Roughness Suppression in Electrochemical Nanoimprinting of Si for Applications in Silicon Photonics.

Metal-assisted electrochemical nanoimprinting (Mac-Imprint) scales the fabrication of micro- and nanoscale 3D freeform geometries in silicon and holds the promise to enable novel chip-scale optics operating at the near-infrared spectrum. However, Mac-Imprint of silicon concomitantly generates mesoscale roughness (e.g.

Electroless Dealloying of Thin-Film Nanocrystalline Au-Ag Alloys: Mechanisms of Ligament Nucleation and Sources of Its Synthesis Variability.

Control of ligament size in nanoporous gold through process inputs in chemical dealloying holds the potential to exploit its size dependent properties in applications in energy and biomedicine. While its morphology evolution is regulated by the kinetics of coarsening, recent studies are focused on the early stage of dealloying (e.g.

Metal-Assisted Electrochemical Nanoimprinting of Porous and Solid Silicon Wafers.

Metal-assisted electrochemical imprinting (Mac-Imprint) is a combination of metal-assisted chemical etching (MACE) and nanoimprint lithography that is capable of direct patterning 3D micro- and nanoscale features in monocrystalline group IV (e.g., Si) and III-V (e.

3D Printing-Enabled Nanoparticle Alignment: A Review of Mechanisms and Applications.

3D printing (additive manufacturing (AM)) has enormous potential for rapid tooling and mass production due to its design flexibility and significant reduction of the timeline from design to manufacturing. The current state-of-the-art in 3D printing focuses on material manufacturability and engineering applications. However, there still exists the bottleneck of low printing resolution and processing rates, especially when nanomaterials need tailorable orders at different scales.

Optical characterization and modeling of nanoporous gold absorbers fabricated by thin-film dealloying.

This work studies the optical reflectance of nanoporous gold (NPG) thin films of varying pore volume fraction (PVF) synthesized by chemical dealloying of Ag-Au alloy precursors. The fabricated samples are characterized by scanning electron microscopy, and spectral hemispherical reflectance is measured with an integrating sphere. The effective isotropic optical constants of NPG with varying PVF are modeled for the wavelength range from 0.

Electrochemical nanoimprinting of silicon.

Scalable nanomanufacturing enables the commercialization of nanotechnology, particularly in applications such as nanophotonics, silicon photonics, photovoltaics, and biosensing. Nanoimprinting lithography (NIL) was the first scalable process to introduce 3D nanopatterning of polymeric films. Despite efforts to extend NIL's library of patternable media, imprinting of inorganic semiconductors has been plagued by concomitant generation of crystallography defects during imprinting.

Enhanced Photoelectrochemical Water Splitting with Er- and W-Codoped Bismuth Vanadate with WO Heterojunction-Based Two-Dimensional Photoelectrode.

A novel two-dimensional (2D) heterojunction photoelectrode composed of WO and (Er,W):BiVO is proposed for water oxidation with efficient photoinduced charge carrier separation and transfer. Er stoichiometric along with W nonstoichiometric codoping was introduced to simultaneously manage vacancy creation during substitutional doping, enhance light absorption, and reduce overall impedance. It was found that Er is substituted at the Bi sites in the BiVO lattice to provide expanded light absorption from 400 to 680 nm.

Quenched phonon drag in silicon nanowires reveals significant effect in the bulk at room temperature.

Existing theory and data cannot quantify the contribution of phonon drag to the Seebeck coefficient (S) in semiconductors at room temperature. We show that this is possible through comparative measurements between nanowires and the bulk. Phonon boundary scattering completely quenches phonon drag in silicon nanowires enabling quantification of its contribution to S in bulk silicon in the range 25-500 K.

Controllable doping and wrap-around contacts to electrolessly etched silicon nanowire arrays.

Top-down electroless chemical etching enables non-lithographic patterning of wafer-scale nanostructured arrays, but the etching on highly doped wafers produces porous structures. The lack of defect-free nanostructures at desired doping and the difficulties in forming reliable electrical side-contacts to the nanostructure arrays limits their integration into high performance nanoelectronics. We developed a barrier layer diffusion technique to controllably dope wafer-scale silicon nanowire arrays (10(17)-10(20) cm(-3)) produced by chemically etching lightly doped silicon wafers.

Porosity control in metal-assisted chemical etching of degenerately doped silicon nanowires.

We report the fabrication of degenerately doped silicon (Si) nanowires of different aspect ratios using a simple, low-cost and effective technique that involves metal-assisted chemical etching (MacEtch) combined with soft lithography or thermal dewetting metal patterning. We demonstrate sub-micron diameter Si nanowire arrays with aspect ratios as high as 180:1, and present the challenges in producing solid nanowires using MacEtch as the doping level increases in both p- and n-type Si. We report a systematic reduction in the porosity of these nanowires by adjusting the etching solution composition and temperature.

Nonlithographic patterning and metal-assisted chemical etching for manufacturing of tunable light-emitting silicon nanowire arrays.

Semiconductor nanowires have potential applications in photovoltaics, batteries, and thermoelectrics. We report a top-down fabrication method that involves the combination of superionic-solid-state-stamping (S4) patterning with metal-assisted-chemical-etching (MacEtch), to produce silicon nanowire arrays with defined geometry and optical properties in a manufacturable fashion. Strong light emission in the entire visible and near infrared wavelength range at room temperature, tunable by etching condition, attributed to surface features, and enhanced by silver surface plasmon, is demonstrated.