Investigations on the Electrochemical and Mechanical Properties of Sb2 O3 Nanobelts by In Situ Transmission Electron Microscopy

Sb₂ O₃ shows great promise as a high-capacity anode material for sodium-ion batteries (SIBs) due to the combined mechanisms of intercalation, conversion, and alloying. In this work, the electrochemical performance and mechanical property of Sb₂ O₃ nanobelts during sodiation/desodiation are revealed by constructing nanoscale solid-state SIBs in a high-resolution transmission electron microscopy. It is found that the Sb₂ O₃ nanobelt exhibits an ultrahigh sodiation speed of ≈13.5 nm s^-1 and experiences a three-step sodiation reaction including the intercalation reaction to form Na_x Sb₂ O₃ , the conversion reaction to form Sb, and the alloying reaction to form NaSb. The alloying reaction is found to be reversible, while the conversion reaction is partially reversible. The Sb₂ O₃ nanobelt shows anisotropic expansion and the orientation of the Sb₂ O₃ nanobelt has great influence on the expansion ratio. It is found that the existence of a {010} plane with large d-spacing in the nanobelt leads to a surprisingly small expansion ratio (≈5%). The morphology of the Sb₂ O₃ nanobelt is well maintained during multiple electrochemical cycles. In situ bending experiments suggest that the sodiated Sb₂ O₃ nanobelts show improved toughness and flexibility compared to pristine Sb₂ O₃ nanobelts. These fundamental studies provide insight into the rational design of anode materials with improved electrochemical and mechanical performance in SIBs.

Piezoresistive effect of n-type 〈111〉-oriented Si nanowires under large tension/compression

Small-scale samples enable us to understand changes in physical properties under larger strain due to their higher tolerance to deformation. In this study, the piezoresistive character of n-type 〈111〉-oriented Si nanowires under large strain was measured during tensile and compressive deformations. The Si nanowires were directly cut from the wafer using top-down technology and deformed while capturing their electrical properties inside a transmission electron microscope. The experimental results show that both tensile and compressive deformation enhanced their electrical transport properties. The piezoresistance coefficient is of the same order of magnitude as its bulk counterpart, but half as large, which may be attributed to a larger strain magnitude. We also studied the circulatory characteristics and influence of electron beam radiation. This study provided new physical insights into piezoresistive effects under large strain.

Orientation Dependence of Electromechanical Characteristics of Defect-free InAs Nanowires

Understanding the electrical properties of defect-free nanowires with different structures and their responses under deformation are essential for design and applications of nanodevices and strain engineering. In this study, defect-free zinc-blende- and wurtzite-structured InAs nanowires were grown using molecular beam epitaxy, and individual nanowires with different structures and orientations were carefully selected and their electrical properties and electromechanical responses were investigated using an electrical probing system inside a transmission electron microscope. Through our careful experimental design and detailed analyses, we uncovered several extraordinary physical phenomena, such as the electromechanical characteristics are dominated by the nanowire orientation, rather than its crystal structure. Our results provide critical insights into different responses induced by deformation of InAs with different structures, which is important for nanowire-based devices.

The effect of tensile and bending strain on the electrical properties of p-type 〈110〉 silicon nanowires

In this study, electromechanical responses induced by uniaxial tensile and bending deformation were obtained for p-type 〈110〉-oriented Si whiskers by in situ transmission electron microscopy (TEM). Ohmic contacts between the nanowires (NWs) and electrodes were achieved using electron-beam-induced carbon deposition. Results show that enhancements in the carrier transport properties were achieved under both uniaxial tensile and bending strains. With the strain increased to 1.5% before fracture, the improvement in the conductance reached a maximum, which was as large as 24.2%, without any sign of saturation. On the other hand, under 5.8% bending strain, a 67% conductivity enhancement could be achieved. This study should provide important insight into the performance of nanoscale-strained Si.

Piezoresistive effect of p-type silicon nanowires fabricated by a top-down process using FIB implantation and wet etching

This work reports the piezoresistance of silicon nanowires fabricated using focused ion beam and wet etching for NEMS mechanical sensors.