Joris Van de Vondel

Dry-deposited metal–organic resists are key enablers for advanced patterning processes in next-generation semiconductor manufacturing. Here, we report halogenated amorphous zeolitic imidazolate framework (a-ZIF) resists deposited entirely by a dry process, which exhibit a pronounced irradiation-source-dependent tone conversion. Smooth a-ZIF films were grown by chemical vapor deposition (CVD) using 4,5-diiodoimidazole (DI-Im) precursors. Partial in situ thermal decomposition of DI-Im produces a ternary linker mixture (DI-Im, 4-iodoimidazole, imidazole), promoting the growth of uniform, amorphous films. Under electron-beam (e-beam) exposure, the resist operates in a positive-tone mode with high sensitivity (D50 = 0.15 mC cm–2, comparable to commercial PMMA resists) and resolves 100 nm line-and-space and 80 nm contact-hole patterns. In contrast, EUV exposure yields high sensitivity in negative-tone development (D50 = 65 mJ cm–2) and exhibits a nonmonotonic dose–thickness response in positive-tone development. We demonstrate positive-tone EUV patterning of 90 nm line-and-space features. X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy trace the tone conversion to distinct reaction pathways: high-energy primary electrons under e-beam exposure drive imidazole ring decomposition into soluble polar fragments, giving rise to the positive-tone response, whereas the low-energy electrons generated under EUV cleave C–I bonds while retaining the ring, and the resulting poorly soluble recombination products account for both the negative-tone behavior and the nonmonotonic positive-tone response. Identifying the electron-energy regimes and reaction pathways responsible for each behavior provides a basis for engineering the resist response through linker design. These results illustrate that electron-beam exposure cannot serve as a universal chemical proxy for EUV lithography.

Planar superconducting resonators are essential components in quantum circuits and highly sensitive sensors. However, their performance is often compromised by magnetic flux penetration, as the interaction of flux quanta and the induced radio-frequency (rf) currents in the superconducting thin film leads to significant energy dissipation. At low operating temperatures, this issue is aggravated as thermomagnetic instabilities can trigger the sudden propagation of magnetic flux avalanches. An important open question is whether the rf excitation itself stimulates the nucleation and propagation of magnetic flux avalanches in the superconducting thin film. The literature remains inconclusive on this point, partly due to the lack of compelling evidence for this phenomenon. In this work, we address this issue by unprecedented direct visualization of magnetic flux penetration through Faraday rotation imaging under simultaneous rf excitation. We demonstrate that the avalanche activity exhibits a weak dependence on the rf intensity for rf excitations within the linear Campbell regime. However, magnetic flux bursts clearly influence the rf transmission properties of the device. Furthermore, it is possible to unambiguously associate a particular avalanche event with a jump in resonance frequency. This enables us to identify the loci of most deleterious events and understand the distinct origins of upward and downward frequency shifts. These observations are supported by electromagnetic simulations in which local changes of the kinetic inductance mimic flux avalanches and confirm the invasive character of the magneto-optical imaging (MOI) technique. The insights gained from this study aim to contribute to the broader understanding of the magnetic resilience of superconducting resonators, with the goal of improving their efficiency and stability.

Strongly coupled plasmonic metasurfaces provide a platform for probing ultrafast light–matter interactions, yet their dynamic response under intense optical excitation remains largely unexplored. Here, we investigate the temporal behavior in metasurfaces composed of adjacent gold dipole and quadrupole resonators on a silicon substrate using time‐resolved mid‐infrared pump–probe spectroscopy. Their near‐field coupling across nanometric gaps facilitates destructive interference and creates a narrow plasmon‐induced transparency (PIT) window. Aside from a transmission increase that lasts several tens of picoseconds as a result of impact ionization, the strongly coupled metasurfaces exhibit an instantaneous sub‐ps transmission spike. We attribute this feature to direct field‐driven interaction that, under strong coupling, simultaneously excites hybrid modes to enable coherent energy exchange—a channel absent in isolated or weakly coupled structures. Notwithstanding these dynamics, the PIT resonance profile evidences a robust, strong near‐field coupling. Numerical analysis reveals the temporal evolution of the bright and dark modes’ damping rates, as well as the inter‐resonator coupling coefficient. Those results establish a well‐grounded mechanism for ultrafast mid‐infrared all‐optical modulation and unveil a previously hidden, ultrafast nonlinearity inherent to strongly coupled plasmonic metasurfaces.

In 2025, the Year of Quantum Science and Technology ( https://quantum2025.org/ ), we celebrate a century of quantum mechanics, witnessing a surge in activities that illuminate its inherent strangeness and drive technological innovation. Superconductivity, discovered 114 years ago, stands as a prime example, offering direct and compelling evidence of macroscopic quantum phenomena. Beyond its ability to conduct immense currents without loss, superconductivity reveals the quantum realm operating on a scale we can directly observe and manipulate. The macroscopic quantum coherence, where an ensemble of particles is described by a single wave function, leads to remarkable consequences: dissipation-less current and flux quantization—the basic properties exploited in superconducting quantum circuit fabrication. This Roadmap has been inspired by intensive discussions and collaborations emerging from the European Cooperation in Science & Technology COST-Action CA21144 (SuperQuMap—Superconducting Nanodevices and Quantum Materials for Coherent Manipulation). The aim of the COST Action SuperQuMap is to establish a strong European network centered on macroscopic quantum behavior in superconductors, bringing together groups of different backgrounds and more than 30 countries. The roadmap outlines the network’s concrete activities, driving advancements in superconductor-based quantum technologies and charting future directions. Spanning fundamental research to practical applications, the roadmap incorporates insights from industry partners developing quantum computation. It begins by exploring quantum materials, highlighting how topology and electronic correlations could catalyze a quantum leap in technology. We then delve into manipulating the superconducting phase, leveraging advancements in magnetism, 3D fabrication, and tunable correlations. Further, we showcase the advanced microscopy techniques—such as angle-resolved photoemission spectroscopy and scanning probes—used to visualize quantum behavior. Finally, and crucially, we detail the quantum devices developed within the network, and their transformative impact on modern quantum computing approaches.

Clusters adsorbed on graphene can alter the electronic and spin-based properties of this two-dimensional material by proximity interactions. However, at room temperature, the adsorbed clusters tend to move freely over the surface. First-principles molecular dynamics simulations are performed to study the motion of size-selected Au_n (n = 3 and 6) clusters adsorbed on the graphene surface. While the clusters are found to be diffusive along the surface of pristine graphene, the presence of C-vacancies in graphene drastically suppresses the diffusion of the clusters and "anchors" them to the vacancy site. Besides carbon vacancies, the presence of resist residues like methyl methacrylate, which is commonly used in the fabrication process of nanoscale devices, was also considered in this work. The presence of residues on the surface of graphene strongly reduces the diffusion of the Au_n clusters.

The demand for cryogenic memory components is driven by the need for ultrafast, low-power, and highly reliable computing systems. Phase-slip-based devices promise to fulfill all these requirements, with potential applications in both classical and quantum information processing. However, previous implementations have faced challenges due to inefficient writing and readout schemes. In this work, we address these limitations with a simple device design and measurement techniques inspired by circuit quantum electrodynamics. We present a memory element that stores information in the winding of a high-kinetic inductance superconducting loop, inductively coupled to a coplanar waveguide resonator. Using 2-$\text{\ensuremath{\mu}}\mathrm{s}$ single-shot measurements, we bring the resonator to the steady state and achieve a readout fidelity of 99.698% with an active measurement time of just 25 ns.

Materials that feature very high permittivity and very low losses at low temperatures offer interesting opportunities for improving the performance of a variety of microwave-optical devices such as phase shifters and quantum transducers. In this Letter, superconducting Al coplanar waveguide resonators between 4 and 6 GHz were used to determine the complex permittivity and loss of thin film SrTiO3 on Si at cryogenic temperatures. We report a permittivity of 1950 ± 140 and a high-power loss tangent (tan δSTO) of 3.4 ± 0.1×10−4 at millikelvin temperatures. To further investigate the potential of SrTiO3 for use in emerging quantum technology applications, the transition of tan δSTO into the single photon regime was analyzed. Our findings reveal a loss scaling that aligns closely with a two-level system loss mechanism. We observe a nearly two orders of magnitude difference in tan δSTO between high and low input power levels, consistent with that two-level system loss picture.

Oxygen‐depleted YBa ₂ Cu ₃ O _7−δ exhibits a substantial drop in the normal‐state resistivity and an increase in the superconducting critical temperature when illuminated with visible light. The photo‐induced states are metastable, slowly decaying at high temperatures and essentially persistent at low temperatures. In this work, this effect is exploited to modify the response of half‐wavelength YBa ₂ Cu ₃ O _7−δ resonators and simultaneously the high‐sensitivity of the resonant circuit is used to investigate the persistent photodoping of this material. Under illumination, the bolometric effect and photodoping are clearly distinguished by the different time scales associated with each mechanism. Using a 60 µm‐wide laser spot, the properties of the resonator are locally and reversibly modified, and the position‐dependent sensitivity of the device is demonstrated. This enables the direct imaging of standing waves at both the fundamental resonance and the second harmonic.

Topological insulators (TIs) are materials with an insulating bulk and topologically protected conductive surface states. Many potential applications can be found in the literature for this class of materials. However, the small bandgap and the poor stability of the TIs extensively studied in the literature, such as Bi2Se3 and Bi2Te3, restrict their potential. One of the proposed alternatives is barium bismuthate (BBO), an oxide perovskite that is predicted to be a TI with a relatively large bandgap of about 0.7 eV. Despite the potential of this material, accessing its TI phase requires increasing the Fermi energy by ∼2 eV, and, to our knowledge, this has not yet been achieved experimentally. One proposed way to shift the Fermi energy is to substitute a part of the oxygen atoms in its structure with fluorine. In this study, we investigated the low-temperature fluorination of MBE-grown BBO thin films using SF6 plasma as a fluorine source. We began our study by using XRD and AFM to identify the processing conditions that allowed us to preserve the quality of the film. Then, we confirmed the incorporation of fluorine into the exposed thin film by XPS and SIMS. Since oxygen deficient films are expected to be easier to alloy, we also compared these results with the fluorination of oxygen-deficient BBO3−x films. Finally, we used DFT to demonstrate that the fluorination of BBO3 is an energetically favorable process, supporting our observations.