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Metal nanostructures are, nowadays, extensively used in applications such as catalysis, electronics, sensing, optoelectronics and others. These applications require the possibility to design and fabricate metal nanostructures directly on functional substrates, with specifically controlled shapes, sizes, structures and reduced costs. A promising route towards the controlled fabrication of surface-supported metal nanostructures is the processing of substrate-deposited thin metal films by fast and ultrafast pulsed lasers. In fact, the processes occurring for laser-irradiated metal films (melting, ablation, deformation) can be exploited and controlled on the nanoscale to produce metal nanostructures with the desired shape, size, and surface order. The present paper aims to overview the results concerning the use of fast and ultrafast laser-based fabrication methodologies to obtain metal nanostructures on surfaces from the processing of deposited metal films. The paper aims to focus on the correlation between the process parameter, physical parameters and the morphological/structural properties of the obtained nanostructures. We begin with a review of the basic concepts on the laser-metal films interaction to clarify the main laser, metal film, and substrate parameters governing the metal film evolution under the laser irradiation. The review then aims to provide a comprehensive schematization of some notable classes of metal nanostructures which can be fabricated and establishes general frameworks connecting the processes parameters to the characteristics of the nanostructures. To simplify the discussion, the laser types under considerations are classified into three classes on the basis of the range of the pulse duration: nanosecond-, picosecond-, femtosecond-pulsed lasers. These lasers induce different structuring mechanisms for an irradiated metal film. By discussing these mechanisms, the basic formation processes of micro- and nano-structures is illustrated and justified. A short discussion on the notable applications for the produced metal nanostructures is carried out so as to outline the strengths of the laser-based fabrication processes. Finally, the review shows the innovative contributions that can be proposed in this research field by illustrating the challenges and perspectives.

In this work, ultrathin nickel films are developed for application as transparent electrodes in thermoelectric devices. The quality of the films is determined systematically by electrical, optical, and morphological characterization in a series of samples with different thickness. The thermal properties of the films show a dramatic dependence of the Seebeck coefficient on the film thickness. This dependence, with values ranging from −16 to +5 𝜇V K−1 for thicknesses from 10 to 2 nm, includes a change in the behavior of the thermoelectric response from n- to p-type. It has also been demonstrated that the accurate estimation of the thermal conductivity in thin films is challenging due to substrate effects. In this situation, a differential measurement method based on scanning thermal microscopy is proposed, as in these conditions the measurements are less sensitive to the substrate effects. In further works, the dependence of the thermal properties of ultrathin nickel films can be exploited as a tuning parameter for the design of thermoelectric devices.

This study proposes a high-performance magnetic shielding structure composed of MnZn ferrite and mu-metal film. The use of the mu-metal film with a high magnetic permeability restrains the decrease in the magnetic shielding coefficient caused by the magnetic leakage between the gap of magnetic annuli. The 0.1–0.5 mm thickness of mu-metal film prevents the increase of magnetic noise of composite structure. The finite element simulation results show that the magnetic shielding coefficient and magnetic noise are almost unchanged with the increase in the gap width. Compared with conventional ferrite magnetic shields with multiple annuli structures under the gap width of 0.5 mm, the radial shielding coefficient increases by 13.2%, and the magnetic noise decreases by 21%. The axial shielding coefficient increases by 22.3 times. Experiments verify the simulation results of the shielding coefficient of the combined magnetic shield. The shielding coefficient of the combined magnetic shield is 16.5%. It is 91.3% higher than the conventional ferrite magnetic shield. The main difference is observed between the actual and simulated relative permeability of mu-metal films. The combined magnetic shielding proposed in this study is of great significance to further promote the performance of atomic sensors sensitive to magnetic field.

Many natural disordered systems such as percolation metal films may be approximated as fractals. Probing their properties can be difficult depending on the length scale involved. Often, characterizing the system at a convenient length scale and building models for extrapolating the measured data to other length scales is preferred. In such situations, a general algorithm for scaling the model network while preserving its statistical equivalence is required. Here, we provide an algorithm that draws inspiration from renormalization group theory for scaling disordered fractal networks. This algorithm includes three steps: expand, map, and reduce resolution, where the mapping is the only computationally expensive step. We describe a way to minimize the computational burden and accurately scale the model network. We experimentally validate the algorithm in a percolating electrical network formed by an ultra-thin gold film on a glass substrate. By measuring the resistance between many pairs of pads separated by a given length, we accurately predict the mean and standard deviation of the resistance distribution measured across pads separated by twice the original distance. The algorithm presented here is general and may be applied to any disordered fractal system.

Ultra-thin metal films are an important element of 2D materials compatible with transparent optoelectronics. As a result, atomically thin continuous metal films are of particular interest for many applications. Nevertheless, obtaining thin and continuous smooth films is challenging. A method based on the growth of noble metals on crystal sheets of transition metal dichalcogenides (TMDs) leads to continuous morphology and low roughness of ultrathin (<10 nm) films. Here, we investigated the surface morphology of ultrathin gold films deposited on exfoliated crystal flakes of MoS 2 , WS 2 , TiS 2 and MoSe 2 on SiO 2 /Si substrate using scanning electron and atomic force microscopy. Our results indicate that TMDs layers are an efficient platform for fabricating continuous ultrathin metals.

Selective thin-film removal is needed in many microfabrication processes such as 3-D patterning of optoelectronic devices and localized repairing of integrated circuits. Various wet or dry etching methods are available, but laser machining is a tool of green manufacturing as it can remove thin films by ablation without use of toxic chemicals. However, laser ablation causes thermal damage on neighboring patterns and underneath substrates, hindering its extensive use with high precision and integrity. Here, using ultrashort laser pulses of sub-picosecond duration, we demonstrate an ultrafast mechanism of laser ablation that leads to selective removal of a thin metal film with minimal damage on the substrate. The ultrafast laser ablation is accomplished with the insertion of a transition metal interlayer that offers high electron–phonon coupling to trigger vaporization in a picosecond timescale. This contained form of heat transfer permits lifting off the metal thin-film layer while blocking heat conduction to the substrate. Our ultrafast scheme of selective thin film removal is analytically validated using a two-temperature model of heat transfer between electrons and phonons in material. Further, experimental verification is made using 0.2 ps laser pulses by micropatterning metal films for various applications.

The nitrogen-vacancy (NV) color center in diamond has demonstrated great promise in a wide range of quantum sensing. Recently, there have been a series of proposals and experiments using NV centers to detect spin noise of quantum materials near the diamond surface. This is a rich complex area of study with novel nano-magnetism and electronic behavior, that the NV center would be ideal for sensing. However, due to the electronic properties of the NV itself and its host material, getting high quality NV centers within nanometers of such systems is challenging. Band bending caused by space charges formed at the metal-semiconductor interface force the NV center into its insensitive charge states. Here, we investigate optimizing this interface by depositing thin metal films and thin insulating layers on a series of NV ensembles at different depths to characterize the impact of metal films on different ensemble depths. We find an improvement of coherence and dephasing times we attribute to ionization of other paramagnetic defects. The insulating layer of alumina between the metal and diamond provide improved photoluminescence and higher sensitivity in all modes of sensing as compared to direct contact with the metal, providing as much as a factor of 2 increase in sensitivity, decrease of integration time by a factor of 4, for NV T 1 relaxometry measurements.

Both electronic and phononic statistical and thermal properties, modulated by the quantum size effect, are suggested in a thin metal film. In order to show the quantum size effect of specific heat, the densities of the electron and phonon states of an ultra-thin film are treated within the framework of quantum statistics. It was found that strong and weak “even–odd layer oscillatory behavior” was exhibited by the ultra-thin metal film in electronic and lattice specific heat, respectively. Such a behavior, which depends on film thickness, results from the quantum confinement of electrons and phonons in the vertical (thickness) direction of the film, where both electrons and phonons form their respective quantum well standing wave modes. If, for example, the thickness of the ultra-thin metal film is exactly an integer multiple of a half wavelength of the standing wave of electrons in the thickness direction, the corresponding density of states would become maximized, and the electronic specific heat would take its maximum. In the literature, less attention has been paid to the size-dependent electron Fermi wavelength for quantum size effects, i.e., the Fermi wavelength in ultra-thin metal films has always been identified as a constant. We shall show how the Fermi wavelength varies with the size of a nanofilm, including an explicit analytic formulation for the thickness dependence of the electron Fermi wavelength. Size-dependent resonantly oscillatory behavior, depending on the ultra-thin or nanoscale film thickness, would have possible significance for researching some fundamental physical characteristics (e.g., low-dimensional quantum statistics) and may find potential applications in new thermodynamic device design.

Tunable emissivity technology is promising for the dynamic regulation of infrared radiation. Herein, infrared electrochromic devices based on thin metal films that operate via a novel hydrogen‐induced metal–insulator transition are demonstrated. The use of thin magnesium–nickel (MgxNi) alloy films as both a variable emissivity material and top conductive electrode simplifies the device structure and ensures that large changes in emissivity can be achieved. The constructed sandwich‐structured electrochromic devices also have polyethyleneimine (PEI) as a middle proton‐conducting electrolyte layer and hydrogen tungsten bronze (HxWO3)/indium tin oxide (ITO) as a bottom ion‐storage layer. Upon application of a voltage of ±2.6 V, the emissivity of the MgxNi/Pd/PEI/HxWO3/ITO device can be reversibly regulated, with emissivity changes of 0.48 and 0.43 in the 3–5 and 7.5–14 µm atmospheric windows, respectively. Under open‐circuit conditions, the high‐emissivity state of the device can be stably maintained for 3 h. The emissivity change is affected by the composition and thickness of the MgxNi film and the device failure mechanism involves the breakage and oxidation of this film after cycling. Corresponding flexible devices that exhibit electrochromism in the visible region have great potential for adaptive thermal camouflage, smart thermal management, and dynamic information displays. An infrared electrochromic device is constructed based on a hydrogen‐induced metal–insulator phase transition from metallic Mg2Ni to dielectric Mg2NiH4. Reversible emissivity changes are achieved by alternately applying ±2.6 V. The high‐emissivity state is maintained for 3 h, with subsequent device failure caused by stress accumulation and oxidation. The device can be modified to also induce visible color changes.

Fredholm integral equations of the second kind are formulated to describe the anomalous skin effect in metal films on dielectric substrates. An algorithm is developed for numerical solution of the equations based on the quadrature method. As a result of its use for processing published experimental data on the spectral ellipsometry of gold films of different thicknesses on a silicon substrate, the density, relaxation time of the conduction electrons, and dielectric constant of gold are uniquely determined. The dependence of the dielectric constant of gold films on their thickness noted in a number of experimental studies is explained by using a model of the normal Drude skin effect that does not take the excitation of space charge in the film into account when solving the inverse optical problems. The optical fields in gold films are studied for different probabilities of mirror reflection of electrons from the boundary of the films It is found that in sensors for biological solutions with a Kretschmann configuration, structures in which the probability of mirror reflection of electrons from the metallic film–liquid interface approaches unity are to be preferred.