Alvaro Rodriguez

In this work, Grazing Incidence Small-Angle X-ray Scattering (GISAXS) is employed as an in situ, real-time technique to monitor the formation of laser-induced periodic surface structures (LIPSS) on semiconducting polymer (PCDTBT) thin films, complemented by ex-situ Atomic Force Microscopy (AFM) analysis by using the recently proposed code REGUΛARITY. Special emphasis is placed on comparing real-space and reciprocal-space approaches to assess the degree of structural order during LIPSS formation. Both methodologies consistently describe the process through a three-stage mechanism comprising incubation, growth, and stabilization. While real-space analysis provides local information at the micrometer scale, reciprocal-space measurements via GISAXS enable statistical averaging over larger surface areas, revealing complementary aspects of structural evolution. The comparison highlights that spatial heterogeneity dominates during the incubation stage, whereas a progressive increase in long-range order is observed during growth and stabilization. The combination of AFM-based Fourier analysis and GISAXS diffraction enables a quantitative evaluation of ordering, including the detection of higher-order contributions associated with improved structural coherence. These results demonstrate that the joint use of real-space and reciprocal-space techniques provides a comprehensive framework for understanding the kinetics and ordering mechanisms of LIPSS formation in semiconducting polymers.

Fluorinated graphene holds significant promise for optoelectronic applications, yet the instability of carbon–fluorine (C‐F) bonds has limited its practical use. This study investigates the long‐term operational and thermal stability of a photodetector containing graphene/fluorinated graphene heterostructure (Gr/F‐Gr HS). In this design, the top graphene serves as a capping layer that stabilizes fluorine atoms in the bottom fluorinated graphene (F‐Gr) via interlayer interactions and suppresses fluorine diffusion. This fluorine‐trapping configuration effectively passivates the defects in the F‐Gr layer, enhancing both the drain current and optical absorption without altering the device structure. The photodetector achieves > 10 ⁴ A/W responsivity, ≈10 ¹² Jones detectivity, and sub‐200 µs response, enabling frequency resolution up to 1 kHz across a broad spectral wavelength range (300–1150 nm). The device retains ≈86% of its initial photocurrent after one year in ambient conditions and remains stable up to 200 °C. All‐atom molecular dynamics simulations support the experimental results, revealing that the capping layer stabilizes C‐F bonds by suppressing fluorine migration and enabling interlayer fluorine redistribution. Together, these findings highlight the superior thermal stability of Gr/F‐Gr, reinforcing its promise for advanced optoelectronic applications.

Strain engineering represents a pivotal approach to tailoring the optoelectronic properties of two-dimensional (2D) materials. However, typical bending experiments often encounter challenges, such as layer slippage and inefficient transfer of strain from the substrate to the 2D material, hindering the realization of their full potential. In our study, using molybdenum disulfide (MoS₂) as a model 2D material, we have demonstrated that layers obtained through gold-assisted exfoliation on flexible polycarbonate substrates can achieve high-efficient strain transfer while also mitigating slippage effects, owing to the strong interfacial interaction established between MoS₂ and gold. We employ differential reflectance and Raman spectroscopy for monitoring strain changes. We successfully applied uniaxial strains of up to 3% to trilayer MoS₂, resulting in a notable energy shift of 168 meV. These values are comparable only to those obtained in encapsulated samples with organic polymers.

Nanobubbles naturally formed at the interface between 2D materials and their substrate are known to act as exciton recombination centers because of the reduced bandgap due to local strain, which in turn scales with the aspect ratio of the bubbles. The common understanding suggests that the aspect ratio is a universal constant independent of the bubble size. Here, by combining scanning tunneling microscopy and molecular dynamics, we show that the universal aspect ratio breaks down in MoS₂ nanobubbles below a critical radius (≈10 nm), where the aspect ratio increases with increasing size. Accordingly, additional atomic-level analyses indicate that the strain increases from 3% to 6% in the sub-critical size range. Using scanning tunneling spectroscopy, we demonstrate that the bandgap decreases as a function of the size. Thus, tunable quantum emitters can be obtained in 2D semiconductors by controlling the radius of the nanobubbles.

Atomically‐thin crystals have been shown to be rich in fundamental phenomena and are promising for various applications. Mechanical exfoliation of (2D) materials from bulk crystals is particularly suited for fundamental studies due to the high quality of the resulting monolayer crystals. To date, several techniques have been developed to increase the exfoliation yield, however, they still suffer drawbacks. In this work, a novel method that exploits gold‐assisted exfoliation to prepare large‐area monolayers of various layered materials followed by their transfer to arbitrary substrates is introduced. X‐ray photoelectron, Raman, and photoluminescence spectroscopies are employed to assess the quality of the prepared layers and their optical properties. Then, field‐effect transistors and photodetectors are fabricated to demonstrate the suitability of this technique for large‐area optoelectronic devices.

The interplay between excitons and phonons governs the optical and electronic properties of transition metal dichalcogenides (TMDs). Even though a number of linear and nonlinear optical-, electron-, and photoelectron-based approaches have been developed and/or adopted to characterize excitons and phonons in single/few-layer TMDs and their heterostructures, no existing method is capable of directly probing ultralow-frequency and interlayer phonons on the nanoscale. To this end, we developed ultralow-frequency tip-enhanced Raman spectroscopy, which allows spectrally and spatially resolved chemical and structural nanoimaging of WSe₂/WS₂ heterostructures. In this work, we apply this method to analyze phonons in nanobubbles that are sustained in these heterobilayers. Our method is capable of directly probing interlayer (de)coupling using our novel structurally sensitive nano-optical probe and the interplay between excitons and interlayer/intralayer phonons through correlation analysis of the recorded spectral images.

Cells communicate with their environment via surface receptors, but nanoscopic receptor organization with respect to complex cell surface morphology remains unclear. This is mainly due to a lack of accessible, robust and high-resolution methods. Here, we present an approach for mapping the topography of receptors at the cell surface with nanometer precision. The method involves coating glass coverslips with glycine, which preserves the fine membrane morphology while allowing immobilized cells to be positioned close to the optical surface. We developed an advanced and simplified algorithm for the analysis of single-molecule localization data acquired in a biplane detection scheme. These advancements enable direct and quantitative mapping of protein distribution on ruffled plasma membranes with near isotropic 3D nanometer resolution. As demonstrated successfully for CD4 and CD45 receptors, the described workflow is a straightforward quantitative technique to study molecules and their interactions at the complex surface nanomorphology of differentiated metazoan cells.

We report experimental results on damage induced by ionizing radiation to DNA origami triangles which are commonly used prototypes for scaffolded DNA origami nanostructures. We demonstrate extreme stability of DNA origami upon irradiation, which is caused by (i) the multi-row design holding the shape of the origami even after severe damage to the scaffold DNA and (ii) the reduction of damage to the scaffold DNA due to the protective effect of the folded structure. With respect to damage induced by ionizing radiation, the protective effect of the structure is superior to that of a naturally paired DNA double helix. Present results allow estimating the stability of scaffolded DNA origami nanostructures in applications such as nanotechnology, pharmacy or in singulo molecular studies where they are exposed to ionizing radiation from natural and artificial sources. Additionally, possibilities are opened for scaffolded DNA use in the design of radiation-resistant and radio-sensitive materials.