Deformation and fracture mechanisms of ultrathin Si nanowires (NWs), with diameters of down to ~9 nm, under uniaxial tension and bending were investigated by using in situ transmission electron microscopy and molecular dynamics simulations. It was revealed that the mechanical behavior of Si NWs had been closely related to the wire diameter, loading conditions, and stress states. Under tension, Si NWs deformed elastically until abrupt brittle fracture. The tensile strength showed a clear size dependence, and the greatest strength was up to 11.3 GPa. In contrast, under bending, the Si NWs demonstrated considerable plasticity. Under a bending strain of <14%, they could repeatedly be bent without cracking along with a crystalline-to-amorphous phase transition. Under a larger strain of >20%, the cracks nucleated on the tensed side and propagated from the wire surface, whereas on the compressed side a plastic deformation took place because of dislocation activities and an amorphous transition.

Impurity doping is the most important technique to functionalize semiconductor nanowires. The crucial point is how the states of impurity atoms can be detected. The chemical bonding states and electrical activity of boron (B) and phosphorus (P) atoms in germanium nanowires (GeNWs) are clarified by micro-Raman scattering measurements. The observation of B and P local vibrational peaks and the Fano effect clearly demonstrate that the B and P atoms are doped into the crystalline Ge region of GeNWs and electrically activated in the substitutional sites, resulting in the formation of p-type and n-type GeNWs. This method can be a useful technique for the characterization of semiconductor nanowire devices. The B-doped GeNWs showed an increasingly tapered structure with increasing B concentration. To avoid tapering and gain a uniform diameter along the growth direction of the GeNWs, a three step process was found to be useful, namely growth of GeNWs followed by the deposition of an amorphous Ge layer with high B concentration and then annealing.

Silicon nanowires (SiNWs) have considerable potential to assist the realization of next‐generation metal‐oxide semiconductor field‐effect transistors (MOSFETs) with vertical structures. Impurity doping and its control is a key technique in the creation of SiNW devices, which renders it necessary to develop characterization methods for dopant atoms in SiNWs. In this Research News, we described how the states of the dopant atoms boron and phosphorus can be detected.

Gaining an understanding the dynamic behaviors of dopant atoms in silicon nanowires (SiNWs) is the key to achieving low-power and high-speed transistor devices using SiNWs. The segregation behavior of boron (B) and phosphorus (P) atoms in B- and P-doped SiNWs during thermal oxidation was closely observed using B local vibrational peaks and Fano broadening in optical phonon peaks of B-doped SiNWs by micro-Raman scattering. Electron spin resonance (ESR) signals from conduction electrons were used for P-doped SiNWs. Our results showed that B atoms preferentially segregate in the surface oxide layer, whereas P atoms tend to accumulate in the Si region around the interface of SiNWs. The radial distribution of P atoms in SiNWs was also investigated to prove the difference segregation behaviors between of P and B atoms.

Local vibrational modes of boron ͑B͒ in silicon nanowires ͑SiNWs͒ synthesized by laser ablation were observed at about 618 and 640 cm −1 by Raman scattering measurements. Boron doping was performed during the growth of SiNWs. Fano ͓Phys. Rev. 124, 1866 ͑1961͔͒ broadening was also observed in the Si optical phonon peak. These results prove that B atoms were doped in the SiNWs. Hydrogen ͑H͒ passivation of B acceptors in the SiNWs was also investigated. A broad peak was observed at around 650-680 cm −1 after hydrogenation, demonstrating that B dopants were passivated by the formation of the well-known H-B passivation centers.

The Al-induced crystallization (AIC) yields a large-grained (111)-oriented Ge thin film on an insulator at temperatures as low as 180 C. We accelerated the AIC of an amorphous Ge layer (50-nm thickness) by initially doping Ge in Al and by facilitating Ge diffusion into Al. The electron backscatter diffraction measurement demonstrated the simultaneous achievement of large grains over 10 lm and a high (111) orientation fraction of 90% in the polycrystalline Ge layer formed at 180 C. This result opens up the possibility for developing Ge-based electronic and optical devices fabricated on inexpensive flexible substrates. V

A gradual downshift and asymmetric broadening of the Si optical phonon peak were observed by Raman scattering measurements of continuously thermally oxidized silicon nanowires ͑SiNWs͒ synthesized by laser ablation. This downshift and broadening can be interpreted by the phonon confinement effect. Further thermal oxidation produced a reverse change; namely, an upshift of the optical phonon peak. This is considered to be due to compressive stress since this stress was relieved by removing the oxide layers formed around the SiNW cores, resulting in a downshift of the optical phonon peak.

Vacancies have been demonstrated to be significant for CO2 reduction reaction (CO2RR) over ZnS, but anion vacancies were easily refilled with oxygen species and could work as both H2 and CO evolution sites, aggravating the competition between hydrogen evolution reaction (HER) and CO2RR. In this study, cation vacancies (VZn) were proposed as new active sites on the ZnS surface. With no cocatalyst, the VZn-rich ZnS acquired a high selectivity of formate production (>85%) in inorganic aqueous solution. In situ attenuated total reflection-infrared (ATR-IR) spectroscopy and first-principle calculations have clarified the CO2RR pathways into formate and proved that the surface VZn could greatly lower the barrier of CO2RR and suppress the proton adsorption, elucidating the origin of the highly selective CO2RR in the presence of competitive HER. This work gives an in-depth understanding of the cation vacancies and inspiration to develop efficient photocatalysts.