This research focuses on the study of the growth quality, by means of the chemical profile analysis, of good structural and morphological quality chemical bath deposited PbSe thin films on glass ...substrates (SiO2) by Rutherford Backscattering Spectroscopy (RBS). RBS results with other complementary techniques like XRD and SEM were contrasted. Thin films by using different NaOH concentrations during the growth process were synthesized. XRD studies showed the films polycrystalline nature and their good structural quality. Pure structural effects of amorphous SiO2 and PbSe face-cubic-centered structure were observed. SEM imaging analysis revealed the good morphological growth quality of the PbSe films, observing well-defined films dimensions (thickness), a clear film-to-substrate transition at the interface and good microstructural homogeneity. According to XRD and SEM results, RBS experiments contrasted with theoretical simulations evidenced the good growth quality of the PbSe films. A good agreement between experimental data and theoretical modelling by assuming a simple film/substrate structure with a perfectly defined interface and negligible film roughness for the PbSe/SiO2 samples was achieved. RBS experimental-theoretical analysis reveal the non-stoichiometric nature of the PbSe films, being consequent with preliminary EDS based chemical studies. In particular, a predominance of Se with respect to Pb (considering the atomic concentration) in all samples was observed, suggesting a possible p-type conductivity. By stopping power analysis, thin films thicknesses between 141 and 296 nm were also estimated, being comparable to those obtained from SEM imaging analysis of the samples cross-sections. General results show that some aspects (chemical profile of the structure and interfaces quality) related to the growth quality of the chemical bath deposited PbSe thin films, studied by RBS experiments, are considerably intercorrelated to those analyzed by other techniques like XRD and SEM. This suggests RBS method as a suitable technique for a complete and rigorous analysis of thin films growth quality.
•Homogeneous and adhesive PbSe films were synthesized by chemical bath deposition.•Rutherford Backscattering Spectroscopy (RBS) was used to study the films growth quality.•RBS revealed the good growth quality, which was supported by XRD and SEM studies.•Samples presented well-defined film-to-substrate interfaces and low roughness.•Results suggest RBS as a suitable technique to analyze the films growth quality.
•Annealing effects on the dewetting of sputtered ultra-thin Ag films were studied.•Different temperatures were used to activate different dewetting regimes.•Dewetting regime activation threshold is ...strongly dependent on film thickness.•Different nanostructures can be fabricated by Dewetting-Regime Engineering (DRE).•DRE is a useful method to design systems of potential interest in optoelectronics.
Annealing-induced dewetting in ultra-thin metallic films continues to be a hot topic because of their prospects for developing versatile components in different optoelectronic applications. In this work, we present a brief but significant study about the effects of high vacuum annealing on the dewetting of sputtered ultra-thin Ag films. Results suggest that the activation threshold of different dewetting regimes is strongly dependent on the initial film thickness and annealing temperature. This enables the fabrication of Ag nanostructures with different microstructural features, which can be tuned by choosing adequate thickness and annealing conditions. This study shows that dewetting-regime engineering to achieve different Ag nanostructures can be a useful method to design optoelectronic components with perspectives to potential applications Thin-Film Solar Cells (TFSCs) and Surface-Enhanced Raman Spectroscopy (SERS).
Ag nanostructures have been widely used in the development of emergent micro electro-mechanical systems (MEMS) and nano electro-mechanical systems (NEMS). Dimensional confinement effects on their ...mechanical properties are a key issue in the field of MEMS/NEMS for understanding their mechanical performances and potential lifespans. In this work, we report a systematic study of 3D confinement effects on the mechanical resistance of Ag nanodisks fabricated by interference laser lithography (ILL). Nanodisks with thicknesses (t) between 20 and 150 nm and radii (r) between 125 and 900 nm have been studied. Mechanical properties have been studied by atomic force microscopy (AFM)-assisted nanoindentation. The results showed a strong influence of substrate effects on the mechanical response of the nanodisks, generally being dominant at the considered scales. Lateral confinement effects have been observed for low indentation depths (<0.1 t), at which the substrate effects become smaller. Confinement effects depend more on relative size effects (r/t ratios) than on absolute length scales. The nanodisks showed greater susceptibility to plastic deformation (lower mechanical resistance) as r decreased; this became clearly appreciable when r was comparable to t. Complementary finite element analysis showed similar tendencies, which could be explained considering pure dimensional confinement effects. This study shows the potential capabilities of modern AFM instruments for understanding confinement effects on the mechanical behavior of solids.
•The mechanical behavior of Ag nanodisks and thin films has been studied by AFM-nanoindentation.•Substrate and lateral confinement effects compete when dimensions are comparable.•3D confinement effects arise when the radius and thickness of the nanodisks are comparable.•This kind of confinement increases the plastic strain susceptibility of the material.•Experimental results were qualitatively consistent with those of finite element analysis.
In the last decades, NiO-GDC and NiO-SDC composites have emerged as interesting anodic materials for low and intermediate-temperature Solid Oxide Fuel Cells (SOFC) due to their high electrical ...conductivities and low activation energies. In this work, we report a simple and efficient Solution Combustion Synthesis (SCS) procedure for fabricating NiO-GDC and NiO-SDC nanocomposites with attractive physical properties for applications in low-temperature SOFC. The nitrate-fuel combustion method using citric acid as organic fuel was chosen due to its relatively low cost and good efficiency. Their potential electrical and mechanical performance for competitive SOFC anode technologies was assessed by characterizing disk-like compacted powders obtained by SCS. Two structurally optimized NiO-GDC and NiO-SDC disks were considered for the study of these properties, which presented good porosity and compaction degree. Vickers hardness tests show the good mechanical properties of both samples, achieving maximum hardness values of 4.7–6.7 GPa and validating the efficiency of the used compaction process. Electrical conductivity studies suggest an insulating-like behavior for both samples, evidenced by an increase in conductivity as the temperature increases. Good conductivities and low activation energies about of 10−2 S/cm and 0.18 eV were estimated for a low-temperature operation regime (400–600 °C), respectively, representing a highly competitive performance concerning similar composites typically reported in the literature. Results show the efficiency of our fabrication procedures to produce efficient and competitive NiO-GDC and NiO-SDC composites with projections for future large-scale manufacturing of low-temperature SOFC anodes.
•Thin film solar cells based on chemically deposited ZnO/PbSe bilayers were studied.•ZnO and PbSe films were grown by simple aqueous phase chemical deposition methods.•Films presented generally good ...physical properties for applications in solar cells.•Cells showed good photovoltaic performances, achieving an efficiency of 3.0%.•Our solar cells were as efficient as those already reported by similar research.
We report for the first time the fabrication of thin film solar cells based only on aqueous-phase chemically deposited ZnO/PbSe junctions. In particular, ZnO and PbSe thin films were synthesized by Successive Ionic Layer Absorption-Reaction and Chemical Bath Deposition methods. The photovoltaic performance was tested by fabricating ITO/ZnO/PbSe/Ag arrangements. Fill factors (FF), open-circuit voltages (Voc) and short-circuit current densities (Jsc) in the range of 25.4–29.2%, 0.39–0.51 V and 17.9–21.5 mA/cm2 were achieved. Power conversion efficiencies varied typically between 1.9% and 3.0%. Results showed the important photovoltaic activity of our solar cells, achieving good and comparable efficiencies to those reported by similar research. Our research represents a considerable improvement of the cost-performance relation for this kind of device.
Cu thin films are nowadays attractive components for emergent MEMS based technologies because their high electrical conductivity (σ) and good mechanical properties. In general, σ is negatively ...affected when the film thickness (t) decreases close to the electron mean free path (le) scale and the mechanical resistance is favored. So, we propose a study of the Cu thin films optimum size conditions to achieve a well-compromise between the mechanical and electrical performance. Films mechanical behavior was studied by Atomic Force Microscopy (AFM) assisted nanoindentation. Results showed considerable increments of the elastic (Ue)-to-total (Ut) strain energy ratios (Ue/Ut) from 0.27 ± 0.02 up to 0.54 ± 0.04 as t was decreased from 2 µm to 100 nm, evidencing a clear films mechanical resistance improvement by reducing t. Our analysis showed that the improvement of the films mechanical resistance easily compensates the negative impact on the electrical conductivity, especially for t>le.
Cantilever deflection sensitivity (
) calibration is a critical issue for a correct transduction of the electric signal into mechanical one in atomic force microscopy (AFM)-nanoindentation. ...Indenter-induced strains in calibration samples can negatively impact on the
calibration reliability, becoming more important as the cantilever deflection (
) set for this calibration process is increased. In this work, we present a systematic study regarding the
setpoint effects on the
value calibration.
setpoints between 0.05 and 1 V were considered for measurements, observing a clear decreasing trend in the
value for
0.125 V concerning the most accurate value
192 nm/V. The results demonstrate that underestimations up to 10% concerning this value may be obtained by choosing non-adequate
setpoints. This study shows the relevance of the
setpoint for accurate
calibration, which is essential for reliable quantitative studies of mechanical properties.
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•BaTiO3 films by hydrothermal modification of Ti sheets were synthesized.•The influence of oleic acid and NaOH on films growth was studied.•Films’ microstructure morphology and size ...was strongly mediated by both compounds.•Relevant experimental insights for BaTiO3 films synthesis optimization were given.•Results can help for optimizing properties for applications in flexible capacitors.
In this work, we report the effects of oleic acid as surfactant on the growth properties of hydrothermally-synthesized BaTiO3films by chemical modification of Ti sheets. Hydrothermal process was carried out in an aqueous solution of Ba(OH)2 with different oleic acid concentrations and using NaOH as mineralizer. Microstructural properties and chemical composition were studied by X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM). This study represents an interesting starting point for the future synthesis of nanostructured BaTiO3 thin films with optimized properties for potential applications in Flexible Capacitors (FCs).
In recent years, noble metal nanoparticle-based periodic nanoarrays (photonic crystals) have received special attention due to their gross potential to achieve exceptionally high Electric-Near Field ...Enhancement (ENFE) factors for visible light and their prospects as candidates for the fabrication of ultra-sensitive Surface-Enhanced Raman Spectroscopy (SERS) substrates. In this work, we report a simple but exhaustive theoretical analysis of the ENFE in Au and Ag nanodisks-based photonic crystals by Finite-Difference Time-Domain (FDTD) method. Nanostructures with arrays periodicities from 200 to 1000 nm, nanodisks diameters from 100 to 500 nm and thicknesses from 20 to 200 nm were studied. Results show that the ENFE is strongly dependent on each one of these geometrical parameters, observing |E/E0|2 factors that can reach up to 1200 for the visible light spectrum. The effects of nanodisks surface curvature-based defects on the ENFE were also analyzed. This kind of defects seem to be also relevant to maximize the ENFE effects, observing that higher surface curvatures tend to considerably attenuate the electric field amplification. Our research provides relevant insights on the design optimization of this kind of photonic crystals to maximize the ENFE effects, which is a critical issue to assess the future fabrication conditions of efficient SERS substrates.
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Nowadays, photoresist-based films are used by photolithography techniques for the fabrication of micro/nanodevices in the modern nanotechnology industry. The impact of thermal-induced polymerization ...on the mechanical resistance of these materials is critical for improving both the mechanical and the chemical performance. In this work, we present a systematic study of the annealing effects on the mechanical resistance (thermally-induced material hardening) of MICROPOSIT™ photoresist films. The mechanical properties were studied by depth-sensing nanoindentation technique using an atomic force microscope. Results show the films' plastic strain susceptibility decreases as the annealing temperature increases, implying an improvement of their mechanical resistance by thermal-induced polymerization. Strain energy dissipation coefficients decreased from 0.725 up to 0.525 as the annealing temperature was increased from 60 up to 200 °C, demonstrating this point. Indentation hardness results were consistent with this behavior, observing an increase from 0.12 up to 0.23 GPa for the highest annealing temperature. Annealing-induced hardening seems to be correlated with the films' resistance to wet chemical etching, observing higher chemical resistance for higher annealing temperatures. The observed increase of the mechanical and chemical resistance of the photoresists with annealing becomes of great importance for their application in the development of novel micro and nanostructures.
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