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Determination of the Elastic Behavior of Silicon Nanowires within a Scanning Electron Microscope
摘要： Three-point bending tests were performed on double-anchored, ?110? silicon nanowire samples in the vacuum chamber of a scanning electron microscope (SEM) via a micromanipulator equipped with a piezoresistive force sensor. Nanowires with widths of 35 nm and 74 nm and a height of 168 nm were fabricated. The nanowires were obtained monolithically along with their 10 ??m tall supports through a top-down fabrication approach involving a series of etching processes. The exact dimension of wire cross sections was determined by transmission electron microscopy (TEM). Conducting the experiments in an SEM chamber further raised the opportunity of the direct observation of any deviation from ideal loading conditions such as twisting, which could then be taken into consideration in simulations. Measured force-displacement behavior was observed to exhibit close resemblance to simulation results obtained by finite element modeling, when the bulk value of 169 GPa was taken as the modulus of elasticity for ?110? silicon. Hence, test results neither show any size effect nor show evidence of residual stresses for the considered nanoscale objects. The increased effect of the native oxide with reduced nanowire dimensions was captured as well. The results demonstrate the potential of the developed nanowire fabrication approach for the incorporation in functional micromechanical devices.
关键词： SEM,silicon nanowires,three-point bending tests,finite element modeling,elastic behavior
更新于2025-09-09 09:28:46
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Optical Trapping, Optical Binding, and Rotational Dynamics of Silicon Nanowires in Counter-Propagating Beams
摘要： Silicon nanowires are held and manipulated in controlled optical traps based on counter-propagating beams focused by low numerical aperture lenses. The double-beam configuration compensates light scattering forces enabling an in-depth investigation of the rich dynamics of trapped nanowires that are prone to both optical and hydrodynamic interactions. Several polarization configurations are used, allowing the observation of optical binding with different stable structure as well as the transfer of spin and/or orbital momentum of light to the trapped silicon nanowires. Accurate modeling based on Brownian dynamics simulations with appropriate optical and hydrodynamic coupling confirms that this rich scenario is crucially dependent on the non-spherical shape of the nanowires. Such increased level of optical control of multi-particle structure and dynamics open perspectives for nanofluidics and multicomponent light-driven nanomachines.
关键词： optical binding,silicon nanowires,light-driven rotations,Optical trapping,light angular momentum
更新于2025-09-09 09:28:46
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Radially resolved electronic structure and charge carrier transport in silicon nanowires
摘要： The electronic structure of silicon nanowires is studied using density functional theory. A radially resolved density of states is discussed for different nanowire diameters and crystal orientations. This approach allows the investigation of spatially varying electronic properties in the radial direction and extends previous studies, which are usually driven by a one-dimensional band structure analysis. We demonstrate strong differences in the electronic structure between the surface and the center of the nanowire, indicating that the carrier transport will mainly take place in the center. For increasing diameters, the density of states in the center approaches the bulk density of states. We find that bulk properties, such as the indirect nature of the band gap, become significant at a nanowire diameter of approximately 5 nm and beyond. Finally, the spatial characteristic of the current is visualized in terms of transmission pathways on the atomic scale. Electron transport is found to be more localized in the nanowire center than the hole transport. It also depends on the crystal orientation of the wire. For the growing demand of silicon nanowires, for example in the field of sensors or field-effect transistors, multiple conclusions can be drawn from the present work, which we discuss towards the end of the publication.
关键词： charge carrier transport,radially resolved density of states,silicon nanowires,density functional theory,electronic structure
更新于2025-09-09 09:28:46
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Design and investigation of a dual-layer grating coupler for efficient vertical fiber-chip coupling
摘要： A novel dual-layer grating coupler was designed for efficient vertical coupling between a single-mode fiber and silicon nanowires, with characteristics of polarization diversity and both wavelength bands of 1.3 and 1.55 μm. Theoretical analysis and two-dimensional finite-difference time-domain simulations were applied to verify the performance of the design. Optimized results show that the coupling efficiencies of a dual-port output of 41% (?3.87 dB) for transverse-electric polarization at 1.56 μm, 32.88% (?4.83 dB) for transverse-magnetic (TM) polarization at 1.58 μm, and 27.06% (?5.68 dB) for TM polarization at 1.32 μm can be achieved. Dual-layer Fabry–Perot resonance was also investigated for high coupling efficiency.
关键词： silicon nanowires,dual-layer grating coupler,vertical fiber-chip coupling,polarization diversity,wavelength bands
更新于2025-09-04 15:30:14