Grazing-incidence small-angle X-ray scattering: application to the study of quantum dot lattices

The modelling of grazing-incidence small-angle X-ray scattering (GISAXS) from three-dimensional quantum dot lattices is described

Depth profiling of Cr-ITO dual-layer sample with secondary ion mass spectrometry using MeV ions in the low energy region

This work explores the possibility of depth profiling of inorganic materials with Megaelectron Volt Secondary Ion Mass Spectrometry using low energy primary ions (LE MeV SIMS), specifically 555 keV Cu ²⁺ , while etching the surface with 1 keV Ar ⁺ ions. This is demonstrated on a dual-layer sample consisting of 50 nm Cr layer deposited on 150 nm In2O5Sn (ITO) glass. These materials proved to have sufficient secondary ion yield in previous studies using copper ions with energies of several hundred keV. LE MeV SIMS and keV SIMS depth profiles of Cr-ITO dual-layer are compared and corroborated by atomic force microscopy (AFM) and time-of-flight elastic recoil detection analysis (TOF-ERDA). The results show the potential of LE MeV SIMS depth profiling of inorganic multilayer systems in accelerator facilities equipped with MeV SIMS setup and a fairly simple sputtering source

Multiple exciton generation in 3D ordered networks of Ge quantum wires in alumina matrix

Thin films containing 3D-ordered semiconductor quantum wires offer a great tool to improve the properties of photosensitive devices. In the present work, we investigate the photogenerated current in thin films consisting of an interconnected 3D-ordered network of Ge quantum wires in an alumina matrix. The films are prepared using nitrogen-assisted magnetron sputtering co-deposition of Ge and Al2O3. We demonstrate a strong photocurrent generation in the films, much stronger than in similar films containing Ge quantum dots. The enhanced photocurrent generation is the consequence of the multiple exciton generation and the films’ specific structure that allows for efficient carrier transport. Thin film with the largest nitrogen content showed enhanced performance compared to other thin films with 1.6 excitons created after absorption of a single photon at an energy nearly equal to the double bandgap value. The bandgap value depends on the geometrical properties of the quantum wires, and it is close to the maximum of the solar irradiance in this case. In addition, we show that the multiple exciton generation is the most pronounced at the photon energy values equal to multiple values of the thin film bandgap

Characteristics of aerosol pollution in the vicinity of an oil refinery near Rijeka, Croatia

Fine aerosol pollution is one of the most important factors in air pollution monitoring. Industrial production often represents significant source of aerosol pollution in surrounding areas, and therefore, it is important to understand its impact on air quality. In order to investigate contribution coming from the oil refinery to air pollution, PM2.5 (particulate matter with aerodynamic diameter smaller than 2.5 μm) samples were collected in the vicinity of an oil refinery during the 1‐year period. At the same time, PM2.5 was sampled in the city of Rijeka, Croatia, at the distance that is about 10 km far from the refinery. This site was used for comparison. The sampling was performed with two cyclone samplers on thin polytetrafluoroethylene filters. PM2.5 was sampled for 24 h every other day, simultaneously at both locations. In total, 306 samples were collected. The samples were analysed using X‐ray fluorescence and particle‐ induced X‐ray emission to obtain concentrations of 17 elements from Na to Pb. Additionally, concentrations of black carbon were determined using laser‐integrated plate method. It was found that concentrations of S, V, and Ni, elements characteristic for oil burning, were substantially higher at the refinery sampling site comparing to the reference location. Obtained concentrations were statistically evaluated by performing positive matrix factorization to identify oil refinery as one of the pollution sources in the vicinity of such a facility. The same method was also performed at the urban site where the contribution from oil refinery was not separated from other similar sources

Deposition of heavy metals in biological tissues of workers in metal workshops

Welding and cutting of metals produce large amounts of particulate matter (PM), which poses a significant health risk to exposed workers. Appropriate biological markers to estimate exposure are of great interest for occupational health and safety. Here, hair and nail samples from metal workers were analyzed, which appear to be more suitable than blood or urine samples for assessing long-term exposure. Four workshops working with steel components were included in the study. The hair and nail samples were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to measure the concentrations of 12 elements. At the workplaces, the concentrations of 15 elements in particulate matter were determined using X-ray fluorescence (XRF) and particle-induced X-ray emission (PIXE) techniques. The hair and nail samples of the workers contained significantly higher metal concentrations than the analytical results of a nonexposed control group. The most significant difference between the groups was found for Ti, Mn, Fe, and Co

Determination of Deposition Order of Toners, Inkjet Inks, and Blue Ballpoint Pen Combining MeV-Secondary Ion Mass Spectrometry and Particle Induced X-ray Emission

Determination of the deposition order of different writing tools is very important for the forensic investigation of questioned documents. Here we present a novel application of two ion beam analysis (IBA) techniques: secondary ion mass spectrometry using MeV ions (MeV-SIMS) and particle induced X-ray emission (PIXE) to determine the deposition order of intersecting lines made of ballpoint pen ink, inkjet printer ink, and laser printer toners. MeV-SIMS is an emerging mass spectrometry technique where incident heavy MeV ions are used to desorb secondary molecular ions from the uppermost layers of an organic sample. In contrast, PIXE provides information about sample elemental composition through characteristic X-ray spectra coming from greater depth. In the case of PIXE, the information depth depends on incident ion energy, sample matrix and self-absorption of X-rays on the way out from the sample to the X-ray detector. The measurements were carried out using a heavy ion microprobe at the Ruđer Bošković Institute. Principal component analysis (PCA) was employed for image processing of the data. We will demonstrate that MeV-SIMS alone was successful to determine the deposition order of all intersections not involving inkjet printer ink. The fact that PIXE yields information from deeper layers was crucial to resolve cases where inkjet printer ink was included due to its adherence and penetration properties. This is the first time the different information depths of PIXE and MeV-SIMS have been exploited for a practical application. The use of both techniques, MeV-SIMS and PIXE, allowed the correct determination of deposition order for four out of six pairs of samples

Inducing periodic structures on multilayers of Ti and Ta by femtosecond laser beam

Nanostructuring of surfaces by femtosecond (fs) laser beam interaction is the topic of research for some time [1]. The emergence of the laser-induced periodic surface structures (LIPSS) on metal-dielectric surfaces is of interest from fundamental and application points of view. The interaction of fs beam with thin films can also generate LIPSS, with the arrangement of thin films in multi-layer structure being important for the quality of the LIPSS [2]. Excellent properties of titanium (Ti) and tantalum (Ta), like corrosion resistance, heat transfer properties and workability, recommend them as useful materials for a wide range of applications - heat exchangers, reactors, and others exposed to extremely corrosive fluids. Combining Ti and Ta could be attractive for applications, but challenging, as they have great difference in melting point and density, therefore, TiTa alloys are still not widely adopted in applications [3]. We have performed the interaction of fs laser beam with multilayer Ti/Ta samples in order to investigate the effects of interaction with ultra-short pulses to surface morphology and to both surface and bulk chemistry of newly generated compounds. Each layer of the sample was 17 nm thick. The interactions were in two regimes: dynamic and static, depending whether the beam scanned over the sample surface or not. SEM and PIXE RBS analyses have shown the LIPSS formed with or without ablation depending on the beam fluence. The LIPSS orientation is dependent on the input beam polarization. Both types of LIPSS were formed, low- and highspatial frequency LIPSS, with periods being as low as 120 nm.VI International School and Conference on Photonics and COST actions: MP1406 and MP1402 : PHOTONICA2017 : program and the book of abstracts; August 23 - September 1, 2017; Belgrad

Laser ablation of nickel/palladium multilayer thin films by nanosecond pulses

Metallic thin films, based on nickel (Ni) and palladium (Pd)are promising material for a wide range of application, as catalytic components [1], optical devices [2], photovoltaic gas sensors [3], dye sensitized solar cells [4], and especially for environmental purposes [5]. The potential of nanosecond laser micro-processing for surface modification of nickel-palladium (Ni/Pd) multilayer thin film deposited on n-type (100) silicon wafer was studied. The multilayer structure composed of five bilayer (Pd/Ni) was deposited by d.c.sputtering from a pure Ni and Pd targets, using Ar ions, to a total thickness of about 180 nm. These multilayer thin films were then exposed to various number of pulses of Er:Glass laser, operating at 1540 nm wavelength with pulse duration of 44 ns. Multi-pulse laser irradiations were done at an incidence angle of 90 in an ambient air environment. The changes of the composition and surface morphology in the 5x(Pd/Ni)/Si system were monitored by Particle Induced X-Ray Emission (PIXE), by Rutherford backscattering spectrometry (RBS), by scanning electron microscopy (SEM) and by profilometry. The main part of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the multilayer surface. The results show an increase in surface roughness, formation of a specific surface topography, appearance of hydrodynamic features and ablation of surface material without shallow or deep crater like characteristics. RBS analysis revealed that laser modification was induced intermixing between the individual Ni and Pd layers, but also with silicon substrate. During the laser processing of 5x(Pd/Ni)/Si system delivered energy was probably sufficient to cause solid-state reactions, the formation of intermetallic compounds and silicides with Ni and Pd. An interesting finding is the 5x(Pd/Ni)/Si thin film has undergone some changes in the chemical composition and structure in the irradiated areas, indicating better crystallinity with an increase of the number of applied pulses.VI International School and Conference on Photonics and COST actions: MP1406 and MP1402 : PHOTONICA2017 : program and the book of abstracts; August 23 - September 1, 2017; Belgrad

Determination of Deposition Order of Toners, Inkjet Inks, and Blue Ballpoint Pen Combining MeV-Secondary Ion Mass Spectrometry and Particle Induced X-ray Emission

Determination of the deposition order of different writing tools is very important for the forensic investigation of questioned documents. Here we present a novel application of two ion beam analysis (IBA) techniques: secondary ion mass spectrometry using MeV ions (MeV-SIMS) and particle induced X-ray emission (PIXE) to determine the deposition order of intersecting lines made of ballpoint pen ink, inkjet printer ink, and laser printer toners. MeV-SIMS is an emerging mass spectrometry technique where incident heavy MeV ions are used to desorb secondary molecular ions from the uppermost layers of an organic sample. In contrast, PIXE provides information about sample elemental composition through characteristic X-ray spectra coming from greater depth. In the case of PIXE, the information depth depends on incident ion energy, sample matrix and self-absorption of X-rays on the way out from the sample to the X-ray detector. The measurements were carried out using a heavy ion microprobe at the Ruđer Bošković Institute. Principal component analysis (PCA) was employed for image processing of the data. We will demonstrate that MeV-SIMS alone was successful to determine the deposition order of all intersections not involving inkjet printer ink. The fact that PIXE yields information from deeper layers was crucial to resolve cases where inkjet printer ink was included due to its adherence and penetration properties. This is the first time the different information depths of PIXE and MeV-SIMS have been exploited for a practical application. The use of both techniques, MeV-SIMS and PIXE, allowed the correct determination of deposition order for four out of six pairs of samples