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The combination of the phase transition in thermochromic vanadium dioxide (VO2) with plasmonic nanoparticles paves the way for applications in various fields, including optical sensing, advanced coatings, and dynamic optical devices. This study presents a simple fabrication method to control both the size and surface coverage of NPs combined with VO2. First, a thermochromic VO2 coating with a phase transition at 68 °C is synthesized using reactive magnetron sputtering. Then, monodisperse 30 nm diameter gold NPs are bonded to the VO2 surface using (3‐aminopropyl)trimethoxysilane (APTMS) linkers, examining the effect of immersion duration on surface coverage. Two platforms are developed: a VO2 thin film with a monolayer of NPs and a configuration with NPs between two VO2 films. The temperature‐dependent plasmonic response of these platforms is measured by extinction spectroscopy, showing a significant wavelength resonance shift of approximately 10 nm for the first platform and 20 nm for the second. Optical simulations analyze this shift over various geometries, from isolated NPs to fully covered NPs, achieving a 60 nm shift for NPs embedded in a thin VO2 film. This study demonstrates an effective approach to synthesizing thermochromic VO2 coatings with gold NPs, offering insights into the plasmonic properties of hybrid platforms. [ABSTRACT FROM AUTHOR]

Although the synthesis of nanoparticles (NPs) by low-pressure plasma-based sputtering onto liquids offers many advantages as compared to classic wet-chemistry-based approaches, not much is known about the nanoparticle formation mechanism in these conditions. Here, we report about an operando absorption spectrophotometry setup which allows recording time- and space-resolved spectra of the liquid into which the sputtered metal atoms are incorporated. The measurements are carried out during the plasma treatment but also afterward while keeping the sample inside the vacuum chamber. The device capabilities therefore allow studying the evolution of unstable systems, i.e., combination of sputtered atoms and host liquids for which aggregation may appear even during the plasma treatment time. As a model system, silver atoms are deposited onto a silicone oil which may be stirred or not. Our operando analysis provides qualitative and quantitative data and highlights that the nanoparticle formation and aggregation dynamics vary according to the process conditions. [ABSTRACT FROM AUTHOR]

This study presents a structuration approach to reach a high luminous transmittance (T l u m ) and solar modulation efficiency (Δ T s o l ) of thermochromic vanadium dioxide ( VO 2 ) thin films. Before starting optical simulations, we confirm that the optical properties of monoclinic VO 2 continuous films deposited by reactive magnetron sputtering show a good correspondence with numerical results. Then, calculations on ordered VO 2 nanostripes demonstrate an enhanced transmittance due to the presence of vertical openings, leading to a variety of photonic effects. A series of optimizations by varying the column width, period, and film thickness establishes that 20 nm wide and 10 nm separated nanostripes have a Δ T s o l of 14.2% and a T l u m of 47.6% for a film thickness of 250 nm. In comparison to a dense film without nanostructuring, the film transparency (related to T l u m ) is significantly enhanced, while Δ T s o l remains unchanged. Furthermore, this also translates into a favorable, less opaque color, so the geometry could be useful for various thermochromic applications, such as smart windows. [ABSTRACT FROM AUTHOR]

We report several effects found in reactive bipolar high-power impulse magnetron sputtering (abbreviated as bipolar HiPIMS or BPH) discharges at the substrate level. The role of the negative peak current and the positive pulse voltage, U + , on the deposition flux at the electrically insulating substrate is discussed and the results are compared to conventional DC discharges. In particular, the normalized energy flux, ϕ n , delivered to the substrate is found higher under BPH conditions at U + = +300 V ( φ n = 3.43 × 10 15 eV·nm−3) as compared to the HiPIMS ( φ n = 0.78 × 10 15 eV·nm−3) and DCMS ( φ n = 1.23 × 10 15 eV·nm−3) regimes which is assumed to be provoked by an intensification of the positive ion bombardment. Accordingly, the mean energy and the count of positively charged metal and gaseous ions increase in line with U + as measured by energy-resolved mass spectrometry. Contrariwise, our analysis has shown a significant decrease (≈20 %) of negative oxygen ion count under BPH conditions. [ABSTRACT FROM AUTHOR]

The plasma is studied by time-resolved optical emission and absorption spectroscopies and the deposition rate is controlled. The pulse length is varied between 2.5 and 20 mus at 2 and 10 mTorr in pure argon.

In this study, resonant absorption diagnostic has been used to estimate densities of neutral and ionic titanium, both in ground and metastable states, in an rf coil amplified magnetron sputtering process. The densities obtained are used to compare the magnetron discharge.

In this work, the direct current (DC) hot magnetron sputtering (HMS) of Nb has been studied and compared with the conventional cold magnetron sputtering (CMS) discharge. Particularly, these two magnetron systems were investigated in terms of currentâ€"voltage trends, behaviour of spectral lines, target temperature, and deposition rate. The currentâ€"voltage evolution showing strong variations over time in the HMS system was used to monitor the moment when thermionic emission becomes considerable. Meanwhile, thanks to the time-resolved optical emission spectroscopy (OES), the dynamics of plasma particles and the population of their electronic levels were analysed as a function of the target temperature. The target temperature was measured owing to both pyrometry and OES-based approach, i.e. by fitting an emission spectrum baseline. Finally, in the HMS configuration used in this work, the deposition rate up to 100 nm minâˆ'1 was obtained at the applied power density of 30 W cmâˆ'2, which is three times higher than the maximum power density applicable to the classical CMS system. However, with further increase in the power density, the deposition rate values were found to be saturated, which is likely caused by a significant increment in a number of thermal electrons in the discharge area. [ABSTRACT FROM AUTHOR]

A titanium target was reactively sputtered in an Ar/O2 atmosphere by (i) conventional direct current magnetron sputtering (DCMS), (ii) high-power impulse magnetron sputtering (HiPIMS), and (iii) bipolar HiPIMS (BPH) discharges for the deposition of titanium dioxide thin films without intentional heating and biasing. In the HiPIMS and BPH cases, the peak current density was set to either 0.32 A cm−2 or 0.86 A cm−2. The time-averaged power density delivered to the plasma was set to ≈1.2 W cm−2 in each case. For the BPH discharge, a positive pulse of +300 V was applied after the negative pulse to accelerate the positive ions toward the substrate. Energy-resolved mass spectrometry analysis has shown a low-energy peak for DCMS while a high energy tail extending in the range of several tens of eV was observed with HiPIMS. In the BPH discharge, the energy reached ≈300 eV for Ti+ ions, which is in agreement with the applied positive potential. According to the x-ray diffraction patterns, amorphous coatings were obtained with DCMS, while rutile TiO2 was obtained with both HiPIMS and BPH. However, in the BPH case, diffractograms were characterized by more intense high-angle diffraction peaks highlighting a modification of the growth process for these conditions. Rutherford backscattering spectrometry analysis has shown that a higher amount of argon atoms were incorporated into the TiO2 films which are found to be slightly understoichiometric for the BPH discharge. It was also found that the refractive index, n, varied as a function of the sputtering regime with the highest value obtained in the HiPIMS case (n = 2.73 at 550 nm). Finally, the experimentally determined optical data were compared to the ones extracted from NASCAM simulations which are found in good agreement except for the BPH case. [ABSTRACT FROM AUTHOR]