Atomic gold–enabled three-dimensional lithography for silicon mesostructures

Abstract

Three-dimensional (3D) mesostructured semiconductors show promising properties and applications; however, to date, few methods exist to synthesize or fabricate such materials. Metal can diffuse along semiconductor surfaces, and even trace amounts can change the surface behavior. We exploited the phenomena for 3D mesoscale lithography, by showing one example where iterated deposition-diffusion-incorporation of gold over silicon nanowires forms etchant-resistant patterns. This process is facet-selective, producing mesostructured silicon spicules with skeletonlike morphology, 3D tectonic motifs, and reduced symmetries. Atom-probe tomography, coupled with other quantitative measurements, indicates the existence and the role of individual gold atoms in forming 3D lithographic resists. Compared to other more uniform silicon structures, the anisotropic spicule requires greater force for detachment from collagen hydrogels, suggesting enhanced interfacial interactions at the mesoscale.

Cellular uptake and dynamics of unlabeled freestanding silicon nanowires

“…Among these materials, silicon nanowires (SiNWs) are of particular interest because of their excellent electronic properties, distinct one-dimensional (1D) structure, and potential biocompatibility ( 8 ). In addition, SiNW synthesis can be controllably tuned to incorporate a diverse set of functionalities, including modulation in structural morphology ( 9 , 10 ), surface functionalization ( 11 ), and composition ( 12 , 13 ). This allows for the realization of a large library of SiNW-based tools.…”

Nongenetic Optical Methods for Measuring and Modulating Neuronal Response

“…Silicon nanowires in particle show promise, as they can be synthesized in a rationale manner, providing precise spatial control over nanowire morphology 82–84 , doping profiles 85–87 , and optical properties 88–90 . This allows for the fabrication of coaxial photovoltaic devices 87 (Figure 3.a), which can be excited across a broad range of wavelengths, including within the near IR optical window for deep tissue penetration 91 .…”

Rational Design of Semiconductor Nanostructures for Functional Subcellular Interfaces

“…Luo et al exploited this phenomenon by inducing periodic pressure modulations during SiNW growth to generate facet-selective and potassium hydroxide (KOH)-resistant bands of atomic Au on the surfaces of the SiNWs (Figure 1B). 13 Both Au deposition and diffusion processes over SiNWs were found to be facet dependent, and thus Luo et al were able to produce 3D graded Au/Si interfaces. KOH etching was then used to remove Si in regions unprotected by the atomic Au, creating Si spicules with skeleton-like morphologies, 3D tectonic motifs, and reduced symmetries (Figure 1B).…”

“…(E,F) Si spicules can enhance biointegration at the tissue level. Adapted with permission from ref 13. Copyright 2015 American Association for the Advancement of Science.…”

“…3,8,11,12 For instance, one can readily control the doping profiles and morphologies in silicon (Si) nanowires via a vapor–liquid–solid (VLS) growth process and specifically by modulating synthesis parameters such as pressure and temperature. 6,13–20 These synthetic controls can effectively encode micro- and nanoscale features, yielding a large toolbox of Si-based biomaterials. 21,22 Other semiconductor-based nanostructured materials or devices can also serve as both sensors and modulators of cellular behavior, including as probes for detecting cellular fluid dynamics 23 and intracellular pressure, 24 transducers for biofuel production, 25,26 and delivery vehicles for nucleic acids.…”