Optical Emission Spectroscopy and Gas Kinetics of Picosecond Laser-Induced Chlorine Dissociation for Atomic Layer Etching of Silicon.

The continuing developments in semiconductor device technologies have prompted the need for advanced nanoscale processing techniques. Laser chemical processing offers significant advantages, including spatial selectivity, high localization, minimal material damage, and fast operation. Pulsed laser-induced dissociation of gas species serves as an essential process step, contributing to doping, etching, and other chemical modifications of semiconductor materials.

Ultrafast Optical Nanoscopy of Carrier Dynamics in Silicon Nanowires.

Carrier distribution and dynamics in semiconductor materials often govern their physical properties that are critical to functionalities and performance in industrial applications. The continued miniaturization of electronic and photonic devices calls for tools to probe carrier behavior in semiconductors simultaneously at the picosecond time and nanometer length scales. Here, we report pump-probe optical nanoscopy in the visible-near-infrared spectral region to characterize the carrier dynamics in silicon nanostructures.

Optical Trapping and Positioning of Silicon Nanowires via Photonic Nozzling.

We have improved the maximum two-dimensional translation rate of optically tweezed silicon nanowires to 30 μm/s while lowering the power usage by an order of magnitude from the ∼100 mW range to 6 mW using a silicon film substrate at 532 nm laser wavelength. We then explain the mechanism for the enhanced tweezing using finite difference time domain simulation as "waveguide nozzling" of the incident radiation, directing the light underneath the nanowire where it is confined and forced to propagate opposite to the direction of nanowire motion. We then demonstrate the robust and deterministic placement of the nanowires on the Si film surface using a nanosecond laser at the same wavelength.

Early dynamics of cavitation bubbles generated during ns laser ablation of submerged targets.

In this study, we observe and study the early evolution of cavitation bubbles generated during pulsed laser ablation of titanium targets in different liquid environments utilizing a high-resolution stroboscopic shadowgraphy system. A hydrodynamic model is proposed to calculate the early pressure changes within the bubble and in the surrounding fluid. Our results show that the cavitation bubble is a low-pressure region that is bounded by a high-pressure fluid lamina after the incipient stage, and its evolution is primarily affected by the liquid density.

Design and validation of a ten nanosecond resolved resistive thermometer for Gaussian laser beam heating.

Pulsed laser processing plays a crucial role in additive manufacturing and nanomaterial processing. However, probing the transient temperature field during the pulsed laser interaction with the processed materials is challenging as it requires both high spatial and temporal resolution. Previous transient thermometry studies have measured neither sub-100 µm spatial resolution nor sub-10 ns temporal resolution.

Site-Selective Atomic Layer Precision Thinning of MoS via Laser-Assisted Anisotropic Chemical Etching.

Various exotic optoelectronic properties of two-dimensional (2D) transition metal dichalcogenides (TMDCs) strongly depend on their number of layers, and typically manifest in ultrathin few-layer or monolayer formats. Thus, precise manipulation of thickness and shape is essential to fully access their potential in optoelectronic applications. Here, we demonstrate site-selective atomic layer precision thinning of exfoliated MoS flake by laser.

Programming Nanoparticles in Multiscale: Optically Modulated Assembly and Phase Switching of Silicon Nanoparticle Array.

Manipulating and tuning nanoparticles by means of optical field interactions is of key interest for nanoscience and applications in electronics and photonics. We report scalable, direct, and optically modulated writing of nanoparticle patterns (size, number, and location) of high precision using a pulsed nanosecond laser. The complex nanoparticle arrangement is modulated by the laser pulse energy and polarization with the particle size ranging from 60 to 330 nm.

Mice engrafted with human hematopoietic stem cells support a human myeloid cell inflammatory response in vivo.

Mice engrafted with human CD34 hematopoietic stem and progenitor cells (CD34 -HSPCs) have been used to study human infection, diabetes, sepsis, and burn, suggesting that they could be highly amenable to characterizing the human inflammatory response to injury. To this end, human leukocytes infiltrating subcutaneous implants of polyvinyl alcohol (PVA) sponges were analyzed in immunodeficient NSG mice reconstituted with CD34 -HSPCs. It was reported that human CD45 (hCD45 ) leukocytes were present in PVA sponges 3 and 7 days postimplantation and could be localized within the sponges by immunohistochemistry.

Designing hollow nano gold golf balls.

Hollow/porous nanoparticles, including nanocarriers, nanoshells, and mesoporous materials have applications in catalysis, photonics, biosensing, and delivery of theranostic agents. Using a hierarchical template synthesis scheme, we have synthesized a nanocarrier mimicking a golf ball, consisting of (i) solid silica core with a pitted gold surface and (ii) a hollow/porous gold shell without silica. The template consisted of 100 nm polystyrene beads attached to a larger silica core.