arXiv subjects

Saulius Juodkazis

Publications and source records attributed to Saulius Juodkazis.

61 records · Page 4Linked to original sources

arXiv2016

Au-Ag-Cu nano-alloys: tailoring of permittivity

Precious metal alloys enables new possibilities to tailor materials for specific optical functions. Here we present a systematic study of the effects of a nanoscale alloying on the permittivity of Au-Ag-Cu metals at 38 different atomic mixing ratios. The permittivity was measured and analyzed numerically by applying the Drude model. X-ray diffraction (XRD) revealed the face centered cubic lattice of the alloys. Both, optical spectra and XRD results point towards an equivalent composition-dependent electron scattering behavior. Correlation between the fundamental structural parameters of alloys and the resulting optical properties is elucidated. Plasmonic properties of the Au-Ag-Cu alloy nanoparticles were investigated by numerical simulations. Guidelines for designing plasmonic response of nano- structures and their patterns are presented from the material science perspective.

cond-mat.mtrl-sci↗

arXiv2016

Solar water splitting: efficiency discussion

The current state of the art in direct water splitting in photo-electrochemical cells (PECs) is presented together with: (i) a case study of water splitting using a simple solar cell with the most efficient water splitting electrodes and (ii) a detailed mechanism analysis. Detailed analysis of the energy balance and efficiency of solar hydrogen production are presented. The role of hydrogen peroxide formation as an intermediate in oxygen evolution reaction is newly revealed and explains why an oxygen evolution is not taking place at the thermodynamically expected 1.23 V potential. Solar hydrogen production with electrical-to-hydrogen conversion efficiency of 52% is demonstrated using a simple ~0.7%-efficient n-Si/Ni Schottky solar cell connected to a water electrolysis cell. This case study shows that separation of the processes of solar harvesting and electrolysis avoids photo-electrode corrosion and utilizes optimal electrodes for hydrogen and oxygen evolution reactions and achieves ~10% efficiency in light-to-hydrogen conversion with a standard 18% efficient household roof Si-solar cells.

physics.chem-ph↗

arXiv2016

UV-photoelectric effect for augmented contrast and resolution in electron microscopy

A new tool providing material contrast control in scanning electron microscopy (SEM) is demonstrated. The approach is based on deep-UV illumination during SEM imaging and delivers a novel material based contrast as well as higher resolution due to the photoelectric effect. Electrons liberated from illuminated sample surface contribute to the imaging which can be carried out at a faster acquisition rate, provide material selective contrast, reduce distortions caused by surface charging, and can substitute metal coating in SEM. These features provide high fidelity SEM imaging and are expected to significantly improve the performance of electron beam instruments as well as to open new opportunities for imaging and characterization of materials at the nanoscale.

physics.ins-det↗

arXiv2016

Percolation threshold gold films on columnar coatings: characterisation for SERS applications

Percolation of gold films of ~15 nm thickness was controlled to achieve the largest openings during Au deposition. Gold was evaporated on 300-nm-thick films of nanostructured porous and columnar SiO2, TiO2 and MgF2 which were deposited by controlling the angle, rotation speed during film formation and ambient pressure. The gold films were tested for SERS performance using thiophenol reporter molecules which form a stable self-assembled monolayer on gold. The phase retardation of these SERS substrates was up to 5% for wavelengths in the visible spectral range, as measured by Stokes polarimetry. The SERS intensity on gold percolation films can reach 10^3 counts/(mW.s) for tight focusing in air, while back-side excitation through the substrate has shown the presence of an additional SERS enhancement via the Fresnel near-field mechanism.

physics.optics↗

arXiv2016

Nanoscale precision of 3D polymerisation via polarisation control

A systematic analysis of polarization effects in a direct write femtosecond laser 3D lithography is presented. It is newly shown that coupling between linear polarization of the writing light electric field and temperature gradient can be used to fine-tune feature sizes in structuring of photoresists at a nanoscale. The vectorial Debye focusing is used to simulate polarization effects and a controlled variation up to 20% in the linewidth is shown experimentally for the identical axial extent of the polymerised features. The revealed mechanisms are relevant for a wide range of phenomena of light-matter interaction at tight focusing in laser-tweezers and in plasmonic or dielectric sub-wavelength focusing where strong light intensity and thermal gradients coexist.

physics.optics↗

arXiv2002

Microfabrication of Three-Dimensional Structures in Polymer and Glass by Femtosecond Pulses

We report three-dimensional laser microfabrication, which enables microstructuring of materials on the scale of 0.2-1 micrometers. The two different types of microfabrication demonstrated and discussed in this work are based on holographic recording, and light-induced damage in transparent dielectric materials. Both techniques use nonlinear optical excitation of materials by ultrashort laser pulses (duration < 1 ps).

physics.optics↗

arXiv2002

Comment: Anomalous Anisotropic Light Scattering in Ge-Doped Silica Glass

This is a comment on a paper by Kazansky et al. appeared in Phys. Rev. Lett., 82, 2199 (1999). We demonstrate that the bremsstrahlung of photoelectrons, which oscillate in the light field of an ultrashort laser pulse, accounts for the anomalous anisotropic light scattering, the "propeller effect", described in the paper of Kazansky et al. This mechanism of light emission could explain some results of white-light continuum generation and dielectric breakdown emission.

physics.plasm-ph↗