crystallize as large grains. Our density functional theory calculations confirm that the quite exotic Pnma GeTe structure we have experimentally identified is more stable than the regular R3m structure at nanometric sizes.

Nitridation of sapphire substrates is used as a precursor to the growth of GaN films to provide a wetting layer which is closer in terms of structure and chemistry to the overlayer. Nitridation has been carried out by metal–organic chemical vapor deposition at 530, 800, and 1100 °C in an environment of NH3 and H2. The structure and chemistry of the nitrided layer grown at these different temperatures have been studied by X-ray photoelectron spectroscopy, electron diffraction, high resolution electron microscopy, and electron energy loss spectroscopy. The low temperature nitridation process results in a nitrided layer in which oxygen has been partially replaced by nitrogen to form a cubic spinel-Al x O y N z structure. Nitridation at 800° and 1100 °C results in complete substitution of oxygen atoms by nitrogen to form a cubic rock salt AlN structure. These structures are stable on thermal annealing at 1000 °C prior to epitaxial GaN growth.