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High-yield epitaxial bottom-up growth of silicon nanowires is still challenging but desirable for various applications such as antireflective coatings, solar cells, and high-aspect-ratio scanning probes. Hence, pristine single-crystalline silicon surfaces are, in principle, required as a growth substrate, but reoxidation occurring prior to nanowire growth obstructs epitaxial growth significantly. Here, we present an approach that relies on Al/Au alloy catalysts for gas-phase silicon nanowire synthesis, allowing intrinsically an in situ removal of a native silicon-oxide layer during the initial growth stages. This approach yields reliable and superior epitaxial growth of silicon nanowires on single-crystalline silicon substrates.

Surface enhanced Raman spectroscopy (SERS) measurements are conventionally performed using assemblies of metal nanostructures on a macro- to micro-sized substrate or by dispersing colloidal metal nanoparticles directly onto the sample of interest. Despite intense use, these methods allow neither the removal of the nanoparticles after a measurement nor a defined confinement of the SERS measurement position. So far, tip enhanced Raman spectroscopy is still the key technique in this regard but not adequate for various samples mainly due to diminished signal enhancement compared to other techniques, poor device fabrication reproducibility, and cumbersome experimental setup requirements. Here, we demonstrate that a rational combination of only four gold nanoparticles (AuNPs) on a DNA origami template, and single silicon nanowires (SiNWs) yield functional optical amplifier nanoprobes for SERS. These nanoscale SERS devices offer a spatial resolution below the diffraction limit of light and still a high electric field intensity enhancement factor ( EF) of about 10 5 despite of miniaturization.

Well-characterized silane layers are essential for optimized attachment of (bio)molecules enabling reliable chem/biosensor performance. Herein, binding properties and orientation of 3-mercaptopropyltrimethoxysilane layers at crystalline sapphire (0001) surfaces were determined by water contact angle measurements, infrared reflection absorption spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Infrared reflection absorption spectroscopy measurements suggest an almost perpendicular arrangement of the MPTMS molecules to the substrate surface. Adhesion force studies between a silicon nitride AFM tip and modified sapphire, gold, and silicon dioxide substrates were investigated by peak force tapping atomic force microscopy and used to define the silane binding properties on these surfaces. As expected, the Al-O-Si bond was determined to be responsible for the layer formation at the sapphire substrate surface.

Nanowire-based field-effect transistors, including devices with planar and three-dimensional configurations, are being actively explored as detectors for extra- and intracellular recording due to their small size and high sensitivities. Here we report the synthesis, fabrication, and characterization of a new needle-shaped nanoprobe based on an active silicon nanotube transistor, ANTT, that enables high-resolution intracellular recording. In the ANTT probe, the source/drain contacts to the silicon nanotube are fabricated on one end, passivated from external solution, and then time-dependent changes in potential can be recorded from the opposite nanotube end via the solution filling the tube. Measurements of conductance versus water-gate potential in aqueous solution show that the ANTT probe is selectively gated by potential changes within the nanotube, thus demonstrating the basic operating principle of the ANTT device. Studies interfacing the ANTT probe with spontaneously beating cardiomyocytes yielded stable intracellular action potentials similar to those reported by other electrophysiological techniques. In addition, the straightforward fabrication of ANTT devices was exploited to prepare multiple ANTT structures at the end of single probes, which enabled multiplexed recording of intracellular action potentials from single cells and multiplexed arrays of single ANTT device probes. These studies open up unique opportunities for multisite recordings from individual cells through cellular networks.