Kernel-inspired algorithm to transform transmission electron microscopy images into discrete dipole approximation geometries.

In this work, we present a code that transforms 2D transmission electron microscopy images into 3D geometries for discrete dipole approximation simulations in DDSCAT 7.3.3 based on Python 3.

CMOS-compatible HfZrO-based ferroelectric memory crosspoints fabricated with damascene process.

We report the fabrication of HfZrO(HZO) based ferroelectric memory crosspoints using a complementary metal-oxide-semiconductor-compatible damascene process. In this work, we compared 12 and 56mcrosspoint devices with the 0.02 mmround devices commonly used as a benchmark.

Unraveling the Heterointegration of 3D Semiconductors on Graphene by Anchor Point Nucleation.

The heterointegration of graphene with semiconductor materials and the development of graphene-based hybrid functional devices are heavily bound to the control of surface energy. Although remote epitaxy offers one of the most appealing techniques for implementing 3D/2D heterostructures, it is only suitable for polar materials and is hugely dependent on the graphene interface quality. Here, the growth of defect-free single-crystalline germanium (Ge) layers on a graphene-coated Ge substrate is demonstrated by introducing a new approach named anchor point nucleation (APN).

Raman spectroscopy investigation of magnesium oxide nanoparticles.

We investigate Raman spectra (100 cm to 3900 cm) of magnesium oxide nanoparticles with nominal sizes of 10 nm, 20 nm, 40 nm, 50 nm, and 300 nm. The crystal structure of MgO prohibits first-order modes and yet, there are numerous reports of relatively intense peaks throughout the literature. Raman signals at approximately 278 cm and 445 cm that were attributed to MgO nanoparticles by previous authors are shown to belong to layers of Mg(OH) formed on the surface of MgO nanoparticles.

In Operando Photoswitching of Cu Oxidation States in Cu-Based Plasmonic Heterogeneous Photocatalysis for Efficient H Evolution.

Metal nanoparticles (NP) supported on TiO are known to be efficient photocatalysts for solar-to-chemical energy conversion. While TiO decorated with copper NPs has the potential to become an attractive system, the poor oxidative stability of Cu severely limits its applicability. In this work, we demonstrate that, when Cu NPs supported on TiO nanobelts (NBs) are engaged in the photocatalytic generation of H from water under light illumination, Cu is not only oxidized in CuO but also dissolved under the form of Cu/Cu ions, leading to a continuous reconstruction of nanoparticles via Ostwald ripening.

Phonon confinement and particle size effect on the low-frequency Raman mode of aurivillius phase BiTiO powders.

We report the systematic measurements in bismuth titanate powders of Raman frequency shift, and full width at half maximum (FWHM), of optical phonons at = 0 obtained between ∼300 K and 673 K in air. Both the particle size and phonon confinement effects are reasonably satisfactory to explain the Raman peak shift and asymmetric broadening observed in the ferroelectric soft phonon mode at 42 cm. It is shown that the lattice parameter varies as particle size , and its contribution to size-dependent Raman shift and broadening of linewidth follows ∝ and ∝ law, respectively.

Catalytic Applications of Non-Centrosymmetric Oxide Nanomaterials.

Noble-metal-free catalytic nanoparticles hold the promise being abundant, low-cost materials having a small environmental footprint and excellent performance, albeit inferior to that of noble metal counterparts. Several materials have a long-standing history of success in photocatalysis, in particular titanium dioxide, and in recent years more complex oxides and added functionality have emerged with enhanced performance. We will discuss different approaches related to the use of non-centrosymmetric and polar oxide nanoparticles and how the bulk photovoltaic effect, piezoelectricity, and pyroelectricity add to photocatalysis and tribocatalysis.

In situ evaluation of plasmonic enhancement of gold tips for plasmon-enhanced imaging techniques.

Plasmonic nanoantennas are at the core of various optical near-field scanning techniques such as tip-enhanced Raman spectroscopy as they provide the amplification and confinement of the electromagnetic field, which ultimately provides sensitivity and spatial resolution. With a cornucopia of different fabrication methods available, the actual performance of a nanoantenna is often only assessed by whether or not near-field imaging is possible, implying the complete alignment and landing procedure of the scanning probe. We present a semi-quantitative approach to assess the plasmonic enhancement of gold tips via localized surface plasmon resonance (LSPR) enhancement of intrinsic gold photoluminescence without the need for interaction with the sample.

Effect of Extrinsic Disorder on the Magnetoresistance Response of Gated Single-Layer Graphene Devices.

Analogous to the case of classical metal oxide semiconductor field-effect transistors, transport properties of graphene-based devices are determined by scattering from adventitious charged impurities that are invariably present. The presence of charged impurities renders experimental graphene samples "extrinsic" in that their electrical performances also depend on the environment in which graphene operates. While the role of such an extrinsic disorder component has been studied for conventional charge transport in graphene, its impact on the magnetotransport remains unexplored.

Integration of 3D nanographene into mesoporous germanium.

Graphene is a key material of interest for the modification of physicochemical surface properties. However, its flat surface is a limitation for applications requiring a high specific surface area. This restriction may be overcome by integrating 2D materials in a 3D structure.

Sample induced intensity variations of localized surface plasmon resonance in tip-enhanced Raman spectroscopy.

Tip-enhanced spectroscopy techniques, in particular tip-enhanced Raman spectroscopy (TERS), rely on a localized surface plasmon resonance (LSPR). This LSPR depends on the near field antenna, its material and shape, and the surrounding medium with respect to its relative permittivity and the volume fraction of the optical near field occupied by the sample. Here, we investigate the effects of the surface composition and topography on the change of the LSPR intensity in tip-enhanced spectroscopy on SrTiO nanoislands by monitoring the LSPR enhanced luminescence of gold tips.

Plasmonic Enhancement of Two-Photon Excitation Fluorescence by Colloidal Assemblies of Very Small AuNPs Templated on M13 Phage.

In this study, an engineered M13 bacteriophage was examined as a biological template to create a well-defined spacing between very small gold nanoparticles (AuNPs 3-13 nm). The effect of the AuNP particle size on the enhancement of the nonlinear process of two-photon excitation fluorescence (2PEF) was investigated. Compared to conventional (one-photon) microscopy techniques, such nonlinear processes are less susceptible to scattering given that the density of background-scattered photons is too low to generate a detectable signal.

Topography-induced variations of localized surface plasmon resonance in tip-enhanced Raman configuration.

We report on topography-induced changes of the localized surface plasmon resonance (LSPR) enhanced luminescence of gold tip on SrTiO nanostructures with apertureless scanning near-field optical microscopy (aSNOM) in tip-enhanced Raman spectroscopy (TERS) configuration. Our experimental and simulated results indicate that the averaged refractive index of the dielectric environment of the tip apex containing both air and SrTiO in variable volume ratios, is dependent on the topography of the sample. This reveals that the local topography has to be taken into consideration as an additional contribution to the position of the LSPR.

Smooth pyroelectric luminescence in LiNbO single crystals.

We investigate the phenomenon of pyroelectric luminescence in LiNbO single crystals. This faint emission of light due to temperature-induced changes of permanent polarization is induced by different types of charge carrier recombination, outside and inside the crystal. With decreasing atmospheric pressure, the external discharge mechanism transitions from sparse intense gas discharge pulses at ambient pressure, to frequent faint discharges close to 1 mbar, to a continuous emission which is referred to as smooth pyroelectric luminescence.

Ultrastructures and Mechanics of Annealed Major Ampullate Silk.

The semicrystalline protein structure and impressive mechanical properties of major ampullate (MA) spider silk make it a promising natural alternative to polyacrylonitrile (PAN) fibers for carbon fiber manufacture. However, when annealed using a similar procedure to carbon fiber production, the tensile strength and Young's modulus of MA silk decrease. Despite this, MA silk fibers annealed at 600 °C remain stronger and tougher than similarly annealed PAN but have a lower Young's modulus.

Contrast Enhancement for the Recovery of Obliterated Serial Numbers in Different Polymers by Correlated Raman Imaging of Strain, Phonon Lifetime, and Strain-Induced Anisotropy.

In the field of forensic science, we have recently introduced Raman imaging as a promising nondestructive technique to efficiently recover obliterated serial numbers in polycarbonate. The present study is extending the investigation toward different polymers for the reconstruction of abraded information by Raman spectroscopy. Samples of polyethylene, nylon, and nylatron, which are mainly used in items such as firearms, banknotes, and package materials, are investigated by monitoring the vibrational modes which are most susceptible to peak shifts and changes in the full width at half-maximum (fwhm) and peak intensity ratios.

Latent Fingermark Imaging by Single-Metal Deposition of Gold Nanoparticles and Surface Enhanced Raman Spectroscopy.

In forensic science, there is a high demand for a technique that allows the revelation of fingermarks invisible to the naked eye as well as the chemical information they contain. Here, we present a feasibility study consisting of using both the luminescence enhanced by surface plasmon of gold nanoparticles, and the surface enhanced Raman spectroscopy signal of fingermark chemical components to image latent fingermarks. A latent fingermark deposited on a transparent glass substrate was visually revealed using single-metal deposition employing gold nanoparticles.

Modeling of the surface plasmon resonance tunability of silver/gold core-shell nanostructures.

Tunable plasmonic noble metal nanoparticles are indispensable for chemical sensors and optical near field enhancement applications. Laser wavelengths within the absorption spectrum of the nanoparticle and Localized Surface Plasmon Resonances (LSPR) in the visible and near infrared range are the key points to be met for the successful utilization in the field of aforementioned high sensitivity sensors. This way, Surface Enhanced Raman Spectroscopy (SERS) has been pushed to the sensitivity level of single molecule.

Extreme temperature stability of thermally insulating graphene-mesoporous-silicon nanocomposite.

We demonstrate the thermal stability and thermal insulation of graphene-mesoporous-silicon nanocomposites (GPSNC). By comparing the morphology of GPSNC carbonized at 650 °C as-formed to that after annealing, we show that this nanocomposite remains stable at temperatures as high as 1050 °C due to the presence of a few monolayers of graphene coating on the pore walls. This does not only make this material compatible with most thermal processes but also suggests applications in harsh high temperature environments.

Permittivity imaged at the nanoscale using tip-enhanced Raman spectroscopy.

Localized surface plasmon resonances are the dominating contribution to the optical enhancement and the lateral resolution in tip-enhanced Raman spectroscopy. This well studied phenomenon may give access to more information about the sample than the enhanced Raman spectra alone due to its sensitivity to the permittivity of the tip environment. In this work, the effects of the permittivity of the sample on the properties of localized surface plasmon resonance are studied through the amplified signal of the luminescence of gold tips.

Reconstruction of Obliterated Characters in Polycarbonate through Spectral Imaging.

In forensic sciences, there is an increasing demand for nondestructive and reliable methods to retrieve obliterated information in polymers. This study demonstrates a case study for the potential of Raman spectroscopy to reconstruct abraded serial numbers. Residual strain and local variations in the structural arrangement are nondestructively imaged through peak shifts and variations of the full width at half-maximum of specific Raman lines, respectively.

Effect of the gold crystallinity on the enhanced luminescence signal of scanning probe tips in apertureless near-field optical microscopy.

The effect of gold tip crystallinity on their spectral amplification characteristics, monitored through the luminescence enhanced by surface plasmon resonance (SPR), is investigated experimentally. As the tip radius increases, the grains composing polycrystalline tips become larger, resulting in a blueshift of the emission while a redshift of the SPR was predicted for monocrystalline gold. This reveals that the effect of the grain size, a parameter that has not been considered so far, is dominant over that of the tip radius.

A Complementary Metal Oxide Semiconductor Process-Compatible Ferroelectric Tunnel Junction.

In recent years, experimental demonstration of ferroelectric tunnel junctions (FTJ) based on perovskite tunnel barriers has been reported. However, integrating these perovskite materials into conventional silicon memory technology remains challenging due to their lack of compatibility with the complementary metal oxide semiconductor process (CMOS). This communication reports the fabrication of an FTJ based on a CMOS-compatible tunnel barrier HfZrO (6 unit cells thick) on an equally CMOS-compatible TiN electrode.