Aluminum induced crystallization of amorphous SiGe at low temperature is studied and a dual-phase stacked structure with different compositions emerges when the annealing temperature is higher than a critical value. This behavior is very sensitive to the oxidization state of the interlayer. A model based on energetics is proposed to elucidate this temperature dependent behavior. Thermodynamically, it can be ascribed to the competition between grain-boundary-mediated and interface-mediated crystallization and kinetically, it stems from the different diffusion rates of Si and Ge. The results are useful to the design and fabrication of high-efficiency solar cells.

Surface-enhanced Raman scattering (SERS) has been considered as a promising sensing technique to detect low-level analytes. However, its practical application was hindered owing to the lack of uniform SERS substrates for ultrasensitive and reproducible assay. Herein, inspired by the natural cactus structure, we developed a cactus-like 3D nanostructure with uniform and high-density hotspots for highly efficient SERS sensing by both grafting the silicon nanoneedles onto Ag dendrites and subsequent decoration with Ag nanoparticles. The hierarchical scaffolds and high-density hotspots throughout the whole substrate result in great amplification of SERS signal. A high Raman enhancement factor of crystal violet up to 6.6 × 10(7) was achieved. Using malachite green (MG) as a model target, the fabricated SERS substrates exhibited good reproducibility (RSD ∼ 9.3%) and pushed the detection limit down to 10(-13) M with a wide linear range of 10(-12) M to 10(-7) M. Excellent selectivity was also demonstrated by facilely distinguishing MG from its derivative, some organics, and coexistent metal ions. Finally, the practicality and reliability of the 3D SERS substrates were confirmed by the quantitative analysis of spiked MG in environmental water with high recoveries (91.2% to 109.6%). By virtue of the excellent performance (good reproducibility, high sensitivity, and selectivity), the cactus-like 3D SERS substrate has great potential to become a versatile sensing platform in environmental monitoring, food safety, and medical diagnostics.

Ferroptosis is an iron-dependent cell death and is associated with cancer therapy. Can it play a role in resistance of postoperative infection of implants, especially with an extracellular supplement of Fe ions in a non-cytotoxic dose? To answer this, "nanoswords" of Fe-doped titanite are fabricated on a Ti implant surface to resist bacterial invasion by a synergistic action of ferroptosis-like bacteria killing, proton disturbance, and physical puncture. The related antibiosis mechanism is explored by atomic force microscopy and genome sequencing. The nanoswords induce an increased local pH value, which not only weakens the proton motive force, reducing adenosine triphosphate synthesis of Staphylococcus aureus, but also decreases the membrane modulus, making the nanoswords distort and even puncture a bacterial membrane easily. Simultaneously, more Fe ions are taken by bacteria due to increased bacterial membrane permeability, resulting in ferroptosis-like death of bacteria, and this is demonstrated by intracellular iron enrichment, lipid peroxidation, and glutathione depletion. Interestingly, a microenvironment constructed by these nanoswords improves osteoblast behavior in vitro and bone regeneration in vivo. Overall, the nanoswords can induce ferroptosis-like bacterial death without cytotoxicity and have great promise in applications with clinical implants for outstanding antibiosis and biointegration performance.

Ultrathin TiO2/Al2O3 stacking structures were fabricated using an atomic layer deposition technique. The effect of the ultrathin Al2O3 interlayer on interfacial thermal stability and leakage current properties were studied. After thermal annealing of the TiO2/Al2O3/TiO2/Al2O3/Si structure at 700 °C for 60 s, the Al2O3 double layers remained amorphous, although the layers of TiO2 were crystallized. The amorphous Al2O3 divided the grain boundaries which would otherwise serve as diffusion paths for atoms and as leakage current channels from the TiO2 layers. As a result, atomic diffusion and surface roughness were suppressed, and the leakage current value was reduced by about a 1.5 order of magnitude compared with TiO2/Al2O3/Si. The improved interfacial stability as well as the reduced leakage current density indicates the present stacking structure has potential application in future high-performance microelectronics.

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