Laser-induced Annealing Research Articles

Probing the cw-Laser-Induced Fluorescence Enhancement in CsPbBr3 Nanocrystal Thin Films: An Interplay between Photo and Thermal Activation.

Perovskite nanocrystals hold significant promise for a wide range of applications, including solar cells, LEDs, photocatalysts, humidity and temperature sensors, memory devices, and low-cost photodetectors. Such technological potential stems from their exceptional quantum efficiency and charge carrier conduction capability. Nevertheless, the underlying mechanisms of photoexcitation, such as phase segregation, annealing, and ionic diffusion, remain insufficiently understood. In this context, we harnessed hyperspectral fluorescence microspectroscopy to advance our comprehension of fluorescence enhancement triggered by UV continuous-wave (cw) laser irradiation of CsPbBr3 colloidal nanocrystal thin films. Initially, we explored the kinetics of fluorescence enhancement and observed that its efficiency (φph) correlates with the laser power (P), following the relationship φph = 7.7⟨P⟩0.47±0.02. Subsequently, we estimated the local temperature induced by the laser, utilizing the finite-difference method framework, and calculated the activation energy (Ea) required for fluorescence enhancement to occur. Our findings revealed a very low activation energy, Ea ∼ 9 kJ/mol. Moreover, we mapped the fluorescence photoenhancement by spatial scanning and real-time static mode to determine its microscale length. Below a laser power of 60 μW, the photothermal diffusion length exhibited nearly constant values of approximately (22 ± 5) μm, while a significant increase was observed at higher laser power levels. These results were ascribed to the formation of nanocrystal superclusters within the film, which involves the interparticle spacing reduction, creating the so-called quantum dot solid configuration along with laser-induced annealing for higher laser powers.

High-performance silver nanowires transparent conductive electrodes fabricated using manufacturing-ready high-speed photonic sinterization solutions

On the long road towards low-cost flexible hybrid electronics, integration and printable solar energy harvesting solutions, there is an urgent need for high-performance transparent conductive electrodes produced using manufacturing-ready techniques and equipment. In recent years, randomly-distributed metallic nanowire-based transparent mesh electrodes have proven highly-promising as they offer a superb compromise between high performances and low fabrication costs. Unfortunately, these high figure-of-merit transparent mesh electrodes usually rely heavily on extensive post-deposition processing. While conventional thermal annealing yields good performances, it is especially ill-suited for deposition on low-temperature substrates or for high-throughput manufacturing solutions. Similarly, laser-induced annealing severely limits the processing time for electrodes covering large surfaces. In this paper, we report the fabrication of ultra high-performance silver nanowires-based transparent conductive electrodes fabricated using optimized manufacturing-ready ultrafast photonic curing solutions. Using conventional indium tin oxide (ITO) as our benchmark for transparent electrodes, we demonstrate a 2.6–2.7 times performance gain using two different figure-of-merit indicators. Based on these results, we believe this research provides an ideal manufacturing-ready approach for the large-scale and low-cost fabrication of ultra high-performance transparent electrodes for flexible hybrid electronics and solar-energy harvesting applications.

Laser‐Induced Annealing of Metal–Organic Frameworks on Conductive Substrates for Electrochemical Water Splitting

AbstractThe conventional thermal transformation of metal–organic frameworks (MOFs) for electrocatalysis requires high temperature, an inert atmosphere, and long duration that result in severe aggregation of metal particles and non‐uniform porous structures. Herein, a precise and inexpensive laser‐induced annealing (LIA) strategy, which eliminates particle aggregation and rapidly generates uniform structures with a high exposure of active sites, is introduced to carbonize MOFs on conductive substrates under ambient conditions within a few minutes. By systematically considering 8 substrates and 12 MOFs, a series of LIA‐MOF/substrate devices with controllable sizes and good flexibility are successfully obtained. These LIA‐MOF/substrate devices can directly serve as working electrodes. Remarkably, LIA‐MIL‐101(Fe) on nickel foam exhibits an ultralow overpotential of 225 mV at a current density of 50 mA cm−2 and excellent stability over 50 h for facilitating the oxygen evolution reaction, outperforming most recently reported transition‐metal‐based electrocatalysts and commercial RuO2. Physical characterizations and theoretical calculations evidence that the high activity of LIA‐MIL‐101(Fe) arises from the favorable adsorption of intermediates at its Ni‐doped Fe3O4 overlayer that is formed during the laser treatment. Moreover, the LIA‐MOF/substrate devices are assembled for overall water splitting. The proposed LIA strategy demonstrates a cost‐effective route for manufacturing scalable energy storage and conversion devices.

Exchange bias and diffusion processes in laser annealed CoFeB/IrMn thin films

The performance of exchanged biased tunnel junctions strongly relies on the annealing process finalizing the fabrication process, which is applied to set a pinned reference magnetization, as well as to enhance the magnetoresistance ratio through the crystallization of the CoFeB layers. With the increasing demand in terms of integration and scalability of tunnel magnetoresistive elements, a laser-induced annealing process presents several advantages against traditional oven annealing technique. It provides the possibility to locally set an individual reference magnetization at the micrometer scale to enable e.g. a Wheatstone bridge or multidimensional sensor fabrication on a wafer level. This study presents the influence of laser-induced localized annealing on the magnetic properties of an exchanged biased CoFeB/IrMn system. The diffusion processes occurring at the interface of CoFeB/IrMn are analyzed in detail utilizing X-ray photoemission spectroscopy depth profiling technique and the results are compared to those obtained by standard vacuum oven annealing and correlated to the magnetic properties investigated by magneto-optical Kerr effect magnetometry.

Magnetic Tunnel Junctions: Laser Annealing Versus Oven Annealing

The performance of CoFeB/MgO tunnel junctions is strongly dependent on an annealing step at the end of the fabrication process to first, set a reference magnetization through the exchange bias effect and second, to crystallize the MgO/CoFe layers while boron diffuses out, in order to maximize the magnetoresistance ratio. In this regard, a laser-induced annealing process presents several advantages against traditional oven annealing techniques, providing a scalable approach with no limitations regarding the defined reference magnetization that can be aligned in different directions on a wafer. This paper concentrates on the mechanisms and dependences of laser annealing on the magnetic properties in comparison to the standard vacuum oven annealing, providing a first insight for the applicability of laser annealing for CoFeB-/MgO-based magnetic tunnel junctions with all concomitant needs.

Raman microspectroscopy of PuO2 particulate aggregates

Raman microspectroscopy is a useful technique with the capability to infer local physical properties of materials such as crystalline order. Crystalline order and morphology of plutonium dioxide (PuO2) grains and aggregates are known to be sensitive to the initial production conditions and represent the baseline for understanding subsequent signatures. PuO2 samples were synthesized and then characterized by scanning electron microscopy prior to Raman analysis. A total of nine laser excitation wavelengths (785, 633, 561, 514, 488, 457, 405, 325 and 244 nm) were evaluated to maximize signal and minimize fluorescence, with 514 nm selected for most subsequent work. The effect of laser-induced heating and annealing on the Raman spectra were investigated with a 514 nm laser beam. The ratio of the Stokes and anti-Stokes band intensities was used to estimate the temperature during the laser-induced heating process. The band position and the band full-width at half-maximum (FWHM) were used to track the degree of sample annealing at an estimated temperature. The Raman spectra showed that laser-induced annealing resulted in significant enhancement of the intensity for most spectral bands. Similarly, the FWHM of most bands decreased with increasing annealing temperature. The largest Raman shift of the T2g band for an annealed sample was measured at 480 cm−1. A new, sharp band at 1047 cm−1 emerged during the material annealing process and the intensity grew proportional to the intensity of the T2g band. Crystal Field Theory computational analysis suggests the 1047 cm−1 band is the long sought Γ1 → Γ4 electronic transition proposed by several researchers. The data acquired in this work helps to explain the variability in band position and FWHM reported in the literature, including the assignment of new weak bands associated with Raman resonance and Raman electronic transitions.

Wear resistance of laser-induced annealing of AISI 316 (EN 1.4401) stainless steel

This paper presents an analysis of the impact of the laser annealing process on the wear resistance and corrosion properties of one of the most commonly used AISI 316 (EN 1.4401) stainless steels. The samples were irradiated using a common available fiber laser (Yb:glass) system in an ambient environment. Considering that laser radiation changes the morphology and physicochemical structure of the surface layer, as well as the mechanical properties, extensive research has been conducted. Electrochemical tests, accelerated corrosion tests in neutral salt spray, x-ray photoelectron spectroscopy chemical analysis, microscopic examination, roughness, as well as friction and wear, were carried out. This study has shown that by properly controlling the energy density of laser radiation, the corrosion resistance of the material can be significantly improved. It has also shown that layers coated with laser-induced oxides are more resistant to wear than the reference samples.

Laser post-processing of halide perovskites for enhanced photoluminescence and absorbance

Hybrid halide perovskites have emerged as one of the most promising type of materials for thin-film photovoltaic and light-emitting devices. Further boosting their performance is critically important for commercialization. Here we use femtosecond laser for post-processing of organo-metalic perovskite (MAPbI3) films. The high throughput laser approaches include both ablative silicon nanoparticles integration and laser-induced annealing. By using these techniques, we achieve strong enhancement of photoluminescence as well as useful light absorption. As a result, we observed experimentally 10-fold enhancement of absorbance in a perovskite layer with the silicon nanoparticles. Direct laser annealing allows for increasing of photoluminescence over 130%, and increase absorbance over 300% in near-IR range. We believe that the developed approaches pave the way to novel scalable and highly effective designs of perovskite based devices.

Growth, structure and stability of sputter-deposited MoS2 thin films.

Molybdenum disulphide (MoS2) thin films have received increasing interest as device-active layers in low-dimensional electronics and also as novel catalysts in electrochemical processes such as the hydrogen evolution reaction (HER) in electrochemical water splitting. For both types of applications, industrially scalable fabrication methods with good control over the MoS2 film properties are crucial. Here, we investigate scalable physical vapour deposition (PVD) of MoS2 films by magnetron sputtering. MoS2 films with thicknesses from ≈10 to ≈1000 nm were deposited on SiO2/Si and reticulated vitreous carbon (RVC) substrates. Samples deposited at room temperature (RT) and at 400 °C were compared. The deposited MoS2 was characterized by macro- and microscopic X-ray, electron beam and light scattering, scanning and spectroscopic methods as well as electrical device characterization. We find that room-temperature-deposited MoS2 films are amorphous, of smooth surface morphology and easily degraded upon moderate laser-induced annealing in ambient conditions. In contrast, films deposited at 400 °C are nano-crystalline, show a nano-grained surface morphology and are comparatively stable against laser-induced degradation. Interestingly, results from electrical transport measurements indicate an unexpected metallic-like conduction character of the studied PVD MoS2 films, independent of deposition temperature. Possible reasons for these unusual electrical properties of our PVD MoS2 thin films are discussed. A potential application for such conductive nanostructured MoS2 films could be as catalytically active electrodes in (photo-)electrocatalysis and initial electrochemical measurements suggest directions for future work on our PVD MoS2 films.

The Enhanced Raman Scattering from Ag Nanoball/ZnO Hollow Nanosphere Arrays Fabricated by Laser-Induced Annealing

In this work, a facile method was presented to produce Ag nanoball (NB)/ZnO hollow nanosphere (HNS) hybrid structure. Large scale, two-dimensional (2D) ZnO HNS arrays were fabricated on sapphire substrates using the polystyrene (PS) nanospheres as the template. Ag film were deposited on ZnO HNS arrays by radio frequency (RF) magnetron sputtering and then aggregated into Ag NBs on the top of ZnO HNS by the laser irradiation treatment. The size and distribution of Ag NB arrays were controlled by employing different ZnO HNS supporting structure templates. The scanning electron microscopy (SEM) was applied to visually study the evolution process of Ag NB/ZnO NHS arrays. X-ray diffraction (XRD) was carried out to characterize crystal structures of the samples. Obvious surface enhanced Raman (SERS) signals were observed from the Ag NB/ZnO NHS nanocomposite structure compared with that in the ZnO HNS structure by using the R6G as the testing agent. Theoretical simulation results demonstrate that the Raman enhancement originates from the significant enhanced local electromagnetic field induced by the surface plasmon resonance (SPR) of Ag NBs.

Semiconducted symphony: ultrafast field emitter array

Semiconducted symphony: ultrafast field emitter array

Formation of Nickel-Silicide Selective Emitter by Laser-Induced Annealing for p-Type Solar Cell Application

not Available.

Pulsed laser-induced silicidation on TiN-capped Co∕Si bilayers

This paper studies the effects of pulsed laser-induced annealing of TiN-capped Co∕Si bilayers with and without preamorphized Si substrate. For a low fluence of 0.2J∕cm2, nonstoichiometry Co silicide with triple-layered structure is formed. On the other hand, highly textured CoSi2 grains in (111) direction are formed for a high fluence of 0.7J∕cm2. The highly textured CoSi2 layer is monocrystalline and fully coherent with the (111) plane of the Si substrate. However, it has a large amount of microstructural defects throughout the layer. Competitive growth mechanisms between crystallization of homogenous intermixed layer and the nucleation from the melt boundary are discussed.

Low-temperature crystallization induced by excimer laser irradiation of SrBi2Ta2O9 films

Transition of a SrBi2Ta2O9 precursor film from amorphous to crystalline was inducedby excimer laser irradiation. Both fluorite and perovskite crystalline structures in suchfilms were obtained by excimer laser irradiation at substrate temperatures between 200and 500 °C. Either an addition of excess bismuth in the precursor film or an increasein the substrate temperature enhanced the formation of the perovskite structure in theexcimer laser-induced annealing process, resulting in the perovskite crystalline phase ata relatively lower temperature of 500 °C. Such a low temperature is preferred whenSrBi2Ta2O9 is used in ferroelectric devices. The mechanism involved in thislaser-induced crystallization is also discussed.

Production and stability of silicon-doped heterofullerenes

Silicon–carbon binary clusters with various mean compositions are generated in a laser vaporization source from targets processed as mixtures of graphite and silicon powders. Their size distribution is first analyzed by time-of-flight mass spectroscopy, which shows the stability of carbon fullerenes doped with silicon atoms in substitutional sites. Further investigations on the level of silicon doping are carried out by means of the laser-induced fragmentation of selected sizes. The photoproduct size distributions give evidence for at least nine silicon atoms substituted into still stable fullerene networks. The synthesis of heterofullerenes is mainly assisted by the nucleation mechanisms from Si-C mixed atomic vapors. Just as in the case of externally doped fullerene precursors, the laser-induced annealing of stoichiometric silicon-carbide clusters appears as an alternative route to produce heterofullerenes in the gas phase.

Short-pulse laser-induced crystallization of intrinsic and hydrogenated amorphous germanium thin films

We report on the laser crystallization of intrinsic (a-Ge) and hydrogenated (a-Ge:H) amorphous germanium thin films using short, i.e., ns range, laser pulses. The influence of hydrogen on the phase transitions was investigated by monitoring the reflectance of the sample during laser irradiation. We determined the thresholds for melting (36 mJ/cm2) and for surface damage (66 mJ/cm2) of the a-Ge film. In a-Ge:H, hydrogen effuses on a short time scale (10 ns) upon laser irradiation. The effusion leads to the formation of a lifted-off (100 nm thick) crystalline Ge membrane, leaving behind a rough and incompletely crystallized surface. In a-Ge, on the other hand, no surface disruption is observed. The Raman spectra of hydrogenated samples are dominated by stress effects, while those corresponding to non-hydrogenated samples are dominated by crystallite size distribution effects. We also conclude that laser-induced annealing, carried out by applying several pulses with increasing intensity, can be used as a tool for the crystallization of a-Ge:H samples without hydrogen-induced surface damage.

A description of the laser-induced annealing and diffusion behaviour of implanted silicon crystals

(1980). A description of the laser-induced annealing and diffusion behaviour of implanted silicon crystals. Radiation Effects: Vol. 47, No. 1-4, pp. 157-161.