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We present equipment for sample synthesis, preparation and modification enabling in-situ studies employing medium energy ion beams at the ion implanter facility of the Tandem Laboratory national research infrastructure at Uppsala University. The integral instrumentation enables controlled thin-film synthesis, modification and characterization applicable to study near-surface processes such as thin-film growth, phase transformation, oxidation, annealing, catalysis or ion implantation. We describe the available instrumentation with its specifications and present four demonstrative experiments with a particular focus on the acquired in-situ capabilities addressing 1) Evaporation and thermal alloying of thin films - nickel silicides 2) Reactive magnetron sputtering and controlled oxidization - photochromic YHO 3) Sputtering and low-energy implantation - hydrogen in tungsten and 4) Surface cleaning of sensitive systems - self-supporting silicon membranes.

Understanding the mechanism behind the photochromic properties and light-induced structural and chemical changes in yttrium oxyhydride remains a challenge. This lack of knowledge limits our ability to address degradation, enhance photochromic performance, control color, improve durability, and fully realize the material’s applications. Here, first-principles calculations indicate that anion vacancies may be responsible for the photochromic effect and other key properties of yttrium oxyhydride. These vacancies form deep localized energy levels in the band gap. Sunlight absorption transfers electrons from the valence band to these defect levels, altering the charge state of the vacancies and triggering both the photochromic effect and lattice relaxation. This relaxation involves yttrium cations shifting outward for positively charged vacancies and inward for negatively charged ones, thereby affecting the local environment around the yttrium cations by altering the second coordination shell. Using extended X-ray absorption fine structure spectroscopy on transparent and photo-darkened yttrium oxyhydride films, we show that UV light induces lattice relaxation in the second coordination shell, in agreement with first-principles calculations.

The tuning of magnetic properties through electrochemical loading of hydrogen has recently attracted significant interest as a way to manipulate magnetic devices with electric fields. In this paper we investigate quantitatively the magneto-ionic effect of hydrogen uptake on the magnetic properties of rare-earth transition-metal alloy TbxCo(100-x) in the composition range of x = 10-39 at.% using ion implantation. Using this technique we are able to link changes in magnetic behavior to exact concentrations of hydrogen, isolated from the movement of any other ions that would be a factor in electrochemical studies. The composition of the alloy has been varied alongside the hydrogen dose to characterize the effect of progressive hydrogen loading on the full range of x displaying out-of-plane magnetic anisotropy. We find large changes in two important properties: the compensation composition and the Co-rich in-plane to out-of-plane magnetic anisotropy transition composition, both of which move by 6 at.% toward higher Tb concentrations after hydrogen implantation. This shift in composition does not increase with a larger dose. From the changes in magnetization we attribute the change in compensation composition to a significant reduction of the moment on the Tb sublattice.

Finite size, straine, and proximity effects are often simultaneously present in nanosized metal hydrides, while it is difficult to discriminate their effect on thermodynamic properties. Here, we present quantitative strain analysis of epitaxially grown V thin films by a combination of real and reciprocal space techniques. We find that films up to ≈ 90 nm preserve tetragonal distortion imposed by the rigid substrate. Free from non-uniform strain profiles, we demonstrate that hydrogenated VH_x films of different thicknesses (30, 60, and 90 nm) feature octahedral occupancy of H.

Understanding the electrically active defects and impurities in semiconductors, especially in intrinsic or unintentionally doped wide bandgap materials, still remains a challenge. Here, time-of-flight (ToF) measurement using a solid state light source (355 and 213 nm) was performed on intrinsic silicon carbide and single-crystalline diamond. The charge transient spectroscopy (QTS) and the inverse Laplace (IL) QTS methods were applied to analyze the ToF results. Using these methods, we were able to trace the existing impurities in both materials. However, ILQTS proved to be more sensitive, with higher resolution for detection of existing multiple defects. The results suggest that this system can successfully be employed to investigate electrically active impurities at different energy states in highly resistive and undoped materials.

We study experimentally the impact of the additive fabrication method on the magnetic properties of Fe+-implanted Pd square artificial spin ice lattices. Our findings show that the lattices exhibit a higher ordering temperature than their continuous film counterparts. This behavior is attributed to the additive fabrication process, which induces an inhomogeneous Fe concentration within the lattice building blocks. Moreover, the implantation process creates a magnetic depth profile, enabling temperature-dependent tunability of the magnetic thickness. These additional internal degrees of freedom broaden the design possibilities for magnetic metamaterials, allowing precise fine tuning of their static and dynamic properties to achieve complex and customizable behaviors.

We report on a study of titanium carbonitride coatings, with potential applications as protective coatings on bipolar plates in fuel cells. Two series of Ti-C-N coatings with a carbon concentration varying between 8 and 34 at.% were deposited by magnetron sputtering, using a graphite target or methane gas as carbon source. Characterisation with X-ray diffraction, ion beam analysis, Raman spectroscopy and electron microscopy shows that the coatings consist of a crystalline titanium carbonitride phase and an amorphous carbon tissue phase: nc-Ti(C,N)/a-C(:N). It was found that the mechanical and electrical properties are primarily dependent on the carbon content and not the choice of carbon source. An increase in C content leads to a decreasing crystallite size and an increasing amount of amorphous carbon. Thus, the phase content and microstructure and thereby the properties are controlled by the carbon content, making the nc-Ti(C,N)/a-C(:N) coatings highly tuneable. Depending on C content hardness of 11-38 GPa and resistivity of 150-623 mu ohm cm was observed. Additionally, the coatings were found to exhibit a contact resistance against silver that was 10 times lower than that of a stainless steel reference. This makes titanium carbonitride nanocomposite coatings promising candidates for the use on bipolar plates in fuel cells.

Oxygen-containing yttrium hydride (YHO) and molybdenum trioxide (MoO₃) bilayer films (YHO/MoO₃) are produced using reactive magnetron sputtering, and their photochromic properties are investigated in relation to the thickness and density of the MoO₃ layer. Compared to single YHO films, the YHO/MoO₃ films exhibit faster coloration and larger contrast, with both parameters adjustable by varying the thickness or deposition pressure of the MoO₃ layer. Transparent YHO/MoO₃ films (∼ 75% at 550nm) demonstrate a photochromic contrast of up to 60 %, significantly higher than the 25-30% contrast observed for single YHO films after 20 h of UVA-violet light exposure. This enhancement arises from hydrogen intercalation from the (200)-textured polycrystalline YHO film into the X-ray amorphous MoO₃, leading to the formation of molybdenum bronze (H_xMoO₃), as confirmed by X-ray photoelectron and optical spectroscopies. However, the darkened YHO/MoO₃ films do not fully recover to their initial transparency after illumination due to the irreversible nature of the coloured MoO₃ layer. Most of the hydrogen intercalated into MoO₃ originates from the YHO layer during the initial darkening process. Furthermore, the bilayer films are chemically unstable, exhibiting gradual darkening over time even without intentional UV illumination, as confirmed by nuclear reaction analysis.

We investigate the effective oxidation state and local environment of yttrium in photochromic YHO thin film structures produced by e-beam evaporation, along with their chemical structure and optical properties. Transmission electron microscopy images reveal the oxidized yttrium hydride thin film sample exhibiting a three-layered structure. X-ray photoelectron spectroscopy (XPS) measurements manifest that the oxidation state of yttrium is modified, dependent on the film's composition/depth. Furthermore, Ion beam analysis confirms that this variability is associated with a composition gradient within the film. X-ray absorption spectroscopy at the Y K-edge reveals that the effective oxidation state of yttrium is approximately +2.5 in the transparent/bleached state of YHO. Spectroscopic ellipsometry investigations showed a complex non-linear optical depth profile of the related sample confirming the dominant phase of YHO and the presence of Y(2)O(3 )and Y towards the middle of the film. The first evidence of (n; k) dispersion curves for e-beam sputtered photochromic YHO thin films are reported for transparent and dark states.

We present in-situ studies of H loss from YHO films using ion beam analysis and its effect on the photochromic properties. The film evaporates loosely bound H under exposure to a beam of 3056 keV He²⁺ without a concomitant increase of O. Annealing at 145 °C decreases both the photochromic contrast and the bleaching speed indicating the importance of mobile H for the photochromic reaction.